MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #3

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

...WEDNESDAY MAY 7 2025 11:20 AM EDT...

Continuing daily posts on the Atlantic tropics... before the official start of the Atlantic Hurricane Season in June... as a deep-layer cyclone that may acquire tropical characteristics is expected to materializes in the Azores and Canary Islands region of the northeastern Atlantic in the days ahead... see area of interest #2 section below for details.

See the introduction section of previous post #2 (https://www.infohurricanes.com/post/my-2025-atlantic-hurricane-season-birdseye-view-post-2) for information on the origins of the broad surface trough of low pressure that has been southeast of Bermuda over the last several days. Since then the deep-layer northwest Atlantic ridge has pushed the surface trough into the waters well south of Bermuda. The previous NW/SE tilted upper trough that aided the surface trough continued on to the east and has dissipated... however another NW/SE tilted upper trough... delivered by the upper vortex that has recently been kicked into the New York/Canada border from the eastern US... is enhancing the surface trough with its eastern divergence zone with an additional bonus of less westerly shear due to the tilt configuration of the upper trough. Under this enhancement the surface trough has strengthened into a tropical low with bands of thunderstorms on its northeast side (the lack of divergence below and west of the upper trough axis is why the rest of the tropical low does not feature thunderstorm bands). Currently not upgrading this tropical low to a tropical area of interest as it does not have a tightly defined center on true-color visible satellite animation and the models agree on weakening the tropical low in the next 24 hours while the NW/SE tilted upper trough continues east... allowing its suppressive western convergence zone to overtop the tropical low. In the longer range what remains of the tropical low curves increasingly north into the waters just southwest of Bermuda while it continues to round the passing northwest Atlantic deep-layer ridge... and less favorable westerly shear gradually increases as the current SW/NE tilted upper trough from eastern Canada nears. Even if there is a delay in the shear increase... the track takes the tropical low over waters below 26 deg C where it is difficult for a tropical low to develop (and there will be no cool pocket of upper air to help increase the instability).

For the Gulf of America... a sprawling cut-off upper vortex will be settling into the south-central US. The southeastern divergence zone of the incoming upper vortex is already producing strong thunderstorms and heavy rainfall with flash flooding potential for the US Gulf coastal region from Louisiana to the western Florida panhandle. Over the next few days this upper divergence pattern could produce a broad surface low over the Gulf of America which then moves into the southern US from the US Gulf coast while it whirls into the core of the quasi-stationary upper vortex. At this time tropical development of the broad surface low appears unlikely as the upper vortex will be parked too far north (too far inland) to sufficiently relax the westerly shear over the Gulf... regardless this means ongoing periods of heavy rain over already-saturated ground (from southeastern Louisiana to the western Florida panhandle) and flash flooding will be the primary concern for a few more days.

AREA OF INTEREST #2... The upper trough that was between Canada and Greenland is now in the far North Atlantic waters southeast of Greenland. The south part of this upper trough is being forced southeast into the western Azores as a cut-off upper vortex due to the amplified northwest Atlantic deep-layer ridge. A divergence zone on the northeast side of the upper vortex triggered a new frontal low just north of the Azores over the last several hours... but the main feature of interest is an additional frontal low/ cyclone forming directly over the western Azores in the southeastern divergence zone of the upper vortex as seen in the latest satellite pictures. Over the next 24 hours the developing surface cyclone over the western Azores will whirl beneath the core of the southeast-diving upper vortex to make a deep-layer cyclone. Note the developing deep-layer cyclone is already forcing the previous deep-layer vorticity that was south of the Azores eastward toward the Iberian peninsula... and during much of the forecast period the deep-layer cyclone will pivot east-southeast toward the Canary Islands while pulled around the southwest side of the remainder Iberian-area deep-layer vorticity. Despite mild water temperatures in the region... the deep-layer cyclone may try to acquire tropical characteristics due to potentially de-stabilizing cold temperatures of the upper vortex. Assigning peak odds of subtropical cyclone formation to 48 hours when the system is passing over its warmest waters along the forecast track (19 deg C). My peak odds are not higher than 20% as of this writing as would have preferred waters of at least 20 deg C for more confidence in a tropical event. Begin trimming odds down from the peak after 48 hours as the surface layer of the deep-layer cyclone will be weakening due to a lack of divergence at the core of the upper vortex... especially if it hasn't gained tropical characteristics (t-storm induced warm core upper outflow layer that helps to lower surface pressures) by then.

Regardless of acquiring tropical characteristics or not... the following impacts to land areas are expected:

(1) Gusty winds will soon be in progress over the western Azores... if not already... due to the quickly-forming deep-layer cyclone overhead. Coastal surf and periods of rainfall are also possible later today for all of the Azores.

(2) Coastal surf continues for the Azores beyond today and spreads east to the Canary Islands through Friday. Given that the surface layer of the cyclone is most likely to weaken (unless it acquires tropical characteristics)... the Canary Islands see relaxing coastal surf with periods of rainfall as the weakening surface circulation moves in from the west by the weekend.

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

IOH 24 Hr Outlook (1200Z May 8)... 15% chance of subtropical cyclone formation (south of the Azores near 35N-29W)

IOH 48 Hr Outlook (1200Z May 9)... 20% chance of subtropical cyclone formation (west of the Canary Islands near 33N-23W)

IOH 72 Hr Outlook (1200Z May 10)... 10% chance of subtropical cyclone formation (just west of the Canary Islands near 33N-21W)

IOH 96 Hr Outlook (1200Z May 11)... 0% chance of subtropical cyclone formation (just east of the Canary Islands near 33N-14W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM 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 (May 7) CMC Model Run...

**For area of interest #2... well-defined surface low develops just south of the western Azores at 24 hours... moves east-southeast toward the Canary Islands through 90 hours while gradually weakening.

**For surface low well south of Bermuda... gradually weakens and dissipates southwest of the island by 66 hours

0000Z (May 7) ECMWF Model Run...

**For area of interest #2... well-defined surface low develops just south of the western Azores at 24 hours but remains a little oblong east-west at its formation... through 42 hours while moving southeast assumes a more circular structure... through 102 hours moves east-southeast into the Canary Islands while gradually weakening.

**For surface low well south of Bermuda... gradually dissipates northeast of the Bahamas through 78 hours

**Divergence zone of upper vorticity currently over the central US produces a broad central Gulf of America surface low by 108 hours... broad surface low advances north into the US Gulf coast in vicinity of the Mississippi/ Alabama... Louisiana coast through 132 hours

0600Z (May 7) GFS Model Run...

**For area of interest #2... well-defined surface low develops just south of the western Azores at 24 hours... through 87 hours moves east-southeast into the Canary Islands while gradually weakening.

**For surface low well south of Bermuda... dissipates southwest of the islands through 72 hours

**Divergence zone of upper vorticity currently over the central US produces a broad central Gulf of America surface low by 72 hours... potentially develops a better-defined center while moving into the Alabama and far western Florida panhandle coastal region by 96 hours... the surface low then whirls northwest into the core of the upper vorticity... over Arkansas by 123 hours... while decaying due to a lack of divergence under the core region of the upper vorticity.

0600Z (May 7) NAVGEM Model Run...

**For area of interest #2... well-defined surface low develops just south of the western Azores at 18 hours... through 90 hours moves east-southeast into the Canary Islands while gradually weakening.

**For surface low well south of Bermuda... gradually dissipates northeast of the Bahamas through 66 hours