MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #30

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

...FRIDAY JULY 4 2025 2:43 PM EDT...

URGENT - see area of interest #8 section below for an update on the quickly developing tropical low currently positioned offshore of the southeastern United States... the potential for notable impacts to parts of the Carolinas during the later part of this weekend into Monday is increasing.

For the low-latitudes of the tropical Atlantic... tropical development is being precluded in the waters between the Lesser Antilles islands and west coast of Africa in the foreseeable future due to ongoing surges of dry Saharan air.

AREA OF INTEREST #8... Satellite imagery of increasingly defined tropical low materializing over east-central Florida last evening (Thursday evening) which has since moved northeast into the waters offshore of the southeastern United States since its formation. The central position of the tropical low in each image is marked with crosshairs:

Quickly developing tropical surface low is present in the waters offshore of the southeastern United States while the upper wind forecast has shifted towards favorability in tropical development... the potential for notable tropical cyclone impacts for parts of the Carolinas during the later part of this weekend into Monday has increased. Details are as follows in the next paragraphs.

Genesis of the tropical low... the broad eastern divergence zone of the upper trough advancing from eastern North America was producing an offshore-moving surface cold front and offshore pre-frontal surface trough as of yesterday. Since then the northeastern US portion of the cold front moved offshore and uneventfully merged with the northern portion of pre-frontal surface trough while the inland southeastern US portion of the cold front was downgraded to a surface trough/ low due to the loss of air mass contrasts on either side of it. As seen by the curvature of shower and thunderstorm bands in the region... the southern portion pre-frontal surface trough appeared to organize into a tropical low over east-central Florida by 1900Z yesterday which proceeded to move east-northeast into the Atlantic from the Cape Canaveral region by 0300Z early today while orbiting the inland southeastern US surface trough/ low. This continued orbit has caused the offshore tropical low to hook increasingly north into the waters offshore of Georgia and South Carolina as of this writing. The genesis of the tropical low was likely aided by split flow upper divergence between southwesterlies ahead of the eastern North America upper trough and northerlies streaming into decaying western Atlantic upper vorticity... perhaps with the divergence zone being focused enough for a well-defined center instead of an oblong surface low.

Forecast... Latest visible satellite animation appears to show a fully-closed surface circulation as seen by the motion of the low clouds. The surface spin is on the west edge of organized shower and thunderstorm bands rather than tucked directly underneath due to some westerly shear being imparted by the eastern North America upper trough... and it appears the system has slowed down forward progress due to a blocking surface ridge approaching from the eastern United States. As of this writing aircraft recon is on the way to investigate... I suspect the resulting data will confirm a slow-moving tropical depression or storm. As such I have begun a tropical cyclone formation forecast with specific track and intensity forecast points as outlined below. Going forward southeastern US upper vorticity will be separating from the rest of the eastern North America upper trough under the influence of a building central/ eastern US warm core upper ridge currently being bolstered by a channel of warm surface southerly flow between the west side of the current eastern US surface ridge and out ahead of the currently developing central Canada frontal system. The evolution of the southeastern US upper vorticity has always been key to how this tropical system evolves... admittedly the models over previous days have not been consistent on this issue with changing solutions from day to day. Today's model runs are back to Wednesday July 2 where the entirety of the southeastern US upper vorticity retrogrades southwest and away from the tropical system and toward Louisiana/ the northwestern Gulf of America... which will promote a reduction in wind shear over the tropical system by Sunday. In this scenario an outflow enhancing upper anticyclone also expands over the tropical system in the increasing gap between the retrograding southeast US upper vorticity and remainder of the current eastern North America upper trough as the trough shifts east into the northwest Atlantic... and the expanse of the favorable upper anticyclone is enforced as the central/ eastern US anticyclonic warm core upper ridge shifts east and overspreads the area later in the forecast period. Combined with warm waters and healthy initial structure of this system... I currently forecast the possibility of brisk strengthening when the forecast wind shear drops on Sunday and as this system closes in on the South Carolina coast. For now I am calling for a top-end tropical storm... however I wouldn't be surprised if this system reaches hurricane force by landfall time. Forecast track is north then north-northeast while arcing around the west side of the steering Atlantic surface ridge... with an initially slow forward speed due to the passing blocking surface ridge approaching from the eastern US... the forward speed later increases once the blocking ridge moves offshore and merges with the Atlantic ridge. Note the updated track is adjusted westward as the models no longer depict a piece of the southeastern US upper vorticity getting caught in the mid-latitude westerlies and sliding offshore from the mid-Atlantic US coast.. this re-enforces the lowered wind shear forecast in the later part of the forecast period and prevents a surface ridge weakness (which would be generated by the divergence ahead of the vorticity) from dragging this system northeast along a coastal track... the updated track now has a sooner landfall time (along South Carolina coast) by midday Sunday instead of later on Sunday.

Impact to land areas with the current forecast are as follows:

(1) Deteriorating weather conditions for northeastern South Carolina and southeastern North Carolina by midday Sunday... gusty and potentially damaging winds particularly along the central and northeastern South Carolina coast... however bouts of inland wind damage cannot be ruled out for inland regions... coastal surf from the central South Carolina coast to the southeastern North Carolina coast... heavy rainfall with flash flooding potential.

(2) The inland remnant tropical low continues north-northeast across North Carolina and mid-Atlantic United States by Monday. As such heavy rainfall with flash flooding potential proceeds across central and eastern North Carolina... central and eastern Virginia... and as far northeast as Maryland and Delaware.

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

0 Hr Position (1200Z Jul 4)... Tropical low centered at 30.5N-79.2W

IOH 24 Hr Forecast (1200Z Jul 5)... 50 mph maximum sustained wind tropical storm centered offshore of South Carolina at 31.5N-79.2W

IOH 48 Hr Forecast (1200Z Jul 6)... 70 mph maximum sustained wind tropical storm centered just offshore of the central South Carolina coast at 32.5N-79.2W

IOH 72 Hr Forecast (1200Z Jul 7)... Remnant low centered over eastern North Carolina at 35.2N-78.5W

*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***********************

Formation chance through 48 hours... 70%

Formation chance through 7 days... 70%

...COMPUTER MODEL SUMMARY...

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

0000Z (Jul 4) CMC Model Run...

**For area of interest #8... broad surface low over Florida consolidates into a better-defined smaller low just offshore of the Georgia/South Carolina border through 54 hours... shortly thereafter makes landfall while continuing north-northeast with the weak inland remnant low reaching central North Carolina by 84 hours... after reaching central Virginia at 96 hours becomes absorbed by weak frontal low developing to the northwest over the Ohio Valley

0000Z (Jul 4) ECMWF Model Run...

**For area of interest #8... broad surface low over Florida consolidates into a better-defined smaller low just offshore of the Georgia/South Carolina border through 60 hours... while continuing north-northeast landfall and inland dissipation occurs shortly thereafter

0600Z (Jul 4) GFS Model Run...

**For area of interest #8... broad surface low over Florida consolidates into a better-defined smaller low just offshore of the southern South Carolina coast through 54 hours... shortly thereafter continues north-northeast as an inland broad remnant low across the Carolinas and Virginia with the centroid of the broad remnant low then reaching the coast of southeastern Maryland by 123 hours... while turning northeast into the waters due south of Long Island New York loses identity along surface front approaching from the northwest by 141 hours

0600Z (Jul 4) NAVGEM Model Run...

**For area of interest #8... broad surface low over Florida consolidates into a better-defined smaller low just offshore of northeast Florida through 30 hours... continues north-northeast and makes landfall in northeastern South Carolina at 60 hours... inland remnant low continues north-northeast across eastern North Carolina and Virginia then into central Maryland through 84 hours shortly after which time it becomes absorbed by cold front sweeping in from the west driven by a frontal low that shifts east from the Great Lakes to the northeastern US