MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #64

*******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 AUGUST 25 2025 11:45 PM EDT...

Regarding current tropical Atlantic areas of interest:

(1) Tropical Storm Fernand is continuing northeast across the open western Atlantic... see Fernand section below for an update on the storm.

(2) See area of interest #21 section below for an update on the fast-moving tropical wave of low pressure which crossed the Lesser Antilles last evening and is now in the eastern Caribbean... continuing to monitor this wave as upper winds potentially become more conducive for possible development through its journey across the remainder of the Caribbean and into Central America and southeastern Mexico.

Elsewhere in the Atlantic basin... tropical development potential has been capped for now in the tropical belt between the Lesser Antilles and Africa due to suppressing upper vorticity that has been pushed into the region by the current mid-latitude central Atlantic upper ridge. With time the upper vorticity is forecast to lift northwest and away while continuing to revolve around the mid-latitude upper ridge... restoring upper winds back to a configuration more conducive to tropical activity. There is some agreement in the models that a tropical wave of low pressure which emerges from the west coast of Africa in about 5 days may become the next area of interest for possible tropical development in the Atlantic basin.

TROPICAL STORM FERNAND... Satellite image of Tropical Storm Fernand as of 1250Z earlier today acquiring peak strength:

The tropical storm in the open western Atlantic has continued to have an east angle in its north track which never reduced... and my updated forecast track shown below is adjusted to the right of previous. Fernand in the upper-levels has been interacting with the northeast fracture of a western Atlantic upper trough chasing the larger north Atlantic upper trough tied to ex-Erin... and at the surface is embedded in the flow between the strong north Atlantic surface ridge to the northeast and approaching pair of frontal lows offshore of the eastern US and over eastern Canada. Shortly after my previous update on Fernand early Sunday... the thunderstorm activity proceeded to become symmetrically distributed around the center instead of being slightly lopsided to the northeast and Fernand began strengthening... perhaps the strengthening allowed it to become strong/tall enough to be pulled by the upper trough fragment from the western Atlantic. And at the surface perhaps the flow ahead of the recently formed eastern US frontal low has a westerly enough component to also push Fernand more east. As of this afternoon Fernand has bumped into the southwest side of the upper trough fragment where upper northerlies have displaced the thunderstorm's south of center. Even though the National Hurricane Center upgraded Fernand to 60 mph maximum sustained winds as of 5 PM EDT that may be generous given the recent appearance where the northerly shear has caused much of the surface swirl to pop out and away from most of the thunderstorms held back to the south... speculating this peak intensity was reached between 11 AM and 5 PM EDT. Going forward the warm southerly flow ahead of the pair of approaching frontal lows will amplify warm core northwestern Atlantic upper ridging which will cut-off the upper trough fragment into an upper vortex. On the updated forecast track... Fernand through 24 hours should track into the lower shear and upper outflow environment to the northwest of the upper vortex and beneath the northwest Atlantic upper ridge. Therefore forecasting weakening Fernand to develop a thunderstorm burst over the center within the next 24 hours and before reaching cooler waters at the 24-hour point... thus I keep the forecast strength for the 24-hour point at 45 mph maximum sustained winds instead of lower. Between 24 and 48 hours cooler waters should weaken Fernand further into a remnant surface trough gradually losing identity to the aforementioned approaching frontal lows.

Update as of 11 PM EDT... the NHC has downgraded Fernand to 50 mph maximum sustained winds as the tropical storm continues to struggle with northerly shear since the afternoon hours.

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

0 Hr Position (1800Z Aug 25)... 60 mph maximum sustained wind tropical storm centered in the western Atlantic at 35.3N-57.2W

IOH 24 Hr Forecast (1800Z Aug 26)... 45 mph maximum sustained wind tropical storm centered in the northwestern Atlantic at 41N-54W

IOH 48 Hr Forecast (1800Z Aug 27)... Remnant trough positioned east-southeast of Newfoundland near 46.2N-46W

*****National Hurricane Center (hurricanes.gov) official forecast as of 5 PM EDT***********************

48-Hour Position (1800Z Aug 27)... Weakening 35 mph maximum sustained wind remnant low centered southeast of Newfoundland at 43N-48W

AREA OF INTEREST #21... The vigorous tropical wave of low pressure that was approaching the Lesser Antilles last night has already crossed the islands and entered the eastern Caribbean. The wave continues moving rapidly west and once again the forecast track has been adjusted to keep up with the wave. Their are currently a pair of closely-spaced upper troughs in the western Atlantic... with the convergence zone of the eastern trough increasing surface pressures to the southwest of Tropical Storm Fernand which in turn has prevented this wave of interest from curving north. The wave will also continue west across the remainder of the Caribbean and into Central America due to the eastern US surface ridge to be produced by the back convergence zone of the amplified upper trough/vortex energy departing eastern Canada... followed by the back convergence zone of another southeast-diving upper trough following closely behind the departing eastern Canada energy. However the forward speed of the tropical wave of interest slows down with time due to the surface front settling into the northern Gulf of America ahead of the eastern US surface ridge. By day 5 the track forecast shows a northward bend as the tropical wave rounds the west extent of the surface ridge.

Regarding odds of tropical cyclone formation... the tropical wave lost its concentrated thunderstorms as it crossed the Lesser Antilles islands while approaching the lack of upper divergence beneath the axis of one of the western Atlantic upper troughs at which point the National Hurricane Center dropped it as an area of interest for tropical development. On this site I am continuing this wave as an area of interest as upper winds gradually become more conducive for possible development... in fact the wave has already re-developed concentrated thunderstorms under the outflow of a central Caribbean upper ridge cell positioned between the pair of western Atlantic upper troughs. However I have lowered peak odds of tropical cyclone formation to 20% as the wave has lost its spin maximum and more resembles an open wave... for example reference the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=). Going forward the central and northwestern Caribbean upper ridge cells unite as the western Atlantic upper troughs migrate north and away while attracted toward the current eastern Canada upper trough/ vortex. The united upper ridge then expands with time as what is the current Gulf of America upper vorticity fades from prolonged isolation from high-latitude cold air. My odds of tropical cyclone formation are lowered to 10% for day 5 due to land interaction with the Yucatan peninsula and as this area of interest potentially becomes broader while possibly merging with the tail end of the northern Gulf surface front (broader systems tend to have a harder time establishing a well-defined low pressure center needed for tropical development)

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

IOH 24 Hr Outlook (1800Z Aug 26)... 20% chance of tropical cyclone formation (southeast of Jamaica near 15N-75W)

IOH 48 Hr Outlook (1800Z Aug 27)... 20% chance of tropical cyclone formation (central Caribbean near 15N-80W)

IOH 72 Hr Outlook (1800Z Aug 28)... 20% chance of tropical cyclone formation (east coast of Honduras near 15.2N-84W)

IOH 96 Hr Outlook (1800Z Aug 29)... 20% chance of tropical cyclone formation (east coast of Belize near 16.8N-88.2W)

IOH 120 Hr Outlook (1800Z Aug 30)... 10% chance of tropical cyclone formation (southwest coast of the Yucatan peninsula near 18.8N-91.2W)

*****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 (Aug 25) CMC Model Run...

**For Tropical Storm Fernand... rapidly weakens to a small remnant low near 39N-55W at 24 hours... through 48 hours while passing southeast of Newfoundland loses identity to incoming low pressure field of large frontal system approaching from Canada

**For area of interest #21... no development shown

**Tropical wave emerges from west coast of Africa at 120 hours... passes south of the Republic of Cabo Verde Islands then becomes a tropical low near 13N-31W at 168 hours

1200Z (Aug 25) ECMWF Model Run...

**For Tropical Storm Fernand... weakens to a remnant low near 41.2N-51.2W at 42 hours... continues east-northeast to 47.5N-39.5W at 72 hours where it loses its identity

**For area of interest #21... no development shown

**Tropical wave emerges from west coast of Africa at 108 hours... evolves into large tropical low rolling into the Republic of Cabo Verde Islands by 156 hours... tropical low continues west away from the islands through 168 hours

1200Z (Aug 25) GFS Model Run...

**For Tropical Storm Fernand... weakens to a remnant low near 40.5N-53.5W at 33 hours... remnant low continues east-northeast into the waters east-southeast of Newfoundland where it dissipates by 57 hours

**For area of interest #21... no development shown

1200Z (Aug 25) NAVGEM Model Run...

**For Tropical Storm Fernand... weakens to remnant trough near 36N-57.5W at 12 hours... while moving into the waters south of Newfoundland through 36 hours the remnant trough loses identity to incoming low pressure field of large frontal system approaching from Canada

**For area of interest #21... no development shown