MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #39

*******Note that forecasts 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.*********

...THURSDAY JULY 17 2025 11:45 PM EDT...

Thursday July 17 marked the forty-sixth official day of the 2025 Atlantic Hurricane Season (which starts June 1 every year)... here is the current situation regarding tropical activity across the Atlantic basin:

For the mid-latitudes of the Atlantic basin:

(1) See area of interest #9 section below for an update on the tropical low that has been hanging around the United States Gulf coast after it previously tracked west across north Florida... this is the final update as the tropical low will soon turn north further inland thus ending its potential for tropical devleopment.

(2) Locked into a repeating pattern where another tropical disturbance could emerge for the United States Gulf coast in 5+ days as follows... the current east Canada upper vortex is expected to become displaced southeast into the northwest Atlantic by a warm core upper ridge that builds over western Canada (in the warm surface southerly flow ahead of a surface frontal system that develops over western Canada). The end result is the tail end of the lengthy United States surface cold front originally generated in the divergence zone ahead of the upper vortex becomes pushed into a position along the United States southeast coast by day 3... then retrogrades southwest toward the United States Gulf coast by 5+ days while pushed around by a building surface ridge produced by the western convergence zone of the upper trough/ vortex shifting into the northwest Atlantic. During this process the tail end of the surface front is likely to be downgraded to a surface trough as it loses airmass contrasts on either side of it while sliding underneath the midst of the persisting warm air mass upper ridge over the southeastern United States... then the surface trough of low pressure possibly becomes a tropical disturbance in the vicinity of the United States Gulf coast as the warm air mass upper ridge provides potential for low shear and upper anticyclonic outflow. Although none of the models explicitly call for tropical development... another tropical area of interest may need to be declared for the United States Gulf coastal region in future updates.

For the tropical latitudes of the Atlantic basin... surges of dry Saharan air continue suppress tropical activity from Africa to the central Caribbean. Upper vorticity across the Caribbean and Bay of Campeche is capping upper outflow potential needed for tropical activity in those regions.

AREA OF INTEREST #9... Since my previous update Wednesday morning... the original center of the tropical surface low that was over the Florida panhandle continued west along the Gulf coast of Alabama and Mississippi without re-generating into the offshore thunderstorms southwest of the center. In recent hours the center of the tropical low arrived into southeastern Louisiana from the Mississippi coast and the sheared-off thunderstorms southwest of center have overspread Louisiana. During the previous 36 hours heavy rainfall never became widespread over southern Mississippi... southern Alabama... or western Florida panhandle despite the west track of the tropical low taking it toward the core of the southeastern United States upper anticyclonic ridge where shear levels would be lower... albeit there was some increase in scattered activity thunderstorm activity over those locations during tonight's sunset which has since fizzled out. During some recent 200 mb layer upper wind analyses (the layer which is published in each of my birdseye view charts)... wind vectors on the southeast side of the upper anticyclonic ridge were convergent which may have contributed to sinking drier air limiting thunderstorms in the northeast half of the circulation... or perhaps northeasterly shear simply remains prominent in the environment of the tropical low but at a different layer. Noting this upper convergence has also helped increased surface pressures to the east of the tropical low... hence helping the west nose of the Atlantic surface ridge expand west... as such the west expansion of the surface ridge has probably aided the tropical low in continuing west instead of north in its recent history. Eventually tropical low is expected to turn north while attracted toward the surface low pressure field of the surface front to the north... and it is also expected to lose identity to the front. Based on the current radar and satellite presentation and this future outlook... heavy rainfall with flash flooding risk is probable for much of Louisiana in the short-term (instead just the southeast part of the state as I stated in my previous update)... then the remnant tropical moisture is dispersed across the southeastern United States by the surface front which could contribute to thunderstorms with flash flooding risk... as such longer-term flash flooding risk across the southeastern United States would be the fault of the front instead of this tropical low as the tropical low is expected to be non-existent after 24 hours.

Odds of tropical cyclone formation have dropped to 0% as the tropical low now tracks further inland going forward... and this is my final statement on this area of interest on this blog.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (0000Z Jul 19)... 0% chance of tropical cyclone formation (northern portion of Louisiana/ Mississippi border near 32.5N-91W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT***********************

Formation chance through 48 hours... 0%

Formation chance through 7 days... 0%

...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).

1200Z (Jul 17) CMC Model Run...

**For area of interest #9... through 42 hours the surface low currently over southeast Louisiana turns northwest into west-central Arkansas while weakening to an east-west oriented surface trough... loses identity to surface front to the north shortly thereafter

1200Z (Jul 17) ECMWF Model Run...

**For area of interest #9... through 30 hours the surface low currently over southeast Louisiana turns northwest into southwest Arkansas while weakening to an east-west oriented surface trough... loses identity to surface front to the north shortly thereafter

1800Z (Jul 17) GFS Model Run...

**For area of interest #9... surface low currently over southeast Louisiana loses identity rapidly

1800Z (Jul 17) NAVGEM Model Run...

**For area of interest #9... surface low currently over southeast Louisiana turns north-northwest into northeast Louisiana through 24 hours... dissipates shortly thereafter