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BIRDSEYE VIEW POSTS

Since 2012 on the now retired Weather Underground blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at IOHurricanes@outlook.com 

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MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #39

*******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.**********


...WEDNESDAY JULY 26 2023 6:55 AM EDT...

Atlantic tropical activity has been increasing with now three areas of interest being watched for possible development:

(1) See area of interest #14 section below for an update on the tropical wave that is now moving across the eastern Caribbean after crossing the Lesser Antilles

(2) See area of interest #16 section below for an update on the western Atlantic surface trough of low pressure forecast to swing toward the northwestern Bahamas and southeastern United States coastline later this week and into the weekend.

(3) See area of interest #17 section below for more information on a tropical wave of low pressure in the eastern tropical Atlantic now being monitored for signs of development by the NHC for the days ahead... this wave is forecast to approach the Lesser Antilles just after five days.


Note my forecasts were completed earlier today at 0000Z. Any changes that have occurred with each area of inerest since then are noted in each area of interest section below.


AREA OF INTEREST #14... The tropical wave of low pressure that has recently crossed the Lesser Antilles is now continuing rapidly westward across the eastern Caribbean... and based on the remaining cloud deck it has as of 0000Z appears to have its maximum spin near 12.5N-66W. While reaching the far southwestern periphery of the steering Atlantic surface ridge where steering is weaker... the tropical wave is likely to gradually slow down and also curve more northward in its westward trajectory. By day 5 the upper trough regime that has been parked over eastern North America will have finally moved eastward and away... with the western convergence zone of the exiting regime building a weak surface ridge over the eastern US that continues the west-northwest track of the wave across the Yucatan peninsula and into the southwestern Gulf of Mexico. My updated forecast track below is a reflection of the above ideas... and is adjusted westward as the wave has been moving faster than my previous forecasts. Regarding odds of tropical cyclone formation... I have lowered odds to a peak of 10% as the wave still lacks computer model support... a closed surface circulation... and has also lost thunderstorm activity. The current lack of a closed circulation is also why I have 24 hour odds at 0%. Noting that the central Atlantic upper vorticity to the northeast is not expected to be pushed into the tropical wave... and the western Caribbean upper vorticity is also forecast to retrograde westward and away while first pushed by the western Atlantic upper ridge... and then by a southern US upper ridge that builds in the wake of the departing eastern North America upper trough regime. Therefore the tropical wave will remain aligned with an upper anticyclone (low shear and upper outflow) in between the two lobes of upper vorticity which is a factor potentially favoring the wave in the days ahead.


Jamaica and the Cayman Islands may see increased rainfall later this week... followed by the Yucatan peninsula by the weekend... should the tropical wave in fact take advantage of the upper anticyclone mentioned in the prior paragraph and redevelop thunderstorms.


Update as of 0600Z... the NHC has removed this area of interest from their tropical weather outlook

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

IOH 24 Hr Outlook (0000Z Jul 27)... 0% chance of tropical cyclone formation (central Caribbean Sea near 14N-72W)

IOH 48 Hr Outlook (0000Z Jul 28)... 10% chance of tropical cyclone formation (just south-southwest of Jamaica near 16N-78W)

IOH 72 Hr Outlook (0000Z Jul 29)... 10% chance of tropical cyclone formation (just southwest of the Cayman Islands near 18N-83W)

IOH 96 Hr Outlook (0000Z Jul 30)... 10% chance of tropical cyclone formation (northeast coast of the Yucatan peninsula near 20N-87W)

IOH 120 Hr Outlook (0000Z Jul 31)... 10% chance of tropical cyclone formation (offshore of the northwestern Yucatan peninsula near 22N-91W)

******National Hurricane Center (hurricanes.gov) official outlook as of 2 AM EDT*****************************

Not in the offical outlook


AREA OF INTEREST #16... The western Atlantic surface trough of low pressure that formed yesterday is continuing west-northwestward around the periphery of the steering Atlantic surface ridge and will arrive toward the northwestern Bahamas and northeastern Florida coast through 48 hours. Once it reaches the western periphery of the steering ridge... a turn to the north and then northeast... paralleling the southeastern US coast from Georgia South Carolina... is anticipated in the 72+ hour window. The forecast track of the surface trough takes it below the upper layers of the western Atlantic upper ridge where low wind shear and upper outflow may make conditions conducive for tropical development... and the NHC continues to monitor this feature into their tropical weather outlook. I agree with the NHC lowering peak odds of tropical cyclone formation to 10% as the computer model support showing development is lacking and the low-level spin as detected on the CIMSS 850 mb vorticity product has weakened (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=). By day day 4 I lower odds to 0% and end the outlook due to potential for increased land interaction and as this system moves into less favorable westerly wind shear associated with the ongoing upper trough regime over eastern North America.


The northwestern Bahamas... and the southeastern US coast from northeastern Florida to South Carolina may see increased rainfall from this feature later this week and into the weekend.


Update as of 0600Z... the NHC has dropped development odds to 0% for this area of interest as computer model support for this feature has continued to be absent.

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

IOH 24 Hr Outlook (0000Z Jul 27)... 0% chance of tropical cyclone formation (just east of the northwestern Bahamas near 26.5N-75W)

IOH 48 Hr Outlook (0000Z Jul 28)... 10% chance of tropical cyclone formation (just offshore of northeastern Florida near 27.5N-79W)

IOH 72 Hr Outlook (0000Z Jul 29)... 10% chance of tropical cyclone formation (just offshore of Georgia near 31.5N-80.2W)

IOH 96 Hr Outlook (0000Z Jul 30)... 0% chance of tropical cyclone formation (coastal northeastern South Carolina near 33N-79W)

******National Hurricane Center (hurricanes.gov) official outlook as of 2 AM EDT*****************************

Formation chance through 48 hours...0%

Formation chance through 7 days (168 hours)...0%


AREA OF INTEREST #17... A typical tropical wave of low pressure with disorganized thunderstorm activity has recently entered the eastern Atlantic from western Africa... and is currently passing just south of the Republic of Cabo Verde Islands. Because the wave has had some intermittent computer model support showing development in the longer range... the NHC has introduced it as an area of interest in their tropical weather outlook... and it is the seventeenth tropical Atlantic area of interest tracked on this site this year. 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... similar to what was recently seen with area of interest #14. Regarding odds of development... I agree with the NHC’s low peak of 20% as the tropical wave only has intermittent computer model support showing development... and I also agree with the peak being in the longer term (toward day 5) when the wave moves into lower concentrations of dry Saharan air and as the wave needs time to organize from its current disorganized state. I also agree that of the current three areas of interest that this has the highest odds of development as this is the only tropical feature in the Atlantic basin with any computer model support (among the GFS... NAVGEM... CMC... ECMWF group) as of this writing. 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 approach the region just after day 5... possibly with a round of heavy rainfall and gusty winds should it in fact develop.


Update as of 0600Z... the NHC has raised development odds to 30% for this area of interest as computer model support for this feature is gradually increasing.

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

IOH 24 Hr Outlook (0000Z Jul 27)... 0% chance of tropical cyclone formation (eastern tropical Atlantic near 11.5N-29W)

IOH 48 Hr Outlook (0000Z Jul 28)... 0% chance of tropical cyclone formation (eastern tropical Atlantic near 11.5N-35W)

IOH 72 Hr Outlook (0000Z Jul 29)... 10% chance of tropical cyclone formation (central tropical Atlantic near 12N-42W)

IOH 96 Hr Outlook (0000Z Jul 30)... 20% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-50W)

IOH 120 Hr Outlook (0000Z Jul 31)... 20% chance of tropical cyclone formation (east of the southern Lesser Antilles near 13N-57W)

******National Hurricane Center (hurricanes.gov) official outlook as of 2 AM EDT*****************************

Formation chance through 48 hours...0%

Formation chance through 7 days (168 hours)...30%


...COMPUTER MODEL SUMMARY...

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


1200Z (Jul 25) CMC Model Run...

**For area of interest #14... no development shown

**For area of interest #16... no development shown

** For area of interest #17... no development shown


1200Z (Jul 25) ECMWF Model Run...

**For area of interest #14... no development shown

**For area of interest #16... no development shown

** For area of interest #17... no development shown


1800Z (Jul 25) 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-54W at 111 hours and becomes a tropical depression near 16.2N-56W at 123 hours... passes just north of the northern Lesser Antilles at 147 hours as a tropical storm


1200Z (Jul 25) NAVGEM Model Run...

**For area of interest #14... no development shown

**For area of interest #16... no development shown

** For area of interest #17... no development shown

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