MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #41

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

...MONDAY JULY 21 2025 4:39 PM EDT...

For the tropical latitudes of the Atlantic basin... watching a tropical wave of low pressure in the open central Atlantic for signs of short-term development and before it crosses the southern Lesser Antilles islands in 48 hours... the potential for development ends when the wave reaches the southern islands due to increasingly unfavorable upper winds... see area of interest #10 section below for details. To the east of this wave... additional well-defined tropical waves of low pressure are at 30W longitude and west coast of Africa as of this writing... with the one at 30W recently succumbing to dry Saharan air. Meanwhile the wave currently departing the west coast of Africa is seeing squalls of thunderstorms aided by anticyclonic outflow at the west end of an north Africa upper ridge. Assuming the wave does not ingest too much dry Saharan air... it may have a chance to become a tropical area of interest as the band of upper vorticity that will negatively affect area of interest #10 begins to shift northwest and away while gravitating toward the upper trough currently entering the northwest Atlantic. Because none of the models currently develop this wave... waiting to see how the wave first negotiates the dry Saharan air and thus not upgrading it to an area of interest in this update.

For the mid-latitudes of the Atlantic basin... a pre-frontal surface trough of low pressure offshore of the southeastern United States is expected to turn west-southwest across north Florida then the northeastern Gulf of America. Will watch this feature for signs of development thru Friday after which time landfall with the central US Gulf coast should end its tropical development potential... see area of interest #11 section below for details.

AREA OF INTEREST #10... Continuing to monitor a surface tropical wave of low pressure moving west across the open central tropical Atlantic for signs of development. Through much of the weekend the tropical wave struggled to maintain organized thunderstorm activity likely due to ingestion of the dry Saharan air lurking just to the north... and the NHC drop their odds of tropical cyclone formation to 10%. Then by late Sunday through early today the NHC odds were re-increased to 20% as the wave developed a better-defined low pressure center and increased thunderstorms. However during the daylight hours of today the thunderstorm activity of the wave is once again on the wane.

For my updated outlook below... the track forecast is faster to the west given the recent history of the wave's faster forward speed. Regarding odds of tropical cyclone formation... I have kept them at a low 10% as the wave continues to struggle with the nearby dry Saharan air mass. As the wave approaches the Lesser Antilles islands... upper winds will become increasingly hostile for development as warm core upper ridging gains intensity in the north Atlantic due to the northward warm air transport ahead of the currently developing Atlantic Canada frontal cyclone. The force of the north Atlantic upper ridge will fuse the upper vorticity bands along 30N and 20N latitude together... then send the merged upper vorticity band south toward the tropical wave. The approaching band will increasingly resist the northern outflow of the tropical wave... then eventually increase the westerly vertical shear. The shear is worsened by the ongoing southeast US warm core upper ridge which will expand due to northward warm air transport ahead of a frontal system ejecting from western Canada... as the southeast US upper ridge will push the tail end of the upper vorticity band southwest toward the northern Lesser Antilles and even closer to this tropical wave. As such I drop odds of tropical cyclone formation to 0% as the wave crosses the southern islands in 48 hours. Because of the faster forward track that brings the wave into the southern Lesser Antilles sooner... there is a higher chance of the wave crossing the southern islands before the worst of the westerly shear associated with the northern islands upper vorticity arrives... thus a higher chance thunderstorms and associated heavy rainfall still being coupled with the wave as it crosses the southern islands on Wednesday. And by 72 hours when the wave is in the eastern Caribbean it may take advantage of relaxed shear and upper outflow in an upper anticyclone present between the northern islands upper vorticity to the northeast... lingering Caribbean upper vorticity to the west... and a band of upper vorticity offshore of the southeast US to the north being separated from the current upper trough entering the northwest Atlantic. However this area of better upper winds does not last long enough for me to raise eastern Caribbean development odds above 0%... as soon after (by 96 hours) the upper vorticity to the northeast... west... and north is fused together and pushed overtop the tropical wave (where it would suppress the wave's upper outflow) by the expansive southeastern US upper ridge.

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

IOH 24 Hr Outlook (1200Z Jul 22)... 10% chance of tropical cyclone formation (east of the southern Lesser Antilles near 11N-55W)

IOH 48 Hr Outlook (1200Z Jul 23)... 0% chance of tropical cyclone formation (southern Lesser Antilles near 12N-61W)

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

Formation chance through 48 hours... 20%

Formation chance through 7 days... 20%

AREA OF INTEREST #11... A southwest-to-northeast pre-frontal surface trough of low pressure is currently present offshore of the southeastern United States... ahead of (south of) the east-west oriented surface front that has been positioned over the eastern United States. The pre-frontal surface trough is well-defined on satellite pictures today with a linear region of thunderstorms... however a look at hovmoller diagrams of the region covering the last couple of days did not show a contiguous area of linear-oriented cloud features or thunderstorms inland over the southeast US that simply migrated offshore (https://www.nhc.noaa.gov/tafb_latest/gehov3latest.gif). It is possible then the pre-frontal surface trough has simply materialized within the last 24 hours... the southwestern part being supported by split flow upper divergence between the west side of the upper vortex near 25N-70W and south side of the ongoing southeast US upper ridge... and the northeast part being supported by upper divergence ahead of the upper trough now advancing into the northwest Atlantic (both upper divergence zones are marked in the above birdseye view chart). The CIMSS 850 mb vorticity product 5-day animation suggested a different story where the faint mid-level remains of the previous July 15 to 17 northern Gulf disturbance took an eastward turn across the southeast US and now into offshore waters (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=)... perhaps then the pre-frontal surface trough is the remains of the previous Gulf disturbance? Regardless... the focus of this area of interest as of today is the southwest end of the pre-frontal surface trough (offshore and east of the Florida/Georgia border region) where a thunderstorm complex appears to have triggered a spin near 31N-76.5W.

Currently forecasting the southwest part of the surface trough to retrograde west-southwest across north Florida and into the northeastern Gulf of America while pushed around by a building surface ridge produced by the western convergence zone of the upper trough currently heading into the northwest Atlantic. Later in the forecast period the steering surface ridge is then re-enforced by the western convergence zone of another upper trough ejecting from western Canada... however a gradual bend/ turn to the north eventually occurs as this disturbance rounds the southwest side of the ridge. Note the updated forecast track in the outlook below is adjusted slightly north due to the initial position of 31N-76.5W... and this is consistent with recent model runs which have also trended north. Under the force of the ongoing southeast US upper ridge... upper vorticity from the tail end of the northwest Atlantic upper trough and upper vortex currently near 25N-70W approach the disturbance from the east... this should keep this disturbance in a split flow upper divergence regime between the west side of the upper vorticity and south side of the southeast US upper ridge which would help promote thunderstorms. However this upper air pattern is also conducive for northeasterly wind shear... and I currently have low 10% odds of tropical cyclone formation due to the potentially disruptive effects of shear.

Regarding impact to land areas... flash flooding heavy rains are possible across northern Florida from late tomorrow thru Thursday... sooner for the northern peninsula and later for the panhandle. The heavy rainfall/ flood risk zone then shifts into southern Louisiana and southern Mississippi for Friday. There is currently a low probability of wind and coastal surf impacts due to low odds of tropical cyclone formation.

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

IOH 24 Hr Outlook (1200Z Jul 22)... 10% chance of tropical cyclone formation (offshore of northeastern Florida near 30.5N-78.5W)

IOH 48 Hr Outlook (1200Z Jul 23)... 10% chance of tropical cyclone formation (just inland from the northwest coast of the Florida peninsula near 29.5N-82.8W)

IOH 72 Hr Outlook (1200Z Jul 24)... 10% chance of tropical cyclone formation (just offshore of the central Florida panhandle near 29N-86W)

IOH 96 Hr Outlook (1200Z Jul 25)... 0% chance of tropical cyclone formation (United States Gulf coast in vicinity of the Louisiana/ Mississippi border near 30.2N-89.8W)

*****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 21) CMC Model Run...

**For area of interest #10... develops into a compact tropical low near 14N-53W at 42 hours... the weak tropical low crosses the northern Lesser Antilles by 72 hours then opens to a wave shortly thereafter... the remnant wave does not redevelop in the long range

**For area of interest #11... pre-frontal surface trough offshore of southeastern US gets pushed west-southwest across north Florida and into the northeastern Gulf of America through 72 hours by expanding surface ridge to the north... surface trough turns west to west-northwest in track and makes landfall near the Louisiana/ Mississippi border at 96 hours without developing beforehand

0000Z (Jul 21) ECMWF Model Run...

**For area of interest #10... no development shown

**For area of interest #11... pre-frontal surface trough offshore of southeastern US gets pushed west-southwest across north Florida and into the northeastern Gulf of America waters just offshore of the panhandle through 60 hours by expanding surface ridge to the north... surface trough turns west in track and makes landfall over southeastern Louisiana at 102 hours without developing beforehand

0600Z (Jul 21) GFS Model Run...

**For area of interest #10... no development shown

**For area of interest #11... pre-frontal surface trough offshore of southeastern US turns west into southern Georgia through 39 hours while developing further into a broad surface low... the surface low proceeds to turn west-southwest onto the eastern US Gulf coast and then into the waters offshore of southeastern Louisiana through 75 hours... shortly thereafter the surface low turns northwest into southeastern Louisiana and dissipates

1200Z (Jul 19) NAVGEM Model Run...

**For area of interest #10... no development shown

**For area of interest #11... pre-frontal surface trough offshore of southeastern US turns west-southwest into the interior section of the Florida/ Georgia border through 42 hours while developing further into a broad surface low... continues west-southwest while weakening to a surface trough and is briefly exposed to north-central Gulf waters before a landfall with southeast Louisiana by 84 hours... shortly thereafter turns north further inland and dissipates