2100 UTC 7/19/2003 TROPICAL DEPRESSION 6 FORECAST DISCUSSION #1

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

Tropical Depression 6 is moving to the west under the influence of the strong ridge to the north. This track should continue during the next few days as the system moves toward the Lesser Antilles. No reason at all as to why the system should turn far enough to clear all of the islands as guidance indicates that the ridge is expected to remain strong throughout the next 3 days. Therefore, only a slightly north of west motion is expected over the next couple of days. Afterward, there are some indications that the ridge may weaken slightly, allowing a track more to the WNW. There is an upper trough to the west, which may also aid in the slightly north of west motion.

Initial intensity is set at 30KT based upon QUIKSCAT. The environment appears to be favorable for now and SHIPS and SHIFOR guidance suggests intensification. The global models continue with their problems of not initializing weak tropical cyclones. Will follow SHIPS due to the increased convective activity, though not quite to hurricane intensity. Max intensity is 60KT at 48 hours. System is being held afterwards due to the environment possibly becoming unfavorable for development. Land interference is factored in, though only slightly and at the 120 hour position

Initial: 12.4N 44.3W 30KT
12 Hour: 12.6N 48.0W 30KT
24 Hour: 12.9N 51.5W 40KT
36 Hour: 13.4N 54.8W 50KT
48 Hour: 14.0N 58.0W 60KT
72 Hour: 15.5N 63.0W 60KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERRORS
96 Hour: 17.5N 67.5W 60KT
120 Hour: 20.0N 72.0W 50KT (over Hispaniola)

No Graphics with forecast 1

Next Discussion: 0900 UTC

Forecaster: Ortt

0900 7/10/200 TROPICAL DEPRESSION 6 FORECAST DISCUSSION #2

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

Tropical Depression 6 has increased its forward speed. The track heading remains accurate. However, the forward speed will be adjusted in this forecast with the 120 hour position now near 80W to reflect the change in forward speed. The long term track is dependent upon whether or not the strong ridge to the north remains in tact. If it does, the system will pass south of Hispaniola and Cuba. If it erodes slightly, as UKMET and NOGAPS indicates, the system could be moving more NW and pose a threat to the Bahamas and Florida. None of the track guidance favors the Florida threat and with the faster motion, this forecast will keep the system south of Hispaniola and Florida during the forecast period.

Initial intensity i being kept at a generous 30KT. The convective activity is not concentrated near the center. Instead, it is more of a popcorn variety, suggesting some disorganization. How much this will intensify is based upon how much this organizes and whether or not the SAL impacts the system. If the SAL impacts this, quick dissipation seems likely. However, this forecast will assume this does not happen and continues to indicate intensification, though not quite to hurricane intensity, in agreement with SHIPS guidance as it may move into a more hostile environment in a couple of days. This time, land is not factored at all into the forecast due to uncertainty in the track forecast

Initial: 12.9N 48.3W 30KT
12 Hour: 13.5N 53.0W 35KT
24 Hour: 14.1N 58.0W 40KT
36 Hour: 14.8N 61.8W 50KT
48 Hour: 15.5N 65.6W 60KT
72 Hour: 16.3N 69.0W 60KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERRORS
96 Hour: 18.0N 75.0W 60KT
120 Hour: 21.0N 80.0W 60KT

Next discussion: 2100 UTC

Forecaster: Ortt

2100 UTC 7/20/2003 TROPICAL DEPRESSION 6 FORECAST DISCUSSION #3

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

Tropical Depression 6 continues to move very rapidly to the west under the influence of the strong ridge to the north. Latest forward speed is in excess of 20KT. Track guidance indicates a slowing, though it often tend to slow these systems too quickly. The global models do not pick up on this system very well. However, they are in agreement that the ridge will remain to the north of the cyclone, forcing this on a heading slightly to the north of west at a fairly rapid speed. The question comes at the end of the period. UKMET and NOGAPS indicate a threat to Florida due to the ridge being eroded by an approaching trough. however, other guidance insists on the continuation of the system into the Gulf of Mexico. With the system moving rapidly and expected to remain fairly weak, the second option will be used for the forecast, though the system will be kept in the eastern GOM. A forward speed reduction is indicatd at the latter forecast points.

Initial intensity is being kept at a generous 30KT. Convection has returned somewhat this afternoon and it appears as if the surface circulation, which appeared to be non-existent this morning, has become slightly better defined. 2 major problems for this system to intensify are its forward motion and it proximity to the SAL. If the system does not slow down, there is a chance that this will degenerate into an open wave. Regarding the SAL, all water vapor and SAL imagery indicate that this depression looks embedded within the SAL. this should limit intensification, at least until it moves well to the west. Therefore, the intensity forecast is being reduced to a 50KT temporary peak in 72 hours, with another 10KT increase at the end of the period. Hispaniola is not being factored into this forecast as the system is expected to remain south of the mountainous island.

Note: This forecast after 48 hours seems faster than the previous one. The reason is because the previous forecast inadvertently gave a 60 hour forecast for the 72 hour.

Initial: 13.4N 52.8W 30KT
12 Hour: 13.8N 57.6W 35KT
24 Hour: 14.2N 62.0W 35KT
36 Hour: 14.7N 66.4W 40KT
48 Hour: 15.3N 70.0W 45KT
72 Hour: 16.8N 76.0W 50KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERRORS
96 Hour: 19.5N 80.0W 50KT
120 hour: 23.5N 84.0W 60KT

Next Discussion:

1500 UTC Forecaster: Ortt

1500 UTC 7/21/2003 TROPICAL DEPRESSION 6 FORECAST DISCUSSION #4

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

Morning QUIKSCAT indicates that Tropical Depression 6 may have degenerated into an open wave. Recon will confirm this afternoon. For now, the forecast assumes the system is a tropical cyclone and will remain as such during the forecast period.

The motion continues to the west under the influence of the strong ridge to the north. Global models are calling for a surface ridge to briefly erode after 2 to 3 days, but become re-established afterward. With the cyclone appearing to be shallow, this solution will be followed. This would place the system in the Gulf of Mexico in 5 days, as is the solution of the majority of the track guidance.

Initial intensity will remain at 30KT until recon determines the status of the cyclone, if there is one. With the SAL and SW winds aloft present, along with guidance not indicating any significant intensification, the system will be maintained as a 30KT depression for 36 hours, with slow intensification. Intensification at a faster rate is forecast later in the period as the system breaks free of the SAL and bypasses the upper trough to the west.

Initial: 14.1N 58.5W 30KT
12 Hour: 14.5N 63.0W 30KT
24 Hour: 15.0N 67.0W 30KT
36 Hour: 15.6N 70.8W 30KT
48 Hour: 16.3N 74.0W 35KT
72 Hour: 17.5N 78.5W 40KT
USE WITH EXTREME CAUTION AS FOLLOWING IS SUBJECT TO LARGE ERRORS
96 Hour: 21.5N 82.5W 50KT
120 Hour: 25.5N 85.5W 65KT

Next Discussion: 2100 UTC (none if recon finds no tropical cyclone)

Forecaster: Ortt

Back to Archives