TROPICAL STORM FORMATION: IDA, INVEST 96L
ALL forecasts contained on this site, are based on my analysis and knowledge of various forecast tools, including information contained in NHC products, and are not copies from any other entity.
*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: 9
INTENSE HURRICANES: 1
U.S. LANDFALLS: 2
StormW’s Seasonal Forecast:
TOTAL STORMS: 8
INTENSE HURRICANES: 1
Good evening everyone!
Tropical Depression NINE dissipated a little earlier this evening. The following is the FINAL advisory on the depression:
5:00 PM AST Sat Sep 19
Location: 18.8°N 49.9°W
Moving: WNW at 5 mph
Min pressure: 1007 mb
Max sustained: 30 mph
Tropical Depression TEN, was upgraded to Tropical Storm IDA yesterday evening. As of the 5:00 p.m. advisory from the NHC, the following information was available:
5:00 PM AST Sat Sep 19
Location: 15.6°N 40.8°W
Moving: WNW at 14 mph
Min pressure: 1006 mb / 29.71 in
Max sustained: 40 mph
Current satellite loop imagery indicates the LLC is still exposed slightly to the NW of IDA. The most recent wind shear product from CIMSS does indicate shear has relaxed over IDA in the past few hours. IDA had been under 20-25 kts of westerly shear as of 1800Z. The current product indicates shear has relaxed to around 15-20 knots. This was pretty much forecast by the GFS wind shear forecast map, but a little later in the period. Given the recent increase in convection, it wouldn’t surprise me to see a center reformation closer to the convection.
As per the NHC discussion on IDA, wind shear may decrease over the next couple days, as forecast by the GFS, which indicates somewhat of an upper level anticyclone lining up briefly with the system, not unlike what is seen in the 2100Z shear graphic. This is forecast to fluctuate, based on the shear forecast between marginal and favorable over the next 36 – 72 hours. Based on my analysis, I do agree with the NHC in that some further strengthening may occur with IDA, and I agree to a point on their intensity forecast, albeit it is slightly above the intensity guidance of the 3 most used models. In nay case, should the shear forecast pan out, IDA should continue to slowly strengthen during the next 72 hours, provided dry air to her west doesn’t impinge on the circulation.
FORECAST POSITIONS AND MAX WINDS
INIT 19/2100Z 15.6N 40.8W 35 KT 40 MPH
12H 20/0600Z 16.4N 42.5W 35 KT 40 MPH
24H 20/1800Z 17.6N 44.5W 40 KT 45 MPH
36H 21/0600Z 18.9N 46.1W 45 KT 50 MPH
48H 21/1800Z 19.9N 47.2W 50 KT 60 MPH
72H 22/1800Z 20.5N 48.0W 55 KT 65 MPH
96H 23/1800Z 20.0N 48.0W 55 KT 65 MPH
120H 24/1800Z 20.5N 47.5W 50 KT 60 MPH
Based on satellite loop imagery and current steering layer, IDA is moving toward the WNW. I expect this motion to continue during the next 24-36 hours. Thereafter, modeling disagrees somewhat on timing, however the steering flow is forecast to collapse, as mentioned in the NHC discussion, and IDA could remain quasi-stationary, and meander about. NHC mentions this to occur 72 hours into the forecast period, up to day 5. The current forecast steering layers maps indicate this could last even to day 6 in the period, with a possible, very slow westward motion thereafter, as ridging is forecast to build again north of IDA. My confidence in this is low at the moment, given that steering patterns can change quite a bit in just 24 hours. For the most part, the storm should move as forecast over the next 3-5 days. This is widely shown in the 18Z dynamic guidance.
Elsewhere, INVEST 96L is located approximately 200 miles off the NE Florida coast. Based on the 18Z ATCF FTP product, the following information was available on INVEST 96L:
2:00 PM EDT Sat Sep 19
Location: 30.9°N 77.9°W
Moving: E at 8 mph
Min pressure: 1007 mb / 29.74 in
Max sustained: 30 mph
Satellite loop imagery indicates the INVEST remains poorly organized, with the LLC clearly noted well west of any convection. The center is also noted to be rather elongated at the moment.
INVEST 96L SHEAR
The current wind shear forecast indicates upper level winds MAY become marginal, briefly, however for the most part, I expect upper level winds to remain unfavorable for development…at least based on the most recent shear forecast. Based on current appearance, it wouldn’t surprise me to see the NHC remain Status Quo on the probability, and possibly even downgrade it within the next 24 hours, should conditions not change.
Analysis of the forecast steering layers maps indicates this should move toward the NE during the next 48 hours. After that, model guidance is suggesting a possible cyclonic loop back toward the west could occur, although it would appear there may not be anything left at that time. Given this is so close to the U.S., I will continue to monitor the INVEST for any significant changes.
Elsewhere, analysis of the Global models this evening tends to indicate the majority of the models develop a rather large, weak area of low pressure over the southern GOMEX, beginning in about 7 days from now. As of analysis this evening, the models keep this a weak low, with an initial, very slow north movement. At the moment, I do not expect anything other than a weak low, as upper level winds over the GOMEX are forecast to be unfavorable for any development. I will however be monitoring this as we get closer to mid week of this upcoming 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