*******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.**********
...THURSDAY JULY 27 2023 8:15 AM EDT...
Atlantic tropical activity remains active with multiple areas of interest in progress:
(1) See area of interest #14 section below for an update on the tropical wave that is now moving across the central Caribbean.
(2) See area of interest #16 and #18 sections below for an update on the disturbed weather in the western Atlantic and northwestern Bahamas
(3) See area of interest #17 section below for more information on a tropical wave of low pressure in the eastern tropical Atlantic being monitored for signs of development by the NHC for the days ahead... this wave is forecast to pass over or near the Lesser Antilles in about five days.
Note my forecasts were completed earlier today at 0000Z. Any changes that have occurred with each area of interest since then are noted in each area of interest section below.
AREA OF INTEREST #14... Satellite image of the current central Caribbean tropical wave of low pressure and a new disturbance over the northwestern Bahamas (Area of Interest #18) as of 0100Z earlier today:
The tropical wave of low pressure that was over the eastern Caribbean has seen a notable increase in thunderstorms while moving across the central Caribbean Wednesday and through the early morning hours of today. While reaching the far southwestern periphery of the steering Atlantic surface ridge where steering is weaker... the tropical wave is likely to continue gradually slowing down while also curving more northward in its westward trajectory. By the end of the 5 day forecast period the upper trough regime that has been parked over eastern North America will finally be moving eastward and away... with the western convergence zone of the exiting regime and eastern converge zone of a southern US upper ridge to build in its wake creating a northern Gulf and eastern US surface ridge. This surface ridge is likely to become bisected by a southeastern US surface front to be driven by the tail end of the exiting eastern North America upper troughing... with this tail end upper vorticity eventually surging southwestward toward the Gulf while pushed around by the southern US upper ridge. The tropical wave is expected to continue west-northwest across the Yucatan peninsula and into the southwestern Gulf of Mexico while steered by the eastern US to northern Gulf surface ridge. Regarding odds of tropical cyclone formation... this tropical wave is finding itself underneath a developing upper anticyclone between central Atlantic upper vorticity to the northeast and northwest Caribbean upper vorticity to the northwest. The low shear and upper outflow of the anticyclone has helped in the redevelopment of the wave’s thunderstorms. Moreover the northwest Caribbean upper vorticity is forecast to shift west and away while guided by the southern US upper ridge... allowing the anticyclone to stay stacked with the wave as it continues west-northwest. I have raised peak odds of tropical cyclone formation to 20%... with the low odds a balance between the above observations while also accounting for the ongoing lackluster computer model support. The odds are lowered from this peak by days 4 and 5 at first due to land interaction with the Yucatan... followed by the arrival of less favorable upper vorticity that surges southwest toward the Gulf and this tropical wave as noted above.
The re-invigorated tropical wave has produced periods of heavy rainfall over Haiti and the Dominican Republic as of Wednesday... and will bring rainfall to Jamaica and the Cayman Islands and possibly Cuba through Friday. The Yucatan peninsula would then be overspread by rainfall this weekend if the wave remains in its current state or develops further.
Update as of 7 AM EDT... the tropical wave has seen a decrease in thunderstorm activity over the last several hours.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jul 28)... 10% chance of tropical cyclone formation (just south-southwest of Jamaica near 16N-78W)
IOH 48 Hr Outlook (0000Z Jul 29)... 20% chance of tropical cyclone formation (just southwest of the Cayman Islands near 18N-83W)
IOH 72 Hr Outlook (0000Z Jul 30)... 20% chance of tropical cyclone formation (northeast coast of the Yucatan peninsula near 20N-87W)
IOH 96 Hr Outlook (0000Z Jul 31)... 10% chance of tropical cyclone formation (offshore of the northwestern Yucatan peninsula near 22N-91W)
IOH 120 Hr Outlook (0000Z Aug 1)... 10% chance of tropical cyclone formation (southwestern Gulf of Mexico near 23.5N-94.5W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************
Not in the official outlook
AREA OF INTEREST #16... The surface trough of low pressure that has been closing in on the northwestern Bahamas is losing dominance relative to a new disturbance that has quickly materialized over the Bahamas (see area of interest #18 section below for more info on the new disturbance). Therefore this trough is no longer an area of interest... this is my final statement on this trough on this blog.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jul 28)... 0% chance of tropical cyclone formation (offshore of the southeastern US near 30N-77.5W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************
Not in the official outlook
AREA OF INTEREST #17... A typical tropical wave of low pressure with disorganized thunderstorm activity is continuing westward in the eastern tropical Atlantic. Because the wave has computer model support showing development in the longer range... the NHC continues to mention it as an area of interest in their tropical weather outlook. The tropical wave is expected to continue westward into the central tropical Atlantic where it then will accelerate to a faster forward speed under the influence of the currently strong Atlantic surface ridge. The current eastern North America upper trough regime is expected to move offshore into the Atlantic by day 5 where it will induce a surface ridge weakness... and a northward bend toward the weakness is anticipated in the longer range. I remain south of the emerging model consensus regarding track as I anticipate the tropical wave is more likely to develop further south... away from the dry Saharan air... than what the models are currently showing in the 72+ hour window. Regarding odds of development... I continue to have a peak of 20% despite growing computer model support due to potential disruption from the dry Saharan air lurking to the north and as the wave has not gotten better organized. However I do agree with the NHC holding peaks odds for the longer term (toward day 5) when the wave eventually moves into lower concentrations of dry Saharan air and as the wave needs time to organize from its current disorganized state. Upper winds through day 5 are forecast to be favorable with the expansive regional tropical upper ridge... featuring low shear and upper outflow... being forecast to persist. Interests in the Lesser Antilles should be aware that this tropical wave will arrive by day 5... possibly with a round of heavy rainfall and gusty winds should it in fact develop.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jul 28)... 0% chance of tropical cyclone formation (eastern tropical Atlantic near 11.5N-35W)
IOH 48 Hr Outlook (0000Z Jul 29)... 10% chance of tropical cyclone formation (central tropical Atlantic near 12N-42W)
IOH 72 Hr Outlook (0000Z Jul 30)... 20% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-50W)
IOH 96 Hr Outlook (0000Z Jul 31)... 20% chance of tropical cyclone formation (east of the Lesser Antilles near 14N-57W)
IOH 120 Hr Outlook (0000Z Aug 1)... 20% chance of tropical cyclone formation (northern Lesser Antilles near 17.5N-61.5W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************
Formation chance through 48 hours...0%
Formation chance through 7 days (168 hours)...40%
AREA OF INTEREST #18... A new disturbance consisting of increased thunderstorms and a surface trough of low pressure appears to be have materialized over the northwestern Bahamas while supported by the outflow of the current western Atlantic upper ridge. Noting that the current central Atlantic upper vorticity and northwestern Caribbean upper vorticity were linked earlier on Wednesday... and split flow upper divergence between easterlies rounding the north side of the linked vorticity and southerlies rounding the west side of the west Atlantic upper ridge may have been a boosting factor to allow this disturbance to materialize. Noting that this disturbance will be interacting with the same features that area of interest (AOI) #14 will be interacting with... including the northwest Caribbean upper vorticity that will move westward and away... the favorable upper anticyclone that is materializing between the central Atlantic and northwest Caribbean upper vorticity lobes... and a surface ridge to build over the eastern US and northern Gulf of Mexico. The track forecast below is based on this disturbance curving around the surface ridge... taking it across the Florida peninsula and Gulf and then turning it north and northeast into Louisiana and Mississippi as it rounds the west side of the ridge and then bends east into the embedded surface ridge weakness/ surface front to be located over the southeastern US (more info on this front is in the AOI #14 section above). Even though this disturbance will be below the aiding low shear and outflow of the above mentioned upper anticyclone... I keep peak development odds below AOI #14 as this system and #14 are likely to compete for surface inflow and upper outflow... and currently AOI #14 has the upper hand while showing a stronger low-level vorticity signature in the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=).
This disturbance has been bringing heavy rainfall to the northwest Bahamas Wednesday and into this morning... and will likely bring heavy rainfall across the Florida peninsula later today. Louisiana may see heavy rainfall this weekend if the disturbance maintains itself while moving across the Gulf of Mexico.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Jul 28)... 0% chance of tropical cyclone formation (southwest Florida coast near 26.2N-81.5W)
IOH 48 Hr Outlook (0000Z Jul 29)... 10% chance of tropical cyclone formation (eastern Gulf of Mexico near 27.2N-85W)
IOH 72 Hr Outlook (0000Z Jul 30)... 10% chance of tropical cyclone formation (offshore of southeastern Louisiana near 27.2N-90W)
IOH 96 Hr Outlook (0000Z Jul 31)... 10% chance of tropical cyclone formation (near southwestern Louisiana coast near 30N-92.5W)
IOH 120 Hr Outlook (0000Z Aug 1)... 0% chance of tropical cyclone formation (northwestern Mississippi near 33.8N-90W)
******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM 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/).
1200Z (Jul 26) CMC Model Run...
**For area of interest #14... no development shown
**For area of interest #16... no development shown
** For area of interest #17... develops into a tropical low near 16N-42W at 60 hours... develops into a tropical depression near 18N-52.5W at 90 hours... while curving north to 22.5N-59W through 126 hours develops into a strengthening tropical storm
**For area of interest #18... no development shown
1200Z (Jul 26) ECMWF Model Run...
**For area of interest #14... no development shown
**For area of interest #16... no development shown
** For area of interest #17... develops into a tropical low near 18N-51W at 90 hours which moves northwest to 21.5N-58W through 120 hours
**For area of interest #18... no development shown
1200Z (Jul 26) GFS Model Run...
**For area of interest #14... no development shown
**For area of interest #16... no development shown
**For area of interest #17... develops into a tropical low near 15.5N-45W at 72 hours and becomes a tropical depression near 16.2N-50W at 84 hours... while curving northwest to 20.5N-57W through 120 hours develops into a strengthening tropical storm
**For area of interest #18... no development shown
1200Z (Jul 26) NAVGEM Model Run...
**For area of interest #14... no development shown
**For area of interest #16... no development shown
** For area of interest #17... develops into a tropical low near 14N-41.5W at 84 hours… develops into a tropical depression while passing just northeast of the Lesser Antilles at 138 hours
**For area of interest #18... no development shown
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