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(T. F. “Storm” Walsh III)
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Good day everyone!
The tropics are somewhat active today, and the NHC has designated a LOW (20%) probability of tropical cyclone development over the next 5 days on two areas we are monitoring
NHC 5 DAY GTWO
Satellite loop imagery today indicates disturbed weather still over a portion of MX, and shifting eastward over a portion of the Yucatan peninsula, Belize, Honduras, and Nicaragua. Based on previous analysis yesterday of MSLP and 1000 mb wind flow forecasts, the current situation appears to be the precursor of the developing low late this weekend into the beginning of next week, courtesy of the EPAC Monsoon trof.
Another area of interest was added in the GTWO, consisting of a strong tropical wave that has exited the African west coast, and is currently moving eastward at around 20 mph.
The first area being monitored is the W. Caribbean. Analysis of global models indicates consistency from run to run, in that an area of low pressure will develop by sometime Sunday. However, there is still some discrepancies in the modeling as far as strength and track. Here is what is forecast to happen, in the early stages of development. As the system takes shape, the ridge/trof pattern over the U.S. will be as such, that ridging (or height rises) will be located NE of the low, in the Atlantic to more or less block any motion toward the east, with height rises also over TX and the central planes. This basically creates an alleyway north. As we get a little further out in time, the ECMWF shows more rising heights nosing in over FL. and some of the Gulf coast states, leaving a weakness over TX. The GFS shows less extensive height rises and pretty much shows lower heights over the entire GOMEX, bringing the low into MX, while the ECMWF solution brings the low inland to TX. The CMC GGEM still insists on bring it to the FL. Big Bend / Panhandle area, but develops and moves it much quicker, having it making landfall by day 6, with another weaker system trailing right behind. I am having the tendency not to buy the CMC solution, however will have to keep a close eye on the pressure pattern, because the timing of the U.S. ridge/trof pattern will be critical in steering.
GFS AND ECMWF NORMALIZED HEIGHT ANOMALIES
GFS MSLP NORMALIZED ANOMALIES
ECMWF MSLP ANOMALY MAP
CMC GGEM MSLP/ 10 METER WIND SPEED
Strength is up in the air with the ECMWF at the current, showing a weak 1002 mb low on the TX coast. The GFS doesn’t even appear to close off the low, while the CMC is inline strength wise with the ECMWF. Although the CMC agrees with the ECMWF strength, I have to rule that out at the moment, as the CMC has the system in the shear zone. Based on analysis of the GFS wind shear forecast, upper level winds are still projected to become favorable over the W. Caribbean / Gulf of Honduras area by 96 hours from 12Z this morning, and remaining favorable through to 168 hours (day 7). We have a trof split coming up over the GOMEX in a few days, and as the piece of the trof backs away, is when the upper level winds will become more favorable. You’ll notice in the 2oo mb maps that an outflow jet becomes established to the north and NE, with the development of the upper level anti-cyclone.
GFS WIND SHEAR FORECAST
ECMWF 200 MB FORECAST
Based on this, I am not sure why the GFS doesn’t indicate a closed low. Based on these factors, I am more inclined at the moment to side with the ECMWF solution as far as development. Again, as far as forecast track, given NONE of the forecast steering maps agrees with each other, we are going to have to wait and see if we get development, and give the guidance models something to latch onto.
Elsewhere, I am monitoring the strong tropical wave in the far eastern Atlantic, which was centered near 6N;26W on the latest satellite loop imagery. This wave is currently moving westward at 20 mph and is embedded in the ITCZ. I expect this westward motion to continue for around the next 48-72 hours, with more of a WNW motion thereafter as it approaches near South America.
Upon my initial look at this system late yesterday, and based on the shear forecast from yesterday, it did not appear at that moment, that it would hold together. This morning, after a more in depth analysis, based on the update wind shear forecast from the GFS, upper level winds may remain slightly favorable to marginal over the next 96 hours, being based on current location and projected motion of the system. By 120 hours however, as the wave approaches South America, upper level winds are forecast to be unfavorable for development, due to westerly shear developing ahead of the wave. Based on this, I believe we could see some further, slow organization of this wave over the next 72-96 hours, before wind shear has a negative effect on it. It’s always a little more difficult for a system to develop while being within the ITCZ
GFS ATLANTIC WIND SHEAR 5 DAY FORECAST
In any event, I will be monitoring both areas closely, and should have another update late Sunday afternoon.
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