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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!
An area of low pressure has formed over the GOMEX, about 100 miles south-southwest of
Apalachicola, Florida. The NHC has designated a LOW (30%) probability of cyclone development during the next 5 days.
A tropical wave located several hundred miles west-southwest of the
Cape Verde Islands continues toward the west. The NHC has designated a LOW (30%) probability of cyclone development during the next 5 days.
The area of low pressure has been designated INVEST 98L. Satellite loop imagery shows some good counterclockwise rotation, however vorticity is rather limited at the 850 mb level, and is displaced south of where the convective cloud mass is located at the moment. Vorticity was currently lacking at the 700 – 500 mb levels.
2:00 PM EDT Sun Jul 30
Location: 28.4°N 85.5°W
Moving: ESE at 10 mph
Min pressure: 1009 mb / 29.80 in
Max sustained: 35 mph
Based on my analysis of the current wind shear product from CIMSS, upper level winds are marginally favorable for sub-tropical cyclone development at the moment. Given that the low is still associated with a stalling front across the Florida Peninsula, and wind shear values are running around 25 kts, although there is some slight divergent flow aloft, baroclinic forcing may be a factor in the well defined satellite presentation. Based on the current forecast motion idea, proximity to land, and upper level wind forecast, INVEST 98L may not be able to take on enough sub-tropical characteristics to be classified a sub-tropical depression, before crossing the Florid Peninsula. Once this low emerges into the Atlantic, the wind shear forecast from the GFS indicates shear may remain a factor, with improving conditions south of the center. Given that wind shear affects systems riding along a frontal boundary somewhat different, as intensification can occur due to baroclinic forcing, INVEST 98L could attain sub-tropical depression or sub-tropical storm status. This is not written in stone, and I’ll have to see what the system looks like once it enters the Atlantic side.
FORECAST WIND SHEAR
The system is moving ESE at the moment, however based on forecast steering maps and initial model track guidance, an eastward turn should occur in about 24 hours. Albeit the initial guidance should be considered preliminary, as model guidance had just been initiated at 2:00 p.m. EDT, forecast steering maps valid for 00Z this evening tend to indicate the track shown in initial guidance. This would allow the system to pass over my area, here in the Tampa Bay region. Indications are, that after the system emerges from Florida, a turn to the ENE should occur at about 48 hours into the period.
INITIAL DYNAMIC TRACK GUIDANCE
Regardless of development, the WPC QPF (Quantitative Precipitation Forecast) indicates 4″ – 5″ of rainfall may accumulate over West Central Florida during the next 5 -7 days.
WPC QPF MAP
Pockets of heavier precipitation may cause localized flooding to occur. Residents of the central and south Florida Peninsula should monitor their local NWS for any statements and advisories on this situation.
I will continue to monitor this area for any significant changes.
Elsewhere, the tropical wave mentioned in the TWO, appears to be west of where the NHC has the mark on the graphic. The mark is located near 31.0W, and satellite loop images do not indicate anything located there. Convective activity is noted however both west and east of that particular location. I do believe the NHC has designated the area just to the west of the mark NEAR 40W – 43W, based on their position per the 2:00 p.m. TWO ( several hundred miles west-southwest of the Cape Verde Islands)
Based on satellite loop imagery, the system remains pretty much disorganized. Although upper level winds are currently somewhat favorable, I believe some drier air located just east of the area could be affecting this wave as it continues west. Good cyclonic turning is noted in satellite loop imagery, however you can detect a stratocumulus cloud deck north of the wave axis, which indicates a stable environment.
Upper level winds are currently somewhat favorable over this wave, however not optimal, and with very little upper divergence at this time.
The GFS wind shear forecast tends to indicate upper level winds may remain weak enough for vertical development, however it is my opinion at the moment, dry air may be an inhibiting factor. There could be some possible slow development over the next few days, however I feel the system(s) to the east of this wave may be looking at better conditions. I will continue to monitor this wave over the next few days for any significant changes however.
Although not included in the NHC TWO, an area of disturbed weather is noted near 10.0N;25.0W, and another just along the African coast. Satellite loop imagery indicates the area near 10.0N;25.0W is displaying excellent cyclonic rotation, and appears to have some slight organization to it.
Based on the current wind shear product, upper level winds are in a somewhat diffluent pattern, and weak to moderate divergence is noted aloft, with some moderate convergence in the lower levels. The shear forecast from the GFS indicates, this wave may remain in somewhat favorable conditions as far as upper level winds, based on the zonal shear forecast. For those not familiar with this product, the blues and greens indict the strength of shear from the east, or “easterly shear”, and the oranges and reds indicate the strength of shear from the west, or ‘westerly shear”. You’ll note a heavier purple contour at various locations. This line represents “zero” zonal shear. So, any system pretty much located within the “zero line”, to, oh, let’s say -14 (ms-1) value, would be under fairly favorable upper level winds.
CURRENT WIND SHEAR
GFS ZONAL SHEAR FORECAST
There does appear to be some drier air to the north and NE of this feature, however it currently seems embedded in enough water vapor.
WATER VAPOR MID AND UPPER LEVEL
Should this survive over the next 24 hours, I would not be surprised to see the NHC add this to the TWO map. My thought on this area is, it is possible for the wave directly behind it, to merge, and become one system. Time will tell however. I will continue to monitor this wave over the next few days for any significant changes
Elsewhere…I am not expecting tropical storm development during the next 5-7days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS