*******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.*********
...WEDNESDAY JULY 24 2024 3:40 PM EDT...

A tropical disturbance has developed in the northwestern Gulf of Mexico region... centered on the coast just south of the Texas/Mexico border as of this writing. See area of interest #12 section below for more information including on impacts expected across eastern Texas... Louisiana... southwestern Mississippi and southern Arkansas. Meanwhile the surface tropical wave of low pressure that was approaching the southwestern Gulf of Mexico from Belize has passed quietly to the south and is already over south-central Mexico... therefore no additional disturbances are expected to develop in the western Gulf of Mexico.
For the mid-latitudes of North America and western Atlantic... over the next few days a hot air mass upper ridge now approaching from western North America is expected to break the current central North America upper trough into one piece of energy in the vicnity of Texas that gradually decays and an upper vortex in the western Atlantic potentially positioned near the United States east coast... with the remainder of the upper trough then continuing east across the higher-latitudes of the north Atlantic. A tropical disturbance is possible in the mid-latitudes of the western Atlantic around day 5... generally between the United States east coast... Bahamas... and Bermuda... which would be supported by the eastern divergence zone of the aforementioned cut-off upper vortex. The surface trigger for such a disturbance would be the tail end of the current north-central US surface front... as that surface front eventually is dragged eastward and offshore by the current Great Lakes surface frontal low. May be declaring another tropical area of interest (for possible tropical cyclone formation) for this region of the Atlantic in future updates.
For the eastern Caribbean and tropical belt of the Atlantic basin (Lesser Antilles to western Africa)... upper ridging favoring tropical activity is currently in place and is forecast to remain in place over the next several days. A large/broad tropical wave of low pressure is currently near 55W longitude with the northwest side ingesting dry Saharan air and southeast side producing a trailing band of thunderstorm activity. Another similarly large/broad tropical wave recently emerged from western Africa and is currently near 20W longitude... with the northwest side of this wave also ingesting dry Saharan air while the southeast side continues to produce thunderstorm activity currently covering southern Mauritania... southwestern Mali... Senegal... and vicinity. None of the computer models forecast either of these waves to develop as they ingest dry Saharan air. Watching for the possibility that dry Saharan air eventually relaxes which could allow a future wave from Africa to develop in the longer range... so far most models do not show development in the tropical belt of the Atlantic (Lesser Antilles to west Africa region) over the next seven days with the exception of this past 0000Z ECMWF which suggested some development around day 7.
AREA OF INTEREST #12... Doppler radar (from weather.gov) of northwestern Gulf of Mexico disturbance showing well-defined center of rotation... pointed to with red arrow... as of 2 PM EDT:

A surface trough of low pressure has been gradually developing along coastal northeastern Mexico and coastal south Texas thanks to persisting upper divergence out ahead of an upper vortex that was over northeastern Mexico and southeast side of the central North America upper trough. Within the last 24 hours the upper vortex has been absorbed by the upper trough... however the upper divergence pattern continues. Based on the latest satellite and doppler radar presentations... this disturbance has become a little better organized with doppler radar showing a well-defined rotation centered just south of the Texas/Mexico border and the strongest thunderstorms lopsided to the east half of the circulation due to shear imparted by the upper trough. However going forward the south part of the upper trough is expected to slowly retrograde westward and away under the influence of a hot air mass upper ridge approaching from western North America... which could drop shear levels over this disturbance. And combined with the improved doppler radar presentation... I have upgraded this disturbance to an area of interest for possible tropical cyclone formation and have already assigned a 50% chance of tropical cyclone formation. This is the 12th area of interest tracked on this site this year.
As the surface ridge building behind the current Great Lakes frontal low teams up with the Atlantic surface ridge... the surface steering will be southerly. The upper-level steering on the east side of the aforementioned upper trough will be more southwesterly. Given that this system originated as a feature supported by the upper trough and somewhat similar to a system of non-tropical origin... I have handled the steering forecast a bit more like a non-tropical system more coupled to upper winds and thus have an east lean in my northward forecast track. From a tropical perspective... an east lean is also possible as the surface low pressure center could regenerate closer to the sheared-off thunderstorms.
Regarding impacts... over the next couple of days this system has potential to bring high rainfall totals and possible flash flooding potential across coastal and inland eastern Texas (from the longitude of Matagorda Bay eastward)... Louisiana... southwestern Mississippi... and southern Arkansas... with rainfall totals notably lower on the west side of the circulation due to the shearing upper-level winds keeping the storngest thunderstorms toward the east. Should tropical cyclone formation in fact occur within the next 24 hours... gusty winds and coastal surf are possible along much of coastal Texas as the core area of the circulation tracks generally parallel to the coastline. The combination of southerly flow on the southeast side of the surface circulation and upper-level southwesterlies ahead of the upper trough will produce directional wind shear favoring severe thunderstorms and possible tornadoes... which will be an additional impact to consider for southeast Texas and southwestern Louisiana.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jul 25)... 50% chance of tropical cyclone formation (vicinity of Matagorda Bay Texas near 28.5N-96.2W)
IOH 48 Hr Outlook (1800Z Jul 26)... 0% chance of tropical cyclone formation (inland and west of the northern part of the Texas/Louisiana border near 32N-95W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT**************************
Not in the official outlook
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Jul 24) CMC Model Run...
**For area of interest #12... surface low briefly defined offshore of far southern Texas in 36 hours after which time makes landfall as a surface trough covering Matagorda and Galveston Bay Texas by 42 hours... surface trough dissipates shortly thereafter
0000Z (Jul 24) ECMWF Model Run...
**For area of interest #12... no development shown
**Tropical wave emerges from western Africa at approximately 66 hours... evolves into a tropical low while approaching the northern Lesser Antilles by 168 hours
1200Z (Jul 24) GFS Model Run...
**For area of interest #12... no development shown
**Frontal low currently over the Great Lakes region of North America drives a surface cold front into the northwest Atlantic in 66+ hours... part of the associated upper trough evolves into a cut-off upper vortex whose eastern divergence zone triggers a surface frontal low with possible tropical characteristics northwest of Bermuda and near 35N-67.5W at 93 hours... continues north into waters offshore of Massachusetts (near 40.5N-68W) through 120 hours after which time cooler waters and lack of upper divergence causes it to weaken to a dissipating remnant low just offshore of southwestern Nova Scotia through 135 hours
0600Z (Jul 24) NAVGEM Model Run...
**For area of interest #12... evolves into tropical low over coastal Texas centered just east of Matagorda Bay at 30 hours... continues north-northeast into the Texas/Arkanas border through 60 hours while weakening to a remnant surface trough... remnant trough then continues north across central US while gradually losing identity ahead of large frontal system approaching from western North America
Comments