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 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #89

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


...TUESDAY AUGUST 24 2021 1:12 AM EDT...

See area of interest #1 through #3 sections below for the latest on tropical wave activity across the Atlantic basin… area of interest #3 poses concern for affecting land areas while forecast to be near Nicaragua… Honduras… Belize… and the Mexican Yucatan provinces of. Quintana Roo and Campeche in the 3 to 5 day window. Elsewhere… the remnants of Atlantic tropical cyclone Grace are currently in the eastern Pacific as Tropical Storm Marty located well southwest of the Baja California peninsula… visit hurricanes dot gov (hurricanes.gov) for more info on Marty.


AREA OF INTEREST #1… A rather large tropical wave of low pressure in the eastern tropical Atlantic is currently passing between 40 and 45W longitude. The wave continues to have a broad northern circulation and a more consolidated spin on its southeast side that has rotated northwestward around the east side of the broad circulation… resulting in the consolidated spin reaching 17N-39W at 0000Z. The consolidated and broad rotations currently lack thunderstorm activity… perhaps an effect of dry Saharan air. Despite this…model runs suggest this wave has some development potential while moving west-northwest into the open central Atlantic. The north angle in track is expected due to a surface ridge weakness being induced by the divergence zone of the current North Atlantic upper trough. By day 2 even though the surface ridge weakness closes… some of the current west Atlantic upper vorticity string will coalesce into a vortex near the Bahamas whose divergence zone will continue a surface ridge weakness to the west… and thus a north angle in track is still expected. By days 3 to 5…the upper trough of the current east Canada front and also the upper vorticity currently over the remnants of Henri will be in the North Atlantic… driving a cold front that creates a surface ridge weakness that traps this system into a north and then east turn.


Due to the loss of thunderstorm activity… I have lowered short-term odds of development. However I have kept the longer range odds at 50% as the model support showing eventual development has actually increased. The models show some of the west Atlantic upper vorticity string coalescing into a nearby upper vortex to the west. The upper vortex may prove to be helpful rather than disruptive by creating an upper divergence zone on its east side as it also retrogrades westward out of the way due the current west Atlantic upper ridging forecast to expand across the mid-latitudes of the Atlantic… which would prevent the upper vortex from shearing this system. Also the upper vortex is forecast to gradually weaken while cut-off from high-latitude cold air… and this system is forecast to end up underneath the low shear and upper outflow of the mid-latitude upper ridging later in the forecast period. By days 4 and 5… some of the upper vorticity that is over Henri will be near the system… potentiality helping to kick this system more east in track but also potentially shearing this system. Thus I do not raise odds above 50% in that window of time.

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

IOH 24 Hr Outlook (0000Z Aug 25)…10% chance of tropical cyclone formation (central Atlantic near 21N-44W)

IOH 48 Hr Outlook (0000Z Aug 26)…30% chance of tropical cyclone formation (central Atlantic near 23N-51W)

IOH 72 Hr Outlook (0000Z Aug 27)… 50% chance of tropical cyclone formation (central Atlantic near 25N-57.5W)

IOH 96 Hr Outlook (0000Z Aug 28)… 50% chance of tropical cyclone formation (southeast of Bermuda near 30N-61.5W)

IOH 120 Hr Outlook (0000Z Aug 29)… 50% chance of tropical cyclone formation (southeast of Bermuda near 30N-57.5W


AREA OF INTEREST #2… The tropical wave of low pressure offshore of Western Africa in the eastern Atlantic has gotten better organized with stronger thunderstorm activity on its west side while maintaining a rotation. This has also prompted the NHC to introduce this wave into its outlook product within the last 24 hours despite ongoing lack of model support showing development. Due to the increase in organization… the South position away from dry Saharan air… and favorable widespread tropical upper ridging with low shear and upper outflow as the wave continues west… I have raised peak development odds to 50%. By days 4 and 5 an upper vortex is forecast to become cut-off from the current North Atlantic upper trough as the current west Atlantic upper ridge expands across the mid-latitudes… placing the vortex just northwest of this wave. I have increased the north angle in track as this system could develop a stronger/taller structure more steered by the upper vortex. However in case the wave does not develop or only slowly develops… I also do not have a sharp north turn on the east side of the upper vortex. It is also possible area of interest #1 helps create a surface ridge weakness that coaxes this system more north in track… especially if the upper vortex can help get a north angle in track started. I taper the odds down from the 50% peak by day 5 as the upper vortex could begin negatively shearing this tropical wave during that timeframe.

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

IOH 24 Hr Outlook (0000Z Aug 25)… 30% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-27.5W)

IOH 48 Hr Outlook (0000Z Aug 26)… 50% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-32.5W)

IOH 72 Hr Outlook (0000Z Aug 27)… 50% chance of tropical cyclone formation (eastern tropical Atlantic near 11N-37.5W)

IOH 96 Hr Outlook (0000Z Aug 28)… 50% chance of tropical cyclone formation (central tropical Atlantic near 12.5N-42W)

IOH 120 Hr Outlook (0000Z Aug 29)… 40% chance of tropical cyclone formation (central tropical Atlantic near 15N-46W)


AREA OF INTEREST #3… A tropical wave of low pressure is currently crossing the southeastern Caribbean Sea with some thunderstorm squalls enhanced by poleward outflow streaming into the current west Atlantic upper vorticity near the Bahamas. Models remain in agreement on developing this wave as it moves across the southern Caribbean and encounters an expanding upper ridge with low shear and upper outflow to develop in the wake of the upper vorticity as the vorticity weakens while remaining cut-off from high-latitude cold air. I have assigned higher odds of development than the NHC as of this writing… at 60%… due to the ongoing strong model support showing development potential. Note the Forecast track angle has a more north component by 3 to 5 days as the tropical wave rounds the southwest side of the Atlantic surface ridge… and is also nudged east due to the current position of the wave axis. Interests in Nicaragua… Honduras… Belize… and the Mexican Yucatan provinces of Quintana Roo and Campeche should be aware of this wave as it will be in the region by days 3 to 5 as a possible tropical cyclone.

******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 (South-Central Caribbean Sea near 13N-71W)

IOH 48 Hr Outlook (0000Z Aug 26)…20% chance of tropical cyclone formation (South-Central Caribbean Sea near 13N-76W)

IOH 72 Hr Outlook (0000Z Aug 27)… 40% chance of tropical cyclone formation (east of northern Nicaragua near 14N-80.5W)

IOH 96 Hr Outlook (0000Z Aug 28)… 60% chance of tropical cyclone formation (just offshore of northeast Honduras near 15.7N-84.5W)

IOH 120 Hr Outlook (0000Z Aug 29)… 60% chance of tropical cyclone formation (east coast of the Yucatan Peninsula at the Belize/Mexico border near 17.8N-88W)


...COMPUTER MODEL SUMMARY...

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


1200Z CMC Model Run...

**For area of interest #1… north end of wave separates and develops into a tropical cyclone near 30N-57W at 66 hours… turns east while intensifying into a Hurricane and reaches 32N-52.5W by 120 hours.

** For area of interest #2… no development shown

* For area of interest #3… wave strengthens to a low pressure spin near 13N-80W at 66 hours… makes landfall on the east Yucatan peninsula coast near 19.9N-88W at 120 hours while strengthening into a tropical cyclone.


1200Z ECMWF Model Run...

**For area of interest #1…North end of wave separates and develops into a tropical cyclone near 32N-53W at 96 hours… drifts east-southeast and intensifies into a hurricane near 31.5N-51W by 120 hours

**For area of interest #2… no development shown

**For area of interest #3… develops into a broad low pressure spin that crosses Central America and southeastern Mexico at 96 to 120 hours… development in the western Gulf of Mexico as the broad low moves northwest suggested in the long range.


1800Z GFS Model Run...

**For area of interest #1… North end of wave separates and develops into a tropical cyclone near 32.5N-55.5W at 120 hours

**For area of interest #2… no development shown

**For area of interest #3… wave strengthens to a low pressure spin near 13N-78W at 66 hours… tropical cyclone formation offshore of northern Honduras near 16N-85W at 111 hours… makes landfall on the Yucatan peninsula just north of Belize near 18N-87.5W at 123 hours.


1200Z NAVGEM Model Run...

**For area of interest #1… North end of wave separates and develops into a tropical cyclone near 30.5N-54W at 78 hours… intensifies into a hurricane while drifting east and reaches 31.2N-49W at 120 hours

**For area of interest #2… no development shown

**For area of interest #3… wave strengthens to a low pressure spin near 12N-77.5W at 48 hours… crosses Central America and southeastern Mexico at 90 to 120 hours…development in the western Gulf of Mexico as the low pressure moves northwest suggested in the long range.

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