*******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.**********
...WEDNESDAY AUGUST 24 2022 3:17 AM EDT...
The Atlantic tropics are making another attempt to wake up with now three areas of interest lined up in the waters between the Lesser Antilles and west coast of Africa as follows:
(1) A pair of vigorous tropical waves of low pressure are expected to merge into a tropical low pressure in the eastern tropical Atlantic in the next 48 hours... see area of interest #20 section below for more information.
(2) See area of interest #21 section below for an update on the tropical low pressure continuing to advance westward from the eastern to central tropical Atlantic.
(3) The southeast side of the tropical wave currently just east of the Lesser Antilles appears to be leaving behind a tropical low pressure. The GFS model currently forecasts this tropical low pressure to develop as it moves west-northwest into and across the Caribbean Sea over the next five days. See area of interest #22 section below for more information.
Elsewhere and over the last couple of days... an increase in rotating thunderstorms over the western Atlantic at a location north of the Caribbean Islands is associated with a cut-off upper vortex. The combination of warm 29 deg C waters and cool temperatures of the upper vortex appears to be generating enough instability for thunderstorm activity. It also appears the upper outflow of the thunderstorm activity... at a layer below the upper vortex... has generated a surface trough of low pressure which has also become increasingly defined in the CIMSS 850 mb vorticity product (http://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=). While passing between Bermuda and the United States east coast...the surface trough is expected to curve north and northeast in track while rounding the west side of the Atlantic surface ridge. As it does so... it will first pass through an unfavorable upper convergence zone between the northwest side of the upper vortex and southeast side of the nearby upper ridge axis... then beneath the upper ridge axis... and then an unfavorable westerly shear environment north of the upper ridge axis. None of the computer models develop the surface trough. However should the surface trough make an attempt to develop further during its short time beneath the favorable low shear/upper outflow environment beneath the upper ridge axis... will consider upgrading the trough to an area of interest for tropical development in future updates.
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 #22 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...The tropical wave of low pressure that was upon the west coast of Africa 24 hours ago has continued to become better defined as it enters the eastern tropical Atlantic with a rapid increase in widespread thunderstorm activity. A second tropical wave of low pressure over western Africa continues to move quickly westward toward the west coast of Africa while maintaining a large area of rotating and organized thunderstorm activity. Over the next 48 hours these two closely spaced and organizing tropical waves are expected to merge into a large tropical low pressure area in the eastern tropical Atlantic. Favoring additional development of the tropical low pressure area will be the widespread tropical upper ridge with favorable low wind shear and upper outflow that has been dominating the region... which is expected to persist. Going against the tropical low pressure area is widespread dry Saharan air located just to the north. However given the pair of seedling tropical waves are maintaining a large area of organizing thunderstorms... it appears this could be the system that finally breaks the suppressing spell of the dry Saharan air and I have therefore raised peak 5-day odds of tropical cyclone formation to 25% (note this is slightly higher than the NHC outlook's 20% as of this writing). However short-term odds of tropical cyclone formation are lowered to give time for the forecast broad low pressure area to consolidate. Regarding the forecast track for this area of interest... the net westward speed is initially slower as the two seedling waves merge into a sprawling area of low pressure. The westward speed around the south side of the steering Atlantic surface ridge is then increased to a typical 5W longitude per day rate.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 25)...0% chance of tropical cyclone formation (southeast of the Republic of Cabo Verde Islands near 12.5N-20W)
IOH 48 Hr Outlook (0000Z Aug 26)...0% chance of tropical cyclone formation (south of the Republic of Cabo Verde Islands near 12.5N-24W)
IOH 72 Hr Outlook (0000Z Aug 27)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-29W)
IOH 96 Hr Outlook (0000Z Aug 28)...20% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-34W)
IOH 120 Hr Outlook (0000Z Aug 29)...25% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-39W)
AREA OF INTEREST #21...The tropical low pressure spin that was moving westward across the eastern tropical Atlantic is now making its way into the central tropical Atlantic. The spin has weakened to an open wave due to prior ingestion of dry Saharan air which earlier brought an end to the thunderstorm activity. The north apex of the wave... in the vicinity of 16N-37.5W... has seen a recent resurgence of shower and thunderstorm activity as this system pulls away from the higher concentrations of eastern Atlantic dry Saharan air. As a result in this update... I am maintaining this system as an area of interest for tropical development. At 72+ hours... changes in the upper atmosphere are expected to make conditions more hostile for development. Specifically warm air advection (northward warm air transport) ahead of the current northeastern US frontal and low and on the west side of the Atlantic surface ridge will continue to amplify the current north Atlantic upper ridge... with the upper ridge pushing a chunk of the upper vorticity tied to the current northeast Atlantic upper trough southward toward the central tropcal Atlantic. The expected surge in central tropical Atlantic upper vorticity will increase westerly wind shear and also suppress upper outflow needed for thunderstorm activity... therefore in the outlook below odds of tropical cyclone formation fall to 0% by 72 hours. I have a slim margin of 5% odds of tropical cyclone formation at 48 hours... a sweet spot when this system reaches warmer water temperatures and before upper atmospheric conditions become hostile.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 25)...0% chance of tropical cyclone formation (central tropical Atlantic near 16N-42.5W)
IOH 48 Hr Outlook (0000Z Aug 26)...5% chance of tropical cyclone formation (central tropical Atlantic near 16N-47.5W)
IOH 72 Hr Outlook (0000Z Aug 27)...0% chance of tropical cyclone formation (central tropical Atlantic near 17N-52W)
AREA OF INTEREST #22...The southeast side of a tropical wave just east of the Lesser Antilles is leaving behind a tropical low pressure area... located in the vicinity of 10N-53W as of 0000Z earlier this evening. Even though this tropical low pressure area currently lacks shower and thunderstorm activity... the GFS model now insists on developing this feature as the remainder northwest portion of the tropical wave and southwest side of the Atlantic surface ridge steer this feature west-northwest into and across the Caribbean Sea over the next five days. This disturbance has potential to find shelter from wind shear while it slides underneath an axis of Caribbean upper ridging currently present... with the upper ridge axis also potentially allowing this system to establish a favorable upper outflow pattern. Given the current lack of shower and thunderstorm activity with this system... and that the GFS model at this time is the only major global model forecasting development... short-term odds of tropical cyclone formation are set to 0% and my peak 5-day odds of tropical cyclone formation are set to 10% (note this is below the NHC's current 20% as of this writing).
In approximately 5 days from now... the forecast track of this disturbance brings it near Jamaica and Haiti. It is too early to speculate on what kinds of tropical cyclone impacts this system would bring to the region if any as their are currently no signs of tropical development. However interests here should be aware that it could bring heavy rainfall with flash flooding potential regardless of tropical cyclone formation or not.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Aug 25)...0% chance of tropical cyclone formation (east of the southern Lesser Antilles near 11.5N-57W)
IOH 48 Hr Outlook (0000Z Aug 26)...0% chance of tropical cyclone formation (southern Lesser Antilles near 12.5N-61W)
IOH 72 Hr Outlook (0000Z Aug 27)...5% chance of tropical cyclone formation (eastern Caribbean Sea near 13.8N-65W)
IOH 96 Hr Outlook (0000Z Aug 28)...10% chance of tropical cyclone formation (south of the Dominican Republic near 15.2N-69W)
IOH 120 Hr Outlook (0000Z Aug 29)...10% chance of tropical cyclone formation (south of Haiti near 16.8N-73W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Aug 23) CMC Model Run...
**For area of interest #20...pair of tropical waves in far eastern tropical Atlantic and western Africa gradually merge into a large tropical low just offshore of Mauritania at 42 hours... moves west-southwest across the Republic of Cabo Verde Islands through 66 hours... tropical low reaches 11.5N-35W through 168 hours in a weakened state
**For area of interest #21...no development shown
**For area of interest #22...no development shown
1200Z (Aug 23) ECMWF Model Run...
**For area of interest #20...pair of tropical waves in far eastern tropical Atlantic and western Africa gradually merge into a large tropical low just offshore of Mauritania at 48 hours... moves west-southwest across the Republic of Cabo Verde Islands betweeen 48 and 72 hours... tropical low reaches 12N-44W at 168 hours.
**For area of interest #21...no development shown
**For area of interest #22...no development shown
**Vigorous tropical wave featuring well-defined low pressure center emerges from the west coast of Africa at 168 hours
1800Z (Aug 23) GFS Model Run...
**For area of interest #20...pair of tropical waves in far eastern tropical Atlantic and western Africa gradually merge into a large tropical low over the Republic of Cabo Verde Islands at 51 hours... tropical low reaches 12N-41W at 168 hours.
**For area of interest #21...no development shown
**For area of interest #22...east side of current tropical wave at 57W longitude leaves behind tropical low near 11.5N-56W at 24 hours... tropical low moves west-northwest into the Lesser Antilles through 48 hours while weakening to a surface trough... trough located south of Haiti at 120 hours... trough redevelops into a tropical low south-southeast of Jamaica at 144 hours and proceeds northwest into Jamaica at 168 hours.
**Vigorous tropical wave featuring well-defined low pressure center emerges from the west coast of Africa at 144 hours... tropical cyclone formation midway between west coast of Africa and Republic of Cabo Verde Islands at 162 hours.
1800Z (Aug 23) NAVGEM Model Run...
**For area of interest #20...no development shown
**For area of interest #21...no development shown
**For area of interest #22...no development shown