MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #21

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

...SATURDAY JUNE 21 2025 11:55 PM EDT...

For the Atlantic basin tropics (Caribbean Sea... Gulf of America... and the mid and low-latitudes of the Atlantic)... noting the following:

The CIMSS 850 mb vorticity product continues to show the mid-level remains of a northwest-to-southeast tilted trough of low pressure across southeastern Mexico and western Central America (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=). For much of yesterday afternoon through much of today... the 850 mb vorticity product and visible satellite animation continued to suggest the spin maximum of the mid-level trough was positioned just inland from the western Gulf of America and over northern Veracruz and Tamaulipas... and the NHC also upgraded the spin maximum to a surface feature in recent TAFB surface analyses by adding a surface trough at that location. Offshore squalls of showers and thunderstorms over the western Gulf continue with this feature... however tropical development is not expected as the spin maximum is inland and as upper vorticity currently over the eastern Gulf begins retrograding westward and covering the entire Gulf under the force of the United States heat wave upper ridge... this upper vorticity will stomp out upper outflow potential needed for tropical development.

For the western Atlantic tropical latitudes (western Caribbean and Bay of Campeche) and eastern Pacific... short-term conditions will not be conducive for development as the currently developing United States heat wave upper ridge is pushing suppressing upper vorticity from the eastern Gulf of America and current northwest Atlantic/ Atlantic Canada upper trough south into the region... note this upper vorticity has shunted the favorable upper anticyclone that was over Central America a few days ago westward and away into southwestern Mexico. However in the longer term... after 48 hours... the upper vorticity begins to weaken from prolonged isolation from high-latitude cold air as the United States heat wave upper ridge passes to the north... fostering the formation of a new Central America upper anticyclone. In particular the upper anticyclone first appears as a gap between the weakening Gulf upper vorticity and weakening western Atlantic upper vorticity... especially as the Gulf vorticity is first pushed westward and away by the United States upper ridge. Eventually the western Atlantic upper vorticity also proceeds west (toward day 7) once the United States upper ridge shifts east and grabs it... which will cause a westward translation of the Central America upper anticyclone but not before it promotes possible eastern Pacific and/or western Caribbean/Bay of Campeche tropical development. The NHC is currently monitoring the possibility of the next eastern Pacific development in their tropical weather outlook which will likely spring up from a new tropical low that will form shortly in the expansive thunderstorms currently over Costa Rica... Panama... and far eastern Pacific being induced by split flow upper divergence between the south side of the aforementioned upper vorticity and southwestern Mexico upper anticyclone. For more on the possible eastern Pacific development... see outlook at hurricanes.gov as this site is focused on Atlantic basin tropical development. Meanwhile not declaring an area of interest for the Atlantic basin side (western Caribbean/ Bay of Campeche) until the global models are in better agreement on development in that area.

For the mid-latitudes of the open Atlantic Ocean... noting that from June 13 to 16 the current semi-permanent northeast Canada polar upper vortex drove in an east-west surface front across the mid-latitudes of the Atlantic... which has since decayed into a surface trough. The western tail end of the surface trough is currently in the vicinity of 30N-60W sandwiched between the surface ridges currently over the eastern US and near the Azores... which in the next 48 hours may be enhanced into a well-defined surface low by the eastern divergence zone of upper vorticity to be deposited by the current northwest Atlantic/ Atlantic Canada upper trough. Acknowledging upper winds could be conducive for tropical development of such a surface low as the western Atlantic upper vorticity retrogrades westward and away while the current United States and northwest Atlantic upper ridges bridge to make a large area of light shear and potential upper outflow in the mid-latitudes of the Atlantic. Any surface low that develops is expected to move increasingly faster to the northeast in the flow ahead of the current Atlantic Canada frontal low... followed by another surface front driven offshore of Atlantic Canada by the northeast Canada polar upper vortex... then finally the current north-central US frontal low when that departs Atlantic Canada in a few days. On that track the surface low will have minimal time over 26+ deg C waters conducive for tropical development... therefore not declaring an area of interest for possible tropical cyclone formation unless satellite observations show quick development before the feature moves into cooler waters.

...COMPUTER MODEL SUMMARY...

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

1200Z (Jun 21) CMC Model Run...

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

0000Z (Jun 21) ECMWF Model Run...

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

1200Z (Jun 21) GFS Model Run...

**Tropical low materializes in the south-central Caribbean near 10.8N-80.5W at 102 hours and makes landfall on the southeast coast of Nicaragua by 138 hours

1200Z (Jun 21) NAVGEM Model Run...

**Tropical low materializes over western Honduras by 126 hours... pushed northwest into the western Caribbean waters offshore of western Honduras and Belize by 144 hours by adjacent eastern Pacific tropical cyclone... makes landfall in Belize at 156 hours possibly as a tropical depression

**Portion of decaying central Atlantic surface trough becomes a surface low near 30N-57.5W at 24 hours... with aid of the eastern divergence zone of upper vorticity deposited by current NW Atlantic/ Atlantic Canada upper trough begins to strengthen into a possible tropical low near 32N-54.5W by 48 hours... beginning at 60 hours the surface low accelerates northeast ahead of offshore-moving surface front induced by current northeast Canada polar upper vortex... by 90 hours the surface low continues northeast in the flow ahead of the current north-central US frontal low once that frontal low reaches Atlantic Canada... while located at 40.5N-41.5W at 102 hours becomes absorbed by the 90-hr Atlantic Canada frontal low as that frontal low moves offshore into the north Atlantic.