MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #63

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

...SUNDAY AUGUST 24 2025 10:45 AM EDT...

It has been 36 hours since my previous update on the Atlantic tropics... and it has taken some time to assemble this update due to a continued busy time in my personal life:

(1) The above graphic was completed early today

(2) My forecasts were completed with satellite and computer model data available through 10:45 AM EDT today.

(3) This update was published early afternoon today after completing the text giving the rationale behind the forecasts.

Regarding current tropical Atlantic areas of interest:

(1) The elongated tropical low pressure southeast of Bermuda consolidated into Tropical Storm Fernand on Saturday afternoon... due to its initial position and current north-northeast angle in track it is now expected to pass well east of Bermuda without notable impacts reaching the island.

(2) See area of interest #21 section below for an update on the fast-moving central Atlantic tropical wave of low pressure still being monitored for signs of development while already closing in on the Lesser Antilles island chain.

Elsewhere in the Atlantic basin... a portion of the lengthy surface front trailing from ex-Erin has developed into a frontal low moving northeast near the coast of the Carolinas due to the flow ahead of the approaching eastern Canada frontal low. So far the spin has remained elongated rather than circular and the associated thunderstorms are not showing signs of organization... time is running out for this system to become an area of interest for possible tropical development as it soon will continue northeast into cooler water.

TROPICAL STORM FERNAND... The north-south elongated tropical low pressure that was moving northwest into the waters southeast of Bermuda proceeded to consolidate into Tropical Storm Fernand as of 5 PM EDT Saturday as confirmed by aircraft recon spotting a well-defined surface center. The consolidation happened towards the north and the tropical storm has been on a north-northeast heading which has shifted the forecast track notably east away from Bermuda for the period of time covering the next 24 hours... and given the small wind field and minimal tropical storm strength it is unlikely that notable impacts including coastal surf will reach Bermuda. The east lean in track is curious as conventional wisdom suggests Fernand is still a relatively weak/shallow system that should be guided by the low-level southerly flow associated with the west end of the Atlantic surface ridge... and if anything a developing surface ridge to the north produced by the western convergence zone of ex-Erin's upper trough would be trying to induce a west lean in Fernand's track. Even if we assume Fernand is a strong/tall system... the 200 mb upper layer of the atmosphere (in the above birdseye view chart) shows Fernand is embedded in upper anticyclonic steering-neutral flow to the east of the western Atlantic upper trough instead of being beside the trough. Noting after 0400Z Fernand's thunderstorm bursts have become increasingly lopsided to the northeast of center as if southwesterly flow at a layer between the surface and 200 mb is raking Fernand... perhaps the neighboring upper trough reaches closer to Fernand in the mid-levels of the atmosphere and is affecting the steering and introducing shear. In the next 24 hours the neighboring upper trough will split into southwest and northeast halves... with the northeast half dragged by the upper trough tied to ex-Erin and the southwest half drifting northwest toward the upper trough/ vortex energy approaching from Canada. I show no strengthening through 24 hours as the passing northeast half of the upper trough creates a burst of westerly shear and I continue the east lean in the northward track thru that time as the upper trough appears to be influencing Fernand's track as discussed above. Right around 24 hours I assume the track will briefly bend straight north as the passing upper trough energy moves away and as the surface ridge to the north gains strength. The upper winds also become more conducive for strengthening as an upper anticyclone with low shear and upper outflow develops in the increasing gap between the fractured upper trough energy to the northeast and southwest... and because Fernand is a compact tropical cyclone where not as much of a pressure drop is needed to increase the pressure gradient between the center and outer edge of the storm I forecast Fernand to begin brisk strengthening right at 24 hours. Between 36 and 48 hours Fernand's northward track should re-gain an east lean as the surface ridge to the north shifts east and frontal low from eastern Canada approaches. By 48 hours the upper trough/ vortex energy associated with the frontal low nears and begins to impart upper southwesterlies in Fernand's environment... however Fernand could still be strengthening at that point as it tracks fast enough to keep up with the initial upper southwesterlies and counteract their shearing effect and as a result I show Fernand at peak strength as a high-end tropical storm at 48 hours. Between 48 and 72 hours Fernand reaches cooler waters below 26 deg C and southwesterly shear intensifies. At 72 hours in agreement with the NHC 5 AM EDT forecast which calls for Fernand to be a rapidly fading remnant low lacking core thunderstorms but still containing low-end tropical storm force winds (around 40 mph) as it needs a little time to spin down from the peak intensity it acquires at 48 hours. Not long after that time Fernand's small remnant low should lose its identity to the large low pressure field of the frontal low incoming from eastern Canada.

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

0 Hr Position (0600Z Aug 24)... 40 mph maximum sustained wind tropical storm centered southeast of Bermuda at 29.7N-60.7W

IOH 24 Hr Forecast (0600Z Aug 25)... 40 mph maximum sustained wind tropical storm centered east-northeast of Bermuda at 33N-60W

IOH 48 Hr Forecast (0600Z Aug 26)... 65 mph maximum sustained wind tropical storm centered in the northwestern Atlantic at 37.5N-57.5W

IOH 72 Hr Forecast (6000Z Aug 27)... Tropical storm force remnant low centered south-southeast of Newfoundland at 43N-53.5W

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

Peak Strength (1800Z Aug 25)... 60 mph maximum sustained wind tropical storm centered in the western Atlantic at 35.7N-57.9W

72-Hour Position (0600Z Aug 27)... Rapidly weakening 45 mph maximum sustained wind remnant low centered southeast of Newfoundland at 44.3N-49.7W

AREA OF INTEREST #21... The vigorous central Atlantic tropical wave has continued to move faster to the west than previous model projections and will now be crossing the Lesser Antilles by tonight... and the updated forecast track in the outlook below is adjusted accordingly. The thunderstorm activity has shifted from being due west of the spin maximum to now being due northwest of the spin maximum as the tropical wave has moved fast enough to catch up to the upper southerlies associated with the neighboring inverted upper trough to the northwest (not to be confused with the current western Atlantic upper trough near Fernand)... with the upper southerlies lifting the thunderstorm activity toward the north. As such the potential for heavy rain and gusty winds for tonight has shifted away from the southern Lesser Antilles and toward the central and northern Lesser Antilles. Regarding forecast track... the inverted upper trough turns northwest into the western Atlantic and flips to a normal upper trough while attempting to link with the amplified upper trough/vortex energy approaching from Canada.... with the western convergence zone of the western Atlantic upper trough then increasing surface pressures to the southwest of Fernand which in turn prevents this tropical wave of interest from curving north. Through day 5 the forecast track remains predominately west across the Caribbean and into Central America due to the eastern US surface ridge produced by the back convergence zone of the amplified upper trough 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 toward day 5 due to the surface front settling into the northern Gulf of America ahead of the eastern US surface ridge.

Regarding odds of tropical cyclone formation... as the tropical wave of interest crosses the Lesser Antilles and enters the Caribbean in the next 24 hours... this system be nearing the axis of the nearby inverted upper trough where upper divergence is lacking and so I have lowered my odds of tropical cyclone formation from my previous 40% to a lower 30%. By 48 hours this wave will be recovering while entering the northwestern Caribbean upper ridge... however I lower odds of development further to a minimum of 20% as the wave will need some time to recover from the 24-hour non-divergent upper winds. After 48 hours the models still agree on the upper vorticity over the southeastern US drifting southeast in the northwesterly flow behind the pair of closely spaced eastern Canada upper troughs mentioned in the previous paragraph... however the models no longer have the upper vorticity reach the northwestern Caribbean such that the upper ridge could now remain intact. As I result I have elevated my longer range odds back up to 30% as the tropical wave of interest could now take advantage of the low shear/ upper outflow beneath the ridge... and have not selected higher odds as the global models do not develop the tropical wave of interest even in the longer range and waiting to see if this new upper wind scenario is maintained in future model runs. Noting that if the scenario persists... beyond day 5 the lingering upper vorticity to the north would fade from prolonged isolation from high-latitude cold air which would allow the favorable upper ridge to expand as the surface wave of interest merges with the northern Gulf surface front... resulting in a possible broad western Gulf of America tropical disturbance in about a week from today.

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

IOH 24 Hr Outlook (0600Z Aug 25)... 30% chance of tropical cyclone formation (central Lesser Antilles near 13N-61W)

IOH 48 Hr Outlook (0600Z Aug 26)... 20% chance of tropical cyclone formation (central Caribbean near 14N-69.5W)

IOH 72 Hr Outlook (0600Z Aug 27)... 30% chance of tropical cyclone formation (southeast of Jamaica near 14.5N-76W)

IOH 96 Hr Outlook (0600Z Aug 28)... 30% chance of tropical cyclone formation (central Caribbean near 15N-79.8W)

IOH 120 Hr Outlook (0600Z Aug 29)... 30% chance of tropical cyclone formation (east coast of Honduras near 15.2N-84W)

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

Formation chance through 48 hours... 40%

Formation chance through 7 days... 40%

...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).

0000Z (Aug 24) CMC Model Run...

**For Tropical Storm Fernand... the gradually strengthening tropical storm passes well east of Bermuda along 60.2W longitude at 24 hours... turns north-northeast and while reaching cooler waters due south of Newfoundland at 66 hours begins weakening... the weakening remnant low passes east of Newfoundland at 84 hours at which point it loses identity to incoming low pressure field of large frontal system approaching from Canada

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

0000Z (Aug 24) ECMWF Model Run...

**For Tropical Storm Fernand... the gradually strengthening tropical storm passes well east of Bermuda along 60W longitude at 24 hours... turns north-northeast and while reaching cooler waters due south-southeast of Newfoundland at 72 hours begins weakening... remnant low accelerates east-northeast into the open north Atlantic where it dissipates by 90 hours

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

0600Z (Aug 24) GFS Model Run...

**For Tropical Storm Fernand... the gradually strengthening tropical storm passes well east of Bermuda along 60W longitude at 18 hours... turns north-northeast and while reaching cooler waters due south-southeast of Newfoundland at 63 hours begins weakening... remnant low accelerates east-northeast into the waters east-southeast of Newfoundland where it dissipates by 81 hours

**For area of interest #21... no development shown while crossing the Lesser Antilles and Caribbean... by 168 hours develops into a broad tropical low over Belize

**Tail end of cold front attached to current eastern Canada frontal low reaches the northern Gulf of America by 51 hours... portion of front becomes a compact tropical low just south of southeastern Louisiana at 69 hours... while drifting west becomes a compact tropical cyclone near 26.5N-90W at 81 hours... compact tropical cyclone quickly weakens back to a remnant low shortly thereafter... remnant low drifts WSW and dissipates offshore of northeastern Mexico at 123 hours

0600Z (Aug 24) NAVGEM Model Run...

**For Tropical Storm Fernand... the gradually strengthening tropical storm passes well east of Bermuda along 59.5W longitude at 18 hours... turns north-northeast into the open northwest Atlantic where it loses identity to incoming low pressure field of large frontal system approaching from Canada at 54 hours

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