*******Note that forecast and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.*********
...SATURDAY JULY 20 2024 10:48 AM EDT...
Tropical activity in the Atlantic basin remains calm due to higher concentrations of dry Saharan air toward the east and pockets of suppressing cut-off upper vorticity across the western half of the basin. Through the next few days the western cut-off upper vorticity is expected to generally decay due to prolonged isolation from high-latitude cold air... allowing for the ongoing eastern Atlantic tropical upper ridging to expand westward into the eastern Caribbean. In addition the warm surface southerly flow ahead of the next slow-moving frontal system that will settle into central North America is forecast to promote warm core upper ridging across the Gulf of Mexico and southeastern United States... with whatever remaining of the decaying upper vorticity lingering across the western and central Caribbean while sandwiched between the Gulf of Mexico and eastern Caribbean upper ridging. Therefore for the next few days expecting the following:
For the western and central Caribbean... no tropical cyclone formation expected as suppressing upper vorticity lingers in the region.
For the eastern Caribbean and tropical belt of the Atlantic basin (Lesser Antilles to western Africa)... despite upper ridging favoring tropical activity the models continue to not show tropical development perhaps while projecting that dry Saharan air will continue to blanket the region.
For the western Gulf of Mexico... including coastal Tamaulipas and coastal Texas... a tropical disturbance is possible within the next few days from either the north end of the surface tropical wave of low pressure currently crossing Guatemala... the tail end of the current southeastern US surface front... or possibly a merger between the two surface low pressure features. In the upper-levels models are increasingly suggesting the south part of the current central US upper trough becomes cut-off and pushed south into Tamaulipas by the current western North America upper ridge and potentially merges with the south end of the next upper trough that will settle into central North America... with the combined upper trough potentially being amplified enough to promote lower wind shear and supportive upper divergence over the surface disturbance. The surface disturbance may also take advantage of anticyclonic outflow on the west side of the forecast Gulf of Mexico upper ridging mentioned in the first paragraph of this post. Therefore will be keeping an eye on this region in the next few days and declare an area of interest in future updates if necessary... currently not declaring a tropical area of interest for the region as the usually more reliable GFS and ECMWF are not showing activity in this region and there is some uncertainty in the configuration of the forecast combined upper trough... for instance the eventual configuration of the upper trough may cause excess shear and/or features an excessively elongated upper divergence zone that keeps the surface low pressure field elongated instead of consolidated for tropical development.
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Jul 20) CMC Model Run...
**Tail end of current southeast US surface front develops into an inland tropical low just south of the Texas/Mexico border by 108 hours... the tropical low continues northeast across coastal Texas through 132 hours but is sheared by upper trough settled over central North America... the tropical low dissipates over inland southeastern Texas shortly thereafter
0000Z (Jul 20) ECMWF Model Run...
**No tropical development shown in Atlantic basin through 168 hours (7 days)
0600Z (Jul 20) GFS Model Run...
**No tropical development shown in Atlantic basin through 168 hours (7 days)
0600Z (Jul 20) NAVGEM Model Run...
**North end of tropical wave currently over Guatemala evolves into a tropical low just offshore of the Veracruz/Tamaulipas border at 72 hours... tropical low continues north along Tamaulipas coast and into Texas/Mexico border through 120 hours... in longer range tropical low continues north-northeast into interior eastern Texas while dissipating
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