MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #49

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

...WEDNESDAY JULY 30 2025 10:30 PM EDT...

For the mid-latitudes of the Atlantic basin... on the lookout for possible development in the waters offshore of the southeastern United States or in the open northwestern Atlantic. The surface front currently being induced by the southeast divergence zone of the eastern Canadian upper trough is expected to shift southeast into offshore waters as the upper trough itself shifts southeast. Then 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 and open northwestern Atlantic. Several days out... the tail upper-level energy merges with surrounding upper troughs to make an eastern North America upper trough regime. The precise position and configuration of the upper trough regime will have an effect on the amount of wind shear over the decaying tail end surface front/ trough and thus an effect on tropical development potential... and those details which are still multiple days out are difficult to accurately forecast. Therefore not currently declaring a new tropical area of interest for the waters offshore of the southeastern US nor open northwestern Atlantic... may do so in future updates if model data or future satellite observations warrant.

For the tropical latitudes of the Atlantic basin:

(1) Thunderstorm activity has notably decreased in association with a gyre forming from the merger between the current eastern and central Atlantic tropical waves of low pressure... as the gyre became large enough to ingest dry Saharan air. As such tropical development of the remnant gyre/ wave is no longer possible... see area of interest #12 section below for more details.

(2) The western Atlantic surface low... near 26N-66W... has not undergone tropical development due to northerly shear induced by the west side of the current western Atlantic upper trough and east side of the ongoing southeastern US upper ridge. The surface low... if it persists... is likely to continue northwest into the weakness between the current eastern Atlantic and US/ Canada border surface ridges and moreover the shear relaxes as the southeastern US upper ridge shifts offshore. However by the time the shear relaxes the surface low is most likely to lose its identity to the surface front to be delivered by the current eastern Canada upper trough... as noted in the previous paragraph discussing the mid-latitudes of the Atlantic basin attention for possible tropical development in the days ahead shifts to the front.

AREA OF INTEREST #12... As of 1800Z this evening the central Atlantic tropical wave of low pressure has moved west to 47.5W longitude and has left behind its small tropical low... currently near 10N-40W. The central and eastern Atlantic waves... and the small tropical low in between the waves... appear to merging into one large gyre on satellite pictures over the last 24 hours. The expanse of the gyre has allowed it to ingest stabilizing dry Saharan air which has brought about the loss of the widespread thunderstorm activity that was present in the region 24 hours ago. Noting since sunset a small area of thunderstorms has re-developed with the tropical low... however it pales into comparison with respect to the larger-scale ingested dry stable air. The updated forecast track in the outlook below is based on using the initial position of the small tropical low as was done during the previous update... and shifting it northwest in the next 24 hours as the models do which is a combination of a fujiwhara type interaction between the small tropical low and the incoming eastern Atlantic tropical wave and the overall west push of the steering Atlantic surface ridge. The northwest track moves the tropical low into the dry stable air where it is likely to lose its current small thunderstorm clump... and I have dropped my odds of tropical cyclone formation of this area of interest to 0%. In the long range the remnant large surface gyre/ wave zooms west-northwest toward the Lesser Antilles islands and Caribbean while upper winds along the forecast path become less conducive for development (see area of interest #12 discussion from the previous update at the following web address for details on the upper wind outlook... https://www.infohurricanes.com/post/my-2025-atlantic-hurricane-season-birdseye-view-post-48). Therefore even if the large gyre/ wave overcomes the dry air... it would unlikely have enough time to develop a well-defined center needed for focusing thunderstorms and supporting tropical development before running into less favorable upper winds. Therefore planning on this being my final statement on this area of interest on this blog.

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

IOH 24 Hr Outlook (0000Z Aug 1)... 0% chance of tropical cyclone formation (central tropical Atlantic near 14N-44W)

*****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 (Jul 30) CMC Model Run...

**For area of interest #12... tropical low near 10N-40W shifts north through 24 hours while becoming absorbed by incoming tropical wave to the east... the absorbing wave merges with wave to the west after which time the merged wave moves briskly west-northwest without development

**Current SW/NE tilted eastern Canada upper trough shifts southeast through 60 hours with which shifts the surface front produced by its southeastern divergence zone into northwestern Atlantic... the majority of the eastern Canada upper trough and an elongated frontal low it produces continue towards the open north Atlantic through 84 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... rapid tropical cyclone formation along the decaying tail end of the front and near 33.5N-71.5W through 102 hours... during tropical cyclogenesis and through 138 hours a pair of central US upper troughs and incoming upper trough from central Canada merge with Great Lakes/ NE US upper vorticity band to make a broad eastern North America upper trough and the tropical cyclone lifts northeast into the waters southeast of Massachusetts where it weakens to a remnant low upon arrival into stronger shear induced by the upper trough... after the remnant low becomes initially supported at 138 hours by the divergence zone of the upper trough the upper trough proceeds to split into northeast and southwest halves... the trailing convergence zone of the northeast half of the trough split produces a surface ridge to the north that pins the remnant low into a quasi-stationary position southeast of Massachusetts and hence the quasi-stationary remnant low weakens through 168 hours while no longer coupled to an upper divergence zone.

1200Z (Jul 30) ECWMF Model Run...

**For area of interest #12... no development shown

1800Z (Jul 30) GFS Model Run...

**For area of interest #12... tropical low near 10N-40W shifts north through 18 hours while becoming absorbed by incoming tropical wave to the east... the absorbing wave merges with wave to the west after which time the merged wave moves briskly west-northwest without development

**Current SW/NE tilted eastern Canada upper trough shifts southeast through 60 hours with which shifts the surface front produced by its southeastern divergence zone into northwestern Atlantic... the majority of the eastern Canada upper trough and a couple of elongated frontal lows it produces continue towards the open north Atlantic through 84 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 84 and 99 hours the Great Lakes/ NE US upper vorticity band begins merging with incoming upper troughs from the central US and central Canada to make a broad eastern North America upper trough... the southwesterly jet ahead of the eastern North America upper trough contributes to enhancing the poleward outflow of a 99-hour surface low with tropical characteristics which forms along the decaying tail end of the surface front near 36N-61.5W... soon after its formation the surface low loses its development potential while drifting northeast into higher southwesterly shear and by 168 hours the northeast drifting surface low transitions into a more elongated non-tropical low near 39N-50W and supported by the divergence zone of the northeast fracture of the broad eastern North America upper trough

**To the west-southwest of the 99-hour tropical low the remainder of the decaying surface front becomes multiple surface lows closer to the southeastern US coast... the dominant surface low is positioned quasi-stationary through 126 hours and due south of the North Carolina Outer Banks with potential for tropical development due to the eastern North America broad upper trough splitting into northeast and southwest halves with the southwest half too far away to induce shear... between 126 and 147 hours the surface low due south of the Outer Banks loses dominance while another one near 36N-69W becomes prominent and is also in a low enough shear environment supporting possible tropical development... the western convergence zone of the northeast half of the upper trough split produces a surface ridge to the north which begins to drift the surface low west to 36N-69.5W by 168 hours

1200Z (Jul 30) NAVGEM Model Run...

**For area of interest #12... tropical low near 10N-40W shifts northwest through 18 hours while becoming absorbed by incoming tropical wave to the east... the absorbing wave merges with wave to the west after which time the merged wave moves briskly west-northwest without development