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(T. F. “Storm” Walsh III)
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STORM W’s SEASONAL HURRICANE FORECAST
TOTAL STORMS: 14-16
MAJ. HURRICANES: 3-4
MAJ. HURRICANES: 0
U.S. LANDFALLS: 1
Good day all!
A Tropical Wave located approximately 1000 miles ESE of the Windward Islands has been designated INVEST 95L by the ATCF and NHC. The NHC has designated a MEDIUM (40%) probability of cyclone development over the next 5 days.
As of the 1800Z ATCF BTK product, the following was available on INVEST 95L:
2:00 PM AST Sun Jul 16
MOVEMENT: W 16 mph
PRESSURE: 1011 mb / 29.85 in
MAX SUSTAINED WIND: 25 mph
Based on my analysis of the latest available current wind shear product from CIMSS, INVEST 95L is in an area where wind shear values are relatively weak. Albeit the pattern is currently lacking an upper level anti-cyclone, conditions are marginal to somewhat favorable, as an upper level low positioned NE of the wave, is aiding in evacuating air in the upper levels, as noted by a northern outflow channel or “jet” north of the wave. The resultant upper level flow is causing limited divergence aloft.
INVEST 95L WIND SHEAR MAP
INVEST 95L UPPER LEVEL WIND PATTERN FROM CIMSS
Based on the current wind shear forecast from the GFS, upper level winds may become a little more conducive during the next 24 hours or so, developing somewhat of a small, upper level anticyclone over the wave as it approaches the Windward Islands. Based on this, there may be a small window of opportunity for some slow development over the next 48 hours, as the upper level winds remain somewhat favorable. There is currently a good TPW signature associated with the disturbance, and although drier air is seen north of the system, high TPW values and with the disturbance approaching an area of more OHC (Ocean Heat Content), it may be able to fight off most of the drier air.
INVEST 95L TPW MAP
INVEST 95L OHC MAP FROM CIMSS
So, this system does have some factors in its favor for at least the next 48 hours. At around 72 hours in the forecast period from 12Z, upper level winds are forecast to become unfavorable for any further chance of development, as it stands right now, based on the premise of increasing wind shear.
GFS WIND SHEAR FORECAST
The GFS and ECMWF do not develop this wave, with the (you guessed it) CMC indicating a tropical storm as it enters the southern Caribbean. Model Intensity guidance (SHIP and DSHP) bring INVEST 95L to CAT 1 hurricane status in 72 hours, and the LGEM indicates a weak tropical storm. Based on my analysis, I am more inline with the LGEM, IF forecast data is accurate. Personally (unless conditions change for a more favorable outlook) I feel we may see only a tropical depression to minimal tropical storm at best, (based on current forecast conditions). But, we’ll see how future conditions pan out. Both track and intensity guidance at this time, should be considered preliminary at best, until models have a better defined system to work with.
18Z ATCF INTENSITY GUIDANCE
INVEST 95L is currently south of the subtropical ridge which is moderately strong at the moment, and is in a strong westerly flow, hence current movement. I expect this motion to continue during the next 36 hours, with a possibility of the INVEST gaining somewhat of a small northward component due to a current weakness in the ridge located north of Hispaniola/Cuba, which is forecast to remain for the next 36 hours. Soon thereafter, the ridge axis shifts more toward the west, and the pattern takes on a more negative NAO type pattern, with a ridge building in north of Puerto Rico, and another center more toward the Eastern Atlantic. The resultant flow SHOULD continue to send the system westward, and is most likely what current model guidance is picking up on. As I stated, I believe the wave could lift slightly more northward over the next 36 hours, but then resume a more westerly component.
Elsewhere, Tropical Storm formation is not expected during the next 5 – 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