SEVERE WEATHER RISK: ENHANCED
TROPICAL CYCLONE FORMATION: NONE
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(T. F. “Storm” Walsh III)
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Good day everyone!
The SPC has designated an ENHANCED risk for Severe Thunderstorms in the day 1 convective outlook.
TROPICAL WEATHER OUTLOOK DISCUSSION
First, satellite imagery indicates another MCS in the GOMEX this afternoon. This area does not pose any threat for development.
The 12Z surface analysis map from NHC TAFB indicated 2 tropical waves moving toward the west. The wave located near 44W is moving at around 15 kts. A second wave, onshore over the extreme north coast of South America is moving at around 10 knots. Both of these waves do not display and discernible satellite signature.
Analysis of the global models today indicate the weak coastal low, which has been being shown over the past 5 days or so, is coming to fruition. Satellite imagery and the TAFB surface analysis indicate a 1008 mb low is just along, or now sightly off the SE NC coastline. The primary low associated with this system is moving toward Nova Scotia, and is east of Cape Cod. The satellite overlay, along with the GFS and ECMWF global models indicate this as what I refer to sometimes as a double barrel low, to become split, with the low off the NC coast becoming the dominant feature. Based on analysis of the 1000-500 mb thickness charts, this low is forecast to phase with a 500 mb cutoff low, and should remain baroclinic in nature. At the moment of the most current model runs, winds will be at their worst, east of the center of the low, and are forecast at the moment to approximately 25 knots tops. I do not foresee any problems right now inland with this, however the possibility of some heavier surf and winds along coastal areas north of the center does exist.
Over the past few days, the global models have been hinting at the possibility of a “situational development” anywhere from the extreme western Caribbean, to the north central Bahamas.
Analysis of the global models 12Z runs indicates the models are still trying to “sniff” something out in the day 6-10 time frame in the forecast period.. The only model not indicating development of a low at them moment, is the ECMWF and CMC GGEM.
The GFS develops a low, east of Florida at about day 6 (147 hours), moving it slowly northward off the east coast, while it strengthens slowly. This low gradually moves inland over Georgia by the 31st of May. The 1000-500 mb thickness indicates at the moment, that IF this occurs, it doesn’t begin a transition to warm core until it comes inland. Right now, pressures (1002 mb…29.59 in.) and wind speed indicate this would only be a tropical depression, IF it develops. The GGEM indicates only a wave in the isobars, however it comes up with a low in the south central Caribbean Sea, north of Panama in 10 days. Both FIM models are in between the GGEM and GFS, indicating a weak system a little further east of FL. at around the 8 day time mark.
ECMWF 240 HOURS
So, we have the dilemma of “which model is correct”. After some thought on this, I cannot totally rule out the GFS at this time, as we don’t know how it’s going to perform since the upgrade earlier in the month. I will say one thing, it did keep up with the ECMWF in forecasting the current low “pattern” off the east coast. Second, I cannot totally rule it out, as we do see some lowering of pressures over the Cuba area in about day 6-7.
Based on the other models solutions (the slower solution), the GFS “COULD” be an outlier, as the FIM indicate slow development at 8-9 days out, with a low going out to sea.
The CMC GGEM then develops a low over the south central Caribbean.
This could possible be the better of the scenarios, as the ECMWF and ESRL PSD 500 mb anomalies indicate a significant lowering of pressures ate 216-240 hours out in the forecast period, and have been consistent run to run over the past 6 days. Regardless of which model is correct, I will be monitoring the area where the significant of the pressure drop is indicated. The GFS does indicate an improvement in the upper level wind pattern, with a weak upper level anticyclone becoming evident off the U.S. east coast at 180 hours out in the forecast period from 12Z today.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS