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 

 
 
Search
  • NCHurricane2009

MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #79A (Special Update)

*******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 14 2021 2:37 PM EDT...

The following is a special update on changes with Fred and tropical depression Seven… which has strengthened to Tropical Storm Grace overnight.


TROPICAL DEPRESSION FRED (RECENTLY DOWNGRADED TO REMNANTS OF FRED)...

Satellite image of the remnants of Fred taken at 1800Z:

Although Fred has weakened to a remnant trough of low pressure this morning due to ongoing struggles with wind shear and land interaction with Cuba… the trough has moved offshore into the southeastern Gulf of Mexico and the wind shear is forecast to reduce. Therefore Fred could still make landfall along the western Florida panhandle or Alabama coast as a tropical storm later this weekend and into Monday… although it is likely the landfall wind intensity will be lower than previously forecast. See full update #79 from last night… available on the home page of this site… for more info on Fred as not much has changed on its expectations other than the forecast wind intensity being nudged lower.

TROPICAL STORM GRACE…Satellite image of Grace taken at 1800Z:


It appears tropical depression seven has moved away from the dry Saharan air to the east… which has allowed the thunderstorms on the west side of the circulation to intensity. As a result the depression became Tropical Storm Grace in the overnight hours… and has strengthened further to 45 mph maximum sustained winds in recent hours. Grace continues its brisk west-northwest march… suggesting Grace is being channeled into strong east-southeasterly flow on the east side of the large tropical wave to the west that used to be tagged as invest 92-L… and the forecast track below is a continuation of the current track for the first 36 hours. Beyond that time… the forecast track is bent a little more north in response to the surface ridge weakness created by Fred in the eastern Gulf of Mexico and also the lingering tail end of a front over the interior southeast US (front to be left behind by the current northeast Canadian frontal low). Note the forecast track has shifted to the west once again due to the faster than anticipated forward speed… and now brings this system into the northern Lesser Antilles by tonight.


This special update is primarily to increase the intensity forecast for Grace due to the intensity and organization of its western thunderstorms… and I forecast a peak strength over the Virgin Islands a little higher than the NHC as of this writing (I forecast 65 mph max sustained winds). After Grace passes through the Virgin Islands… I still forecast weakening as the storm battles with westerly shear to be generated by the patch of upper vorticity lingering northeast of the Bahamas. By 96 and 120 hours the forecast track will take the center of Grace directly below the axis of upper vorticity…and so I forecast Grace to struggle as a tropical depression whose thunderstorms become displaced east of the upper vorticity axis. Of note the 0600Z GFS has a little different idea… keeping Grace as a bonafide tropical cyclone as it moves across the Bahamas and toward south Florida while having Grace’s center reform or stay a little further east while more coupled with the thunderstorms…. resulting in a compact tropical cyclone with a small area of warm core upper anticyclonic outflow (caused by thunderstorm latent heat release) that battles the axis of upper vorticity. Because of this solution… I have now kept Grace as a tropical depression instead of a remnant low by days 4 and 5… but the longer term intensity of Grace is now in question… does it slide under the axis of upper vorticity and weaken or does it stay coupled with the thunderstorms and fight off the upper vorticity?


** Interests in the northern Lesser Antilles should finish preparing for Grace… weather conditions will deteriorate by tonight

**Interests in the Virgin Islands and Puerto Rico should finish preparing for Grace… weather conditions will deteriorate by tomorrow morning. Wind damage and coastal

sea swell potential is higher here as Grace could strengthen to a more high-end tropical storm.

** Interests in the Dominican Republic are more likely to see tropical storm conditions (some gusty winds and coastal sea swells) by Monday on the north coast… now is the time to start preparing. Heavy rainfall with flash flooding could become a concern for all of the Dominican Republic.

**Interests across the Bahamas and south Florida and the Florida Keys should be aware of Grace as the intensity forecast is now uncertain by days 4 and 5.

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

0 Hr Position (1200Z Aug 14)… 45 mph maximum sustained wind tropical storm centered at 16.2N-57.9W

IOH 24 Hr Forecast (1200Z Aug 15)… 65 mph maximum sustained wind tropical storm centered over the Virgin Islands at 17.5N-64W

IOH 48 Hr Forecast (1200Z Aug 16)… 50 mph maximum sustained wind tropical storm centered just northeast of the Dominican Republic north coast at 19N-68.5W

IOH 72 Hr Forecast (1200Z Aug 17)…40 mph maximum sustained wind tropical storm centered between the northwestern Dominican Republic and southeast Bahamas at 20.7N-72W

IOH 96 Hr Forecast (1200Z Aug 18)…30 mph maximum sustained wind tropical depression centered over the central Bahamas at 22.5N-75.2W

IOH 120 Hr Forecast (1200Z Aug 19)… 30 mph maximum sustained wind tropical depression centered over the southwest coast of Andros Island in the western Bahamas at 24N-78.2W

20 views0 comments