*******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.*********
...FRIDAY AUGUST 30 2024 12:30 PM EDT...
Atlantic tropical activity remains elevated with the presence of multiple hot spots as follows:
(1) In the northwestern corner of the Gulf of Mexico... thunderstorms continue in association with the eastern divergence zone of the upper vortex over Texas which has decayed into a fading upper trough... and the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=vor&zoom=&time=) shows a mid-level low pressure rotation that has developed which is already making landfall over southeastern Texas while moving northwest around the sprawling surface ridge centered over eastern Canada. Tropical cyclone formation is not expected due to the landfall. However heavy rainfall is possible across southeast Texas and southern Louisiana for another 24 hours until the fading upper trough dissipates and the mid-level tropical low dissipates due to landfall.
(2) Thunderstorms have erupted over the central Bahamas due to the combination of surface convergence on the north apex of the surface tropical wave crossing the central Caribbean and upper divergence on the southeast side of a pocket of ongoing western Atlantic upper vorticity. However tropical development is not expected here as the north apex of the tropical wave continues west-northwest into a zone of suppressing upper convergence on the back side of the upper vorticity.
(3) The tropical low pressure swirl that was east of Bermuda has weakened to a trough due to immense westerly vertical wind shear. However over the next couple of days the surface ridge that is about to move offshore from eastern Canada will push the surface trough into the northwest Atlantic. At the same time the current Ohio Valley shortwave upper trough advances into the northwest Atlantic while amplifying into a cut-off upper vortex due to upstream amplification of warm core upper ridging to the northwest... with the forecast upper vortex increasing upper divergence and dropping wind shear levels over the surface trough. Therefore the surface trough has potential to be re-upgraded to an area of interest for tropical development in the days ahead.
(4) See areas of interest #19 and #21 sections below for an update on the pair of central and eastern Atlantic tropical waves of low pressure which may attempt to develop underneath the currently expanding regional tropical upper ridge axis.
AREA OF INTEREST #19... The tropical wave of low pressure that was previously in the eastern tropical Atlantic is now in the central tropical Atlantic. The tropical wave is not well-organized while not featuring distinct curved thunderstorm bands... instead it is located at the east end of an elongated band of thunderstorms being supported by the outflow of a tropical upper ridge axis that is expanding overhead. The tropical wave is expected to continue generally west across the Lesser Antilles and into the Caribbean Sea in the days ahead as the currently developing Canadian frontal cyclone passes too far north when it later enters the Atlantic to influence the track of this system. During the five day forecast period the southwest-northeast tilted string of upper vorticity to the northwest becomes stationary while trapped between the tropical upper ridge axis and the upper ridge that has recently flared up north of the Caribbean Islands. Whether or not this system develops hinges on how fast the disruptive upper vorticity string decays... and since there is uncertainty on this matter my peak odds of tropical cyclone formation in this update are only 20%. My short-term odds of development are 0% as this system will first need time to get better organized... and then I stop ramping odds above 20% by 72+ hours as this is when this system would encounter shear or upper outflow suppression from the upper vorticity string if it hasn't decayed sufficiently by that time. Regardless of tropical cyclone formation or not... this tropical wave may bring heavy rain and gusty winds to the Lesser Antilles by early this upcoming week.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0600Z Aug 31)… 0% chance of tropical cyclone formation (central tropical Atlantic near 12N-46W)
IOH 48 Hr Outlook (0600Z Sep 1)… 10% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-50W)
IOH 72 Hr Outlook (0600Z Sep 2)… 20% chance of tropical cyclone formation (central tropical Atlantic near 13N-54W)
IOH 96 Hr Outlook (0600Z Sep 3)… 20% chance of tropical cyclone formation (just east of the central Lesser Antilles near 13.5N-59W)
IOH 120 Hr Outlook (0600Z Sep 4)… 20% chance of tropical cyclone formation (eastern Caribbean Sea near 14N-64W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT***************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 40%
AREA OF INTEREST #21... The vigorous tropical wave of low pressure that was previously over western Africa has moved offshore within the last 36 hours and is passing south of the Republic of Cabo Verde Islands. The tropical wave appears to have become elongated east-to-west while featuring a broad rotation near 11N-21W featuring a small area of thunderstorms close to the Republic of Cabo Verde Islands... and an area of thunderstorms further west... toward 10N-32W as of this writing... that has been racing off to the west. The focus of this tropical wave has been toward the rotation near 11N-21W which is used as the initial position for the updated outlook below. This tropical wave is at risk of developing underneath the expanding tropical upper ridge axis that area of interest #19 may also take advantage of. For the 5-day window... I have set peak odds of tropical cyclone formation at 30%... which is higher than area of interest #19... as this tropical wave will spend all five days away from the unfavorable string of upper vorticity that will be positioned toward the eastern Caribbean Islands. Noting that after day 5... should this system be a stronger/taller tropical cyclone... it could curve more north in track while pulled by the upper southerly flow that would be on the west side of the tropical upper ridge axis and out ahead of the string of upper vorticity. Final note regarding this area of interest... I weight the 30% odds toward day 5 instead of the short-term to give time for the wave to move away from higher concentrations of dry Saharan air toward the east part of the Atlantic basin.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0600Z Aug 31)... 0% chance of tropical cyclone formation (south-southwest of the Republic of Cabo Verde Islands near 12N-25W)
IOH 48 Hr Outlook (0600Z Sep 1)... 10% chance of tropical cyclone formation (eastern tropical Atlantic near 12.5N-29.5W)
IOH 72 Hr Outlook (0600Z Sep 2)... 20% chance of tropical cyclone formation (eastern tropical Atlantic near 12.8N-33.5W)
IOH 96 Hr Outlook (0600Z Sep 3)... 30% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-38W)
IOH 120 Hr Outlook (0600Z Sep 4)... 30% chance of tropical cyclone formation (central tropical Atlantic near 13.5N-42W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT***************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 20%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
1200Z (Aug 29) CMC Model Run...
**For area of interest #19... develops into a tropical low near 13N-53.5W at 84 hours… crosses the central Lesser Antilles as a strengthening compact tropical cyclone around 120 hours… passes just south of Haiti at 168 hours
**For area of interest #21... no development shown
**Tropical wave emerges from west coast of Africa at 84 hours… crosses the Republic of Cabo Verde Islands as a broad tropical low at 126 hours… broad tropical low located just west of the Republic of Cabo Verde Islands by 168 hours
1200Z (Aug 29) ECMWF Model Run...
**For area of interest #19... crosses there central Lesser Antilles as a tropical low at 108 hours… tropical low located southeast of Jamaica by 168 hours
**For area of interest #21... develops into a tropical low near 15.5N-44W by 168 hours
0000Z (Aug 30) GFS Model Run...
**For area of interest #19... no development shown
**For area of interest #21... no development shown
1800Z (Aug 29) NAVGEM Model Run...
**For area of interest #19... crosses the northern Lesser Antilles as a tropical low at 96 hours with tropical cyclone formation suggested just south of Hispaniola by 138 hours… as a strengthening tropical cyclone located south of eastern Cuba at 168 hours
**For area of interest #21... passes south of the Republic of Cabo Verde Islands as a broad tropical low at 36 hours… tropical low opens back to a wave that nears the Lesser Antilles by 168 hours
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