MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #47

*******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 JULY 28 2025 8:54 PM EDT...

For the mid-latitudes of the Atlantic basin... the potential for tropical development in the days ahead has shifted from the northern Gulf of America to the waters offshore of the southeastern United States. Noting the surface warm front that was over North Carolina and Virginia has moved into offshore waters while being downgraded to a surface trough from the loss of airmass contrasts on either side of it... and this feature is expected to turn southwest under the force of the current US Gulf coast surface ridge... followed by a sprawling surface ridge to descend from the US/Canada border while induced by the back convergence zone of the current central Canada upper trough when that trough later shifts southeast. The surface front induced by the southeast divergence zone of the Canadian upper trough is expected to absorb the southwest-shifting surface trough before that trough gets a chance to reach the northern Gulf. Then over the next several days the Canadian upper trough leaves behind its tail over the Great Lakes and northeastern US whose southeastern divergence zone maintains the tail end of the surface front at a position offshore of the southeastern US... then the tail upper-level energy merges with an upper trough incoming from the central US. There are some indications in the modeling that the merged upper trough could stay too far away to shear the offshore decaying surface front while splitting into a northeastern half that stays well north and southwestern half that stays well west... thus the decaying surface front might become an area of interest for potential tropical development. More details on this potential situation is provided in the description of this past 12Z GFS model run in the computer model summary section below. May have to add an area of interest in the waters offshore of the southeastern United States in future updates if appropriate.

For the tropical latitudes of the Atlantic basin:

(1) Upper winds in the eastern tropical Atlantic have returned to a mode more conducive for thunderstorm activity after a wave of suppressing upper vorticity retreated northwest and away toward the upper trough west of the Azores and upper trough fragment in the northwest Atlantic. Despite this surges of dry Saharan air continue to suppress tropical development... for instance the tropical wave of low pressure that was at 37.5W longitude as of this writing continues to lack thunderstorms in its north side... and the tropical wave that was producing strong thunderstorms over southwestern Mali yesterday has seen a notable decrease in thunderstorms while rolling off of the west coast of Africa today. Noting the models are not in agreement in showing tropical development in the waters between the Lesser Antilles and Africa in the days ahead.

(2) Further west where dry Saharan air concentrations tend to be lower... a tropical disturbance has materialized in the western Atlantic waters due north of northeastern Caribbean Islands from the combination of surface convergence at the north apex of two closely-spaced tropical waves of low pressure and a more favorable upper wind pattern. The surface waves emerged from Africa in the July 19 to 21 window... and as of this writing the axes of the waves are at the eastern Caribbean longitudes. Aloft the once solid string of cool core suppressing upper vorticity spanning the central Atlantic to Gulf of America is finally weakening and breaking up due to prolonged isolation from high-latitude cold air... which has allowed for an upper anticyclone north of the northeastern Caribbean Islands whose outflow supported a circular region of increased thunderstorms early today which since pulsed down during the daylight hours... and the CIMSS 850 mb vorticity product shows a mid-level spin formed in the thunderstorms (https://tropic.ssec.wisc.edu/real-time/atlantic/movies/wg8vor4/wg8vor4_loop.html). Around sunset time (0000Z) some pockets of thunderstorms have redeveloped but not to the extent seen early today... and surface analysis and CIMSS 850 mb vorticity shows the surface waves and mid-level spin have continued west while the canopy of thunderstorms and cirrus upper outflow clouds have remained in placed... a sign that some of the upper vorticity to the west may still be vertically shearing this disturbance. Over the next 48 hours the disturbance is likely to turn increasingly north in the weakness between the current eastern Atlantic and US Gulf coast surface ridges. In the next 24 hours the westerly shear may relax as the upper vorticity to the west shifts away while revolving around the southeast US upper ridge. However by 48 hours another wave of disruptive upper vorticity... associated with the current western Great Lakes shortwave upper trough... is pushed south into the environment of the disturbance and also by the southeast US upper ridge. With upper winds only being favorable for development for a short time at 24 hours... this disturbance has NOT been upgraded to an area of interest for possible tropical development.

...COMPUTER MODEL SUMMARY...

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

1200Z (Jul 28) CMC Model Run...

**No tropical development shown in the Atlantic basin through 7 days (168 hours)

0000Z (Jul 28) ECWMF Model Run...

**No tropical development shown in the Atlantic basin through 7 days (168 hours). Also checked this ECMWF model run at tropical tidbits as the above-mentioned source had data from several forecast timestamps missing (https://www.tropicaltidbits.com/analysis/models/?model=ecmwf&region=atl&pkg=mslp_pcpn_frzn&runtime=2025072806&fh=12)

1200Z (Jul 28) GFS Model Run...

**Current SW/NE tilted central Canada upper trough reaches eastern Canada through 99 hours with the surface front produced by its southeastern divergence zone draped across the northwestern Atlantic by that time... the majority of the eastern Canada upper trough and a couple of elongated frontal lows it produces continue towards the open north Atlantic through 132 hours however the tail end of the front persists offshore of the southeastern US due to the southeastern divergence zone of a band of upper vorticity over the Great Lakes and NE US left behind by the upper trough... between 132 and 147 hours an upper trough incoming from the central US and the Great Lakes/ NE US upper vorticity band begin merging into one upper trough however the merged upper trough is too far away to shear a surface low developing near 32.5N-71.5W... between 147 and 168 hours the northeast half of the merged upper trough separates and moves toward the open north Atlantic while scooped into a high-latitude upper trough that dives in from central Canada with the western convergence zone of that feature finally allowing the blocking surface ridge to the north to shift east... the surface low proceeds north between 147 and 168 hours while steered around the west side of the departing surface ridge and becomes a possible tropical cyclone near 35N-71.5W as the remainder southwest half of the merged upper trough remains too far away (and over the SE US) to shear the possible tropical cyclone.

1200Z (Jul 28) NAVGEM Model Run...

**No tropical development shown in the Atlantic basin through 7 days (168 hours)