TROPICAL STORM FORMATION: TROPICAL DEPRESSION 9 / INVEST 95L
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*NOTE: In the TROPICAL STORM FORMATION line above, probabilities are for during the next 5 day period. My personal probability will be listed as either NONE, MONITORING or PROBABLE. This does not necessarily mean something will develop, but that certain forecast conditions are likely to be present, favoring development. Once NHC products become available, then the appropriate probability and percentage will be used.
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Current Storm Total for 2015:
TOTAL STORMS: 8
INTENSE HURRICANES: 1
U.S. LANDFALLS: 2
StormW’s Seasonal Forecast:
TOTAL STORMS: 8
INTENSE HURRICANES: 1
Good evening everyone!
INVEST 93L was upgraded to Tropical Depression 9 earlier today. Based on the NHC 5:00 p.m. AST advisory, the following was available on TD9:
5:00 PM AST Wed Sep 16
Location: 15.2°N 44.6°W
Moving: NW at 8 mph
Min pressure: 1009 mb / 29.80 in
Max sustained: 30 mph
Satellite loop imagery indicates the system is being sheared, with the LLC plainly exposed to the west of the convection. The current wind shear product from CIMSS indicates the depression is under approximately 25 knots of westerly shear. It is noted, the center of the upper level anticyclone which aided in the better organization hours ago, is now located south of the depression.
TD9 WIND SHEAR
Some very dry air is noted to the west of the depression, and based on my analysis of visible and RGB satellite loops, TD 9 has taken in some drier air, noted by some outflow boundaries to the W and SW of the center.
The current wind shear forecast calls for shear to increase over the system, with upper level winds becoming even less favorable for further development. Based on the situation with dry air, and the premise of the wind shear forecast, I concur with the NHC intensity forecast, however I feel at this time, TD9 may become a remnant sooner than forecast.
FORECAST POSITIONS AND MAX WINDS
INIT 16/2100Z 15.2N 44.6W 25 KT 30 MPH
12H 17/0600Z 15.9N 45.1W 25 KT 30 MPH
24H 17/1800Z 17.0N 45.8W 30 KT 35 MPH
36H 18/0600Z 18.0N 46.4W 25 KT 30 MPH
48H 18/1800Z 19.3N 47.6W 25 KT 30 MPH…POST-TROP/REMNT LOW
72H 19/1800Z 20.5N 49.5W 25 KT 30 MPH…POST-TROP/REMNT LOW
96H 20/1800Z 21.5N 52.0W 20 KT 25 MPH…POST-TROP/REMNT LOW
Analysis of current and forecast steering layers maps indicates the depression is now moving toward the NW, and I expect this motion to continue as per the NHC forecast track, with a bend toward the west near day 5, as the ridge builds over the remnant of TD9 briefly, then steers it toward another weakness which will be located close to 50W at that time in the forecast period. This is reflected in the 18Z dynamic guidance, and lies close to the TVCN/TVCC consensus models.
I will continue to monitor this system until it dissipates.
INVEST 95L is located to the ESE of TD9. The recent information was available on INVEST 95L in the 18Z ATCF FTP product:
2:00 PM AST Wed Sep 16
Location: 11.1°N 29.3°W
Moving: WNW at 10-15 mph
Min pressure: 1010 mb / 29.82 in.
Max sustained: 30 mph
Satellite loop imagery indicates 95L has not changed much in organization over the past few hours. The recent wind shear product did indicate upper level winds were favorable for further slow development of this INVEST, however some dry air entertainment may be ongoing at the moment, although the environment is a little more favorable in the terms of the amount of dry air surrounding the system, as opposed to 93L.
The upper level 200 mb pattern is forecast to remain favorable during the next 96 hours, before they begin to become somewhat marginal, then back to favorable. Should 95L be able to mix out dry air, then the probability of a tropical depression seems relatively likely. Should this occur, and the upper level wind pattern pans out, I cannot rule out development of a Tropical Storm within the next 36-48 hours. In fact, the 18Z Intensity Guidance brings this to a strong Tropical Storm in about 4 days. Based on the wind shear forecast, this may not be out of the question, if it survives the dry air near it.
Based on analysis of the forecast steering layers maps, 95L should pretty much follow a path similar to INVEST 93L due to the weakness in the subtropical ridge.
Elsewhere, some of the global models are beginning to hint at a possible system developing off the SEUS during the next 5 -7 days, due to a trof split. Some of the models have backed off on strength, and pretty much start with an elongated area of low pressure. The GFS and CMC seem the most interested, with the NOGAPS a little weaker, and the ECMWF not really interested at the moment. I will be monitoring the area of the SEUS maritime area beginning next week.
Elsewhere, Tropical Storm formation is not expected during the next 7 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS