SEVERE WEATHER RISK: SLIGHT
TROPICAL CYCLONE FORMATION: MONITORING
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(T. F. “Storm” Walsh III)
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Good day everyone!
TROPICAL WEATHER OUTLOOK DISCUSSION
Over the next 8-10 days, we have somewhat of a complex pattern forecast to evolve off the U.S. East Coast, and the Caribbean, Bahamas area.
First, closer to home, the MCS system that originated in the GOMEX yesterday, and crossed the Florida peninsula, has now emerged off the U.S. East Coast, with a 1011 mb low centered off the FL./GA. coast, with convection extending sown into the Bahamas.
Click on satellite images to access loops.
Based on satellite loop imagery, the low can be clearly seen. Analysis of the 850 mb vorticity map indicates strong vorticity near the lower levels. The 925 mb vorticity product from the PSU e-WALL site was not available. Analysis of vorticity at 700-500 mb indicates this low is tilted to the SE.
Based on analysis of the Cyclone Phase Evolution diagrams from FSU, this low is forecast to remain cold core. Analysis of the current wind shear product from CIMSS indicates upper level winds are somewhat conducive at the moment and the low could become more discernible over the next 12 hours. Albeit conditions are currently marginally favorable, I am not expecting this to take on sub-tropical characteristics, or develop into a sub-tropical storm given the global models take this quickly to the NNE to NE, and into increasingly strong SWLY shear in the current model runs. The GFS and CMC GGEM did a good job on initialization of this early this morning, and are the only two that did. Just FYI, this IS NOT the low that is forecast to develop off the DELMARVA area as mentioned in my previous forecasts.
The global models seem to be in excellent agreement of another area of low pressure to develop off the Eastern Seaboard, initiating in approximately 96 hours. Based on the consensus of the global models (forecast times approximate), the low strengthens, and moves off quickly to the NE by 114 hours from 12Z this morning. Between 114 – 120 hours in the period is where we encounter the trof split at 500 mb, associated with the surface low. Both the GFS and ECMWF are in agreement on this. The low which moves NE, leaves energy behind, with a new low forecast to develop (location approximate) east of the SC area. This low is forecast to move in a general northerly to NNE direction, where it is forecast to phase with the 500 mb cutoff low. Analysis of the 1000-500 mb thickness maps tends to indicate this feature may try to transition to warm core. Based on analysis of the current wind shear forecast from the GFS, 200 mb streamlines will not be optimal, however 850-200 mb wind shear is forecast to relax over the low to around 10-15 mph. This setup COULD allow for subtropical characteristics to begin, however given the fact the low will be associated with a 500 mb cutoff low, I would at this time, expect it to remain baroclinic in nature, more inline as a gale center. The GFS keeps this offshore just enough to miss the U.S. directly, and the ECMWF has the center “clipping” Cape Cod. Given the complex nature, I feel it will be better to monitor and handle this in real time.
GFS 84, 96, AND 147 HOUR FORECAST MAPS
ECMWF 120, 144, AND 168 HOUR FORECAST MAPS
GFS WIND SHEAR
In regard to the trof split mentioned above, this is where we could possibly see some “mischief” either in the W. Caribbean or the northern Bahamas beginning in 8-10 days. This scenario has been consistent with the ECMWF over the past 3 days and numerous runs. The current ECMWF MSLP anomaly and 850 mb MSLP and wind speed indicate a “kink” or wave in the isobars as well as lowering surface pressure. The NCEP ESRL 500 mb mean norm. anomaly map still indicates lowering of pressures over the Caribbean.
I will be monitoring this area was we get close to that time in the forecast period.
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