TROPICAL STORM FORMATION: IDA
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!
INVEST 96L has been dropped. The NHC has lowered cyclone formation probabilities to 0% The area continues to be sheared, and upper level winds are forecast to remain unfavorable for any development.
Tropical Storm IDA is still hanging on, despite her LLC having been displaced to the NW of the convection most of today. The following information was available on IDA in the NHC 5:00 p.m. advisory:
5:00 PM AST Sun Sep 20
Location: 18.4°N 46.3°W
Moving: NW at 17 mph
Min pressure: 1005 mb
Max sustained: 45 mph
Current satellite loop imagery indicates a burst of convection, is appearing very close, to almost over the LLC. This began around 20Z, and seems to be continuing in the last couple of frames. This may be due wind shear relaxing over the system. The previous analyzed shear product did indicate wind shear was affecting IDA, on the order of 20-25 knots. However, the most recent image from 21Z, indicates shear to have backed off, with values of around 15 knots. Again, this may be the brief window the NHC has mentioned in their forecast discussion, and what has been shown in the GFS wind shear forecast over the past 24 hours. Given this, if this trend continues, some slight strengthening may occur. However, it is unknown at this time whether or not IDA will be able to mix out the dry air entering on the western periphery. This may be one reason the NHC and the intensity modeling only depicts a slight strengthening. I currently agree with the NHC intensity forecast, which is pretty much inline with the more accurate intensity forecast models, if IDA can maintain herself in the lower shear environment and fight off the dry air during the next 4-5 days.
NHC INTENSITY FORECAST
INIT 20/2100Z 18.4N 46.3W 40 KT 45 MPH
12H 21/0600Z 19.6N 47.5W 40 KT 45 MPH
24H 21/1800Z 20.9N 48.5W 45 KT 50 MPH
36H 22/0600Z 21.5N 48.7W 45 KT 50 MPH
48H 22/1800Z 21.5N 48.5W 45 KT 50 MPH
72H 23/1800Z 21.0N 48.2W 45 KT 50 MPH
96H 24/1800Z 20.9N 48.5W 45 KT 50 MPH
120H 25/1800Z 22.5N 49.5W 45 KT 50 MPH
IDA is moving toward the NW, and there really isn’t much change in the steering forecast, based on analysis of the current steering layers forecast maps. I expect IDA to continue to the NW over the next 24 – 30 hours, becoming quasi-stationary and meandering for approximately 3-4 days, before picking up a possible NW track again, then out to sea. Again, this is based on the CURRENT steering forecast. However, for the next 72 hours, the storm should follow the 18Z dynamic model guidance, and NHC track.
I will continue to monitor IDA for any significant changes to the surrounding environmental conditions.
Elsewhere, global models are still in agreement with a large, weak area of low pressure beginning by next weekend, developing IVO the extreme NW Caribbean Sea, to the extreme southern GOMEX.
Based on my analysis of the recent wind shear forecast, I am not expecting this to be more than a large, weak area of low pressure. However, I will be monitoring further model runs for any changes to the forecast upper level pattern, and for any changes in the modeling solutions.
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