TROPICAL CYCLONE FORMATION: EATL DISTURBANCE (70%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 8
MAJOR HURRICANES: 1
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
The NHC issued its last advisory on HERMINE yesterday evening.
INVEST 92L which I was monitoring in the Caribbean, had dissipated yesterday evening, and has been dropped from the system. I was somewhat surprised that the system didn’t at least become better organized before it dissipated. In fact, on the projected path, modeling had been pointing toward improving conditions toward further development Dry air was not an issue. TPW and OHC were very robust, and an upper level anticyclone was with the system for some time, albeit waxing and waning. However, having gone back and re-analyzing some water vapor loop imagery, and previous wind shear items, I have concluded that ex 92L was in too close proximity of an upper level low that was to the west of the system. This, combined With a TUTT, kept a constant 25-30 kts of SW wind shear, just on the west side of the system. Although shear was not located directly over the Invest, the zone was close enough to impinge on the western portion of the heaviest convection, which in turn, exposed the LLC. The rotation you see over Hispaniola this morning, is the remnant mid level circulation and convection of ex-92L. In a nutshell, what basically happened, is the system in effect became tilted, exposing the LLC. This allowed for moisture and heat energy to be spread out over the area, not allowing for it to be focused over the system. Without this heat energy and moisture to hold onto, the system dissipated. A ULL is noted backing away over the GOMEX, and as it backs away to the SW, upper level conditions should improve over the Caribbean.
While I am not concerned with the mid level convection, I will be curious as to see what becomes of it, as it moves toward the WNW over the next few days.
Elsewhere, I am still monitoring 2 areas in the CATL…ONE NEAR 15.0N;52.0W and the other near 7.0N and from 45-40W. The area further south I am not too concerned with, as it is moving toward the west, and should run into South America in a few days. The area near 15N, while I am not expecting development, I will be looking at down the road as it could enter the Bahamas. At the moment, forecast conditions in that area in about 5 days are not favorable for development.
Elsewhere, a rather large circulation is located just to the south of the Cabo Verde islands. This wave continues to move very slowly at the moment, toward the WNW, due to the westerly flow in the steering, and a weakness in the ridge to its north.
Based on my analysis of the current steering layers forecast maps, I expect a WNW motion to continue during the next 48 hours, but the steering suggests maybe more of a bend toward the west by 72 hours as the subtropical ridge builds back north of it, but still maintaining a general WNW (280 deg?). Based on the current wind shear product, shear and upper level winds indicate the wave is under favorable conditions for slow development. Based on current track thinking, the upper level environment becomes more conducive in about 4-5 days, where the disturbance should be located. From around 48 hours out, upper level winds could become somewhat less favorable, up until the 4-5 day mark (96-120 hours). Based on these parameters, I do believe we should see some slow development during the next 5 days. As of the 8:00 a.m. EDT Tropical Weather Outlook, the NHC has designated a HIGH (70%) probability of cyclone development during the next 5 days.
I know it seems rather quiet for this time of the season, when the climatological peak is in 3 days. There is still some subsidence noted over the Atlantic. I believe the main factor in this is the once again, strong subtropical ridge. Vertical instability in the Atlantic however, is just near climatology. The ridge is expected to weaken over the next few days, which should allow for greater instability over the Atlantic. Are we done? Well, it doesn’t look like Africa is finished yet, as both the GFS and ECMWF are in agreement of another development off the coast of Africa in approximately 9-10 days. Upper level winds are forecast to be favorable at that time, however being in the medium range, this scenario can change.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS