*******Note that forecasts 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.**********
...SATURDAY AUGUST 27 2022 5:47 AM EDT...
Opportunities for tropical cyclone formation in the Atlantic basin are increasing as we end the month of August due to the following three areas of interest:
(1) See area of interest #20 for more information on a broad but organizing tropical low pressure forming in the eastern tropical Atlantic from the merger of two tropical waves.
(2) See area of interest #22 section below for an update on the surface trough of low pressure continuing westward across the eastern Caribbean Sea.
(3) Computer models are in agreement that a large tropical disturbance will emerge from the west coast of Africa in approximately three days... consisting of a pair of tropical waves currently over inland central and western Africa. See area of interest #23 section below for more information.
New to this site this year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development. In this scheme... will reset back to #1 at the start of next year (January 2023). The current areas of interest in this blog post are designated #20 through #23 as I designated the other nineteen of this year in previous birdseye view posts on the home page. This scheme is to reduce confusion as Atlantic tropical activity increases during the peak of the hurricane season... when multiple simultaneous areas of interest begin and end which previously required shuffling around the area of interest numbers from update to update.
AREA OF INTEREST #20...A pair of closely spaced and vigorous tropical waves of low pressure continue sliding west across the eastern tropical Atlantic and are now nearing the central tropical Atlantic. As of 0000Z earlier today eastern of the two waves was crossing 30W longitude. Meanwhile the western of the two appeared to be located near 10N-40W with its associated thunderstorm bands lopsided to its west side... as its east side appears to be open to the eastern wave. The two waves appear to be merging into an oblong and broad tropical low pressure system. Previously it appeared the eastern of the two waves was becoming the dominant feature in the merger... however dry Saharan air has since eroded its thunderstorm activity such that the dominant center of rotation now appears to be located further west midway between the two tropical waves. As a result the updated forecast track in the outlook below is adjusted westward. Also note some slight northward angle in the westward track is possible in the 5+ day range as this system reaches the weaker western side of the Atlantic surface ridge. Favoring this system is the ongoing tropical upper ridge in the region featuring low shear and upper outflow. However I have lowered shorter-term odds of tropical cyclone formation as it took longer than I previously anticipated for the two seedling waves to merge into a broad tropical low pressure area... and now that this is finally happening some additional time will be needed for the broad low to consolidate enough to support tropical cyclone formation. However I have raised my peak 5-day odds of tropical cyclone formation to 50% as the materializing broad low pressure area is making progress in becoming better organized when studying satellite animation spanning from 0000Z to 0800Z this morning (note the NHC has also raised their peak odds for this system to 30% in their tropical weather outlook). Odds are trimmed back down to 40% by day 5 as the current central Atlantic upper vorticity could retrograde southwest into the path of this system... which would increase westerly wind shear over this system. Therefore even though this system will be nearing the Lesser Antilles during this time... the associated heavy rainfall and gusty winds may arrive just after day 5 should shear push the activity off to the east side of this disturbance.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 28)...5% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-39W)
IOH 48 Hr Outlook (0000Z Aug 29)...15% chance of tropical cyclone formation (central tropical Atlantic near 13N-44W)
IOH 72 Hr Outlook (0000Z Aug 30)...35% chance of tropical cyclone formation (central tropical Atlantic near 13N-49W)
IOH 96 Hr Outlook (0000Z Aug 31)...50% chance of tropical cyclone formation (central tropical Atlantic near 13N-54W)
IOH 120 Hr Outlook (0000Z Sep 1)...40% chance of tropical cyclone formation (just northeast of Barbados near 13.5N-59W)
AREA OF INTEREST #22...A surface trough of low pressure continues to make its way westward across the eastern Caribbean Sea and was passing 67.5W longitude as of 0000Z earlier today. The trough has become increasingly harder to define on satellite imagery as it has lost thunderstorm activity and its previous maximum spin. Despite this... the GFS and NAVGEM models insist on reviving this feature as it later reaches the western Caribbean Sea. The trigger for the revival appears to be interaction with the upper vortex currently located north of the Dominican Republic as the vortex retrogrades southwest into the path of the surface trough. The GFS model has trended more north with the path of the upper vortex... causing the surface trough to interact with upper divergence on the southeastern side of the upper vortex (instead of the upper divergence zone to setup between the northwest side of the vortex and southeast side of the Gulf of Mexico upper ridge as previously suggested). After the divergence zone of the upper vortex potentially enhances the surface trough... wind shear is expected to relax by day 5 as the cold core upper vortex dissipates while it remains cut-off from high-latitude cold air. However I have very low 5% odds of tropical cyclone formation for this timeframe due to the current weak state of the surface trough... raising the possibility the trough simply dissipates before it gets a chance to be revived by the upper vortex as discussed above.
Regarding the forecast track of the surface trough... an increase in the northward angle is anticipated by 72+ hours as it rounds the southwest side of the Atlantic surface ridge. The forward speed is also slowed to stay aligned with the above-mentioned divergence zone of the upper vortex... in anticipation the trough in fact transitions into a system supported and re-invigorated by the vortex. On a final note... the risk of heavy rainfall this weekend for the Dominican Republic... Haiti... and Jamaica has diminished due to the current weak state of the surface trough.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 28)...0% chance of tropical cyclone formation (south of Haiti near 16N-72.5W)
IOH 48 Hr Outlook (0000Z Aug 29)...0% chance of tropical cyclone formation (south of Jamaica near 16N-77.5W)
IOH 72 Hr Outlook (0000Z Aug 30)...0% chance of tropical cyclone formation (south of the Cayman Islands near 17N-80W)
IOH 96 Hr Outlook (0000Z Aug 31)...0% chance of tropical cyclone formation (just southwest of the Cayman Islands near 18N-82W)
IOH 120 Hr Outlook (0000Z Sep 1)...5% chance of tropical cyclone formation (west of the Cayman Islands near 19.5N-84W)
AREA OF INTEREST #23...Satellite imagery of Africa as of 0300Z earlier today. Red dashed lines indicate the location of a pair of inland central and western Africa tropical waves. The pair of waves may combine to make a large tropical disturbance that enters the eastern tropical Atlantic in approximately three days:
Over the last few days... models were in agreement that the tropical wave currently over central Africa would emerge into the eastern tropical Atlantic as a well-organized feature... potentially developing into a tropical cyclone rather quickly once over water. However since Thursday and Friday... the model solutions abruptly switched to a notably more gradual development rate as the system initially struggles as a large/broad system with multiple centers instead of a single consolidated center. I speculate that models were not previously picking up on a nearby second tropical wave to the west of the central African wave... which has recently become much better defined in the vicinity of 12.5N-3W with a large area of concentrated thunderstorm activity. Meanwhile the central African wave in the vicinity of 13N-9E is currently the least impressive of the two waves. The scenario of two closely spaced waves would explain the recent model solutions of an initially broad disturbance with multiple centers. This area of interest... designated #23 on this blog... currently encompasses both tropical waves in anticipation of both congealing into the large tropical disturbance that the models have been showing departing the west coast of Africa in approximately three days from now. Odds of tropical cyclone formation by day 5 are set at an initially low 10% as the large disturbance will likely consolidate after the 5-day window instead of during. However even if this system does not consolidate by day 5... it has the potential to bring heavy rain and gusty winds to the Republic of Cabo Verde Islands during that timeframe.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 28)...0% chance of tropical cyclone formation (western Africa near 12.5N-4W)
IOH 48 Hr Outlook (0000Z Aug 29)...0% chance of tropical cyclone formation (western Africa near 12.8N-9W)
IOH 72 Hr Outlook (0000Z Aug 30)...0% chance of tropical cyclone formation (western Africa near the eastern tropical Atlantic coast near 13.2N-14W)
IOH 96 Hr Outlook (0000Z Aug 31)...0% chance of tropical cyclone formation (just offshore of western Africa near 13.8N-19W)
IOH 120 Hr Outlook (0000Z Sep 1)...10% chance of tropical cyclone formation (just south of the Republic of Cabo Verde Islands near 14.2N-24W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Aug 26) CMC Model Run...
**For area of interest #20...broad low pressure area splits into two centers at 90 hours (western center near 10N-49W and quasi-stationary eastern center near 11.5N-42.5W)...eastern center becomes a tropical cyclone near 12N-40W at 126 hours after which time it drifts westward to 12.5N-42.5W through 168 hours... western center moves west-northwest and is located just east of the northern Lesser Antilles at 168 hours.
**For area of interest #22...no development shown
**For area of interest #23...vigorous tropical wave emerges from the west coast of Africa at 72 hours... organizes into a large broad tropical low over the Republic of Cabo Verde Islands through 126 hours... center of broad tropical low reaches 16N-30W at 168 hours
1200Z (Aug 26) ECMWF Model Run...
**For area of interest #20...tropical cyclone formation suggested near 15N-46.5W at 96 hours... approaches northern Lesser Antilles by 168 hours as a strong tropical storm.
**For area of interest #22...no development shown
**For area of interest #23...vigorous tropical wave featuring southwest-to-northeast elongated circulation emerges from west coast of Africa at 72 hours... northeast end of the elongated circulation consolidates into a low pressure spin just offshore of Mauritania at 96 hours which proceeds to become a tropical cyclone while passing just north of the Republic of Cabo Verde Islands through 120 hours... tropical cyclone located at 18.5N-35W at 168 hours
1800Z (Aug 26) GFS Model Run...
**For area of interest #20...no development shown
**For area of interest #22...surface trough currently in the eastern Caribbean evolves into broad tropical low southwest of the Cayman Islands at 114 hours...tropical cyclone formation suggested as center of circulation moves between the west tip of Cuba and Yucatan peninsula at 159 hours... tropical cyclone drifts west along north coast of the Yucatan peninsula through 168 hours.
**For area of interest #23...vigorous tropical wave featuring southwest-to-northeast elongated circulation emerges from west coast of Africa at 75 hours... gradually coalesces into a more circular but still large low pressure area over the Republic of Cabo Verde Islands through 129 hours... large low pressure area gradually strengthens to a tropical depression whose center reaches 16.2N-33W at 168 hours.
1800Z (Aug 26) NAVGEM Model Run...
**For area of interest #20...eastern side of broad low pressure area becomes trapped stationary near 11.5N-40W at 102 hours while tugged by large wave that emerges from west coast of Africa... while drifting eastward toward the large wave the low pressure area becomes a tropical cyclone near 12.5N-38W at 144 hours...tropical cyclone located near 12.5N-37.5W at 168 hours.
**For area of interest #22...surface trough currently in the eastern Caribbean evolves into broad tropical low covering the Yucatan peninsula... southern Gulf of Mexico... and western Caribbean Sea by 156 hours... a smaller circulation over western Caribbean water develops within the east side of the broad tropical low near 18.5N-85W by 168 hours
**For area of interest #23...vigorous tropical wave featuring southwest-to-northeast elongated circulation emerges from west coast of Africa at 84 hours... gradually organizes into a tropical depression over the Republic of Cabo Verde Islands through 138 hours... while generally stationary over the islands the tropical depression becomes increasingly elongated southwest-to-northeast through 168 hours.