0300 UTC 9/3/2004 TROPICAL DEPRESSION 9 FORECAST #1

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Tropical Depression 9 is embedded within the low-level flow in a mainly barotropic environment. This gives the beta advection models, as well as LBAR some credibility for this forecast. The models are in agreement regarding a track mainly to the west, reaching the Lesser Antilles in 5 days. The weakness indicated by CMC and NOGAPS is related to the models forming the disturbance to the NW of Tropical Depression 9 into a significant tropical cyclone. Even if this were to form, this weakness appears to be too far to the north to affect the track of this cyclone. Therefore, this motion will be mainly to the west in agreement with the tropical model guidance.

The intensity forecast is a bit harder. Water vapor imagery shows a very impressive ridge over this cyclone. However, a large trough in response to the outflow of Frances extends into the Tropical Atlantic. As Frances moves away, it is possible that this low may also move away. Guidance intensifies this significantly over the next few days to varying degrees, with SHIPS indicating a category one storm, while all of the GFD models show a category four hurricane. Due to the shear over the islands, I will be conservative and only intensify this to 75KT as it moves through the Caribbean. However, it could very well be significantly more intense by then.

Initial: 9.7N 28.7W 25KT
12 Hour: 9.9N 31.7W 30KT
24 Hour: 10.2N 35.2W 40KT
36 Hour: 10.5N 38.7W 50KT
48 Hour: 10.8N 42.2W 60KT
72 Hour: 11.5N 48.7W 65KT

USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 12.3N 54.5W 70KT
120 Hour: 13.2N 61.0W 75KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/4/2004 TROPICAL STORM IVAN FORECAST #2

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Guidance is limited for this forecast; though that should not be any significant problem as the system is embedded in the deep easterly flow, which is expected to continue, bringing the storm into the Caribbean in 5 days. A high-pressure ridge is located to the north. NOGAPS insists upon forming a tropical cyclone from a poor disturbance, weakening the ridge; thus, turning Ivan too far north. Therefore, NOGAPS is being discounted and a track just to the north of due west is indicated. This is along with the GFS and BAMD, though faster as these models may be slowing the storm too quickly.

Initial intensity is set to 40KT. Visible satellite imagery shows good banding, though a slight amount of easterly shear. However, the 15KT increase from last evening can qualify as rapid intensification. SHIPS brings Ivan to 83KT in 72 hours before weakening it to 79KT at 120. There may be some westerly shear near the end of the forecast period due to the large trough over the Caribbean. However, before then, conditions are expected to remain quite favorable for further intensification and Ivan is now expected to become a category three hurricane prior to moving through the Islands, more in agreement with the GFD models.

Initial: 9.6N 32.0W 40KT
12 Hour: 9.7N 35.8W 50KT
24 Hour: 10.0N 39.8W 60KT
36 Hour: 10.5N 43.8W 70KT
48 Hour: 11.0N 47.6W 80KT
72 Hour: 12.0N 54.6W 90KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 13.0N 60.0W 100KT
120 Hour: 14.0N 65.0W 100KT

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/4/2004 TROPICAL STORM IVAN FORECAST #3

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As has been the case in the past couple of model runs, the NOGAPS weakens the ridge too much. The disturbance to the north that this model insists will develop likely will not. This eliminates his model and the GFD models that run based upon its initial fields. WV imagery shows the ridge in tact; thus, the southern track from previous forecasts is retained, although a leftward adjustment initially due to the southward motion today. Once the system moves farther west, the beta effect should allow for a motion slightly north of due west, and this may be starting now.

Ivan continues to organize and there does not appear to be anything to keep it from becoming a major hurricane before the Caribbean, except for an unexpected SAL surge. This forecast is slightly more aggressive that the previous since SHIPS has also increased, indicating that conditions may be more favorable for development, although this may merely be due to the fact that the GFS model is similar to the NHC track, as SHIPS uses the GFS analysis and the NHC track to compute shear.

Initial: 9.1N 35.0W 45KT
12 Hour: 9.1N 38.5W 55KT
24 Hour: 9.3N 42.0W 65KT
36 Hour: 9.7N 46.0W 75KT
48 Hour: 10.2N 50.0W 85KT
72 Hour: 11.2N 56.5W 95KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 12.5N 62.0W 105KT
120 Hour: 14.0N 67.0W 110KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/4/2004 TROPICAL STORM IVAN FORECAST #4

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Morning satellite imagery shows that Tropical Storm Ivan has become somewhat ragged. The SSM/I pass from this morning shows a possible SAL interaction, even though the pass missed most of the storm. However, since shear is low, this forecast will still indicate a major hurricane for the Caribbean since shear is low. If an SSM/I pass can catch the eastern portions of Ivan and it does show a more significant SAL, then I will reduce the intensity forecast.

A track mainly to the west through the period is expected due to the system being embedded within the easterly flow and underneath the ridge. Some of the models, as usual, are tending to turn the hurricane too far to the north too quickly, moving the system through the Leeward Islands. The ridge appears to be stronger; therefore, a more southerly track is expected.

Initial: 8.8N 38.1W 55KT
12 Hour: 8.8N 42.0W 60KT
24 Hour: 9.0N 45.7W 65KT
36 Hour: 9.5N 49.2W 75KT
48 Hour: 10.0N 52.2W 85KT
72 Hour: 11.0N 58.5W 100KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 13.0N 64.0W 105KT
120 Hour: 15.0N 69.5W 110KT

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/5/2004 TROPICAL STORM IVAN FORECAST #5

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Tropical Storm Ivan has moved slightly slower and to the right of the previous forecast track. Guidance suggests that the storm may move slightly slower and a little to the right of the previous forecast track. Since the ridge is in place, though apparently not strong enough to keep the storm from overcoming the beta-effect, a slight rightward adjustment is indicated. For now, this forecast keeps the storm south of Hispaniola, though this is subject to change.

Initial intensity is increased to 60KT based upon a banding feature wrapping into the center. I would have called this a hurricane had there been a little more deep convection. The previous intensity trends for a major hurricane affecting the Lesser Antilles are retained as conditions are favorable for further intensification.

Initial: 9.3N 41.4W 60KT
12 Hour: 9.8N 45.0W 65KT
24 Hour: 10.4N 48.5W 75KT
36 Hour: 11.0N 52.0W 85KT
48 Hour: 11.6N 55.5W 95KT
72 Hour: 13.0N 61.5W 105KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 14.5N 66.0W 110KT
120 Hour: 16.5N 70.5W 110KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/5/2004 HURRICANE IVAN FORECAST #6

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An eye has become clear on satellite imagery with very deep convection in the eye wall. This indicates that Ivan is in yet another rapid intensification phase. For now, the intensity is being set to 80KT. With upper winds expected to remain quite favorable; Ivan is now forecast to become a major hurricane in just 24 hours and move through the Windward Islands as an upper category three hurricane as there is no shear or significant dry air that Ivan will encounter before moving into the Caribbean.

Newer guidance is shifting to the south, which appears more in tune with what has been happening. The COMU consensus keeps the system in the Caribbean, in agreement with previous forecasts. The upper low in the eastern Caribbean appears to be lifting out at this time. Based upon this, a track through the Caribbean remains the forecast after moving through the Windward or extreme southern Leeward Islands.

Initial: 9.8N 45.1W 80KT
12 Hour: 10.3N 48.6W 95KT
24 Hour: 10.8N 51.1W 105KT
36 Hour: 11.5N 54.5W 110KT
48 Hour: 12.2N 57.7W 110KT
72 Hour: 13.5N 63.7W 115KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 15.5N 68.7W 115KT
120 Hour: 17.5N 73.7W 115KT

Next Forecast: 0300 UTC

Forecaster: Ortt

2100 UTC 9/5/2004 HURRICANE IVAN SPECIAL FORECAST #7

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This special forecast is primarily to increase the intensity forecast. At 1800 UTC, the best estimate of the intensity is 110KT; however, this will likely be higher in the 5 P.M. update. Since there is no sign of a concentric eye wall on the latest AMSR pass, it appears as if Ivan will be able to intensify almost at will, at least until it enters the Caribbean. SHIPS brings Ivan to near category five status as it enters the Caribbean while GFDI does indicate a category five storm. Because I don't really want to forecast a category five hurricane due to their rarity, I will opt to move this through the islands as a 135KT hurricane, borderline category 4/5, though I would not be the least bit surprised to see this enter at least as a weak five. Once in the Caribbean, there may be slight shear, although WV imagery continues to show the UL lifting out, so shear likely will not be a factor and there is no significant SAL to speak of. Due to the uncertainty, I will maintain this as a strong four through the forecast period.

WV imagery shows that the large ridge to the north of Ivan is not going anywhere anytime soon. The only factor that should cause much northward movement for at least the next three days is the beta effect, and this should not account for much northward motion. Afterwards, a WNW motion is more likely as the storm Since Ivan is slightly right of the previous forecast track, a slight rightward adjustment is necessary for this one, and a little faster since newer guidance suggests that Ivan will not slow as it turns WNW, closely resembling the tracks of the GFDL and GFDI and indicating a threat to extreme western Haiti and Cuba.

Initial: 10.2N 46.8W 110KT
12 Hour: 10.9N 50.3W 120KT
24 Hour: 11.6N 53.8W 130KT
36 Hour: 12.3N 57.3W 135KT
48 Hour: 13.0N 60.7W 135KT
72 Hour: 14.5N 67.0W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 17.0N 72.5W 130KT
120 Hour: 19.5N 78.0W 130KT

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/6/2004 HURRICANE IVAN FORECAST #8

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No forecast graphics with this forecast.

GFS again has to be discounted as it is again bringing a tropical wave northward into a 500mb ridge. This has caused the tropical models to shift somewhat. Long term, the question is whether or not a trough is coming off of the East Coast and will turn the system more to the north. Since GFS has had a history of under doing features, I am again setting this model aside. I really do not feel comfortable making a rightward adjustment to the forecast track just to go along with the model guidance, especially since the hurricane is right on the previous forecast track.

Ivan continues to rapidly intensify. Eye wall replacement cycles cannot be ruled out, though there is no evidence of this starting currently, and microwave imagery is not available at the present time. I still prefer not to forecast a category five hurricane, but will continue to bring this into the Caribbean at 135KT and keep the storm as a very strong category four hurricane through the period

Initial: 10.6N 48.5W 125KT
12 Hour: 11.3N 52.0W 130KT
24 Hour: 12.0N 55.5W 135KT
36 Hour: 12.7N 59.0W 135KT
48 Hour: 13.5N 62.5W 135KT
72 Hour: 15.0N 68.5W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 17.5N 74.0W 130KT
120 Hour: 20.0N 79.0W 130KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/6/2004 HURRICANE IVAN FORECAST #9

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Ivan appears to be as disorganized today, as it was organized yesterday. Microwave satellite imagery does not indicate any presence of concentric eye walls, instead, it appears to be more of a complete collapse of the eye; therefore, this is not related to internal dynamics, but instead due to ambient environment. Based upon water vapor imagery, a SAL intrusion appears the likely culprit of this unexpected weakening, in a similar manner as it caused Hurricane Georges to weaken. Intensity guidance insists upon suggesting re-intensification of Ivan; however, based upon its appearance, this does not seem likely. Due to the uncertainties with the intensity forecast, the initial intensity of 105KT is maintained throughout the entire forecast period.

Ivan has moved faster and slightly south of the previous forecast track. The ridge to the north is persisting. NASA model is being discounted as it is forming spurious cyclones ahead of the storm, forcing a movement too far north, and it weakens the ridge as it tries to develop the disturbance to the north of Ivan and weakens the ridge. The models have had the ridge weakening too much throughout the duration of this cyclone and they appear to be doing the same here. After 48-72 hours, Ivan should begin to turn to the WNW as it starts to reach the western extent of the ridge and feels the lingering weakness from Frances. However, I am going to remain south of all models at this time as they are intiialzing the storm too far north and too weak, causing a motion too far to the north.

Latest satellite images show that the eye is returning. If recon finds an intensificiation trend, a special forecast will be issued at 2100 UTC.

Initial: 11.0N 52.5W 105KT
12 Hour: 11.6N 56.5W 105KT
24 Hour: 12.3N 60.0W 105KT
36 Hour: 13.0N 63.5W 105KT
48 Hour: 13.7N 67.0W 105KT
72 Hour: 15.5N 73.5W 105KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 18.0N 77.5W 105KT
120 Hour: 20.5N 81.5W 105KT

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/6/2004 HURRICANE IVAN FORECAST #10

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No graphics with this forecast

Dvorak estimates are disregarded for this update as they seem illogical. Despite the increase in organization, TAFB has a data t number that has decreased from 5.0 to 4.0 since 1800 UTC and SSD has an increase in the data T number, but a lowering of the CI number. Earlier this afternoon, recon found that the pressure had fallen from 969mb to 963mb and that maximum flight level winds were 106KT, equivalent to 95-100KT at the surface. Since then, an eye has become visible on satellite imagery. Based upon this, the initial intensity is set to 100KT.

Recon fixes have shown that the motion is close to 260, to the south of due west. WV imagery shows that the ridge remains in place, suggesting that little, if any, northward motion will occur for at least the next 24 hours. This track will bring the storm very close to Venezuela, but does keep it just offshore. I have no choice to shift even farther to the left of previous forecasts since the ridge is remaining in place and guidance finally is providing a realistic scenario of a threat to the NW Caribbean. A turn to the WNW and possibly NW is still expected before reaching Nicaragua and Honduras as Ivan will be reaching the western extent of the ridge before then.

SHIPS guidance needs to be disregarded in the short term as it is initialized at 90KT after an incorrect initialization of 100KT six hours earlier, forcing a negative influence due to the persistence factor. Little change in intensity is expected within the next 36 hours, mainly due to the proximity to land. Afterwards, a gradual intensification is expected, with a faster rate of intensification expected in the NW Caribbean where the oceanic heat content is the highest in the entire basin.

Initial: 11.3N 56.3W 100KT
12 Hour: 11.4N 60.0W 100KT
24 Hour: 11.6N 63.6W 100KT
36 Hour: 11.8N 67.2W 100KT
48 Hour: 12.6N 70.3W 105KT
72 Hour: 14.5N 76.0W 110KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 17.5N 80.5W 120KT
120 Hour: 21.0N 85.0W 130KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/7/2004 HURRICANE IVAN FORECAST #11

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There may not be graphics with this forecast. Please check to see if the forecast graphics show Ivan forecast #11.

Recon confirmed the marginal category three intensity based upon 108KT at 700mb in the NE quadrant.

Global model guidance again is divergent with NOGAPS and GFS right of CMC/UKMET. With the strong ridge in place, it appears as if GFS has the incorrect solution, which after Frances, is not the least bit surprising. However, the fast motion from last evening does need to be reduced due to the large upper low located to the west of the cyclone. Therefore, with the exception of a slight rightward adjustment to account for the initial position, this forecast is quite similar to the previous.

For a category three hurricane, Ivan is quite disorganized. Shear from the upper low, along with the SAL continues to inhibit any rapid intensification. The UL is moving to the west and may eventually be out of the way and allow for more favorable conditions to prevail once Ivan moves into the NW Caribbean. However, it does appear as if this will not occur until later in the forecast period. Therefore, there is a slight reduction in the intensity forecast.

Initial: 11.6N 59.4W 100KT
12 Hour: 11.9N 62.9W 100KT
24 Hour: 12.2N 66.2W 100KT
36 Hour: 12.9N 69.2W 100KT
48 Hour: 13.9N 72.0W 100KT
72 Hour: 15.9N 77.6W 100KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 18.9N 82.0W 110KT
120 Hour: 22.0N 85.0W 125KT

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/8/2004 HURRICANE IVAN FORECAST #12

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There are no track graphics with this forecast

The westward motion continues and, despite consistent model projections of a NW motion, there does not appear to be any on the horizon. The models seem to be poorly handing the 500mb ridge to the north of the hurricane and allow for too much latitude to be gained. However, the Canadian provides a voice of logic and reason and suggests only a small latitude gain. Since thsi is the only model that seems to be providing the appropriate initial motion and ridge initialization, this forecast will follow the Canadian and represents a slight shift to the left of the previous forecast, though nowhere near as far left as I would like to go, out of respect of the consensus of the other models, even though they seem flawed, also to avoid any flip flopping that may occur due to too dramatic of a change.

Initial intensity of 115KT is justified by recon reporting 129KT in the nrothern quadrant at 700mb. WV imagery does show that there is some shear associated with the UL moving to the west ahead of the system and this has flattened out the outflow pattern and I would not be surprised to see some weakening in the short term. However, due to the uncertainties in intensity forecasting, no change is indictated through 36 hours. Afteerwards, the hurricane should slow, allowing for the UL to move farther away and the shear to decrease. In addition, the hurricane at the same time will be moving over the NW Caribbean, where the oceanic heat content is the highest in the entire basin. While Ivan will likely become a category five hurricane in the NW Carib, I have enough respect for the all mighty category five so that I will not yet forecast a category five hurricane, instead, I will maintain 135KT from 72-120 hours.

Initial: 12.0N 62.6W 115KT
12 Hour: 12.4N 66.7W 115KT
24 Hour: 12.8N 70.0W 115KT
36 Hour: 13.5N 72.9W 115KT
48 Hour: 14.5N 75.5W 120KT
72 Hour: 17.0N 79.5W 135KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 20.0N 83.0W 135KT
120 Hour: 23.5N 86.0W 135KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/8/2004 HURRICANE IVAN FORECAST #13

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Track graphic may be delayed. Please check to see if it has been updated.

The ridge remains in place to the north of Ivan, while the trough remains over the mid-west USA. This suggests that a track mainly to the west and only slightly north of the ABC islands is likely, though it must be said that any WSW wobble will place them in the eye of the hurricane. After another 12 to 24 hours of a westerly motion, a turn to the WNW and then NW should occur around the western extent of the ridge. This is very consistent with the previous forecasts and continues to follow the Canadian model closely, though the 0Z UKMET now supports this as well. I am not even going to consider the GFS as it is currently GFS, forecasting a track to the east of Florida. 120 hour position is in the central Gulf of Mexico.

Recon overnight had 133KT in the northern eye wall and a pressure of 946-950. However, the latest recon fix had the pressure rising to 955mb. The plane did not have the chance to sample the northern eye wall since then. With the pressure rise and satellite imagery depicting only a cloud filled eye, the initial intensity is being reduced to 115KT, still a borderline category 3/4 hurricane. There is still some shear in form the UL to the west that is affecting the storm and we may see a little more short term weakening, though as the hurricane slows slightly in a day or so, the UL will move farther away, providing a more favorable environment. It is probably that Ivan will become a category five hurricane in the NW Carib, though respect does need to be paid to the holy grail of hurricanes, the category five storm. Therefore, category five intensity still is not reflected in the forecast.

Initial: 12.5N 65.5W 115KT
12 Hour: 13.0N 68.5W 110KT
24 Hour: 13.5N 71.5W 110KT
36 Hour: 14.5N 74.2W 115KT
48 Hour: 15.5N 76.7W 120KT
72 Hour: 18.0N 80.7W 135KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 21.5N 84.7W 135KT
120 Hour: 26.0N 86.7W 1355KT

Next Forecast: 0300 UTC

Forecaster: Ortt

2100 UTC 9/8/2004 HURRICANE IVAN FORECAST #14

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Graphics will not be posted due to technical difficulties.

Ivan continues moving fairly swiftly just north of due west. A large sub-tropical ridge remains in place to the north of Ivan, this will be the main sterring feature for the next 3 days. Based upon this motion, Ivan will move very close to the island of Jamiaca in 36 hours or so. After this point, it becomes more uncertain upon where Ivan may travel to. The GFS and BAMM models depict a very sharp trough developing in the central U.S., bringing Ivan over Cuba and to the east of Florida. The NOGAPS and UKMET models suggest a more westward path into the eastern Gulf of Mexico, while the CMC and GFDL are in the central Gulf. Due to the uncertainity of the amplitude of the developing trough and position of the sub-tropical ridge it is difficult to pinpoint a direct position, however due to the eastward shift in the model consenses beyond 72 hours and continued north of west heading, this forecast track is a bit right of the previous one.

Ivan has become much better organized in the past few hours with deep convection surrounding its well developed eye. SHIPS and GFDL hold Ivan at 120kt through 24-36 hours or so as there is some southerly shear ahead of the storm system. Beyond 2 days, both models suggest intensification as the upper winds become more favorable. It is probably that Ivan will become a category five hurricane in the NW Carib, though respect does need to be paid to the holy grail of hurricanes, the category five storm. Therefore, category five intensity still is not reflected in the forecast.

Initial: 13.1N 67.0W 120KT
12 Hour: 14.0N 70.0W 120KT
24 Hour: 15.1N 72.7W 120KT
36 Hour: 16.3N 75.4W 125KT
48 Hour: 17.8N 77.5W 130KT
72 Hour: 19.8N 80.7W 135KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 21.8N 83.5W 135KT
120 Hour: 24.3N 85.5W 135KT

Next Forecast: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/9/2004 HURRICANE IVAN FORECAST #15

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We apologize for any confusion that the previous forecast may have had. The one by Cangialosi was the NWHHC forecast, not the one by Ortt.

Model guidance is not entirely accurate for this package. The GFS totally ruins the CONU as well as the tropical track models. Best bet is to use old fashioned synoptic reasoning. WV imagery shows the ridge maintaining itself to the north of Ivan and there is no reason as to why this feature will not persist. Frances is lifting to the north; thus, its weakness likely will not be as great as some of the models are suggesting. In addition, the guidance is not depicting this continued westward motion, but instead has been insisting since Ivan has formed that the storm would be moving more northerly. Only the CMC has had a believable solution. I will wait at least one more model run before making any significant westward adjustments to the track forecast and will just extend the previous track.

Initial intensity is set to 125KT. The reasoning behind this is the fact that recon found the pressure falling rapidly to 938mb and flight level winds in excess of 130KT outside of the NE quad. The UL appears to be enhancing the outflow more than it is shearing the cyclone. A nearly symmetric CDO surrounds a nearly cloudless eye. Based upon this, category five intensity is now predicted by tomorrow morning with a peak of 145KT. Eye wall replacement cycles are likely to play a role in the intensity changes, as well as land influence. However, since the hurricane will soon be over the NW Caribbean where there is extreme oceanic heat content, cat 5 intensity is expected to be maintained until Cuban landfall. Once in the Gulf of Mexico, any shear depicted by the models may be related to the fact that the hurricane is located too far east on the models. Near cat 5 is indicated for the GOM.

Initial: 13.4N 68.4W 125KT
12 Hour: 14.4N 71.2W 140KT
24 Hour: 15.5N 74.0W 145KT
36 Hour: 16.7N 76.5W 150KT
48 Hour: 18.0N 79.0W 140KT
72 Hour: 21.0N 83.0W 145KT (near Cuba)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 24.0N 85.0W 130KT (Gulf of Mexico)
120 Hour: 27.5N 85.5W 135KT

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/9/2004 HURRICANE IVAN FORECAST #16

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Powerful Hurricane Ivan has reached the elite category 5 status as of earlier this morning.

Ivan continues to track towards the WNW at 13 kt towards the island of Jamaica. A large mid-level ridge remains established to Ivan's north tracking it in this general direction. This motion is likely to continue through 36-48 hours, followed by a more northward heading therafter in response to an upper level trough over the central U.S. It seems likely that Ivan may pass in the general vicinty of Jamaica in 36 hours, and towards western Cuba in 72 hours. After this point, there is a significant spread in the global models. The GFS solution tracks Ivan far to the east towards the Bahamas while the UKMET, NOGAPS and CMC track Ivan towards the eastern Gulf of Mexico, with GFDL in between. Due to excellent previous forecasts, I will continue with this thinking briniging Ivan west of the Florida pennisula, however Florida remains at a high risk of a direct landfall as forecasts beyond 72 hours are subject to large errors.

Initial intensity is set to 140KT, a powerful cat 5. Latest recon reports a pressure of 921 mb, up from the previous 919mb. It is often difficult to forecast intensity on these powerful hurricanes as internal dynamics often controls the fluctuations. However, it must be said that Ivan will only move over warmer and warmer waters up until the Cuban landfall. Therefore, I will maintain this storm as a category 5 hurricane up until the Cuban landfall. Depending upon where Ivan tracks over Cuba, will alter its intensity therafter.

Initial: 14.2N 70.7W 140KT
12 Hour: 15.3N 73.3W 140KT
24 Hour: 16.9N 75.4W 140KT
36 Hour: 18.4N 77.3W 140KT
48 Hour: 19.9N 79.2W 145KT
72 Hour: 22.8N 82.5W 145KT (near Cuba)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 25.6N 84.5W 130KT (Gulf of Mexico)
120 Hour: 29.5N 84.8W 125KT (near land)

Next Forecast: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/10/2004 HURRICANE IVAN FORECAST #17

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Microwave satellite imagery indicates that Hurricane Ivan has completed an eye wall replacement cycle. TMI and AMSR passes from this afternoon showed a collapsing inner eye wall with an outer wind maximum. This evening, an SSM/I pass indicates that only an outer eye wall remains. Typically, the winds increase after one of these cycles; thus, re-intensification into a category five hurricane is expected prior to making landfall on Jamaica. The initial intensity, however, is lowered to 125KT. I would have went as low as 115KT since flight level winds in the NW quad are not as high as they were yesterday when Ivan has winds of 120KT. However, recon did find winds to 144KT in the NE quad at 700mb this afternoon so 125 can be justified. In the Caribbean, the only weakening that is likely to occur is due to landfall on Jamaica, and mainly due to the conservation of potential vorticity in a barotropic atmosphere, with re-intensification afterwards due to the same principle. In the Gulf, the intensity models, such as SHIPS and GFDL show significant weakening due to shear; however, this is not logical since the GFS has the storm well to the east of the forecast position, and the storm is under an upper ridge. GFDN maintains category four intensity all the way to the northern Gulf coast; therefore, this forecast does as well.

Global models are converging upon the idea of a motion to the west of Florida. CMC, UKMET, NOGAPS, as well as GFDN all show a track similar to the previous forecast. GFS has been slightly weak with the ridge to its north, resulting in a track well east of the remainder of the models. I am not going to indicate much of a change at this time, only a slight rightward shift to be in agreement with UKMET and NOGAPS. This also matches up well with Ivan being slightly right of the previous forecast track and a little slower. This track still brings Ivan over Jamaica and Cuba, and shows a significant threat to the Florida Keys. It should be noted that there have been many studies conducted regarding mountain affects on tropical cyclone tracks and one finding is that the cyclones can move in a cyclonic motion around the mountains. This is not reflected in this forecast at the present time.

Initial: 15.2N 72.8W 125KT
12 Hour: 16.5N 75.0W 135KT
24 Hour: 17.8N 77.0W 140KT (inland, Jamaica)
36 Hour: 19.2N 79.0W 120KT (over water)
48 Hour: 20.5N 80.9W 140KT
72 Hour: 23.0N 83.0W 130KT (inland, Cuba)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 26.5N 84.0W 130KT (Gulf of Mexico)
120 Hour: 30.0N 84.0W 125KT (near land)

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/10/2004 HURRICANE IVAN FORECAST #18

This is an independent product

Hurricane Ivan remains a dangerous powerful category 4 hurricane that is likely to make landfall on the island of Jamaica within the next 12 hours.

Ivan continues on a WNW path at a bit of slower pace than yesterday near 11 kt. This track is likely to continue through 36 hours. The synoptic reasoning remains unchanged a large mid-level ridge is located to the north of Ivan with a weakness in the ridge in the Gulf of Mexico. As of early this morning the ridge appears to be extending further to the west towards the east coast of Florida. If this ridge continues moving towards the west, the center of the storm may track just west of the Gulf Coast of Florida. However, this is highly uncertain and depends upon the position of the ridge and weakness in the next few days. Global models have been converging some bringing Ivan through Jamaica then through the west coast of Cuba and towards the Florida Peninsula. Exactly where the storm makes a northward turn is critical to where the landfalls will occur.

Initial intensity remains at 125 kt, the structure this morning is a bit more ragged than last night, however as of the past hour or two Ivan appears to be making a come back and perhaps be strengthening once again. Ivan is in a favorable environment for strengthening so it is possible that Ivan may strengthen once again before affecting Cuba. Thereafter some weakening is expected as the system moves over land.

Initial: 16.2N 74.7W 125KT
12 Hour: 17.5N 76.7W 135KT
24 Hour: 19.0N 78.6W 135KT
36 Hour: 20.5N 80.3W 140KT
48 Hour: 21.9N 82.1W 135KT
72 Hour: 24.5N 83.5W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 27.5N 83.6W 125KT
120 Hour: 31.0N 83.6W 85KT Inland)

Next Forecast: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/11/2004 HURRICANE IVAN FORECAST #19

This is an independent product

Ivan completed its eye wall replacement cycle just prior to moving near Jamaica and the results are devastating. Recon data indicated that Ivan was rapidly becoming better organized just prior to making landfall. The flight level winds do not support category four intensity; however, in storms that are as convectively active as Ivan currently is, it is possible for the surface winds to equal the flight level winds, if not exceed them. This, along with TAFB and SSD estimates of 127KT is enough justification to use the 0000 UTC initial intensity of 125KT and this will be increased at the 11 P.M. update.

500mb observations from the region show that a ridge that has been over the Caymans is remaining, with the trough being located as far west as the Yucatan. This may explain why the previous track was ever so slightly to the right of the observed track. Water vapor imagery shows a narrow weakness between a ridge over Texas and a ridge east of Florida. Since a hurricane follows the path of least resistance, Ivan is expected to move through this weakness. Most global models, except for GFS, which has been well right of reality, have shifted left. I am not going to make any significant changes to the track at this time, though I will shift about 1 degree to the left at 120 hours.

There is nothing to prevent Ivan from regaining category five status. Shear is low and Ivan will not be passing over the highest terrain that Jamaica has to offer. GFDN indicates that Ivan is going to become the most intense hurricane ever, with its pressure falling to 887mb. I am not ready to go that far, though I am going to increase the previous intensity forecast to indicate a peak intensity of 150KT. Eye wall replacements are not factored into this forecast, though are likely to occur. As for the intensity at the Gulf landfall. GFDN keeps this as a category four hurricane, as does SHIPS. There does not appear to be any significant shear in the Gulf at the present time. I will retain the previous intensity forecast of 125KT at landfall on the northern Gulf coast.

Note: On this track, the Florida Keys will still receive hurricane force winds.

Initial: 17.3N 76.5W 125KT
12 Hour: 18.4N 78.3W 135KT
24 Hour: 19.5N 80.0W 150KT
36 Hour: 21.0N 81.5W 150KT
48 Hour: 22.3N 82.8W 145KT (near Cuba)
72 Hour: 25.5N 84.0W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 29.5N 84.6W 125KT (near land)
120 Hour: 34.5N 84.5W 40KT (inland)

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/11/2004 HURRICANE IVAN FORECAST #20

This is an independent product

Ivan remains a powerful category 4 hurricane and may be nearing cat 5 strength once again. Ivan appears to be going through eyewall replacement cycles which is the main culprit to its fluctuating intensity. Ivan has a very clear eye and well defined eyewall region, as the hurricane heads towards western Cuba intensification is possible as SST's and oceanic heat content are very favorable for strengthening.

Track reasoning remains unchanged. A mid-level ridge to Ivan's north continues to steer the system on a WNW track. However, overnight the forward speed has slowed to 6 kt, due to the collapse of the well defined steering currents as anticipated. A trough in the central U.S. continues to dig to the southeast. At the same time the mid-level ridge continues to dig to the southwest, therefore it is likely that Ivan will have a slow motion for the next day or two, before a northerly component develops in response to the southwesterly flow. Exactly when the system takes this northerly turn will make a big difference in the U.S. landfall. Global model have shifted left of the previous run, keeping Ivan west of the west coast of Florida. The previous track forecasts have suggested this motion, therefore this track will be right on top of the previous one, however if Ivan does speed up some, this track forecast may be shifted left, while if Ivan slows down substantially this track may be shifted to the right.

Initial: 17.7N 78.4W 130KT
12 Hour: 19.1N 79.9W 135KT
24 Hour: 20.5N 81.4W 145KT
36 Hour: 22.0N 82.9W 145KT
48 Hour: 23.5N 83.9W 140KT (near Cuba)
72 Hour: 26.5N 84.3W 125KT (Gulf of Mexico)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 32.5N 84.6W 65KT (inland)
120 Hour: Remnant low

Next Forecast: 2100 UTC

Forecasters: Cangialosi/Ortt

2100 UTC 9/11/2004 HURRICANE IVAN FORECAST #21

This is an independent product

Since Hurricane Ivan is not an immediate threat to the United States, starting at 0300 UTC, forecasts will revert back to every 12 hours, instead of every six.

Observations from Grand Cayman Island indicate that the ridge remains in place and Ivan continues to the WNW, if not west. Water vapor imagery shows that this ridge is holding. A trough over Kansas does not appear as if it will dip far enough south to bring this system to the NE. Based upon the above, I have no choice but to make a leftward shift in the forecast track from 1500 UTC. This agrees with the global model consensus. This track now brings Ivan across western Cuba and still indicates a landfall in the Florida Panhandle. I would Ave shifted even farther left, but it is best to wait and see what the 0Z guidance shows before diverting too significantly from the previous forecast.

Initial intensity is at 125KT, based upon 141KT from recon. The pressure is falling and the hurricane is becoming more symmetric since it has completed its eye wall replacement cycle. Since everything indicates further intensification, category five intensity is expected before Ivan reaches Grand Cayman and category four intensity continues to be depicted up until landfall in Florida.

Initial: 18.0N 79.0W 125KT
12 Hour: 18.8N 80.5W 140KT
24 Hour: 20.0N 81.9W 145KT
36 Hour: 21.5N 83.4W 145KT
48 Hour: 23.0N 84.9W 140KT (near Cuba)
72 Hour: 26.5N 85.9W 125KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 32.5N 85.5W 65KT (inland)
120 Hour: 38.0N 83.5W 25KT (inland)

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/12/2004 HURRICANE IVAN FORECAST #22

This is an independent product

Latest recon pressure is 910mb. Satellite imagery shows that the eye is starting to become cloud-free and that the northwest quadrant, which had been a little ragged during the day today is becoming much better defined. GFDN continued to indicate a sub 900mb pressure. The eye is still somewhat large; thus, it can still contract. Based upon this, the intensity forecast for a direct hit on the Cayman Islands is 155KT. Due to the favorable upper oceanic heat content and atmospheric conditions, category five intensity is expected to be maintained at least as long as the system remains in the Caribbean. Only a slow weakening is expected as the hurricane moves into the Gulf of Mexico toward the northern Gulf Coast, consistent with guidance.

There is still some ridging to the north of the hurricane and the result has been a track between 275 and 285 today. This means that the eye may pass just south of Grand Cayman, a solution that as early as 24 hours ago seemed impossible. The weakness to the north appears to be quite weak at the present time. Models suggest that Ivan will simply rotate around the western extent of the ridge off of Florida, which appears to be building westward. It should be noted that models have now started to trend as west as New Orleans with the CMC and near the AL/MS border with the NASA experimental model. This requires yet another shift to the west by roughly one full degree for the U.S. landfall location, as ell as a leftward shift for the Cuban landfall location. I am tempted to bring the storm even farther to the west, into the Channel and close to the Yucatan, but it is best to wait until tomorrow morning to do so, as that would be too dramatic of a forecast shift.

Initial: 18.2N 79.6W 145KT
12 Hour: 18.7N 81.1W 155KT
24 Hour: 19.5N 82.5W 150KT
36 Hour: 21.0N 83.9W 145KT
48 Hour: 23.0N 85.0W 150KT
72 Hour: 27.0N 86.5W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 33.0N 86.3W 50KT (inland)
120 Hour: 39.0N 85.0W 20KT (remnant low)

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/12/2004 HURRICANE IVAN FORECAST #23

This is an independent product

500mb observations continue to indicate some ridging to the north of the storm. The trough that was previously believed to be the mechanism that would turn the hurricane more to the north toward Florida is passing by to the north of the system and it is not very strong based upon the 500mb observations. With a ridge located behind this feature, I again have no choice but to make another shift to the left, now bringing the hurricane closer to the Yucatan and another .5-1 degree shift to the left for U.S. landfall. This is in best agreement with the 0Z NOGAPS and 12Z CONU, but is right of the Canadian model.

The outflow has become better defined this morning and the hurricane seems ready to complete another eye wall replacement cycle. GFDN now indicates a minimum pressure of 885mb. With the increased organization shown this morning, this may not be unreasonable, though I will opt to peak the intensity at 150KT. Bad news for the northern Gulf coast is that the intensity guidance keeps trending higher with SHIPS, which had been forecasting significant weakening, now keeping Ivan as a borerline category 3/4 storm, while GFDN keeps Ivan as a bordeline 4/5 all the way until landfall. WV imagery does show some shear over the Gulf; however, upper wind forecasts leave a lot to be desired; therefore I will just trend with the guidance and previous forecasts and go with a cat 4 at landfall.

Initial: 18.7N 81.1W 135KT
12 Hour: 19.2N 82.5W 145KT
24 Hour: 19.9N 84.0W 150KT
36 Hour: 20.9N 85.5W 150KT
48 Hour: 23.0N 86.0W 140KT
72 Hour: 27.5N 87.0W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 33.5N 86.8W 50KT (inland)
120 Hour: 39.0N 82.5W 20KT (remnant low)

Next Forecast: 0300 UTC

Forecaster: Ortt

0300 UTC 9/12/2004 HURRICANE IVAN FORECAST #24

This is an independent product

Hurricane Ivan continues to the WNW, a little faster than previously forecasted. Upper air observations continue to indicate higher heights to the north of the system, although not quite as high as before. The geopotential height gradient still may be enough to force the system west of the previous forecast track. . The weakness to the north remains quite weak and is showing signs of lifting out. Furthermore, the consensus of the global models is indicating a track left of the previous forecast. Based upon all of the above, I have no choice but to shift left again, by roughly another full degree, and there may have to be further shifts tomorrow.

Recon has recently found 155KT at flight level of 700mb. The general rule is that the 700mb winds are equivalent to 90 percent of the surface winds. However, in this case, the 700mb level is significantly lower than it normally is due to the lower than normal surface pressure. Therefore, I do not feel comfortable calling this a category five hurricane again yet, though it may very well become one by the 11 P.M. update. Instead, the initial intensity will be set to 135KT. Some re-intensification is expected to near 145-150KT as the hurricane continues to have concentric eyes. Once the inner eye collapses, the outer eye can become dominant and contract, which would allow for a significant increase in the wind speed. Once in the Gulf of Mexico, the intensity forecast becomes very complicated. There is currently shear associated with the trough and weakness. however, as this feature lifts out, there should be more favorable conditions. The other complication regarding Hurricane Javier, which is expected to be a major hurricane near the west coast of Mexico. Some of the outflow from Javier could impart shear over the system. For now, I will keep the previous intensity forecast of a category four hurricane at landfall, with the caveat that GFDN continues to insist upon a 4/5 at landfall, and this has been one of the better intensity models with this hurricane.

Initial: 19.5N 82.8W 135KT
12 Hour: 20.4N 84.3W 145KT
24 Hour: 21.5N 85.6W 150KT
36 Hour: 23.0N 86.7W 145KT
48 Hour: 24.8N 87.5W 140KT
72 Hour: 28.8N 87.7W 125KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 34.5N 85.0W 50KT (inland)
120 Hour: 40.0N 80.0W 20KT (remnant low)

Next Update: 1500 UTC

Forecaster: Ortt

1500 UTC 9/13/2004 HURRICANE IVAN FORECAST #25

This is an independent product

Ivan continues to track towards the WNW near 7 kt. Ivan is approaching the Yucutan Channel and then should remerge into the Gulf of Mexico within the next 24 hours or so. Global model track forecasts continue to shift towards the left. Based upon the 500 mb height data there only appears to be an ever so slight weakeness in the ridge to Ivan's north in the central Gulf. This weakness may not be deep enough to attract Ivan towards it, therfore this track forecast has shifted even further left of the previous one, bringing the storm inland in the vicinity of coastal Louisana in about 3 days.

Ivan is a powerful category 5 hurricane with a large clear eye, very strong eyewall and well defined structure. Ivan still may intensify a bit more within the next 12 hours as it continues to go through eyewall replacement cycles. Therafter, some weakening is expected as some vertical shear in the Gulf of Mexico may disturb Ivan's circulation, however it does appear the shear may be decreasing, therfore Ivan is forecasted to be a very powerful major hurricane at U.S. landfall, which is expected within 3 days.

Initial: 20.4N 84.1W 140KT
12 Hour: 21.6N 85.6W 145KT
24 Hour: 23.3N 87.1W 145KT
36 Hour: 24.6N 88.2W 140KT
48 Hour: 26.5N 89.7W 125KT
72 Hour: 30.4N 90.4W 100KT (inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 34.4N 85.3W 50KT (inland)
120 Hour: 40.0N 79.7W 20KT (remnant low)

Next Update: 0300 UTC

0300 UTC 9/13/2004 HURRICANE IVAN FORECAST #26

This is an independent product

Powerful Hurricane Ivan has tracked into the Yuctuan Channel hugging the western tip of Cuba. Ivan has been wobbling to the north and west over the last several hours but the general motion now appears to be to the NNW near 9 kt. This more northerly motion is in resonse to the trough over the southeast U.S. A general motion to the north/northwest should continue for about a day followed by a more northeast motion as a reinforement trough sweeps Ivan to the northeast. Due to a slight shift eastward in the global models and a more northerly motion, this track forecast has been shifted well east of the previous one. Based upon this track landfall may occur in the Florida panhandle area in about 60 hours or so.

Ivan is a powerful category 5 hurricane with a large clear eye, very strong eyewall and well defined structure. Ivan still may intensify a bit more within the next 12 hours as it continues to go through eyewall replacement cycles. Therafter, some weakening is expected as some vertical shear in the Gulf of Mexico may disturb Ivan's circulation, however it does appear the shear may be decreasing based upon the UW CIMSS shear anlaysis, therfore Ivan is forecasted to be a very powerful major hurricane at U.S. landfall, which is expected within 48-72 hours.

Initial: 21.6N 85.1W 140KT
12 Hour: 23.3N 86.1W 145KT
24 Hour: 24.9N 87.1W 140KT
36 Hour: 26.5N 87.4W 135KT
48 Hour: 28.4N 87.1W 125KT
72 Hour: 32.4N 86.2W 90KT (inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 36.4N 83.2W 35KT (inland)
120 Hour: 40.0N 79.7W 20KT (remnant low)

Next Update: 1500 UTC

Forecaster: Cangialosi

1500 UTC 9/13/2004 HURRICANE IVAN FORECAST #27

This is an independent product

Hurricane Ivan remains on the previous forecast track and there is no change in the synoptic reasoning. A ridge is building in behind the trough, but a second trough is behind the current ridge, bringing the storm onshore sometime within the next 36-48 hours. A slight left shift has been made to be in better agreement with the global model consensus.

Initial intensity is being lowered to 125KT based upon the latest recon data. Shear and dry air should prevent any re-intensification, though the healthy satellite appearance and the very warm water should prevent any significant weakening. 110KT is the landfall intensity.

Initial: 23.0N 86.0W 125KT
12 Hour: 24.8N 86.7W 120KT
24 Hour: 26.8N 87.4W 115KT
36 Hour: 28.8N 87.7W 110KT
48 Hour: 30.8N 87.7W 100KT (inland)
72 Hour: 34.5N 85.5W 60KT (inland) USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 37.5N 83.2W 35KT (inland)
120 Hour: 40.0N 79.7W 20KT (remnant low)

Next Update: 2100 UTC

Forecaster: Ortt

2100 UTC 9/14/2004 HURRICANE IVAN FORECAST #28

This is an independent product

Water vapor imagery indicates a little more ridging to the nroth than was expected just six hours ago. The trough appears to be about 18-24 hours away from picking up Ivan. Therefore, Ivan will likely maker it slightly west of the projection from six hours ago and this requires a slight shift of less than .5 degrees to the left, still indicating a landfall in the same general area, though.

Initial intensity will remain at 125KT based upon 138KT at 700mb. This afternoon, a larger eye has become clear and recon has reported a concentric eye cycle. Intensity guidaance is slightly above the previous forecast. To err on the side of caution, the landfall intensity is being increased to 115KT, borderline category 3/4. It should be noted that Ivan may be passing over a warm water eddy. If the shear were to relax, we could see some significant re-intensification just offshore.

Initial: 23.7N 86.5W 125KT
12 Hour: 25.5N 87.4W 120KT
24 Hour: 27.5N 87.9W 120KT
36 Hour: 29.5N 88.1W 115KT
48 Hour: 31.5N 88.1W 80KT (inland)
72 Hour: 35.0N 85.5W 35KT (inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 38.5N 82.5W 20KT (inland)

Next Update: 0300 UTC

Forecaster: Ortt

0300 UTC 9/15/2004 HURRICANE IVAN FORECAST #29

This is an independent product

0Z 500mb obs confirms the fears from satellite imagery earlier today. A ridge is located north of the hurricane, and the weakness is located back in Oklahoma. For this reason, Ivan is already to the left of the 1800 forecast track. It appears as if this movement will continue to the NNW for at least 12 more hours, allowing for about 1.5 degrees of longitude to be gained. In short, this requires yet another leftward shift of the forecast track, now indicating a landfall near 88.7W, instead of 88.1W. It should be noted that if Ivan accelerates, it will be able to move farther west before encountering the weakness; therefore, a direct hit on New Orleans cannot be ruled out. This track is very close to the GFDN track and right of CONU. After landfall, this track is slowed considerably from previous tracks as guidance suggests that Ivan will not be picked up by the trough, but instead be left behind.

Recon has found that the pressure is 928mb and that the maximum flight level winds are 147KT. This equates to 130KT at the surface. Satellite imagery shows a more symmetric outflow pattern, indicating that the shear has reduced. In addition, the hurricane has to cross over a warm water eddy. The current eye diameter is 43NM. If the eye starts to contract over the warm eddy, Ivan could explode back into a category five hurricane and possibly become more intense than it was before. However, there could be some weakening before the eye reaches the coast due to some shear associated with the approaching trough. Due to the uncertainties in the intensity forecast, 130KT is now being retained until landfall.

Initial: 24.7N 87.0W 130KT
12 Hour: 26.7N 87.9W 130KT
24 Hour: 28.7N 88.7W 130KT
36 Hour: 30.7N 88.7W 110KT (inland)
48 Hour: 32.0N 88.0W 60KT (inland)
72 Hour: 34.0N 86.0W 30KT (inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 35.0N 85.0W 20KT (inland, remnant low)

Next Forecast: 1500 UTC

Forecaster: Ortt

1500 UTC 9/15/2004 HURRICANE IVAN FORECAST #30

This is an independent product

500mb obs from 12Z show that the weakness is almost to Hurricane Ivan. Recent satellite imagery also shows more of a northerly component to the motion. Therefore, Ivan may gain a couple of tenths of latitude, but no more than that, and the new forecast indicates a landfall in a little more than 12 hours near the Mobile Bay area.

Latest recon indicated 120KT was the initial intensity with 132KT at 700mb. Recent satellite imagery suggests increased organization due to moving over the warn eddy. Ivan has become more symmetric. It is possible that we will have some increase in intensity before landfall; however, Ivan is expected to remain as a category four hurricane.

Initial: 26.7N 87.9W 120KT
12 Hour: 29.0N 88.1W 120KT
24 Hour: 31.0N 88.0W 90KT (inland)
36 Hour: 32.5N 87.0W 55KT (inland)
48 Hour: 34.0N 86.0W 30KT (inland)
72 Hour: 35.0N 85.0W 20KT (inland)

Next Forecast: 2100 UTC

Forecaster: Ortt

2100 UTC 9/15/2004 HURRICANE IVAN FORECAST #31

This is an independent product

The northward turn is underway and a northward trakc should bring the storm inland near Mobile.

Satellite imagery indicates that Ivan is undergoing rapid intensification, though we will wait for recon before increasing the winds any more that the 120KT that they are. Landfall is now expected to be 125KT, instead of 120KT.

Initial: 27.9N 88.2W 120KT
12 Hour: 30.2N 88.4W 1205KT (just onshore)
24 Hour: 32.0N 88.0W 90KT (inland)
36 Hour: 33.0N 87.0W 55KT (inland)
48 Hour: 34.0N 86.0W 30KT (inland)
72 Hour: 35.0N 85.0W 20KT (inland)

Since the 12 hour forecast is onshore, this is the final forecast for Ivan

Forecaster: Ortt

0000 UTC 9/22/2004 TROPICAL DEPRESSION IVAN FORECAST #32

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Ivan the Terrible may now deserve to be called Ivan the Legend. After making the entire trip across the Atlantic, Caribbean, and Gulf of Mexico as a major hurricane, Ivan completed a large anti-cyclonic loop around a large ridge of high-pressure, which has brought the storm back into the Gulf of Mexico.

Track reasoning is very straight forward, as it has been throughout much of the life of Ivan. A motion to the WNW should occur for about 12-24 hours around the south side of the large ridge that is steering Jeanne toward the coast. There after, Ivan should encounter a trough, which should bring the storm more northward and into western Louisiana or extreme eastern Texas.

Currently, there is fairly strong southerly shear from an upper low to the south and west over the storm, displacing all of the convection well to the north of the center. WV shows a region where the shear is somewhat weaker farther to the west near the coast. Since recon has found 38KT at flight level, Ivan is close to tropical storm intensity. Therefore, this forecast will indicate that Ivan will regain tropical storm status before making landfall. 35KT is the landfall intensity.

Initial: 27.0N 89.5W 30KT
12 Hour: 27.5N 91.5W 35KT
24 Hour: 28.5N 93.0W 35KT
36 Hour: 29.5N 94.0W 35KT (inland)
48 Hour: 31.0N 94.0W 25KT (inland)
72 Hour: Merged with trough

Next Forecast: 1500 UTC

Forecaster: Ortt

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