0900Z Tropical Update

Tropical Depression Four

At 5:00 AM EDT...Tropical Storm Warnings are in effect for the Alabama/Florida border to Suwannee River Florida. Tropical storm warnings mean that tropical storm conditions are expected in 12 to 24 hours.

At 5:00 AM EDT (0900Z)...the center of newly developed Tropical Depression Four is located near 27.0 N 83.5 W. Maximum sustained winds are near 35 mph...and strengthening is expected and the depression is expected to become a tropical storm before landfall. Movement is to the northwest at 15 mph and this motion is expected to continue. Estimated minimum central pressure is 1011 mb/29.85 in.

This depression have developed rapidly over the past few hours as it is sitting under a very light shear environment and water temperatures between 28 and 30C. I am fully expecting this depression to become a tropical storm later today and continue to strengthen before making landfall by this time Monday morning to around a 45 kt tropical storm. Following landfall...expect this system to weaken as it heads to the northeast and whatever is left of this system could move off the New Jersey coast in about 5 days.

Initial motion 330/13 kts. Expect this motion to continue until landfall in about 24 hours then in response to a high pressure off the East Coast...a turn to the northeast and could bring heavy rains across the southeast...and Mid-Atlantic. Though this will be a weak to moderate tropical storm...expect heavy rain across the Florida Panhandle to the Mississippi/Alabama border.

Forecast Positions and Intensity:

16/21Z 28.6 N 84.9 W 35 kts

17/09Z 30.0 N 86.3 W 40 kts

17/21Z 31.2 N 87.4 W 45 kts...inland

18/09Z 32.4 N 88.0 W 30 kts...inland

19/09Z 34.5 N 87.5 W 25 kts...inland

20/09Z 37.0 N 82.0 W 25 kts...inland

21/09Z 39.5 N 73.5 W 30 kts...offshore

Tropical Storm Bill

At 5:00 AM EDT (0900Z)...the center of Tropical Storm Bill is located near 11.3 N 40.3 W. Maximum sustained winds are near 45 mph...additional strengthening is expected and Bill could become a hurricane in about 36 hours. Movement is to the west at 17 mph and this motion is expected to continue with a gradual motion to the west-northwest in 24 hours. Estimated minimum central pressure is 1002 mb/29.59 in.

Bill have increased in strength slightly with T numbers around 2.5 to 3.0 and thus have increased the intensity to 40 kts. Light to moderate shear environment and warmer water temperatures will be factors in Bill increasing in strength over the next five days. New forecast calls for Bill to become a hurricane in about 36 horus and very near major hurricane strength in 4 days. Forecast models do indicate that wind shear is expected to increase further by days 4 and 5...so have level intensity off at 95 kts which is well below several of the models that are still predicting that Bill could reach category 3 or 4 status in the same time frame. Right now...do not see this due to the expected increasing shear.

Initial motion 270/15 kts. Again...do not see much difference in the forecast track from previous forecast packages...so made little change to the forecast track and expect for Bill to move to the west-northwest and stay north of the Leeward Islands and Puerto Rico...but could affect the Bahamas in about 7 days.

Forecast Positions and Intensity:

16/21Z 11.8 N 40.3 W 45 kts

17/09Z 12.5 N 43.2 W 55 kts

17/21Z 13.3 N 46.1 W 65 kts

18/09Z 14.1 N 48.8 W 75 kts

19/09Z 16.0 N 54.5 W 90 kts

20/09Z 20.0 N 59.5 W 95 kts

21/09Z 23.0 N 64.5 W 95 kts

Tropical Storm Ana

At 5:00 AM EDT...Tropical Storm Watches are in effect for Puerto Rico...the U.S. and British Virgin Islands...and the Northern Leeward Islands. Tropical storm watch means that tropical storm conditions are possible in 24 to 36 hours. Warnings could be issued for a portion of the watch area later today.

At 5:00 AM EDT (0900Z)...the center of Tropical Storm Ana is located near 14.5 N 52.7 W. Maximum sustained winds are near 40 mph...little change in strength is expected in the next 24 to 36 hours. Movement is to the west at 20 mph and this motion is expected to continue. Estimated minimum central pressure is 1005 mb/29.68 in.

Ana continues to struggle with the shear and dry air...and her fast motion is not helping to keep her together. Initial intensity remains at 35 kts. I am expecting for the shear and dry air to continue to impact Ana and she will struggle to maintain her strength for the next 36 hours. Beyond 36 hours...the shear is expected to relax some and she will begin to strengthen as she moves through the Northern Leeward Islands. Ana will also move through Hispaniola and Cuba towards the end of the forecast period and during this time...Ana will weaken back to a weak tropical storm...if not a depression...have kept the forecast from becoming a depression for now and also knocked down the overall intensity forecast for Ana and for her not to reach hurricane strength.

Initial motion 270/17 kts. This rapid motion is expected to continue for the next 12 to 24 hours. Ana will gradually move to the west-northwest and move through the Northern Leeward Islands...Puerto Rico...Hispaniola...and Cuba through the forecast period. If Ana can survive this rash of landfalls and the shear...she will move into the southeast Gulf of Mexico towards the end of the forecast period.

Forecast Positions and Intensity:

16/21Z 15.3 N 56.5 W 35 kts

17/09Z 16.1 N 60.4 W 35 kts

17/21Z 17.3 N 64.4 W 45 kts

18/09Z 18.2 N 68.3 W 50 kts

19/09Z 20.0 N 75.5 W 35 kts...inland

20/09Z 22.0 N 81.0 W 35 kts...inland

21/09Z 23.5 N 85.5 W 45 kts...offshore

Byron Jackson
Tropical Specialist