MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #29

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

...THURSDAY JULY 3 2025 1:05 PM EDT...

Noting the following for the mid-latitudes of the Atlantic basin:

(1) See area of interest #8 section below for more information on the area of interest the National Hurricane Center has marked in their tropical weather outlook in the waters offshore of the southeastern United States... the area most likely to see notable impacts from this disturbance will be the coastal Carolinas from Sunday evening through Monday.

(2) The same surface frontal system/ upper trough associated with area of interest (AOI) #8 may drop off a small cut-off upper vortex west of Bermuda in the days ahead. However models are not depicting another surface disturbance developing under the eastern divergence zone of this vortex.

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. A surface tropical wave of low pressure near 54W longitude is located ahead of the latest dry Saharan air surge and is seeing its thunderstorm activity enhanced by a poleward upper outflow channel associated with upper southerlies ahead of the current western Atlantic upper vorticity. Tropical development of this wave is not expected as it crosses the Lesser Antilles and enters the Caribbean as warm southerly flow ahead of the coastal southeastern United States surface low... and also the latent heat release of its associated thunderstorms (area of interest #8) generates a warm core upper anticyclone that displaces the upper vorticity southward into the Caribbean... resulting in increased wind shear for the surface wave as it nears the upper vorticity followed by a cap on its upper outflow needed for thunderstorms once the surface wave slides under the upper vorticity by 72 hours.

AREA OF INTEREST #8... A surface cold front is currently positioned across the northeastern United States coast and interior southeastern United States... and a pre-frontal surface trough of low pressure with an associated axis of showers and thunderstorms runs parallel to the United States east coast. Both surface features... which over the next 24 hours are forecast to merge over offshore waters... are being supported by the eastern divergence zone of an upper trough currently positioned over eastern North America. The segment of the pre-frontal surface trough offshore of northeastern Florida and Georgia in particular is being 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. Watching for the merging pre-frontal surface trough and surface front to evolve into a southwest-to-northeast oblong surface low in that area due to the elongated nature of the divergence zone associated with the leading edge of interior southeastern US upper vorticity that will be separating from the eastern North America upper trough. The separation of the upper vorticity from the rest of the upper trough will be due to a building warm core upper ridge over the central/ eastern US to be induced by the warm southerly flow ahead of the next surface frontal system currently developing over western Canada... and the evolution of this upper vorticity is the key to how the oblong surface low evolves. Admittedly the models over previous days have not been consistent in handling the upper vorticity with changing solutions from day to day... however today's model data still shows the upper vorticity remaining parked over the southeastern US instead of over offshore waters which can help with tropical development and odds of tropical cyclone formation have increased. I have kept my peak odds of tropical cyclone formation below the NHC's latest and less than 50% as the oblong surface low may struggle to have a well-defined center needed for cyclone status due to the elongated region of upper divergence... and I have reserved those peak odds in the 00Z to 12Z July 6 window where the model data suggests the inland southeastern US upper vorticity is most circular and hence has its best chance to have a focused upper divergence zone over offshore waters. After that time I trim down odds of tropical cyclone formation as the model data has the upper vorticity re-elongating while separating into two parts... one that retrogrades southwest into the western Gulf of America/ northern Mexico and another that moves offshore from the US mid-Atlantic coast while caught in the flow ahead of the upper trough associated with the next frontal system ejecting from western/ central Canada.

The forecast track of the surface low is north then northeast while arcing around the west side of the steering Atlantic surface ridge. The forward speed is initially slow due to a passing blocking surface ridge to the north supported by the back convergence zone of the current eastern North America upper trough... then increases once the blocking ridge moves offshore and merges with the Atlantic ridge. On the current forecast track... increased westerly shear from the upper vorticity departing the mid-Atlantic US is another negative factor for tropical development by day 4... with ongoing westerly shear and decreased sea-surface temperatures along the forecast track making tropical development even less likely by day 5... and my ever-decreasing odds of tropical cyclone formation at days 4 and 5 are also a reflection of these negative factors. Regardless of whether or not this system is an elongated but vigorous tropical low... or a tropical cyclone with well-defined center... the coastal Carolinas are at risk of seeing heavy rainfall with flash flooding potential... gusty winds... and surf from Sunday evening through Monday.

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

IOH 24 Hr Outlook (1200Z Jul 4)... 0% chance of tropical cyclone formation (offshore of the southeastern United States near 30.5N-79.5W)

IOH 48 Hr Outlook (1200Z Jul 5)... 10% chance of tropical cyclone formation (offshore of South Carolina near 31.2N-78.5W)

IOH 72 Hr Outlook (1200Z Jul 6)... 30% chance of tropical cyclone formation (just offshore of the Carolinas near 32.5N-78.5W)

IOH 96 Hr Outlook (1200Z Jul 7)... 20% chance of tropical cyclone formation (just offshore of North Carolina between Cape Fear and Cape Lookout near 34.2N-77W)

IOH 120 Hr Outlook (1200Z Jul 8)... 10% chance of tropical cyclone formation (offshore of southeastern Maryland near 37N-74.2W)

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

Formation chance through 48 hours... 20%

Formation chance through 7 days... 60%

...COMPUTER MODEL SUMMARY...

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

0000Z (Jul 3) CMC Model Run...

**For area of interest #8... tail end of current eastern US surface front becomes an oblong broad surface low covering the northeastern Gulf of America... central and northern Florida... and waters offshore of northeast Florida by 36 hours due to the elongated eastern divergence zone of upper vorticity separating from frontal upper trough at a location over the inland SE US... the oblong surface low proceeds north with the centroid ending up over inland Georgia by 84 hours... while drifting north into the Appalachian mountains through 120 hours the oblong surface low loses identity to low pressure field of next surface front moving across the eastern US

0000Z (Jul 3) ECMWF Model Run...

**For area of interest #8... tail end of current eastern US surface front becomes an oblong broad surface low covering the northeastern Gulf of America... Florida peninsula... and waters offshore of northeast Florida by 36 hours due to the elongated eastern divergence zone of upper vorticity separating from frontal upper trough at a location over the inland SE US... a divergence maximum aids in the oblong surface low's consolidation into a tropical cyclone near 30.5N-79.5W at 60 hours... southwesterly shear and the ongoing elongated nature of the upper divergence zone induced by a remainder band of inland SE US upper vorticity causes the tropical cyclone to weaken and become a re-elongated remnant low with the remnant low making landfall into southeastern North Carolina by 90 hours... remnant low continues north-northeast toward coastal New Jersey where at 120 hours it loses identity to low pressure field of next surface front moving across the eastern US

0600Z (Jul 3) GFS Model Run...

**For area of interest #8... tail end of current eastern US surface front becomes an oblong broad surface low covering northern Florida and vicinity by 27 hours due to the elongated eastern divergence zone of upper vorticity separating from frontal upper trough at a location over the inland SE US... northeast end of oblong circulation consolidates into a circular surface low centered at 31N-79.5W at 57 hours... while moving north-northeast parallel to the southeastern US coast the ongoing elongated nature of the upper divergence zone induced by a remainder band of inland SE US upper vorticity causes the circular surface low to re-elongate through 78 hours... centroid of re-elongated surface low reaches Cape Hatteras North Carolina at 102 hours... the surface low transitions into a remnant frontal low while merging with next surface front moving offshore of the eastern US with the remnant frontal low positioned just offshore of Nova Scotia by 168 hours

0600Z (Jul 3) NAVGEM Model Run...

**For area of interest #8... tail end of current eastern US surface front becomes an oblong broad surface low covering northern Florida and vicinity by 24 hours due to the elongated eastern divergence zone of upper vorticity separating from frontal upper trough at a location over the inland SE US... east-northeast end of oblong circulation consolidates into a circular surface low centered at 30.5N-79.5W at 36 hours... the surface low continues north into South Carolina coast by 78 hours while possibly becoming a tropical cyclone... due to slowly eroding blocking surface ridge to the north the possible tropical cyclone moves slowly and erratically northeast into the NE South Carolina coast through 102 hours... next upper trough moving across the eastern US leaves behind a large upper vortex reaching the western GA/ SC border whose eastern divergence zone causes the possible tropical cyclone to transition into a possible subtropical cyclone more dependent on the upper vortex with the possible subtropical cyclone centered just offshore of Cape Fear North Carolina by 168 hours