MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #2

*******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 MAY 6 2025 1:30 AM EDT...

Temporarily resuming 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.

Elsewhere... a broad surface trough is currently present southeast of Bermuda and is currently not a tropical area of interest while lacking a well-defined surface low pressure center. The surface trough has been a remarkably persistent feature since mid-April... originating from the decaying tail end of a surface cold front that departed eastern North America and moved across the western and central Atlantic from April 16 to 18. The surface trough was maintained as the base of the upper trough tied to the front became a cut-off upper vortex producing overhead supportive upper divergence beneath its east side... and evolved into a surface low that whirled southwest into the core of the upper vortex (between Puerto Rico and Bermuda) through April 21. Although the surface low dissipated due to a lack of divergence at the core of the upper vortex by April 22... the eastern divergence zone of the upper vortex maintained a surface trough that was always attached to the now-dissipated surface low. Through April 24 the deep-layer ridge that was west of the cut-off upper vortex eroded and de-amplified due to the approach of a broad upper trough from eastern North America... which in turn caused the cut-off upper vortex to de-amplify over the surface trough... and the surface trough became suppressed by an associated increase in westerly shear and less upper divergence. Upper divergence helping the surface trough's existence soon re-increased by April 27 due the arrival of a southern fracture of the broad upper trough that was over eastern North America... but this upper trough fragment was not amplified enough to reduce westerly shear. From April 27 to 29... the upper trough fragment and surface trough merged with another frontal system/ upper trough that surged offshore from Atlantic Canada... but the surface trough maintained its identity from the surface front. From April 30 through the start of May... yet another frontal system and its upper trough surged offshore from Atlantic Canada (this is the same frontal system mentioned at the beginning of the area of interest #2 discussion below)... this latest frontal system ended up absorbing the prior frontal system to the north but the surface trough and nearby supporting upper trough escaped absorption. By Friday May 2 the surface trough developed a short-lived surface low with the help of the supporting upper trough's eastern divergence zone... however the surface trough then weakened as the cool-core upper trough weakened due to prolonged isolation from high-latitude cold air. As of early Monday (May 5) the surface trough then became re-invigorated by a NW/SE tilted upper trough axis that ejected from the current eastern US cut-off upper vortex whose eastern divergence zone increased t-storm squalls northeast of the surface trough axis while also featuring low westerly shear due to the tilt configuration of the upper trough. Watching to see if the surface trough becomes a tropical disturbance somewhere south of Bermuda in next 48 hours as the eastern US cut-off upper vortex delivers another NW/SE titled upper trough axis that arrives toward the surface trough... again not upgrading the surface trough to an area of interest in this update as it lacks a well-defined center. After 48 hours tropical development conditions for the surface trough become hostile as westerly shearing upper winds increase across the western Atlantic with the approach of SW/NE tilted upper trough currently approaching from western North America.

AREA OF INTEREST #2... At the beginning of May a surface frontal cyclone and associated upper trough entered the North Atlantic from Canada. Since then the northwest part of this system merged with another trailing upper trough/ surface frontal system that ejected northeast from the central US... across eastern Canada... and into the waters between Canada and Greenland. The remainder southeastern part of this system became a cut-off upper vortex centered just south of the Azores whose eastern divergence zone triggered a weak surface frontal low... the frontal low has already whirled into the core of the upper vortex to make a deep-layer low. Over the next 48 hours the southern part of the current upper trough between Canada and Greenland is expected to deposit another upper vortex that dives southeast toward the waters south of the Azores... with this feature kicking the current deep-layer low south of the Azores eastward toward the Iberian peninsula of Europe. The eastern divergence zone of the upper vortex is expected to trigger a surface cyclone over the western Azores by 48 hours... with the surface cyclone then whirling beneath the core of the upper vortex to make a deep-layer cyclone. 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. Note the deep-layer cyclone is expected to track southeast to east-southeast while orbiting the southwest side of the deep-layer low expected to be displaced toward the Iberian peninsula. Assigning initially low 10% chance of acquisition of tropical characteristics while the deep-layer cyclone is born over waters at 17 deg C... then raise odds to a peak of 20% by 96 hours when the deep-layer cyclone reaches warmer 19 deg C waters (peak odds are not higher 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 by 120 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) Periods of showers continue for the eastern Azores through tonight due to current deep-layer low centered just south of the Azores.

(2) Increasing gusty winds for the western Azores over the next 48 hours (through Wednesday night) due to quickly-forming deep-layer cyclone overhead. Coastal surf and periods of rainfall throughout all of the Azores as the deep-layer cyclone materializes.

(3) Coastal surf continues for the Azores 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 (1800Z May 6)... 0% chance of subtropical cyclone formation (just northwest of the western Azores near 40N-32W)

IOH 48 Hr Outlook (1800Z May 7)... 10% chance of subtropical cyclone formation (western Azores near 39N-31W)

IOH 72 Hr Outlook (1800Z May 8)... 15% chance of subtropical cyclone formation (south of the Azores near 35N-28.5W)

IOH 96 Hr Outlook (1800Z May 9)... 20% chance of subtropical cyclone formation (west of the Canary Islands near 33N-23W)

IOH 120 Hr Outlook (1800Z May 10)... 10% chance of subtropical cyclone formation (just west of the Canary Islands near 33N-20W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 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 (May 5) CMC Model Run...

**For area of interest #2... well-defined surface low develops over the western Azores at 54 to 60 hours... moves east-southeast toward the Canary Islands through 132 hours while gradually weakening.

**For broad surface trough currently southeast of Bermuda... develops into a broad surface low well south of Bermuda by 54 hours... surface low loses identity while SW of Bermuda by 102+ hours due to surface low pressure field moving offshore of eastern US.

1200Z (May 5) ECMWF Model Run...

**For area of interest #2... well-defined surface low develops over the western Azores at 54 hours... moves east-southeast toward the Canary Islands through 132 hours while gradually weakening.

**For broad surface trough currently southeast of Bermuda... develops into a broad surface low well south of Bermuda by 42 hours followed by dissipation southwest of Bermuda afterwards

**Divergence zone of upper vorticity left behind by current western North America upper trough produces broad eastern Gulf of America surface low by 138 hours... broad surface low advances north-northeast toward Big Bend region of Florida panhandle through 168 hours

1800Z (May 5) GFS Model Run...

**For area of interest #2... well-defined surface low develops over the western Azores at 51 hours... moves east-southeast toward the Canary Islands through 135 hours while gradually weakening.

**For broad surface trough currently southeast of Bermuda... develops into a broad surface low well south of Bermuda by 36 hours followed by dissipation southwest of Bermuda afterwards

**Divergence zone of upper vorticity left behind by current western North America upper trough produces broad central to eastern Gulf of America surface low by 138 hours... moves north-northeast toward western Florida panhandle through 168 hours

1800Z (May 5) NAVGEM Model Run...

**For area of interest #2... well-defined surface low develops over the western Azores at 60 hours then dives southeast then east into the waters between the Azores and Canary Islands through 108 hours while maintaining strength... the surface low undergoes a cyclonic loop just north of the Canary Islands from 108 to 156 hours.

**For broad surface trough currently southeast of Bermuda... develops into a broad surface low well south of Bermuda by 36 hours followed by dissipation southwest of Bermuda afterwards