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 #74 (Weekend Edition)

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


...SUNDAY AUGUST 8 2021 10:11 PM EDT...

Satellite image as of 2350Z. Areas of interest circled in yellow are not mentioned in the NHC tropical weather outlook. Areas circled in a green dashed line are in the NHC 5-day tropical weather outlook. Areas circled in a solid green line are in the NHC 2-day tropical weather outlook:

NHC TAFB Surface Analysis 1200Z:

GFS Model Upper-Level Winds 1200Z:

See the area of interest sections below for the current trifecta of tropical low pressure systems in the central and eastern tropical Atlantic being monitored for possible development in the coming days. Please note the following:

(1) The tropical low pressure currently at 55W longitude continues to show some signs of organized thunderstorms…and will be crossing the Lesser Antilles in 24 hours. See area of interest #3 section for details

(2) The tropical low pressure currently at 44W longitude may cross the northern Lesser Antilles… Virgin Islands…Puerto Rico…Haiti… and the Dominican Republic in the 3 to 5 day timeframe. Interests here should monitor the progress of this system…see area of interest #2 section for details


Elsewhere…another strong tropical wave of low pressure is in progress over Western Africa

with widespread thunderstorms on its west side….and is poised to enter the eastern tropical Atlantic over the next 24 hours or so. The wave appears positioned toward 15N latitude…which may allow it to ingest dry Saharan air to the north and also potentially be negatively affected by cooler waters in the far east Atlantic north of 15N. This could be why models do not develop this wave despite the presence of expansive tropical Atlantic upper ridging with low shear and upper outflow.


AREA OF INTEREST #1...The tropical wave of low pressure moving across the eastern tropical Atlantic features a cloud swirl on its east side at a location west of the Republic of Cabo Verde Islands…and bands of clouds on its west side. The wave has lacked thunderstorms for the better part of the last 24 hours due to dry Saharan air to the north and the cooler far east Atlantic waters north of 15N latitude….therefore the NHC has recently dropped this wave from their tropical weather outlook. However I forecast this wave to still potentially recover and develop once it reaches warmer waters west of 40W longitude as the wave will remain below expansive tropical upper ridging with low shear and upper outflow…and place 20% odds of development by days 4 and 5. Forecast track thru day 5 is steady to the west at a typical 5W longitude per day speed while steered by the south side of the Atlantic surface ridge. A slight increase in the north angle in track is show around 48 to 72 hours as some of the upper vorticity currently in the northeast Atlantic will retrograde southwest around the Northeast Atlantic upper ridge and potentially try to pull the track of this system more north…especially if this system develops a stronger/taller structure that could allow for more interaction with the upper vorticity. By days 4 and 5…the upper vorticity is forecast to retreat away from this system while coaxed on a northeast drift ahead of the current eastern North America upper trough as that trough moves across the North Atlantic…and so I reduce the north angle in track by that time.

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

IOH 24 Hr Outlook (1800Z Aug 9)…0% chance of tropical cyclone formation (eastern tropical Atlantic near 15.5N-36W)

IOH 48 Hr Outlook (1800Z Aug 10)…0% chance of tropical cyclone formation (central tropical Atlantic near 16N-41W)

IOH 72 Hr Outlook (1800Z Aug 11)…10% chance of tropical cyclone formation (central tropical Atlantic near 17N-45W)

IOH 96 Hr Outlook (1800Z Aug 12)…20% chance of tropical cyclone formation (central tropical Atlantic near 17.5N-50W)

IOH 120 Hr Outlook (1800Z Aug 13)…20% chance of tropical cyclone formation (central tropical Atlantic near 18N-55W)


AREA OF INTEREST #2...The tropical low pressure currently centered near 14.5N-44W continues to exhibit thunderstorm activity to the southwest of the center…and over the last 24 hours this activity has gradually increased in intensity and its closeness to the center. As a result… I agree with the NHC’s increased 40% odds of development by day 5. Forecast track thru day 5 is steady to the west at a typical 5W longitude per day speed while steered by the south side of the Atlantic surface ridge. I forecast a slight increase in the north angle of the track by day 5 as a large frontal cyclonic system forecast to be over North America may weaken the west extent of the steering Atlantic surface ridge. This system is expected to cross the northern Lesser Antilles… then pass over or near the Virgin Islands… Puerto Rico… Haiti… and the Dominican Republic in the 3 to 5 day window. Interests here should monitor the progress of this system in case it does develop further…which is a possibility as the west Atlantic upper vorticity string is forecast to weaken which will allow for tropical upper ridging with low shear and upper outflow to stay over this system thru day 5.

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

IOH 24 Hr Outlook (1800Z Aug 9)…20% chance of tropical cyclone formation (central tropical Atlantic near 15N-49W)

IOH 48 Hr Outlook (1800Z Aug 10)…30% chance of tropical cyclone formation (east of the Lesser Antilles near 15.5N-54W)

IOH 72 Hr Outlook (1800Z Aug 11)…40% chance of tropical cyclone formation (just east of the northern Lesser Antilles near 16N-59W)

IOH 96 Hr Outlook (1800Z Aug 12)…40% chance of tropical cyclone formation (northeast Caribbean Sea near 16.5N-64W)

IOH 120 Hr Outlook (1800Z Aug 13)…40% chance of tropical cyclone formation (south of the Dominican Republic near 17.5N-69W)


AREA OF INTEREST #3…The tropical low pressure currently centered near 13N-55W has continued to show some signs of organized thunderstorm activity…and as a result I have increased odds of development to 50% by day 5. I have not chosen odds higher than 50% just yet like the NHC has recently shown as the activity has not yet gotten much better organized than yesterday (albeit as of 0140Z a small Central area of thunderstorms has developed…will have to wait and see if this persists before raising development odds further). Forecast track thru day 5 is steady to the west at a typical 5W longitude per day speed while steered by the south side of the Atlantic surface ridge. I currently forecast no north angle in the track through day 3 as the close proximity of area of interest #2 may allow for some slight fujiwhara influence. I do finally show some north angle in the track by days 4 and 5 however as a large frontal cyclonic system forecast to be over North America may weaken the west extent of the steering Atlantic surface ridge. Conditions will be favorable for development over the next five days as the west Atlantic upper vorticity string is forecast to weaken which will allow for tropical upper ridging with low shear and upper outflow to stay over this system. Regardless of tropical cyclone formation or not… expect the possibility of gusty winds and heavy rains for Barbados… Grenada… St Vincent and the Grenadines… St Lucia… and Martinique by tomorrow afternoon and evening.

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

IOH 24 Hr Outlook (1800Z Aug 9)…30% chance of tropical cyclone formation (near Barbados at 13N-60W)

IOH 48 Hr Outlook (1800Z Aug 10)…40% chance of tropical cyclone formation (eastern Caribbean Sea near 13N-65W)

IOH 72 Hr Outlook (1800Z Aug 11)…50% chance of tropical cyclone formation (central Caribbean Sea near 13N-70W)

IOH 96 Hr Outlook (1800Z Aug 12)…50% chance of tropical cyclone formation (central Caribbean Sea near 14N-75W)

IOH 120 Hr Outlook (1800Z Aug 13)…50% chance of tropical cyclone formation (central Caribbean Sea near 15.5N-79.5W)

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