MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #40

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

...SATURDAY JULY 19 2025 7:20 PM EDT...

Forty-eight days into the Atlantic Hurricane Season... the Atlantic tropics are becoming busier with two new areas of interest to watch for possible tropical development in the days ahead:

(1) See area of interest #10 section below for information on a tropical wave in the open tropical belt of the Atlantic that the National Hurricane Center is mentioning in their tropical weather outlook.

(2) See area of interest #11 section below for information on a surface front expected to sag south into the northeastern Gulf of America by day 5... where it could become a focal point for tropical development. Any disturbance that develops is expected to turn west in the general direction of southern Louisiana.

AREA OF INTEREST #10... Formation of this area of interest... a typical summertime surface tropical wave of low pressure of African origin emerged into the eastern tropical Atlantic on July 15 featuring limited thunderstorm activity while embedded in a dry Saharan air surge... and by Thursday July 17 was completely void of thunderstorm activity. However by late on the 17th through today... various runs of the CMC... GFS... and ECWMF models suggested the wave may develop in the open central Atlantic before later weakening as it approached the Lesser Antilles islands. The National Hurricane Center introduced this wave as an area of interest in their tropical weather outlook beginning 8 PM EDT Friday July 18... and this will mark the tenth tropical Atlantic area of interest tracked on this site this year. Over the last 36 hours indeed the tropical wave has seen an increase in thunderstorms... currently in the vicinity of 10N-36W... as overhead upper winds switched to a mode aiding this tropical wave as follows:

(1) From July 8 to 9 a typical north Atlantic upper trough became a trans-Atlantic cut-off upper vorticity string due to amplification of northwest Atlantic warm core upper ridging supported by warm air being fanned northeast into the area by a series of eastern North America frontal lows.

(2) From July 9 to 13 the eastern half of the trans-Atlantic upper vorticity string was pushed east toward northwest Africa by the next north Atlantic upper trough that moved across the north Atlantic which also contained the remnant frontal low of former tropical cyclone Chantal. Then an additional north Atlantic upper trough by July 14 was producing a frontal cyclone north of the Azores which by July 17 moves into the waters just west of the British Isles... northward warm air transport ahead of this frontal cyclone produced enough warm core upper ridging that finally pushed the east end of the trans-Atlantic upper vorticity string further east across north Africa. From July 17 through today the north Africa upper vorticity combined with the northeast Atlantic upper trough associated with cool air behind the British Isles front to weaken the east end of the tropical Atlantic upper ridge... which has resulted in an inverted upper trough on the south side of the weakened part of the tropical upper ridge and in the vicinity the Republic of Cabo Verde Islands and the waters just to the east.

(3) From July 9 through today the west end of the trans-Atlantic upper vorticity string has been hanging around the western Atlantic... Caribbean... and the Gulf while pinned by the now-persistent southeast US anticyclonic upper ridge that materialized since July 13

(4) The surface tropical wave is now taking advantage of divergent upper anticyclonic flow established in relatively higher upper air pressures between the inverted upper trough to the east and western Atlantic/ Caribbean upper vorticity to the west... which has helped it produce increasing thunderstorm activity in the last 36 hours.

Forecast track in the outlook below is generally based on the typical 5W longitude per day pace seen with tropical waves that are pushed by an Atlantic subtropical surface ridge... which the models are in good agreement with. By looking at the upper wind pattern in the 5-day forecast period it is apparent why the models weaken the wave as it approaches the Lesser Antilles. A north Atlantic warming event and associated warm core upper ridge becomes established through day 3 due to northward warm air transport ahead of a frontal cyclone that will be produced in the vicinity of Atlantic Canada... the force of the north Atlantic upper ridge will push the current northeast and northwest Atlantic upper vorticity bands south toward the tropical wave which will increasingly resist the northern outflow of the tropical wave. Then from days 3 to 5 the ongoing southeastern US anticyclonic upper ridge is expanded by northward warm air transport ahead of a frontal system ejecting from western Canada... this freshly expanded upper ridge will help push a portion of the consolidated upper vorticity band just north of the tropical wave southwestward toward the Lesser Antilles and closer to the tropical wave... resulting in increasing westerly shear over the tropical wave and suppressed upper outflow directly below the upper vorticity as the wave moves into the Lesser Antilles. In the long range beyond day 5... it doesn't appear the tropical wave has a chance to develop in the Caribbean as what is the current west Atlantic/ Caribbean upper vorticity is still forecast to be present in the region. I have kept my odds of tropical cyclone formation at 10%... and slightly below the NHC outlook's peak odds... due to the increasingly unfavorable upper winds during the 5-day forecast period and potential for the wave to ingest the dry Saharan air lurking to the north. The potential for notable impacts to the Lesser Antilles islands around day 5 appears low as the batch of the upper vorticity nearing the islands from the northeast will have its southeastern divergence zone east of the islands rather than over the islands... thus the tropical wave is likely to lose thunderstorms as it exits the divergence zone and nears the islands... and on the home page bulletins of this site I have not mentioned the Lesser Antilles in regards to this area of interest.

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

IOH 24 Hr Outlook (1800Z Jul 20)... 10% chance of tropical cyclone formation (central tropical Atlantic near 11N-40W)

IOH 48 Hr Outlook (1800Z Jul 21)... 10% chance of tropical cyclone formation (central tropical Atlantic near 11.5N-45W)

IOH 72 Hr Outlook (1800Z Jul 22)... 10% chance of tropical cyclone formation (central tropical Atlantic near 12N-50W)

IOH 96 Hr Outlook (1800Z Jul 23)... 5% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-55W)

IOH 120 Hr Outlook (1800Z Jul 24)... 0% chance of tropical cyclone formation (Lesser Antilles near 13N-61W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***********************

Formation chance through 48 hours... 10%

Formation chance through 7 days... 20%

AREA OF INTEREST #11... After the previous northern Gulf of America disturbance from July 15 to 17... another northern Gulf disturbance looks to be in the cards by day 5 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 southeast US coast by days 2 and 3... then retrogrades southwest into the northeastern Gulf of America by day 5 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 northern Gulf as the warm air mass upper ridge provides potential for low shear and upper anticyclonic outflow. The northwest Atlantic upper trough is currently forecast to leave behind a larger upper vortex that moves toward the open central Atlantic... and more crucially for this area of interest a smaller upper vortex offshore of the southeast US which proceeds to retrograde southwest around the southeast US warm air mass upper ridge and toward the day-5 position of this area of interest while weakening to an inverted upper trough from prolonged isolation from high-latitude cold air. If the current forecast holds... the approaching inverted upper trough could produce unfavorable northeasterly shear over this area of interest... however the west side of the inverted upper trough will also produce upper divergence aiding in thunderstorm generation. I currently have low 10% odds of tropical cyclone formation for the northern Gulf... in the 5+ day window... due to the disruptive effects of northeasterly wind shear and possible upper outflow suppression should the incoming inverted upper trough axis take longer to dissipate and instead overtops the central position of this area of interest.

The long term track of this area of interest... in the 5+ day window... appears to be generally west across the northern Gulf and toward the Louisiana and southeast Texas coast due to another surface ridge that builds to the north of this area of interest... under the western convergence zone of an upper trough that eventually ejects from western Canada. On the home page bulletins of this site currently only mentioning southern Louisiana being in the heavy rainfall/ flooding risk zone for the late part of this upcoming week as southeast Texas is currently well outside the 5-day forecast window when forecast track errors tend to be large... for instance if the best-defined low pressure center materializes further north the track around the southwest side of the steering surface ridge would make for a landfall into southern Louisiana... a further south development of the best-defined center would result in an arc into southeastern Texas which would still put southern Louisiana in the heavy rainfall zone... this early out its hard to know where the best-defined center would materialize if it happens at all but all scenarios looks to include southern Louisiana and so confidence is higher there for heavy rainfall. 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 (1800Z Jul 20)... 0% chance of tropical cyclone formation (eastern North Carolina near 35.5N-78W)

IOH 48 Hr Outlook (1800Z Jul 21)... 0% chance of tropical cyclone formation (coastal Carolinas near 33.9N-78.8W)

IOH 72 Hr Outlook (1800Z Jul 22)... 0% chance of tropical cyclone formation (coastal southeastern United States in vicinity of Georgia/ South Carolina border near 32N-81W)

IOH 96 Hr Outlook (1800Z Jul 23)... 0% chance of tropical cyclone formation (northwest coast of Florida peninsula near 29N-82.8W)

IOH 120 Hr Outlook (1800Z Jul 24)... 10% chance of tropical cyclone formation (northeast Gulf of America near 28.5N-85.5W)

*****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/).

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

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

**For area of interest #11... no development shown

0000Z (Jul 19) ECMWF Model Run...

**For area of interest #10... tropical wave evolves into tropical low near 11N-39W by 36 hours... becomes a tropical depression near 13N-44W at 60 hours then compact tropical storm near 13N-46.5W at 78 hours... weakens back to a tropical depression near 14.5N-56W at 114 hours and then a remnant low shortly thereafter... the remnant low weakens further to a tropical wave while crossing the Lesser Antilles at 138 hours with the remnant wave not redeveloping thereafter

**For area of interest #11... surface front currently over the eastern US is pushed south into the waters offshore of the southeastern US and Gulf Florida panhandle coast through 102 hours by expanding surface ridge to the north... the west part of the decaying surface front becomes a possible tropical low in the eastern Gulf of America just west of Tampa Bay Florida by 126 hours... the weak tropical low continues west across the northern Gulf and reaches the waters south of southwestern Louisiana by 168 hours

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

**For area of interest #10... tropical wave evolves into very compact tropical low near 10.5N-39.5W by 24 hours... after continuing west-northwest the compact tropical low opens back to a wave near 16N-49W by 81 hours... the wave does not develop thereafter

**For area of interest #11... surface front currently over the eastern US is pushed south into the waters offshore of the southeastern US and over the eastern Gulf of America through 86 hours by expanding surface ridge to the north... the northwest Atlantic upper trough whose western convergence zone is producing the expanding surface ridge leaves behind a small upper vortex which then retrogrades southwest into the Florida peninsula as an inverted upper trough by 123 hours... divergence on the west side of the inverted upper trough transitions the tail end of the decaying surface front into a WSW/ENE tilted surface trough covering the central and eastern Gulf of America also by 123 hours... the surface trough evolves into an WSW/ENE northern Gulf oblong tropical low positioned due south of southeastern Louisiana by 138 hours... the inverted upper trough trying to overtop the tropical low from the east finally dissipates from its prolonged isolation from high-latitude cold air which allows for an increase in upper anticyclonic outflow over the tropical low and it begins to consolidate into a tropical cyclone while moving west-northwest into the waters just offshore of southwest Louisiana by 168 hours

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

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

**For area of interest #11... no development shown