1500 UTC 9/6/2003 TROPICAL STORM ISABEL FORECAST DISCUSSION #1

This is an independent product and not from the National Hurricane Center

Guidance indicates a track mostly to the west or WNW over the next 5 days. Ulness henri significantly intensifies and erodes the ridge; Isabel should be nearing the Lesser Antilles on Thursday, tracking south of the ridge.

Initial intensity is being set to 35KT. Upper winds appear to be very favorable for development and ther eis no SAL. Therefore, hurricane intensity is expected within the next 36 hours. SHIPS levels the system off near 90KT in 72 hours. Therefore, the system will be peaked at 90KT, following SHIPS

Initial: 13.6N 34.5W 35KT
12 Hour: 14.0N 37.0W 45KT
24 Hour: 14.5N 39.5W 55KT
36 Hour: 15.0N 42.0W 65KT
48 Hour: 15.5N 44.5W 75KT
72 Hour: 16.3N 49.0W 90KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 17.0N 53.5W 90KT
120 Hour: 18.0N 58.0W 90KT

Next discussion: 0300 UTC

Forecaster: Ortt

0300 UTC 9/7/2003 TROPICAL STORM ISABEL FORECAST DISCUSSION #2

This is an independent product and not from the National Hurricane Center

Isabel continues to the west, though slower and to the left of the pervious forecast track. Currently, Isabel is being steered by the ridge to its north. After about 72 hours, the models diverge. The reason is Henri off of the U.S. East Coast. UKMET and NOGAPS, maintain Henri and weaken the ridge, allowing for a NW turn. GFS dissipates Henri, allowing Isabel to move more to the west. Since Henri is forecast to maintain itself, this forecast will be shifted to the north of the pervious one, and will be slightly slower.

Initial intensity is being set to 50KT. SHIPS is intensifying the system to about 80KT in 72 hours and then basically maintains the system beyond. Satellite imagery indicates some shear will be encountered in 3-4 days. However, this forecast is more aggressive than the previous one, bringing the system to a major hurricane in 72 hours, with only slight intensification beyond, out of respect for SHIPS. The reason for this increase is because of the greater than expected intensification and the well-organized cloud pattern.

Initial: 13.4N 36.0W 50KT
12 Hour: 13.6N 38.0W 60KT
24 Hour: 14.0N 40.0W 70KT
36 Hour: 14.7N 41.9W 80KT
48 Hour: 15.5N 43.7W 90KT
72 Hour: 17.0N 47.5W 100KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 19.0N 51.0W 105KT
120 Hour: 21.5N 56.0W 105KT

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/7/2003 HURRICANE ISABEL FORECAST DISCUSSION #3

This is an independent product and not from the National Hurricane Center

Isabel has move about 1 full degree to the north of the expected forecast track. In fact, it is close to the projected latitude for this time tomorrow. The reason for this turn may be its proximity to a large upper low to its west. Most global models continue a NW track until the system reaches roughly 20N in about 48 hours. After this time, the model consensus is for a turn back to the west. I will not deviate significantly from the previous track as many of the models are indicating a weak system turning back west, when this is likely to be a major hurricane. However, this forecast is slightly to the left of the previous one after 72 hours.

Initial intensity is being set to 65KT based upon satellite estimates and the appearance of a large, cloud-filled eye, making Isabel a hurricane. No reason not to forecast a continuation of the rapid intensification for another 12-24 hours. All guidance levels off Isabel or weakens it after 72 hours. The above mentioned upper low may cause some shear at this time. Therefore, after intensifying this to 110KT in 72 hours, the forecast will bring the intensity down to 100KT at 120 hours. This is well above all guidance, though the guidance has been too low with the intensity so far.

Initial: 14.8N 37.7W 65KT
12 Hour: 15.8N 39.5W 80KT
24 Hour: 16.8N 41.4W 90KT
36 Hour: 17.8N 43.2W 100KT
48 Hour: 18.8N 45.5W 105KT
72 Hour: 19.5N 50.0W 110KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR 96 Hour: 20.0N 55.0W 105KT
120 Hour: 20.5N 60.0W 100KT

Next Discussion: 0300 UTC

Forecaster: Ortt

0300 UTC 9/8/2003 HURRICANE ISABEL FORECAST DISCUSSION #4

This is an independent product and not from the National Hurricane Center

Isabel has been moving on roughly the same heading as the previous forecast indicated, though slightly faster. The 12Z global models continued their trend of turning the hurricane more to the west in about 36 hours. This forecast is slightly faster than the previous one and has a 120 hour position farther west due to the time lag between the forecasts. 120 position is now NNW of the Leeward Islands.

Initial intensity is being set at 90KT, in agreement with the SSD satellite estimate. I would have went with 85KT had the system not been on a significant intensification trend this evening; thus, the higher estimate is in order. Further significant intensification is likely as the eye should contract over the next couple of days. Due to the faster than expected rate of intensification, the peak intensity needs to be raised, this time to 120KT in 72 hours, followed by a slight weakening due to the possibility of encountering more unfavorable conditions.

Initial: 16.0N 40.0W 90KT
12 Hour: 17.0N 42.8W 100KT
24 Hour: 18.0N 45.5W 105KT
36 Hour: 18.8N 48.0W 110KT
48 Hour: 19.3N 50.0W 115KT
72 Hour: 19.8N 54.5W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 20.3N 59.0W 120KT
120 Hour: 20.5N 64.0W 115KT

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/8/2003 HURRICANE ISABEL FORECAST DISCUSSION #5

This is an independent product and not from the National Hurricane Center

Isabel has been moving on roughly the same heading as the previous forecast indicated, though slightly faster. The global models are in some disagreement on it's long term track. This forecast closely follows the previous forecast. The 120 hourposition is now NNW of the Leeward Islands.

Initial intensity is being set at 95KT. Isabel is likely to further strengthen as the environment ahead of Isabel is very favorable.

Initial: 17.0N 42.8W 95KT
12 Hour: 17.0N 45.5W 100KT
24 Hour: 18.0N 47.0W 105KT
36 Hour: 18.8N 49.5W 110KT
48 Hour: 19.3N 52.0W 115KT
72 Hour: 19.8N 57.0W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 20.3N 61.5W 120KT
120 Hour: 21.5N 65.5W 115KT

Next Discussion: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/9/2003 HURRICANE ISABEL FORECAST DISCUSSION #6

This is an independent product and not from the National Hurricane Center

Isabel has been moving to the right and slower of the previous forecast track. The reason for this has been the upper low to its west. However, recent satellite images indicate that the long anticipated turn to the west may be underway. This is expected due to the ridge to the north. Guidance seems a bit slow in that in 5 days it brings the system only to about 60W, which implies an average motion between 5 and 10KT, which seems a tad slow. The tropical model solution of a SW turn into the Caribbean is being discounted as is the UKMET of a northward turn. Will go with the remainder of the model consensus and forecast a track mainly to the west after 24 hours, with the system approaching the Bahamas in 5 days.

Initial intensity is being set at 115KT, the upper limit of category 3 intensity. For some reason that I cannot understand, SHIPS weakens the system to a category 1 hurricane by the end of the period. This is not likely to happen due to the favorable atmospheric conditions that are expected to be present. However, some fluctuations in intensity are indicated in this forecast, as these are likely due to eye-wall replacement cycles and other inner-core dynamics. However, Isabel is expected to remain a dangerous major hurricane through the forecast period.

Initial: 18.5N 44.5W 115KT
12 Hour: 19.3N 46.5W 115KT
24 Hour: 19.6N 48.8W 120KT
36 Hour: 19.8N 51.2W 115KT
48 Hour: 19.8N 53.5W 115KT
72 Hour: 19.8N 58.0W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 19.8N 62.5W 110KT
120 Hour: 20.0N 67.0W 115KT

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/9/2003 HURRICANE ISABEL FORECAST DISCUSSION #7

This is an independent product and not from the National Hurricane Center

Hurricane Isabel continues on its NW path at 12 mph. Isabel remains impressive on satellite imagery with intense convection and eye. Models are in agreement on the initial motion of Isabel to the WNW in 48 hours or so. After 2 days or so, the GFS and NOGAPS suggest a bit of a southward turn bringing a threat to the Caribbean, while the GFDL, UKMET and CMC keep Isabel on a more westward path. This forecast leans toward the more westward path.

Initial intensity is being set at 115KT, the upper limit of category 3 intensity. Further intensification is likely as Isable remains in favorable conditions. However, some fluctuations in intensity are indicated in this forecast, as these are likely due to eye-wall replacement cycles and other inner-core dynamics. However, Isabel is expected to remain a dangerous major hurricane through the forecast period.

Initial: 19.4N 46.2W 115KT
12 Hour: 19.7N 48.2W 120KT
24 Hour: 19.9N 50.3W 120KT
36 Hour: 20.1N 52.4W 115KT
48 Hour: 20.3N 54.5W 115KT
72 Hour: 20.3N 58.8W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 20.3N 62.8W 110KT
120 Hour: 20.7N 67.0W 115KT

Next Discussion: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/10/2003 HURRICANE ISABEL FORECAST DISCUSSION #8

This is an independent product and not from the National Hurricane Center

Hurricane Isabel appears very impressive on satellite imagery. Strong convection, CDO, and outflow exist with Isabel. Isabel is heading WNW at 13 knots. Global models have become in much better agreement with Isabel's track. Most of the models bring Isabel on a more westward path nearing the Bahamas in 5 days. This forecast track agrees with the model forecasts.

The initial intensity is set at 110 KT. Isabel's intensity is expected to fluctuate over the next few days. There is a cool SST wake in Isabel's path that may weaken the storm a bit; however the environment ahead of the wake appears favorable for Isabel to intensify again.

Initial: 20.7N 49.0W 110KT
12 Hour: 21.1N 51.0W 110KT
24 Hour: 21.3N 53.0W 110KT
36 Hour: 21.3N 55.0W 110KT
48 Hour: 21.3N 57.3W 105KT
72 Hour: 21.3N 61.2W 95KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 21.3N 65.0W 105KT
120 Hour:21.3N 69.0W 110KT

Next Discussion: 1500 UTC

Forecaster: Cangialosi

1500 UTC 9/10/2003 HURRICANE ISABEL FORECAST DISCUSSION #9

This is an independent product and not from the National Hurricane Center

Hurricane Isabel appears very impressive on satellite imagery. Strong convection, CDO, and outflow exist with Isabel. A change in Isabel's heading as occurred this morning. It nowe appears that Isabel is heading nearly due west at 12 knots. Global models have become in much better agreement with Isabel's track. Most of the models bring Isabel on a westward track through 5 days. The GFS actually drives Isabel a bit further south than the other models. This westward steering is due to the strong ridge that has developed to the north of Isabel. This forecast track agrees with most of the model forecasts.

The initial intensity is set at 115 KT. Isabel's intensity is expected to fluctuate, yet can not be predicted, over the next few days due to inner core dynamics and eye wall replacements. However, the environment appears favorable so Isabel is forecasted to remain a major hurricane through the forecast period.

Initial: 21.1N 51.0W 115KT
12 Hour: 21.3N 53.0W 115KT
24 Hour: 21.4N 55.0W 115KT
36 Hour: 21.5N 57.1W 110KT
48 Hour: 21.5N 59.2W 110KT
72 Hour: 21.5N 62.5W 115KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 21.8N 66.5W 110KT
120 Hour:22.0N 70.5W 110KT

Next Discussion: 0300 UTC

Forecaster: Cangialosi 0300 UTC 9/11/2003 HURRICANE ISABEL FORECAST DISCUSSION #10

This is an independent product and not from the National Hurricane Center

Isabel continues to the west this evening, moving in small cyclonic loops; however, the tangential motion has been straight westerly. The reason for this is the fact that it is under the influence of a large ridge to its north. Global model guidance, for the most part, re-enforces this ridge in about 24-36 hours, making a northward track more unlikely. However, the tropical guidance has shifted to the right; however, it is faster as many of the models are now bringing the system between 72 and 75W in a mere 5 days. This seems reasonable; however, the turn may be based upon a weakness that the GFS has, which is the fields that the tropical guidance is initialized with. However, out of respect for the guidance, I will shift slightly to the right, though not to the 26 or 27N latitude in 5 days that much of the guidance is suggesting at this time. I prefer to wait for a few more model runs, to make sure that this is not based upon a usual poor GFS run, or at least poor with regards to Isabel.

The initial intensity is being set at 120KT, slightly below the 127KT estimate by SSD due to the fact that the cloud temperatures have been fluctuating around the eye in recent hours. Will ignore SHIPS guidance to over weakening of the system. Shear is expected to remain low and the system should track to the north of the coldest portion of the cold wake caused by Hurricane Fabian a week ago. therefore, the intensity will be guided by eye wall replacement cycles and other inner-core dynamics, that are next to impossible to forecast. To attempt to acknowledge these in the forecast, fluctuations in intensity are indicated. However, Isabel is expected to remain a dangerous major hurricane throughout the forecast period.

Initial: 21.1N 52.7W 120KT
12 Hour: 21.1N 54.5W 120KT
24 Hour: 21.3N 56.3W 115KT
36 Hour: 21.7N 58.2W 120KT
48 Hour: 22.2N 60.2W 110KT
72 Hour: 23.0N 64.2W 110KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 24.0N 68.5W 120KT
120 Hour: 25.0N 72.8W 115KT

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/11/2003 HURRICANE ISABEL FORECAST DISCUSSION #11

This is an independent product and not from the National Hurricane Center

Isabel continues to the west this morning, moving in small cyclonic loops; however, the tangential motion has been straight westerly near 9 KT. The reason for this is the fact that it is under the influence of a large ridge to its north. Global model guidance are in agreemnent with Isable's track. The UKMET, NOGAPS, GFDL, and GFS bring Isabel mostly westward or just north of west through at least 72 hours. Thereafter, a WNW to NW motion exist in most models.

The initial intensity is being set at 140 KT. This is now a category 5 hurricane, the highest class on the Saffir-Simpson scale. Isabel is beautiful and powerful on satellite imagery. A clear eye, symmetric intense convection around the eye and impreesive outflow channels exist with Isabel. Shear is expected to remain low and the system should track to the north of the coldest portion of the cold wake caused by Hurricane Fabian a week ago. Therefore, the intensity will be guided by eye wall replacement cycles and other inner-core dynamics, that are next to impossible to forecast. To attempt to acknowledge these in the forecast, fluctuations in intensity are indicated. However, Isabel is expected to remain a dangerous major hurricane throughout the forecast period.

Initial: 21.3N 54.6W 140KT
12 Hour: 21.3N 56.3W 140KT
24 Hour: 21.4N 58.2W 135KT
36 Hour: 21.7N 60.2W 130KT
48 Hour: 22.2N 62.2W 125KT
72 Hour: 23.2N 66.2W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 24.2N 69.8W 120KT
120 Hour: 25.4N 73.4W 125KT

Next Discussion: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/12/2003 HURRICANE ISABEL FORECAST DISCUSSION #12

This is an independent product and not from the National Hurricane Center

Hurricane Isabel continues to maintain itself as a very powerful storm this evening, with an extremely well-defined and circular eye. The eyewall is still quite symmetric, although it is a bit more elliptical than this afternoon, and cloud tops have warmed a bit on the northern semi-circle of the storm. However, it is a bit early to judge what is going on in Isabel's inner core, so the intensity will remain at 140 kt this advisory.

The outflow is restricted somewhat to the north, indicating strong mid- and upper-level high pressure to the north of Isabel. Some of the models seem to weaken this high pressure feature too quickly, taking Isabel on a west-northwest course too soon.

Unfortunately, the steering for Isabel seems to be dependent upon subtle features... it is unclear whether or not ridging or troughing will dominate Isabel's track beyond 48 hours. The current models indicate that relatively weak ridging or troughing will be responsible for Isabel's future track, suggesting that a west-northwest turn will occur. Whether or not Isabel turns back to the west in 96-120 hours (implying that ridging will ultimately prevail) or turns to the northwest in 96-120 hours (favoring troughing) depends upon the model solutions, which are in disagreement. It is still too far in advance to know what will happen for certain, and the forecast tries to remain in the middle of ridging or troughing scenarios. Nonetheless, the current ridge to the north of Isabel should hold for at least the next 24 hours. Isabel's own intensity may help to inhibit or delay its northward turn, so the forecast, while trying to remain in the middle, does prefer the ridging scenario slightly and does not take Isabel quite as far north as the average of model scenarios.

As for intensity, Isabel is probably a category-5 for the moment and is probably near its peak (at least, hopefully). North Atlantic hurricanes rarely maintain such intensity for extended periods. This forecast weakens Isabel to strong category-3 statues 36-48 hours from now, as eyewall replacement and upwelled waters from Fabian impact Isabel. Waters beyond 68 degrees west are warm and have not been upwelled-- the water temperatures are 29 degrees Celsius and above west of this longitude, so Isabel may well regain category-4 intensity in the future. The forecast will have Isabel around 115 kts 72 hours and beyond, which is the category-3/ category-4 boundary. Fluctuations in intensity are possible, if not likely, although this forecast attempts to make an average of intensity and seeks trends more so than attempting to predict eyewall dynamics.

Initial: 21.6N 56.1W 140KT
12 Hour: 21.8N 57.5W 130KT
24 Hour: 22.1N 59.6W 120KT
36 Hour: 22.5N 62.1W 110KT
48 Hour: 23.0N 63.6W 110KT
72 Hour: 23.8N 66.1W 115KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 24.8N 68.7W 115KT
120 Hour: 25.5N 73.2W 115KT

Next Discussion: 1500 UTC

Forecaster Kozich

1500 UTC 9/12/2003 HURRICANE ISABEL FORECAST DISCUSSION #13

This is an independent product and not from the National Hurricane Center

Isabel remains a dangerous category 5 hurricane. However, there are indications that this intensity will not be maintained much longer, if it is has not already started to weaken. The system is starting to lose some of its symmetry and the outflow on the western semi-circle is being restricted due to the upper low. Therefore, weakening is indicated in the forecast, down to a category 3 hurricane in 36 hours. Afterwards, the system is expected to remain steady, with possible slight increase.

Track guidance is shifted to the right again for this update. Water vapor imagery shows a large trough off of the U.S. East Coast and this is not showing any signs of lifting at the present time. Therefore, this forecast is being adjusted to the right of the previous. This is still expected to threaten the U.S. east Coast; however, the chances for a miss seem to be improving. CMC actually keeps this system well offshore as it does not build in a strong ridge behind this trough. It needs to be noted that the models have been shifting dramatically multiple times per day; therefore, future forecasts may need to be adjusted farther to the left.

Initial: 21.6N 57.8W 140KT
12 Hour: 21.7N 59.4W 125KT
24 Hour: 21.9N 61.0W 115KT
36 Hour: 22.5N 62.8W 110KT
48 Hour: 23.3N 64.3W 110KT
72 Hour: 24.7N 67.0W 110KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 26.5N 69.5W 115KT
120 Hour: 28.5N 72.5W 115KT

Next Discussion: 0300 UTC

Forecaster: Ortt

2100 UTC 9/12/2003 HURRICANE ISABEL SPECIAL DISCUSSION #14

This is an independent product and not from the National Hurricane Center. This special discussion is also intended for internal planning, though it is being made available to the public

Recon finds that Isabel is a category 5 hurricane. The pressure was measured on two separate occasions to be 920mb. The latest vortex message indicated maximum flight level winds at 700mb. The standard reduction factor for this level to determine the surface winds in 90 percent. This yields a value of roughly 140KT, which is the initial intensity for this forecast.

This afternoon, recon data has indicated a slight north of due west component. However, latest satellite imagery indicates that this has ended, and that Isabel is again moving in a due westerly manner. This type of wobbling is common in hurricanes of this intensity. To keep things simple, the motion is being initialized as due west, or 270 degrees.

Model data remains somewhat divergent this afternoon. GFS and CMC favor a track well away from the Bahamas, while UKMET is remaining consistent with a track toward the NW Bahamas. An extended run out to 144 hours was available this afternoon, and this run brought the system near the border of North and South Carolina. The reason for the GFS/CMC solution is that each is maintaining a low off of the Carolina Coast to 500 and 300mb. Water vapor imagery indicates that there is a cold low in the area. UKMET also has this feature. However, the divergence between the tracks is what happens afterwards. GFS and CMC brings a 500mb trough off of the east coast in 4 or 5 days, resulting in a more northerly movement, while the UKMET lifts the feature out, allowing the more westerly track. Water vapor imagery indicates that the trough is digging over Montana and that the upper low over Texas is cutting off, and is moving slightly to the east. Therefore, we prefer to go with the GFS/CMC solution over the UKMET solution. This is also in agreement with the GFDL track. As a side note, often times, hurricanes of this intensity can influence their own environment. In 1997, Hurricane Linda created a ridge of high-pressure to its north, due to its low pressure, as did Mitch in 1998. Both times, these features were not resolved by the computer guidance models. Therefore, to take this into account, the track forecast is slightly to the left of GFS/CMC, though far enough north to spare the South Florida region and the NW Bahamas.

The intensity forecast is just as problematic as is the track forecast. it is rare for category 5 hurricanes to maintain their intensity for this period of time. Very few have lasted for more than 24 hours, though Isabel has done so. It did not weaken, despite undergoing an eye wall replacement cycle and having its outflow restricted by the upper low to its west. In fact, recent satellite imagery suggests that Isabel may be slightly more intense than earlier today based upon the clearness of the eye. Therefore, the forecast will keep Isabel as a category 5 hurricane for 24 more hours, before indicating weakening of the system, most likely due to a new eye wall replacement. Near the end of the period, some shear may enter into the picture; however, shear forecasts are poor quite often. Therefore, shear will be assumed to remain out of the system for now and this question will be further addressed in future forecasts. The forecast keeps Isabel as a category 4 or 5 hurricane through the forecast period.

Initial: 21.8N 58.6W 140KT
12 Hour: 22.1N 60.4W 140KT
24 Hour: 22.6N 62.0W 130KT
36 Hour: 23.3N 63.5W 135KT
48 Hour: 24.1N 65.1W 125KT
72 Hour: 26.0N 68.0W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 28.0N 71.0W 120KT
120 Hour: 30.5N 73.0W 125KT

Next Discussion: 0300 UTC

Forecasters: Kozich, Ortt

0300 UTC 9/13/2003 HURRICANE ISABEL FORECAST DISCUSSION #15

This is an independent product and not from the National Hurricane Center

The model consensus favors the track given in the special discussion earlier this afternoon. Therefore, there is no reason to deviate too significantly from that track. The reasoning remains the same. The trough is located off of the east coast. This should impart some northerly component to the storm. Then a second trough should follow behind, preventing a track back to the west. This forecast is basically an extension of the previous forecast.

Initial intensity is being lowered to 135KT for this update, based upon the warming of the cloud tops. This is not a total surprise since cat 5 hurricanes often go through these minor fluctuations. Isabel seems to be overcoming the shear and restricted outflow. Therefore, fluctuations in intensity are anticipated through the forecast period. Continuing to keep things simple by keeping shear out of the forecast.

Initial: 21.9N 59.5W 135KT
12 Hour: 22.1N 61.1W 130KT
24 Hour: 22.5N 62.8W 135KT
36 Hour: 23.4N 64.4W 125KT
48 Hour: 24.3N 66.0W 130KT
72 Hour: 26.0N 68.5W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 28.0N 71.5W 125KT
120 Hour: 31.0N 73.5W 120KT

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/13/2003 HURRICANE ISABEL FORECAST DISCUSSION #16

This is an independent product and not from the National Hurricane Center

No change to the track reasoning. CMC and NOGAPS bring the system nearly on the previous forecast track with a final landfall in the mid atlantic or NYC in 5 or 6 days. Since there is nothing obvious to discount this, and due to the GFS having its usual problems, this forecast merely extends the previous one.

Initial intensity is lowered slightly to 130KT. Isabel remains a very dangerous category 4 hurricane. More fluctuation in intensity are expected due to the eye wall replacement cycles, which based upod data from the aircraft yesterday and satellite today, it has been undergoing frequently. Continuing to keep things simple and going with no shear for now.

Initial: 22.2N 61.5W 130KT
12 Hour: 22.6N 63.3W 130KT
24 Hour: 23.3N 65.0W 135KT
36 Hour: 24.3N 66.8W 125KT
48 Hour: 25.5N 68.5W 130KT
72 Hour: 28.0N 71.0W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 32.0N 73.5W 120KT
120 Hour: 36.5N 75.5W 120KT

Next Discussion: 0300 UTC

Forecaster: Ortt

0300 UTC 9/14/2003 HURRICANE ISABEL FORECAST DISCUSSION #17

This is an independent product and not from the National Hurricane Center

Hurricane Isabel has been moving faster that previously forecast, though roughly on the correct heading. Latest data and model guidance do not give much hope for the U.S. East Coast. The 500mb heights associated with the upper low over Texas have risen by about 40m from 0Z last night to 12Z this morning and water vapor imagery from today suggests that the feature has also begun lifting to the NE. An upper low is located off of the U.S. East Coast near the Carolinas; however, the height field analysis from 12Z indicates that there is a 300mb high over New England. This may serve to prevent the system from moving out to sea.

Now to the newest guidance. Faster and converging on a track toward North Carolina to Delaware. BAMD indicates a landfall between 96 and 120 hours, as does NGPI and AVNI. With the increase in the forward speed today, I have seen enough this evening to bring the eye inland before the end of the forecast period somewhere between Cape Fear and Delaware. One should not focus on the precise coordinates of the landfall location as this is subject to large error. It should be noted, that the 18Z GFDL and the 0Z GFDI keep the eye offshore and have a threat towards Long Island and New England.

The initial intensity is being lowered to 125KT for this update. This is based upon latest satellite estimates and declining data T numbers. The reasons for this weakening likely are due to eye dynamics regarding replacement cycles, as well as a temporary weakening as it is crossing the minor cold wake left over by Fabian. However, sea surface temperatures increase as the system moves farther to the west. This, along with a favorable upper environment should allow for the system to re-intensify tomorrow and into Monday. As the system approaches the coast, there may be some shear encountered due to the trough and some weakening may occur if the system makes landfall north of North Carolina due to cooler waters. However, this forecast will only lower the intensity to 115KT at landfall to take some of the uncertainty regarding the track into play.

Initial: 23.1N 63.9W 125KT
12 Hour: 23.9N 66.1W 130KT
24 Hour: 25.0N 68.1W 135KT
36 Hour: 26.1N 70.0W 135KT
48 Hour: 27.0N 71.0W 130KT
72 Hour: 29.0N 72.8W 130KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 32.5N 74.5W 125KT
120 Hour: 37.5N 76.3W 115KT (inland)

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/14/2003 HURRICANE ISABEL FORECAST DISCUSSION #18

This is an independent product and not from the National Hurricane Center

The situation is starting to look very grave. The model consensus is for a landfall along the mid-Atlantic coast, anywhere from North Carolina to Delaware. CMC is the right outlier, and this indicates a landfall on Long Island. water vapor imagery indicates that the upper low remains off of the East Coast. This should soon cause Hurricane Isabel to turn more to the NW, then NNW. However, the high pressure system is expected to keep Isabel from ever making a turn out to sea. Water vapor imagery also indicates that a second trough is sweeping towards the East Coast from Texas. This should force the storm to move to the NNW; thus, the solution provided by the BAMD of a landfall near Morehead City is being discounted. This forecast is basically an extension of the previous one, taking the storm inland in a little more than 96 hours.

Initial intensity will be set to 130KT for this update. Overnight, satellite imagery and recon data indicated that Isabel has re-intensified. However, recent satellite imagery indicates that the cloud tops temperatures have warmed slightly. This is likely due to the eye wall dynamics that are in place. As has been the trend, SHIPS has been indicating weakening of the system. However, SHIPS cannot be taken seriously at this point for the long range as it has been consistently been forecasting Hurricane Isabel to have weakened to a category 1 hurricane by now, and we still have a very dangerous category 4 storm. The GFDL brings the system inland as a category 2 hurricane, though it was initialized at 115KT. GFDL, initialized correctly, also forecasts a category 2 hurricane. However, this model has been consistently been indicating that the system should weaken 15-20KT in the first 12 hours. Therefore, these solutions are being placed aside. The global models are in agreement of Isabel maintaining its intensity, if not becoming more intense prior to landfall. This may be partially due to the approaching trough, which often causes the global models to predict intensification. As the system approaches the coast, there is likely to be somewhat of a shear increase. Therefore, a slow weakening is indicated in the 24 hours before the system makes landfall, after a period of fluctuations. It must be noted that the effects of the shear may be partially offset by the Gulfstream waters, which often cause tropical cyclones to rapidly intensify before making landfall. Category 3 intensity is the forecast landfall intensity.

Initial: 23.7N 66.3W 130KT
12 Hour: 24.3N 68.3W 130KT
24 Hour: 25.3N 70.0W 125KT
36 Hour: 26.5N 71.4W 120KT
48 Hour: 28.0N 72.8W 130KT
72 Hour: 32.0N 74.5W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERRORS 96 HOUR: 36.0N 76.0W 110KT (near Outer Banks)
120 HOUR: 42.5N 76.5W 50KT (inland)

Next Discussion: 0300 UTC

Forecaster: Ortt

0300 UTC 9/15/2003 HURRICANE ISABEL FORECAST DISCUSSION #19

This is an independent product and not from the National Hurricane Center

The models continue to converge on an NC or Virginia landfall for Hurricane Isabel. The reasoning is straight forward. The current upper low over the U.S. East Coast is lifting out; however, it is being followed by a much stronger, long-wave trough. However, due to the presence of a mid-level ridge south of Nova Scotia, a track out to sea appears quite unlikely. The previous forecasts have been verifying nicely, and since there has been no significant change to the reasoning, this track remains basically an extension of the previous one. It should be noted that any shift to the right would bring the system up the entire coast north of Cape Hatteras and bring the system into New England. This does not appear likely at this time due to the Nova Scotia ridge.

Initial intensity is being held at 135KT for this update. Cloud top temperatures have continued to fluctuate. This afternoon, there appears to have been some shear over the system as evidenced by the temporary sharpening of the western edge of the outflow. However, the upper low that was producing the shear is lifting out, and global models insist on an extremely favorable environment over the next couple of days. This should allow Isabel to at least maintain its current intensity, if not intensify. AVNI and AF1I are indicating further intensification, while SHIPS and GFDL are having their usual problems. It is conceivable that Isabel could regain category 5 status. However, the forecast will not reflect this, but maintain the intensity at 135KT through 24 hours. This is followed by a very slow weakening as the shear increases afterwards from the approaching long wave trough. However, the sea surface temperatures will continue to increase as the system moves farther to the west and Hurricane Isabel will have to cross the Gulfstream before making landfall. Therefore, only very slow weakening is being forecast until the system impacts extreme eastern North Carolina and moves into Virginia.

Note: Guidance is suggesting a very fast motion. Therefore, hurricane force winds are likely to extend very far inland. it is not totally impossible that a secondary landfall may occur on the shores of Lake Ontario, in Canada.

Initial: 24.5N 68.3W 135KT
12 Hour: 25.3N 70.0W 135KT
24 Hour: 26.3N 71.2W 135KT
36 Hour: 27.8N 72.7W 130KT
48 Hour: 29.3N 73.7W 125KT
72 Hour: 32.3N 74.7W 120KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 37.0N 76.2W 105KT (inland)
120 Hour: 44.0N 76.7W 45KT (inland)

Next Discussion: 1500 UTC

Forecaster: Ortt

1500 UTC 9/15/2003 HURRICANE ISABEL FORECAST DISCUSSION #20

This is an independent product and not from the National Hurricane Center

The track has shifted right and slowed as expected. Guidance suggests as the trough approaches from the west, the storm will accelerate to the NNW, bringing the storm inland on Thursday. This forecats is similar to the last one and left of CMC.

Initial intensity is being lowered to 120KT as the inner core is disintegrating at the present time. There could be some intensification as suggested by global models, though this is looking unlikely due to the structure. Slow weakening until landfall is expected.

Note: Guidance is suggesting a very fast motion. Therefore, hurricane force winds are likely to extend very far inland. it is not totally impossible that a secondary landfall may occur on the shores of Lake Ontario, in Canada.

Initial: 25.2N 69.4W 120KT
12 Hour: 26.2N 70.9W 115KT
24 Hour: 27.5N 71.9W 110KT
36 Hour: 29.0N 72.7W 105KT
48 Hour: 30.7N 73.7W 105KT
72 Hour: 35.0N 75.0W 100KT(near land)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 41.0N 75.5W 60KT (inland)
120 Hour: 48.0N 76.0W 25KT (inland)

Next Discussion: 1500 UTC

Forecaster: Ortt

0000 UTC 9/16/2003 HURRICANE ISABEL FORECAST DISCUSSION #21

This is an independent product and not from the National Hurricane Center

Isabel has been changing in character throughout the day.. The large eye has fallen apart and has been replaced by a much smaller eye, which appears to be more fully surrounded by convective clouds. In addition, Isabel's structure has changed in the past day, with all of the quadrants having weakened and the wind profile becoming asymmetric. The northeast quadrant is now clearly the dominant sector of Isabel. Isabel remains a large and major hurricane nonetheless.

Isabel has been moving slowly throughout the day, with the heading now more to the north-northwest. Slow motion should be the trend for the next 24 hours or so. Afterwards, Isabel should accelerate to the north-northwest, with a possible slight westward turn towards landfall, suggesting possible ridging after interaction with the current trough affecting the system. Landfall may well occur within 72 hours. Hurricane force winds may extend well inland, due to the rapid forward movement of the system anticipated during and after landfall.

The hurricane should remain a major hurricane up until and including landfall. The circulation has been incredibly persistent with this system, and its large size should work to the storm's advantage in resisting shear. The frequent eyewall replacement cycles that this tropical cyclone has undergone suggest that Isabel attaining category-4 status once again is a definite possibility. The mid-Atlantic and northeastern states should pay close attention to storm developments.

Forecast points verified starting at 5 A.M. tomorrow

Initial: 25.8N 69.9W 110KT
12 Hour: 27.0N 70.5W 110KT
24 Hour: 28.4N 71.3W 115KT
36 Hour: 30.0N 72.2W 115KT
48 Hour: 33.0N 73.8W 110KT
72 Hour: 38.0N 76.5W 95KT(inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 46.0N 77.5W 45KT(inland near Lake Ontario)
120 Hour: Extra-Tropical

Next Discussion: 1500 UTC

Forecasters: Kozich/Ortt

1500 UTC 9/16/2003 HURRICANE ISABEL FORECAST DISCUSSION #22

This is an independent product and not from the National Hurricane Center

Isabel has been weakening this morning. Westerly shear appears to be disorganizing Isabel and reducing the amount of intense convection. Isabel's structure shows all of the quadrants having weakened and the wind profile becoming asymmetric. Even the northeast quadrant, the dominant quadrant last night, has been weakening with warmer cloud top temperatures denoted on the IR satellite imagery. Isabel remains a powerful hurricane nonetheless.

Isabel continues to move slowly this morning with a heading to the north/northwest. Slow motion should be the trend for the next 24 hours or so. Afterwards, Isabel should accelerate to the north-northwest, with a possible slight westward turn towards landfall, suggesting possible ridging after interaction with the current trough affecting the system. Landfall may well occur within 60-72 hours. Hurricane force winds may extend well inland, due to the rapid forward movement of the system anticipated during and after landfall.

Isabel's initial intensity is being set to 90 KT. Some further slow weakening is likely. The circulation has been incredibly persistent with this system, and its large size should work to the storm's advantage in resisting shear. The frequent eyewall replacement cycles that this tropical cyclone has undergone suggest that Isabel attaining category-4 status once again is a definite possibility. The mid-Atlantic and northeastern states should pay close attention to storm developments.

Initial: 26.9N 70.8W 90KT
12 Hour: 27.8N 71.5W 85KT
24 Hour: 29.2N 72.4W 85KT
36 Hour: 31.0N 73.6W 80KT
48 Hour: 33.2N 74.8W 80KT
72 Hour: 38.2N 77.5W 65KT(inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 47.0N 78.5W 40KT(inland near Lake Ontario)
120 Hour: Extra-Tropical

Next Discussion: 0300 UTC

Forecasters: Cangialosi

2100 UTC 9/16/2003 HURRICANE ISABEL FORECAST DISCUSSION #23

Click Here for a storm update

This is an independent product and not from the National Hurricane Center

Isabel continues to be somewhat disorganized. Westerly shear appears to be making Isabel assymetric and reducing the amount of intense convection. Due to the westerly shear the NE quadrant appears to be the dominant quadrant of the storm with the greatest amount of rain and convection. The outflow of Isabel appears to be better defined than earlier this morning.

Isabel continues to move slowly with a heading to the north/northwest near 6 KT. Slow motion should be the trend for the next 24 hours. Afterwards, Isabel should begin to accclearate to the north/northwest followed by a more westerly turn as the ridge builds westward to the north of Isabel. Global forecast models are in fairly good agreemnet in all lifting out the shortwave trough and building the ridge westward which should steer Isabel inland. Hurricane force winds may extend well inland, due to the rapid forward movement of the system anticipated during and after landfall.

Isabel's initial intensity remains at 90 KT. Some slight further weakening is possible in the next 12-24 hours as westerly shear remains over the system. Thereafter, as the trough lifts north/northeastward, Isabel should become in a more favorable environment to briefly strenghten a bit before landfall. The circulation has been incredibly persistent with this system, and its large size should work to the storm's advantage in resisting shear and holding together to have a chance to breifly restrenghten.

Initial: 27.7N 71.3W 90KT
12 Hour: 28.8N 71.9W 85KT
24 Hour: 30.3N 72.8W 85KT
36 Hour: 32.3N 73.8W 90KT
48 Hour: 34.5N 75.2W 95KT
72 Hour: 40.2N 78.5W 65KT(inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 49.0N 79.0W 35KT(inland near Lake Ontario)
120 Hour: Extra-Tropical

Next Discussion: 0300 UTC

Forecasters: Cangialosi

0300 UTC 9/16/2003 HURRICANE ISABEL FORECAST DISCUSSION #24

Click Here for a storm update

This is an independent product and not from the National Hurricane Center

Isabel is showing signs of re-strengthening. The westerly shear that was making Isabel assymetric and reducing the amount of intense convection has appeared to let up a bit. The outflow of Isabel appears to be better defined than earlier this evening, and a clear eye is visible. However; from the water vapor imagery is appears as a dry tongue of air is wrapped in toward the center.

Isabel continues to move slowly with a heading to the north/northwest near 7 KT. Slow motion should be the trend for the next 12-24 hours. Afterwards, Isabel should begin to accclearate to the north/northwest followed by a more westerly turn as the ridge builds westward to the north of Isabel. Global forecast models are in fairly good agreement in all lifting out the shortwave trough and building the ridge westward which should steer Isabel inland. Hurricane force winds may extend well inland, due to the rapid forward movement of the system anticipated during and after landfall.

Isabel's initial intensity has been raised to 95 KT. Global models are forecasting a possibilty of some slight re-strenghtening as the trough lifts north/northeastward, Isabel should become in a more favorable environment. This forecast is more conservative holding Isabel at its current intensity up until landfall.

Initial: 28.5N 71.7W 95KT
12 Hour: 29.6N 72.2W 90KT
24 Hour: 31.4N 73.5W 95KT
36 Hour: 33.8N 75.3W 95KT
48 Hour: 36.5N 77.3W 70KT(inland)
72 Hour: 42.8N 78.5W 45KT(inland)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: 52.0N 77.0W 30KT(inland near Lake Ontario)
120 Hour: Extra-Tropical

Next Discussion: 0300 UTC

Forecasters: Cangialosi

0900 UTC 9/17/2003 HURRICANE ISABEL FORECAST DISCUSSION #25

Click Here for a storm update

This is an independent product and not from the National Hurricane Center

Isabel is beginning to accelerate to the NNW, as has been expected. This is due to the combination of the approaching trough to the west and the ridge to the NE. The end result should be to bring the system inland over the Outer banks within the next 36 hours, in good agreement with the guidance. This is faster than the previous forecast.

Initial intensity remains 95KT. I could have lowered the intensity slightly; however, the satellite signature has changed little and the recon aircraft continues to report a pressure of 957mb. Guidance is indicating little change in intensity before the system makes landfall. Due to the presence of dry air near the system and sea surface temperatures near the coast being well below normal, I will call for 5KT of weakening before landfall. However, this would still make Isabel a category 2 hurricane, which is capable of producing significant damage. The 90KT is not reflected in this forecast due to the fact that landfall is expected between the 24 and 36 hour forecast points. Extra-tropical transition is now expected to occur in about 72 hours, after Isabel crosses Lake Ontario.

Initial: 29.5N 72.0W 95KT
12 Hour: 31.5N 73.0W 95KT
24 Hour: 33.0N 74.5W 95KT
36 Hour: 36.0N 76.0W 80KT(inland)
48 Hour: 40.0N 78.0W 45KT(inland)
72 Hour: 45.0N 78.5W 35KT(inland, across Lake Ontario)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR
96 Hour: Extra-Tropical

Next Update: 1500 UTC

Forecaster: Ortt

2100 UTC 9/17/2003 HURRICANE ISABEL FORECAST DISCUSSION #26

Click Here for a storm update

This is an independent product and not from the National Hurricane Center

Isabel has begun to accelerate to the NNW near 14 mph. The dynmaics of Isabel's track has not changed much and agrees with the previous forecasts. A developing trough digging into the Southern States will assist in driving Isabel to the northwest onshore in about 24 hours. The ridge remains in place in the Western Atlantic.

Initial intensity is 90KT. The satellite signature has changed little and the recon aircraft continues to report a pressure near 955mb. Guidance is indicating little change in intensity before the system makes landfall. Due to the presence of dry air near the system and sea surface temperatures near the coast being well below normal, I will go with the guidance and keep Isabel at steady intensity. However, this would still make Isabel a category 2 hurricane, which is capable of producing significant damage. Extra-tropical transition is now expected to occur in about 72 hours, after Isabel crosses Lake Ontario.

Initial: 31.1N 73.3W 90KT
12 Hour: 32.6N 74.5W 90KT
24 Hour: 34.8N 76.5W 90KT(inland)
36 Hour: 37.5N 78.5W 65KT
48 Hour: 41.0N 78.5W 40KT
72 Hour: 48.0N 77.0W 30KT(ExtraTropical)
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERROR 96 Hour: Extra-Tropical

Next Update: 0300 UTC

Forecaster: Cangialosi

0300 UTC 9/18/2003 HURRICANE ISABEL FORECAST DISCUSSION #27

This is an independent product and not from the National Hurricane Center

Isabel has been captured this evening. it is now moving to the NNW and is expected to accelerate as it is under the influence of the trough. This should bring the system inland in about 12-15 hours.

Initial intensity remains 90KT, though this is likely generous. Recent recon reports indicate that flight level winds are lower. Earlier today, winds were reported in excess of 120KT at flight level; however, these winds are not being transported to the surface due to the limited deep convection. Recent satellite imagery shows a little more convection and a weak eye feature. Therefore, the forecast will indicate no change in intensity until landfall. However, if convection can fire again overnight, there would likely be some last minute intensification.

Initial: 31.9N 73.5W 90KT
12 Hour: 34.5N 75.0W 90KT
24 Hour: 37.0N 76.5W 65KT (inland)
36 Hour: 40.5N 77.5W 40KT (inland)
48 Hour: 44.5N 78.5W 35KT (inland)
72 Hour: Extra-Tropical

Next Discussion: 0900 UTC

Forecaster: Ortt

0900 UTC 9/18/2003 HURRICANE ISABEL FORECAST DISCUSSION #28

This is an independent product and not from the National Hurricane Center

Hurricane Isabel is closing in on the coast of North Carolina this morning. Recent radar imagery suggests that the NNW motion is continuing. Model guidance agrees on a landfall in 6 to 9 hours, depending upon the forward motion that the system takes. This forecast will be slightly to the left of the previous, but not all that much.

Initial intensity remains 90KT. Overnight recon peak winds were 109KT, usually equivalent to about 100KT at the surface; however, previous data suggests that these winds are not being transported efficiently to the surface. early morning satellite imagery indicates that the system remains disorganized with no CDO nor well-defined eye. The radar is a bit more impressive, but not the signature of a major hurricane. No change is being indicated before making landfall; however, it is possible that there could be a small change in intensity either way prior to crossing the coast.

0Z models indicate that Isabel will be merging with the larger trough in about 48 hours. Therefore, the 48 hour forecast is now for the system to have become extra-tropical. There is now a chance that this will occur prior to crossing Lake Ontario; however, weather conditions will be the same, regardless as to what the classification is.

Initial: 33.0N 74.6W 90KT
12 Hour: 35.5N 76.0W 75KT (inland)
24 Hour: 38.5N 78.0W 45KT (inland)
36 Hour: 42.5N 79.0W 35KT (inland)
48 Hour: Extra-Tropical

Next Update: 1500 UTC

Forecaster: Ortt

Back to Archives