MY 2025 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #7

*******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 JUNE 2 2025 11:59 PM EDT...

In the days ahead will be watching the evolution of the current large-scale eastern North America upper which may allow for tropical development in the western part of the Atlantic basin as follows:

(1) Over the next couple of days the strength of the current central North America warm core upper ridge will break the upper trough into three components... a northern fragment that continues quickly east across the far north Atlantic... a cut-off upper vortex over the northwestern Atlantic that will be quasi-stationary for days until the upper ridge passes by to the north... and a cut-off upper vortex over Florida.

(2) Regarding the northwestern Atlantic upper vortex... it is forecast to evolve into a deep-layer low as its eastern divergence zone initiates a surface low pressure that then whirls into the core of the upper vortex. The deep-layer low is not likely to acquire tropical characteristics as the combination of 22 deg C waters and not so cold upper air layer (200 mb heights above 1200 dekameters) will not be enough for instability needed for thunderstorms and tropical characteristics.

(3) Regarding the Florida upper vortex... its eastern divergence zone is expected to develop a tropical surface low positioned near the southeastern US coast... see area of interest #4 section below for details.

(4) Regarding the central Caribbean waters toward Central America... by day 6 the models suggest the cold-core Florida cut-off upper vortex will be fading due to prolonged isolation from high-latitude cold air. This would allow a central Caribbean upper ridge cell to expand to the south of the fading upper vortex... the outflow of which could trigger a central Caribbean tropical disturbance. For now the GFS model has been leading this idea... and even then the GFS has been on and off regarding this situation from run to run. This is because some model runs allow for some of the upper vorticity associated with the current western Canada upper trough to dive south toward the Caribbean around the currently semi-permanent Mexico hot air mass upper ridge... if this were to happen the upper vorticity would shunt or delay the development of a central Caribbean upper ridge cell. Not declaring an area of interest for the central Caribbean at this time as the modeling is uncertain.

AREA OF INTEREST #4... Thunderstorm-packed disturbance has materialized across the south Florida... western Cuba... and western Bahamas region within the last 24 hours under the supportive eastern divergence zones of a southeast-diving shortwave upper trough and large-scale eastern North America upper trough... tropical development is possible as the disturbance pivots northeast across the waters offshore of the southeastern United States in the days ahead. The disturbance has been added into the National Hurricane Center tropical weather outlook as of 2 PM EDT Monday... and this marks the fourth such area of interest tracked on this site this year (the other three were tracked during the pre-season period in previous birdseye view posts #1 to #6).

Due to the strength of the current central North America upper ridge passing by to the north... the shortwave upper trough will amplify into a cut-off upper vortex in the vicinity of the Florida peninsula in the next 24 hours... with its eastern divergence zone of the vortex potentially initiating a surface low pressure just offshore of east-central Florida. The surface low is likely to be tropical in nature while coupled with warm core upper ridging just east of the upper vortex whose outflow will help sustain the surface low. In the 48-hour period an additional part of the current eastern North America upper trough becomes another cut-off upper vortex in the northwest Atlantic... the western convergence zone of which transitions the current eastern US surface ridge into a blocking surface ridge to the northeast of the tropical surface low such that it tracks north close to the northeast Florida and Georgia shore rather than northeast. However in the long range (72+ hours)... the track bends increasingly faster to the northeast as the next upper trough and its surface front in the mid-latitudes... currently over western Canada and the central US... approaches and erodes the blocking surface ridge... replacing it with deep-layer southwesterly flow in the environment. The long-range forecast track has some uncertainty as the western Canada upper trough breaks down into multiple shortwave upper troughs due to its low strength relative to the current central North America upper ridge it displaces... and models vary on the positions of the shortwave upper troughs in such a scenario. The NHC suggests a low 10% chance of tropical cyclone formation perhaps as the current and usually more reliable GFS/ECMWF consensus has a long-range track too close to the Carolina coast. I have slightly higher 15% peak odds of cyclone formation as I do see enough upper divergence offshore in the GFS model fields to allow the surface low to have an initial offshore position in as soon as 24 hours... such that the longer-range track has a chance of being just offshore of rather than along the Carolina coast. By 96 hours I trim development odds below the peak as the northeast speed of the tropical surface low is low enough to be sheared by the upper southwesterlies. The northeast acceleration is enough to reduce the effect of the shear by 120 hours... however by that point the approaching surface front's low pressure field is too close that this system is likely to lose its identity by then.

Regarding impact to land areas:

(1) Rainfall... heavy rainfall will continue through tonight across western Cuba and the western Bahamas... and should abate over southern Florida as the de-stabilizing upper divergence zone has moved off to the east. Expecting the upper vortex over Florida to then block the western outflow of the surface tropical low such that rainfall along the northeast Florida and Georgia coast is unlikely. Although upper southwesterly shearing flow arrives in the longer range (which would also keep the heaviest rainfall shunted to the east)... the surface low could still track close enough to the Carolina coast to bring periods of heavy rainfall Thursday evening for points further southwest and Friday evening for points further northeast.

(2) Coastal surf and rip currents are possible from northeastern Florida to the Carolinas if tropical cyclone formation occurs... toward Wednesday night further south and toward Friday evening further north. For the coastal Carolina rain event Thursday evening to Friday evening... gusty winds are possible in squalls of heavy rain should tropical cyclone formation occur.

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

IOH 24 Hr Outlook (0000Z Jun 4)... 0% chance of tropical cyclone formation (just offshore of east-central Florida near 27.5N-80W)

IOH 48 Hr Outlook (0000Z Jun 5)... 10% chance of tropical cyclone formation (just offshore of northeastern Florida near 30N-80W)

IOH 72 Hr Outlook (0000Z Jun 6)... 15% chance of tropical cyclone formation (just offshore of South Carolina near 32N-79W)

IOH 96 Hr Outlook (0000Z Jun 7)... 10% chance of tropical cyclone formation (just south of Cape Hatteras North Carolina near 34.5N-75.5W)

IOH 120 Hr Outlook (0000Z Jun 8)... 0% chance of tropical cyclone formation (northwestern Atlantic near 36.5N-70W)

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

Formation chance through 48 hours... 0%

Formation chance through 7 days... 10%

...COMPUTER MODEL SUMMARY...

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

1200Z (Jun 2) CMC Model Run...

**For area of interest #4... surface low develops just offshore of South Carolina by 72 hours... drifts east-northeast to 33N-77.5W through 96 hours as a possible tropical cyclone... loses identity near 35N-69W by 138 hours ahead of a frontal low approaching from the mid-Atlantic US coast

1800Z (Jun 2) ECMWF Model Run...

**For area of interest #4... broad surface low develops over coastal and inland areas of South Carolina by 78 hours... the broad surface low moves east-northeast increasingly into offshore waters through 90 hours (data beyond 90 hours not available at above-mentioned source... the 1200Z run which usually has longer range data is down at the above-mentioned source)

1800Z (Jun 2) GFS Model Run...

**For area of interest #4... broad surface low develops over coastal North Carolina by 84 hours... while pulled into waters offshore of the mid-Atlantic US coast becomes absorbed by a frontal low approaching from the interior northeastern US by 114 hours

**In long range Florida upper vortex that triggers area of interest #4 weakens which allows for a tropical upper ridge cell to expand in its wake in the central Caribbean... by 156 hours the outflow of the upper ridge cell contributes to formation of a broad tropical low centered just offshore of the Nicaragua/Honduras border

1800Z (Jun 2) NAVGEM Model Run...

**For area of interest #4... surface low develops inland over southern Georgia by 54 hours... while moving northeast across the inland Carolinas it loses its identity to next frontal system approaching from the west through 90 hours