TROPICAL CYCLONE FORMATION: INVEST 99L: HIGH (80%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 14
MAJOR HURRICANES: 3
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
The area of cloudiness and showers NE of the Turks and Caicos Islands associated with a broad surface low, remains very disorganized. The NHC states that upper level winds could become a little more conducive by Wednesday, and have now designated a HIGH (80%) probability of development during the next 5 days.
The following information was available on INVEST 99L in the ATCF BTK 12Z product:
8:00 AM EDT Wed Oct 19
Location: 24.8°N 68.6°W
Moving: N at 5 mph
Min pressure: 1008 mb / 29.65 in
Max sustained: 35 mph
The 12 hour averaged motion yielded a 5 mph North drift.
Based on analysis of satellite loop imagery, a broad surface low can be identified. Thunderstorm and shower activity is well east of this surface feature, as INVEST 99L continues to be affected by 30-40 kts of westerly wind shear. The NHC indicates upper level winds are still forecast to become more conducive, and that a sub-tropical or tropical cyclone within the next couple of days. The operational GFS and ECMWF do indicate development of 99L, however, there appears to be some conflicting data regarding wind shear. The GFS wind shear forecast does indicate a small upper level anticyclone develops, which would allow for development of the system, however based on my analysis of the shear/200 mb streamline pattern forecast, upper elves winds may not become conducive until after 48 hours in the forecast period from 06Z this morning, or when 99L is well to the east of FL. On the other hand, information on shear magnitude from the NOAA RUC TC Diagnosis page, indicate shear values remaining on an average of 20-30 kts. Based on this, if development occurs, I believe it may be somewhat slower than forecast, and would most likely favor sub-tropical development.
Forecast track should be considered preliminary given there isn’t any organized system at the moment. For all intents and purposes at the moment, the forecast thinking is for 99L to eventually begin to move toward the NNW, then begin a turn to the NNE by the end of the week. Now, this is where we have 2 different scenarios. Both the GFS and ECMWF EPS guidance keeps the system offshore and away from the U.S., which appears to be the idea the NHC is proposing. The Operational GFS and ECMWF, indicate that the system merges with the 500 mb trof, creating another low which absorbs 99L, affecting portions of the New England area (GFS), or the system remaining subtropical, and coming ashore over the NE and New England region (ECMWF) in about 4 days. This poses an unknown variable at the moment as far as future path. Should this remain well offshore as indicated by the NHC, the possibility of some minor beach erosion at the time of high tide, as the system makes its CPA to the NE states, does exist, given the large SE to NW fetch, with seas possibly reaching 5-7 ft close to the coast.
I will continue to monitor this, however will not have another update until late Sunday, which would place the system north of the New England area at that time. The following NWS Warnings and Hazards display is provided, which will allow you to pull information from your local NWS office, should any hazards occur from this system by the weekend. Mouse over, and click on your area of interest. Please note, the graphic itself does not update automatically.
Elsewhere, both the GFS and ECMWF indicate a lowering of 500 mb pressure heights ENE of the Lesser Antilles in about 6 days
Elsewhere, Tropical Storm formation is not expected during the next 7-10 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS