*******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 2 2024 4:08 PM EDT...
See area of interest #14 section below for more information on the organizing tropical wave of low pressure currently moving across Cuba that is expected to strengthen into a tropical storm while curving north across the Florida peninsula and then into the Atlantic waters just offshore of the southeastern United States. See area of interest #15 section below for a final statement on the northwest Atlantic low-level low pressure spin which is now transitioning into a surface cold front... tropical cyclone formation here is no longer possible.
Elsewhere... a tropical wave of low pressure is producing curved bands of thunderstorms near 10N-41W. However in the next 72 hours as the wave moves into the Lesser Antilles... upper winds are forecast to be less favorable for tropical development as follows... (1) a warm core northwestern Atlantic upper ridge is expected to setup due to warm southerly flow ahead of the currently developing eastern North America surface frontal system... (2) 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 toward the Lesser Antilles ... therefore this wave is not expected to develop. Further east... satellite imagery over Africa suggests the African Easterly Jet and associated surface tropical waves of low pressure are positioned further north. This will likely make the waves prone to ingesting dry air from the north Africa Sahara desert as they later move southwestward into the eastern tropical Atlantic around the southeast side of the Atlantic surface ridge... and none of the current computer model runs are developing these waves.
AREA OF INTEREST #14 (POTENTIAL TROPICAL CYCLONE FOUR)... The surface tropical wave of low pressure that has been passing westward across the northern Caribbean Islands continues to show signs of organization while featuring curved bands of thunderstorms overspreading much of the Bahamas and eastern Cuba as of this writing. The thunderstorm bands suggest there are double rotations... with a southern one south of eastern Cuba and north of Jamaica and a northern one on the north coast of eastern Cuba. The southern rotation is likely an upper-level one as the upper vortex that was near Hispaniola has recently merged with the upper vortex that was near the southern Lesser Antilles to make an axis of upper vorticity that lines up with Jamaica. The northern one... which has been following the previous forecast tracks... remains the low-level rotation of interest... albeit the CIMSS 850 mb vorticity product suggests the low-level rotation is elongated north to south and a southward relocation of the best-estimated center cannot be ruled out entirely (https://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=vor&zoom=&time=). For now my forecast track assumes that a southward relocation does not occur as the upper-level wind profile toward the north is improving with an expanding upper anticyclone (area of low shear and outflow) in between the Caribbean axis of upper vorticity and western Atlantic upper vortex currently near 25N-62.5W... and the upper anticyclone is expected to continue expanding as the cool core Caribbean axis of upper vorticity continues to weaken from prolonged isolation from high-latitude cold air. And combined with rather warm 30+ deg C waters and current well-organized state of the northern rotation it appears tropical cyclone formation is just about imminent... and I have begun a tropical cyclone formation forecast with specific track and intensity forecast. The NHC has also begun to issue advisories on this system under the header of potential tropical cyclone four in order to issue tropical storm watches/warnings ahead of time for the Florida Keys and portions of the Florida peninsula which are in the path of this system.
Over the next 72 hours a northward turn across the Florida peninsula and into the waters just offshore of the southeastern United States is shown as this system rounds the west side of the Atlantic surface ridge and into the ridge weakness associated with the currently developing eastern North America surface frontal system. My forecast track during this time is based on the forecast isobar contours of the surface ridge which takes the center in the waters between the south tip of Florida and Cuba by 24 hours... then across the Keys and very close to the southwest Florida peninsula coast until it finally moves north into the peninsula from Fort Myers through 36 hours. Because my forecast track has more land interaction with the Florida peninsula than the NHC... the initial part of my intensity forecast is lower than the NHC and assumes a first peak of 50 mph maximum sustained winds followed by a slightly lower intensity by 48 hours due to landfall. The forecast intensity in the shorter term is precarious as only a slight shift in the forecast which keeps the center over water for longer could yield a higher intensity than currently shown given that we have an organizing system over very warm waters and underneath a favorable upper anticyclone. In 72+ hours the models have come into better agreement on the longer term fate of this system. Even though this system misses the northeastward exit with the currently developing eastern North America frontal system... not much of a blocking surface ridge builds behind the frontal system as a shortwave upper trough and second surface frontal system quickly move in to the Ohio Valley region of the United States... far south enough and close enough to this system to keep this system moving northeastward parallel to the southeastern United States shoreline. The models are also coming into better agreement that the upper vorticity to be left behind by the eastern North America frontal system will likely setup as an amplified upper trough or vortex just to the west... which would favor this system by keeping longer-range southwesterly shear levels lower and upper divergence higher as opposed to an east-west elongated upper vorticity band that wouldn't have a focused upper divergence zone and higher shear. Thus after this system leaves the Florida peninsula my forecast (and also the NHC) show gradual re-intensification through 120 hours. The amount of divergence and lower shear would honestly support a hurricane in the longer range... so if the current upper wind forecasts hold steady I will raise the longer-term intensity forecast in future updates.
Expect heavy rains and possible gusty winds across much of the Bahamas and Cuba in the next 24 hours... spreading into the Keys and Florida peninsula. I recommend interests across the Keys and Peninsula should now be making preparations for tropical cyclone conditions (gusty winds... heavy rains... and coastal surf)... the only exception is the southeastern part of the peninsula toward Miami where the forecast track keeps the gusty winds away. Interests across the southeastern United States shoreline from Georgia to the Carolinas should closely monitor the progress of this system carefully as tropical cyclone impacts for the early part of this upcoming week have become increasingly likely. Cannot also rule out more inland tropical cyclone impacts (combo of heavy rain and gusty winds) for eastern North Carolina and southeastern Virginia... especially if an upper vortex sets up just west of this system instead of an upper trough as the northeast side of such a vortex might try to pull this system toward land around day 5.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1800Z Aug 2)... 30 mph maximum sustained wind tropical low centered on the north coast of eastern Cuba at 21N-77W
IOH 24 Hr Forecast (1800Z Aug 3)... 40 mph maximum sustained wind tropical storm centered just offshore of the north coast of Cuba and south of the Florida peninsula at 24N-80.8W
IOH 48 Hr Forecast (1800Z Aug 4)... 45 mph maximum sustained wind tropical storm centered inland and just north of Fort Myers Florida at 27N-82W
IOH 72 Hr Forecast (1800Z Aug 5)... 50 mph maximum sustained wind tropical storm centered just offshore of Georgia at 30.5N-80W
IOH 96 Hr Forecast (1800Z Aug 6)... 60 mph maximum sustained wind tropical storm centered just offshore of the Carolinas at 31.5N-77.5W
IOH 120 Hr Forecast (1800Z Aug 7)... 65 mph maximum sustained wind tropical storm centered just south of Cape Hatteras North Carolina at 34N-75.5W
*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT************************
Landfall (0000Z Aug 5)... 65 mph maximum sustained wind tropical storm centered on the northwest coast of the Florida peninsula at 29.2N-82.7W
5-Day Position (1200Z Aug 7)... 60 mph maximum sustained wind tropical storm centered just southeast of Cape Fear North Carolina at 33.6N-77.5W
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT**************************
Formation chance through 48 hours... 80%
Formation chance through 7 days... 90%
AREA OF INTEREST #15... The northwestern Atlantic low-level low pressure rotation has continued accelerating east-northeastward around the north side of the steering Atlantic surface ridge. This system remains supported by divergence on the east side of an upper trough fast approaching from eastern Canada. In satellite pictures this system has seen a reduction in thunderstorms and appears to be transitioning into an elongated cloud band that is becoming attached to the surface frontal low also approaching from the east coast of Canada. As such the surface trough associated with this area of interest... marked on the 1200Z NHC TAFB surface analysis... will likely be upgraded to a non-tropical cold front once air mass contrasts become more established on either side of it... and tropical cyclone formation is no longer possible. This is 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 (1800Z Aug 3)... 0% chance of tropical cyclone formation (north Atlantic near 41N-45W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 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/).
0000Z (Aug 2) CMC Model Run...
**For area of interest #14... organizes into a tropical low moving northwest into the Florida Keys by 36 hours... while turning north the tropical low makes landfall on the northwest coast of the Florida peninsula between 60 and 66 hours... through 96 hours while moving across the far eastern part of the Carolinas begins to intensify as a subtropical (less tropical) low/cyclone supported by the divergence zone of a southern upper trough fragment left behind by the eastern North America frontal system... the subtropical low/cyclone then turns eastward and offshore of the North Carolina Outer Banks by 120 hours... the subtropical cyclone then grows in size and intensity while continuing northeastward with the center reaching the waters southeast of Massachusetts (near 40.2N-69.5W) at 138 hours... completes transition into a more elongated non-tropical frontal cyclone thereafter that moves across eastern Newfoundland by 162 hours.
**For area of interest #15... develops into a rather compact possible tropical cyclone near 39N-63.5W at 12 hours... while racing east-northeast into the open north Atlantic merges with cold front tied to frontal low approaching from eastern Canada by 36 hours while located near 41.5N-48.5W... remnant frontal low loses identity along the front while approaching the British Isles of Europe by 90 hours
0000Z (Aug 2) ECMWF Model Run...
**For area of interest #14... organizes into a broad tropical low centered just southwest of the Florida Keys by 42 hours... while turning north the tropical low makes landfall on the northwest coast of the Florida peninsula at 78 hours... while becoming entangled with and steered by South Carolina coastal upper vortex deposited by eastern North America frontal system the tropical low proceeds to hook east into offshore waters and then north and strengthens into a tropical or subtropical cyclone supported by the eastern divergence zone of the upper vortex while centered just south of southeastern North Carolina at 144 hours... the tropical/subtropical cyclone then proceeds to move north-northwest into and across eastern North Carolina through 168 hours while pulled in by northeast quadrant of upper vortex.
**For area of interest #15... small surface low racing east-northeast into the open north Atlantic loses identity when absorbed by cold front driven by currently approaching eastern Canada frontal low while positioned near 41.5N-52.5W at 30 hours
1200Z (Aug 2) GFS Model Run...
**For area of interest #14... organizes into tropical low centered between Cuba and the Florida Keys at 27 hours... tropical low proceeds to turn north and become a compact strengthening tropical cyclone centered just northwest of Fort Myers Florida and just southwest of Tampa Bay Florida by 48 hours... tropical cyclone makes landfall over Tampa Bay Florida by 51 hours and emerges into the Atlantic from northeastern Florida by 60 hours... while taking advantage of lower shear and increased divergence on east side of upper vortex deposited by eastern North America frontal system the tropical cyclone strengthens into a hurricane through 102 hours while arcing north toward the southeastern North Carolina coast under the upper vortex's steering influence... frontal system approaching from the Ohio Valley region of the US pulls the tropical cyclone north-northeast across the North Carolina Outer Banks through 129 hours... while gradually transitioning into an intense non-tropical frontal cyclone the center passes just offshore of Cape Cod Massachusetts by 153 hours and moves into the eastern tip of Nova Scotia by 165 hours
**For area of interest #15... small surface low racing east-northeast into the open north Atlantic merges with cold front driven by currently approaching eastern Canada frontal low while positioned near 43N-50W at 18 hours... remnant frontal low proceeds to lose identity along the front shortly thereafter (through 39 hours)
0600Z (Aug 1) NAVGEM Model Run...
**For area of interest #14... organizes into tropical low centered between Cuba and the south tip of the Florida peninsula at 30 hours... proceeds to arc north in track across the Florida Keys and into the southwest coast of the peninsula through 42 hours... while continuing to gradually curve more northeast in track the center of the tropical low emerges into the Atlantic from northeastern Florida and coastal Georgia and proceeds to become a tropical cyclone centered just offshore of the central South Carolina coast at 72 hours... tropical cyclone center continues northeast parallel to and just offshore of the North Carolina coast from the NC/SC border to Cape Hatteras through 114 hours... while transitioning into an intense remnant non-tropical frontal cyclone approaches southeastern Newfoundland by 156 hours.
**For area of interest #15... no development shown
Comments