*******Note that forecast 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.*********
...TUESDAY JULY 30 2024 3:20 PM EDT...
For the mid-latitudes of the Atlantic basin... a northwest Atlantic surface frontal low heading north-northeast toward Nova Scotia (while moving around the steering Atlantic surface ridge) gained a small core of shower and thunderstorm activity while approaching 40N-65W. However tropical development of this feature is not anticipated as the most recent satellite frames show the core of activity waning while this system is beginning to move into cooler waters.
In the tropical latitudes of the Atlantic basin... continuing to monitor a large central Atlantic tropical disturbance heading for the northern Caribbean Islands and Bahamas in the days ahead as upper winds over the feature gradually become more conducive for its potential development... see area of interest #14 section below for more information. Elsewhere... satellite imagery suggests that another large tropical wave of low pressure has recently emerged from western Africa and is now passing south of the Republic of Cabo Verde Islands while featuring curved bands of thunderstorms on its south side. However its development is not anticipated as the north side of the circulation has ingested dry Saharan air. In addition a warm core northwestern Atlantic upper ridge is expected to setup in about five days due to warm southerly flow ahead of a forecast eastern North America surface frontal system... relatively lower pressures between the eastern tropical Atlantic upper ridge and northwestern Atlantic upper ridge will result in suppressing upper vorticity in the central part of the tropical Atlantic... therefore this wave is also not expected to develop while later moving into the suppressing upper vorticity.
AREA OF INTEREST #14... A large swirl of low surface pressures in the central tropical Atlantic... much of it void of thunderstorm activity due to dry Saharan air... is tumbling its way westward toward the northern Caribbean Islands while it continues to be pushed along by the Atlantic surface ridge. The swirl is a merger of a pair of closely-spaced tropical waves that emerged from Africa a few days ago and a pre-existing southern spin that remains near 12N-50W... previous post #52 has more information on the origins of the pre-existing spin (https://www.infohurricanes.com/post/my-2024-atlantic-hurricane-season-birdseye-view-post-52). For this update I am initializing the large swirl near its centroid which was in the vicnity of 15N-54W as of 1200Z... and noting the NHC TAFB surface analysis is handling the large swirl as a broad tropical wave axis. The track of the wave is likely to gain some north angle toward the latter part of the 5-day forecast period as the current upper trough which has recently moved into western North America later generates an expansive eastern North America surface frontal system... with the wave bending more north in track toward the surface ridge weakness associated with the frontal system.
Over the next 48 hours the broad surface tropical wave should remain suppressed while the inverted upper trough incoming from the east merges with the current cut-off upper vorticity to the northwest... as a result impacts to the northeastern Caribbean Islands from this wave are expected to be minimal. Beyond that time models are generally agreeing that the overhead upper vorticity... due to prolonged isolation from high-latitude cold air... decays into one area of upper vorticity toward Central America and another area of upper vorticity in the mid-latitudes of the western Atlantic... with an expanding area of anticyclonic outflow between the two decaying lobes of upper vorticity potentially evolving the surface tropical wave into a tropical low or cyclone. Even the GFS which continues to have a slower decay rate of the upper vorticity now develops this system in the long range. Noting the CMC and ECMWF are now slower to develop this system... perhaps an indication that this system will take some time to mix out the dry Saharan air it has inhaled in previous days. Another factor that could cause a delay in development as the upper winds switch to a more favorable mode is the fact this system is starting out large and broad... and will likely need time to develop a well-defined center necessary for tropical cyclone status. I set my day 5 odds of tropical cyclone formation at a low 20% as the emerging GFS... CMC... and ECMWF model consensus shows development just after day 5 instead of within the 5-day period.
Regardless of tropical cyclone formation or not... the increasingly favorable upper wind pattern toward the latter part of the 5-day forecast period indicates potential for increasing thunderstorms and rainfall across Haiti... Jamaica... Cuba... the Cayman Islands... the Bahamas... and Florida peninsula during the weekend.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Jul 31)... 0% chance of tropical cyclone formation (just east of the southern Lesser Antilles near 15.5N-59.5W)
IOH 48 Hr Outlook (1200Z Aug 1)... 0% chance of tropical cyclone formation (northeastern Caribbean south of Puerto Rico near 16N-66W)
IOH 72 Hr Outlook (1200Z Aug 2)... 0% chance of tropical cyclone formation (north-central Caribbean just offshore of the Haiti/Dominican Republic border near 17N-71.5W)
IOH 96 Hr Outlook (1200Z Aug 3)... 10% chance of tropical cyclone formation (between eastern Jamaica and eastern Cuba near 19N-76.2W)
IOH 120 Hr Outlook (1200Z Aug 4)... 20% chance of tropical cyclone formation (just east-southeast of the Isle of Youth of western Cuba near 21N-82W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT**************************
Formation chance through 48 hours... 0%
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 30) CMC Model Run...
**For area of interest #14... north side of tropical wave develops into a tropical low just southwest of the western Bahamas at 108 hours... tropical low subsequently turns north along Florida peninsula east coast through 144 hours and then curves north-northeast parallel to and offshore of the Carolina coast through 168 hours while strengthening into a tropical cyclone
0000Z (Jul 30) ECMWF Model Run...
**For area of interest #14... north side of tropical wave develops into a broad tropical low over the Florida peninsula through 132 hours... as the broad tropical low lifts north into the southeastern US it develops a better-defined center just offshore of the Georgia/South Carolina border at 168 hours
1200Z (Jul 30) GFS Model Run...
**For area of interest #14... north side of tropical wave fractures into a surface trough that turns north across the eastern Gulf of Mexico through 123 hours... becomes quasi-stationary in the northeastern Gulf after that time while trapped between the Atlantic surface ridge to the east and eastern North America surface ridge building behind a departing lengthy front to the north... quasi-stationary feature develops into a tropical depression just offshore of the Florida Panhandle Big Bend by 153 hours which then slowly drifts west through 168 hours while staying a weak tropical cyclone
0600Z (Jul 30) NAVGEM Model Run...
**For area of interest #14... no development shown
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