*******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 SEPTEMBER 3 2024 5:35 PM EDT...
The following are special updates on current areas of interest in the Atlantic basin while I am settling back at home after returning from vacation. Note that area of interest #19 may bring impacts to the Yucatan peninsula by this weekend... and area of interest #23 may bring impacts to the Republic of Cabo Verde Islands within the next few days.
AREA OF INTEREST #19... Over the labor day holiday weekend... the tropical wave of low pressure that was in the central tropical Atlantic became low in amplitude and was hard to define... and appeared to relocate westward. This has allowed it to cross the Lesser Antilles and eastern Caribbean sooner. As of this writing the tropical wave has seen an increase in thunderstorms just south of Haiti and the Dominican Republic while enhanced by split flow upper divergence in between two cells of the decaying regional upper vorticity string that previously suppressed the tropical wave. As the tropical wave continues across the central and western Caribbean... Yucatan peninsula... and into the eastern Bay of Campeche through day 5 it will encounter a sprawling regime of low shear and potentially enhancing upper outflow underneath the south side of an upper ridge (the upper ridge will be the merger between the upper ridges currently over the Bahamas and Gulf of Mexico). Despite this overall favorable upper wind outlook... over the next 24 hours I do not expect tropical cyclone formation as the wave crosses through the nearby cell of suppressing upper vorticity to the west... then through 96 hours only expect a low 15% chance of tropical cyclone formation as the wave crosses through the western Caribbean (and before landfall with the Yucatan peninsula) as the wave will then have to spend some time recovering from its short-term encounter with the suppressing upper vorticity cell. By 120 hours... for the eastern Bay of Campeche... I still hold a low 15% chance of tropical cyclone formation as the tropical wave will likely be recovering from land interaction with the Yucatan peninsula. Noting that beyond 120 hours (day 5)... if current trends continue I expect sharply higher odds of tropical cyclone formation for the Bay of Campeche or southwestern Gulf of Mexico as the emerging CMC... NAVEGM... and ECMWF model consensus suggests tropical cyclone formation for that timeframe. Noting the possible tropical cyclone may also be a merger between the tail end of the current surface front in the northwestern Gulf of Mexico and the tropical wave associated with this area of interest (more information on the tail end of the front is in area of interest #22 section below). Note that regardless of tropical cyclone formation or not... the Yucatan peninsula of Mexico may see heavy rainfall and gusty winds from this system by this weekend.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 15% (eastern Bay of Campeche)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 30%
AREA OF INTEREST #21... A tropical wave of low pressure that was previously in the eastern tropical Atlantic over the Labor Day weekend is now in the central tropical Atlantic... and as of this afternoon (based on satellite imagery) has its maximum rotation near 14N-40.5W. The tropical wave during the weekend was removed from the NHC outlook while the major computer models (CMC... NAVGEM... GFS... and ECMWF) did not develop it and its thunderstorm activity dwindled due to regional dry Saharan air. As of today however... despite still not having major computer model support... the NHC has re-introduced the wave back into its outlook as the wave has rebuilt a good amount of thunderstorm activity just northwest of the maximum rotation. I currently forecast the tropical wave to angle west-northwest toward the waters just north of the northeastern Caribbean Islands through day 5... at first due to the surface ridge weakness in the west Atlantic which will likely expand as the current central US low-amplitude upper trough moves offshore and enhances the current frontal low just offshore of the Carolinas. The western Atlantic surface ridge weakness is then maintained through day 5 as a high-amplitude upper trough roams toward the Atlantic from western North America... with its eastern divergence zone supporting a surface frontal system positioned on the east coast of North America by day 5. The warm surface southerly flow of the day-5 eastern North America surface frontal system will help bolster a warm core northwest Atlantic upper ridge that will push the decaying upper vorticity string to the west of the tropical wave westward and away... and should the tropical wave indeed become a stronger/taller tropical system within the next 5 days the upper-level southerly flow on the east side of the upper vorticity string may also help with the north angle of my forecast west-northwest track. Because of the recent increase in thunderstorms... and because I expect southerly shear levels to not be high enough to prevent development as the upper vorticity string moves west and away... I continue to set my odds of tropical cyclone formation for this tropical wave at 30%. I have not set higher odds due to the ongoing lack of computer model support.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 30% (north of the northern Lesser Antilles)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Formation chance through 48 hours... 10%
Formation chance through 7 days... 10%
AREA OF INTEREST #22… The tropical low pressure area that was in the northwestern Gulf of Mexico… positioned near the Texas and Louisiana coast… has spent the last couple of days drifting southwest instead of west and has made landfall over southern Texas. The south angle of the track may have been aided by the strength of the current eastern US surface ridge and tail end of the surface cold front that has arrived into the northwestern Gulf while driven by the large eastern Canadian frontal cyclone. The tropical low has been cancelled from the NHC tropical weather outlook as tropical cyclone formation is no longer expected from the landfall... and this will also be my final statement on this area of interest on this blog.
For the northwestern Gulf of Mexico and vicinity... the aforementioned tail end of the surface cold is expected to take over as the dominant feature in the region over the next five days. The surface front is expected to be maintained by the divergence zones of the current passing central US low-amplitude upper trough... then the arrival of the divergence zone of a passing high-amplitude upper trough that comes in from western North America. The surface front is currently forecast to merge with a tropical wave that arrives from the eastern Bay of Campeche in 5+ days... with the combined surface low pressure area resulting in a possible tropical cyclone (see area of interest #19 section above for details).
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 0% (due to landfall with southern Texas)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Not in the official outlook
AREA OF INTEREST #23... Over the Labor Day weekend a tropical wave of low pressure featuring curved thunderstorm bands entered the eastern tropical Atlantic from western Africa... and due to the organization of the bands... favorable upper winds (low shear/outflow) associated with the ongoing regional tropical upper ridge... and some computer model support showing development it was added into the NHC tropical weather outlook. This marks the twenty-third such area of interest tracked on this site this year. As of this afternoon the maximum rotation associated with the tropical wave was south of the Republic of Cabo Verde Islands near 12.5N-24W. For the next 24 hours I forecast the tropical wave to continue toward 30W longitude... after which time it stalls and then drifts north toward 20N latitude through day 5 due to a developing large-scale eastern Atlantic surface ridge weakness caused by a combination of the large current western Africa surface tropical wave when it later moves offshore... plus surface pressure falls associated with the eastern divergence zone of a mid-latitude eastern Atlantic upper trough (due to the forecast warm core northwest Atlantic upper ridge noted in area of interest #21 section above... the south part of the current eastern Canada upper trough dives southeast toward the eastern Atlantic... once the south fracture of the upper trough absorbs some of the current eastern Atlantic upper vorticity the mid-latitude eastern Atlantic upper trough materializes). I expect there is a high probability that the tropical wave associated with this area of interest merges with the current large western Africa tropical wave... for now plan to handle the two waves as one area of interest as they merge... however this may change if the NHC later plans to handle the two waves as two separate areas of interest in their tropical weather outlook. The merged wave may produce heavy rainfall and gusty winds across the Republic of Cabo Verde Islands within the next few days.
For odds of tropical cyclone formation through day 5... I set them at 20% which is slightly lower than what I assign for neighboring area of interest #21 to the west. This is because this wave is forecast to stay toward the eastern part of the Atlantic basin where dry Saharan air concentrations tend to be higher. Some light southerly shear associated with the aforementioned mid-latitude eastern Atlantic upper trough may become another negative factor by day 5.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days... 20% (eastern Atlantic near 20N-31W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Formation chance through 48 hours... 20%
Formation chance through 7 days... 30%
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