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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 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #52

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


...SATURDAY AUGUST 12 2023 12:30 AM EDT...

The tropical disturbance moving through the Bahamas has developed a surface trough of low pressure now moving into the western Bahamas. Although the thunderstorm activity has also increased... a large portion of the thunderstorms have become displaced northeastward into the waters northeast of the Bahamas by disrputing upper vorticity still located in the disturbance's environment. In general the upper winds in the region are forecast to become more supportive for tropical development as the nearby upper vortcity dissipates from prolonged isolation from high-latitude cold air and becomes replaced by upper ridging to approach from the southern United States... featuring low shear and upper outflow. However the disturbance only has 24 more hours before making landfall with the Florida peninusla while continuing to be steered by the Atlantic surface ridge... therfore tropical development of the disturbance is not anticipated and this disturbance is not an area of interest as of this update.


Elsewhere... the current mid-latitude upper ridge over the Atlantic is forecast to push upper vorticity trapped in the Atlantic tropics westward toward the Caribbean. Within the next five days this will allow tropical upper ridging with low shear and upper outflow to recover in the eastern and central tropical Atlantic. Therefore will keep an eye on surface tropical waves of low pressure currently in the eastern Atlantic and Africa which may later take advantage of the recovering tropical upper ridging. The first such wave is currently in the eastern Atlantic near 25W longitude and is currently large in size which has allowed its northern side to inhale suppressing dry Saharan air. Meteosat imagery (https://www.goes.noaa.gov/FULLDISK/GMIR.JPG) shows another large wave over western Africa near 4W longitude and yet another large wave over central Africa... these additional large waves are also at risk of ingesting dry Saharan air and the model support is mixed regarding the development of these waves in the days ahead (i.e. some models develop one or more of the waves in the long range... other models do not). Should any of these waves later show signs of developing a consolidated spin with thunderstorms that wall off the dry air... will declare an area of interest as needed in future updates.


METEOSAT satellite image showing the position of eastern Atlantic and Africa surface tropical waves of low pressure as of 0000Z August 12. The position of each wave axis is marked with a yellow dashed line:

...COMPUTER MODEL SUMMARY...

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


1200Z (Aug 11) CMC Model Run...

**Tropical wave currently at 25W longitude organizes into a tropical low near 13.5N-40W at 168 hours

**Tropical wave currently over western Africa passes over the Republic of Cabo Verde Islands at 150 hours as a tropical low... develops into a tropical cyclone just west of the islands at 168 hours.


1200Z (Aug 11) ECMWF Model Run...

**Tropical wave currently over western Africa passes over the Republic of Cabo Verde Islands at 132 hours as a large tropical low... center of tropical low reaches 17.5N-28.5W at 168 hours


1800Z (Aug 11) GFS Model Run...

**Tropical wave currently over western Africa enteres the eastern tropical Atlantic from the west coast of Africa at 105 hours... smaller tropical low develops within the southeast side of the large tropical wave and near 12.5N-20W at 120 hours... the small tropical low cyclonically orbits northwestward within the eastern outer circulation of the large tropical wave and passes north and northwest of the Republic of Cabo Verde Islands through 168 hours.


1800Z (Aug 11) NAVGEM Model Run...

**Tropical wave currently over western Africa reaches the west coast of Africa at 72 hours while featuring a tropical low near 16N-18W... the tropical low within the wave passes just north of the Republic of Cabo Verde Islands through 108 hours and accelerates westward to 18.5N-45.5W through 168 hours

**Additional tropical wave emerges from western Africa at 168 hours featuring a tropical low near 14.5N-18W

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