MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #48

*******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.*********

...TUESDAY JULY 29 2025 4:47 PM EDT...

For the mid-latitudes of the Atlantic basin... on the lookout for possible development in the waters offshore of the southeastern United States or in the open northwestern Atlantic. The surface front currently being induced by the southeast divergence zone of the central Canadian upper trough is expected to shift southeast into offshore waters as the upper trough itself shifts southeast. Then the Canadian upper trough leaves behind its tail over the Great Lakes and northeastern US whose southeastern divergence zone maintains the tail end of the surface front at a position offshore of the southeastern US and open northwestern Atlantic. Several days out... the tail upper-level energy merges with surrounding upper troughs to make an eastern North America upper trough regime. The precise position and configuration of the upper trough regime will have an effect on the amount of wind shear over the decaying tail end surface front/ trough and thus an effect on tropical development potential... and those details which are still multiple days out are difficult to accurately forecast. Therefore not currently declaring a new tropical area of interest for the waters offshore of the southeastern US nor open northwestern Atlantic... may do so in future updates if model data or future satellite observations warrant.

For the tropical latitudes of the Atlantic basin:

(1) Thunderstorm activity has increased in association with tropical waves of low pressure at 41W and 25W longitude... the two waves are forecast to merge then migrate toward the Lesser Antilles islands over the next five days and monitoring for possible tropical development... see area of interest #12 section below for more details.

(2) The western Atlantic mid-level low pressure disturbance due north of the northeastern Caribbean Islands has been upgraded to a weak surface low. Despite the neighboring northwestern Caribbean upper vorticity to the west shifting away... the satellite presentation continues to be one of a sheared disturbance where thunderstorms are displaced east of the low-level cloud swirl. Therefore this is likely the early rumblings of northerly shear to be induced by a pair of shortwave upper troughs sliding south toward this disturbance under the force of the ongoing southeastern US upper ridge... and tropical development of this disturbance is not expected.

AREA OF INTEREST #12... Thunderstorm activity associated with a surface tropical wave of low pressure in the open central Atlantic has increased since 0000Z last evening and under an improving upper outflow pattern that has developed in the wake of eastern Atlantic upper vorticity that retreated north and away. As of 1200Z the NHC TAFB surface analysis had the wave axis at 41W longitude... however visible satellite animation and CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) has the rotation maximum southeast of the strongest thunderstorms and toward 9N-39W... and that is the initial position I have selected for this new area of interest in this update cycle. This will mark the twelfth tropical Atlantic area of interest I have tracked on this site this year.

The models are in fairly good agreement regarding the future evolution of this area of interest as it interacts with an additional tropical wave to the east... the current eastern Atlantic surface ridge... and current central Canada upper trough and southeastern US upper ridge. Noting the additional wave to the east (analyzed at 25W longitude as of 1200Z earlier today) has seen a steady increase in thunderstorms since 0600Z also due to the improving upper outflow regime... however I have not declared it another area of interest nor used it as the initial position of this area of interest as the models agree that through 48 hours that this eastern wave vaults west-northwest in the flow around this area of interest and closer to the unfavorable dry Saharan air mass... after which time it then merges with this area of interest from the northeast. Noting during the merger this area of interest is forecast to drift only slowly northwest due to the tug of the incoming eastern wave dampening the steering effect of the eastern Atlantic surface ridge. In the longer range current central Canada upper trough ushers in an eastern North America upper trough regime... with southwesterly flow ahead of the upper trough regime's surface front spreading warm air associated warm core southeastern US upper ridge across the mid-latitudes of the Atlantic. In turn the southeastern convergence zone of the mid-latitude Atlantic upper ridge expands the eastern Atlantic surface ridge westward... with the models showing the merged surface tropical wave moving briskly west-northwest under the influence of the expanded surface ridge. The mid-latitude Atlantic upper ridge could also be a detriment to the long-term future of this area of interest as it fuses together current pockets of suppressing mid-latitude upper vorticity... then pushes the upper vorticity south toward this area of interest and also southwest toward the Caribbean where the long-term destination of this area of interest is likely to be.

My long-term track forecast is a little slower than the model consensus as the models do not develop the merged wave... perhaps as the models see dry Saharan air getting mixed in during the merger or have the merged wave positioned closer to the disruptive long-term upper vorticity descending from the north. With current observations of increased thunderstorms as well as increased spin near 9N-39W I see some development risk which is different than the current model consensus of a non-developing low-amplitude surface wave that flows more easily (faster) around the steering surface ridge. I initially ramp up odds of tropical cyclone formation to a low 20% as short-term development may be deterred by the broadening nature of this area of interest as the two surface waves merge... and broad systems often struggle to have a well-defined low pressure center needed for focused thunderstorms and tropical development. I then cap longer-term development odds at 20% due to the shaky long-term upper wind outlook. Regarding impact to land areas... noting this area of interest may bring periods of heavy rain to the Lesser Antilles islands this weekend.

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

IOH 24 Hr Outlook (1800Z Jul 30)... 10% chance of tropical cyclone formation (central tropical Atlantic near 10N-40.5W)

IOH 48 Hr Outlook (1800Z Jul 31)... 20% chance of tropical cyclone formation (central tropical Atlantic near 11N-42W)

IOH 72 Hr Outlook (1800Z Aug 1)... 20% chance of tropical cyclone formation (central tropical Atlantic near 11.5N-47.5W)

IOH 96 Hr Outlook (1800Z Aug 2)... 20% chance of tropical cyclone formation (central tropical Atlantic near 12N-53W)

IOH 120 Hr Outlook (1800Z Aug 3)... 20% chance of tropical cyclone formation (Lesser Antilles near

*****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 29) CMC Model Run...

**For area of interest #12... tropical wave/low currently near 41W longitude slowly drifts northwest through 54 hours while merging with additional wave to the east... the merged wave then proceeds briskly west-northwest and reaches the northeastern Caribbean Islands by 102 hours then central Bahamas by 150 hours... the wave turns northwest into the northwestern Bahamas by 168 hours while gravitated toward a surface trough (decaying surface front) offshore of the southeastern US

0000Z (Jul 29) ECWMF Model Run...

**For area of interest #12... tropical wave/low currently near 41W longitude slowly drifts northwest through 54 hours while merging with additional wave to the east... the merged wave then proceeds briskly west-northwest and reaches the northeastern Caribbean Islands by 108 hours then central Bahamas by 162 hours

1200Z (Jul 29) GFS Model Run...

**For area of interest #12... tropical wave/low currently near 41W longitude slowly drifts northwest through 54 hours while merging with additional wave to the east... the merged wave then proceeds briskly west-northwest and reaches the northeastern Caribbean Islands by 114 hours... then Hispaniola (Haiti and the Dominican Republic) by 129 hours... then across Cuba thereafter and enters the southeastern Gulf of America by 168 hours.

**Current SW/NE tilted central Canada upper trough reaches eastern Canada through 81 hours with the surface front produced by its southeastern divergence zone draped across the northwestern Atlantic by that time... the majority of the eastern Canada upper trough and a couple of elongated frontal lows it produces continue towards the open north Atlantic through 108 hours however the tail end of the front persists offshore of the southeastern US due to the southeastern divergence zone of a band of upper vorticity over the Great Lakes and NE US left behind by the upper trough... between 108 and 126 hours the Great Lakes/ NE US upper vorticity band merges with incoming upper troughs from the central US and central Canada to make a broad eastern North America upper trough... the southwesterly jet ahead of the eastern North America upper trough contributes to enhancing the poleward outflow of a 126-hour surface low with tropical characteristics which forms along the decaying tail end of the surface front near 35N-64W... through 168 hours the possibly tropical low weakens while moving northeast into cooler waters along 40N latitude due south of Newfoundland and into southwesterly shear and becomes increasingly absorbed by elongated non-tropical frontal low developing to the west under the supportive divergent southwesterly upper jet.

1200Z (Jul 29) NAVGEM Model Run...

**For area of interest #12... tropical wave/low currently near 41W longitude slowly drifts northwest through 54 hours while merging with additional wave to the east... the merged wave then proceeds briskly west-northwest without development