TROPICAL CYCLONE FORMATION: INVEST 96L (40%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 4
INTENSE HURRICANES: 0
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 14-16
INTENSE HURRICANES: 3-4
Good day everyone!
Another area of disturbed weather, associated with a Tropical Wave and broad area of low pressure has just entered the eastern Atlantic Ocean along the African coast, and has been designated INVEST 96L by the NHC. As of the 18Z ATCF BTK (Automated Tropical Cyclone Forecast System…Best Track) summary, the following information was available on INVEST 96L:
2:00 PM EDT Wed Jul 27
Location: 10.2°N 17.6°W
Moving: W at 22-24 mph
Min pressure: 1011 mb/29.85 in
Max sustained: 25 mph
The NHC has designated a MEDIUM (40%) probability of Tropical Cyclone formation during the next 5 days regarding 96L:
RAMSDIS METEOSAT FLOATER SATELLITE LOOP IMAGERY (96L)
Upon analysis of upper level winds, SAL analysis, water vapor imagery, and other forecast tools, I have to agree at the moment, with the NHC on the 40% probability for development. This takes us out to 5 days in the forecast period. Current upper level winds are not really optimal at the moment, as the disturbance is in an area where a small strip of 20 knots of easterly wind shear is situated. One piece of evidence that backs this up is, if you notice in the satellite loop imagery, all of the higher clouds are being blown off toward the west. Upper level winds do however improve past 40W Longitude becoming lighter. So bottom line as far as upper level winds, 96L will have to make it past 30W, where the upper level flow becomes more diffluent (spreading apart) which will aid in upper level divergence.
Analysis of the current wind shear forecast indicates 96L could come under somewhat more favorable conditions over the next 72-96 hours, should it continue on an average westerly course, as wind shear is forecast to decrease. SHOULD steering change, and 96L take more of a track toward the Bahamas (north of the Lesser Antilles), it could come under the influence of an upper level anticyclone.
Two items that are favorable for it are, it has decent TPW (Total Precipitable Water) to work with, and analysis of relative humidity forecasts from 850-500 mb shows a more favorable RH pattern than we have seen over the past 10 days.
One other item that may aid 96L if it makes it past 40W is, OHC (Ocean Heat Content) doubles in value, to values that are supportive to hurricanes.
The disturbance is moving in a general westward direction (just north of due west), and I expect this motion to possibly change to a WNW motion in approximately 18-24 hours, allowing for the disturbance to gain some latitude, with track shifting to more of a westerly component after 48 hours in the period. This is based on analysis of the current forecast steering layers models, which show a break in the subtropical ridge near 50W at the moment. which will work to impart a more WNW track. Over the next 5 days, the subtropical ridge and weakness are forecast to shift westward, with the ridge also shifting slightly south. This is also implicated in model track guidance, which most are ensemble members, and statistical models. I have only one dynamic model available at the moment, as the site I use has not update the information on 96L. It takes a while during the initialization of a system. Given that this information is based on the initialization of the disturbance, this forecast is not written in stone or a given certainty.
Most of the global modeling dissipates this, which COULD happen, given conditions are still not OPTIMAL over the MDR at the moment, and then again, things could improve. It’s pretty much a wait and see situation. The ECMWF takes what may be left, toward the Caribbean, and the CMC GGEM brings it over the OBX area as a Tropical Storm. The CMC is also hinting that the wave in front of 96L, may enter the GOMEX from the Yucatan Channel area, and affect the TX coast. This will remain to be seen, as that wave is not in too good of shape, but I will be keeping an eye out. IF 96L does dissipate, remember, it has taken a good chunk out of the SAL, and looking at the current shear forecast, there are two more waves over Africa in that once they exit, COULD encounter a more favorable environment than 96L.
The current intensity forecast models I feel are a little bullish at the moment, which is not unusual during the initialization period of a disturbance, given no closed LLC.
So for the short term, given what favorable conditions we do have ahead at the moment, I have to call for some further SLOW development of this disturbance, with the probability of it becoming a Tropical Depression during the next 5 days. I’ll have to revisit the prospect again on Sunday, as I work the next 3 days. At that time, I’ll be doing a re-assessment of the surrounding conditions…current and forecast.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS