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 #81 (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.**********


...MONDAY AUGUST 16 2021 12:51 AM EDT...

Satellite image as of 0210Z. 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 1800Z:

GFS Model Upper-Level Winds 1800Z:



See Fred… Grace… and tropical depression eight sections below for an update on all active tropical cyclones in the Atlantic basin.


In addition...satellite imagery suggests the recent round of tropical waves emerging from Africa are being suppressed by dry Saharan air as they enter the Atlantic. None of the models forecast development from these waves at this time.

TROPICAL STORM FRED... As forecast… the remnant low pressure trough of Fred in the eastern Gulf of Mexico regenerated into a tropical storm on Sunday morning towards the east and offshore of western Florida where the thunderstorm bands have been located over the last day. Fred remains aligned with my previous track and so my updated one remains the same. Fred is tracking northwest toward the surface ridge weakness associated with the lingering front over the eastern US being supported by the divergence zone of cut-off upper vorticity over the north-Central US.


The tropical storm is already up to 50 mph max sustained winds… so I agree with the NHC on raising the landfall intensity forecast back up to 60 mph. Fred’s redevelopment has been made possible by the dissipation of eastern Gulf upper vorticity that had been shearing this system…. however the shear is not zero due to upper southwesterly flow ahead of the aforementioned north-Central US upper vorticity. Thus is why I do not anticipate a wind intensity much higher than 60 mph for landfall.


**Interests across the west Florida peninsula coast are not expected to see tropical storm conditions… however coastal sea swells and rip currents are likely till Fred makes landfall

**Interests across the eastern Florida panhandle and southwest Georgia are less likely to see tropical storm force winds if the latest forecast holds. However heavy rains and coastal sea swells are likely until Fred makes landfall.

**I recommend interests in the western Florida panhandle and southern Alabama finish preparing for Fred by morning or early afternoon. Fred is forecast to be a 60 mph max sustained wind tropical storm just offshore or making landfall by tomorrow (Monday) night.

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

0 Hr Position (0000Z Aug 16)… 50 mph maximum sustained wind tropical storm centered offshore of western Florida at 27.3N-85.9W

IOH 24 Hr Forecast (0000Z Aug 17)… 60 mph maximum sustained wind tropical storm centered over the northeastern Gulf of Mexico at 28.5N-87.5W

IOH 48 Hr Forecast (0000Z Aug 18)… 30 mph maximum sustained wind tropical depression centered over the southern Mississippi/Alabama border at 32N-88.5W

IOH 72 Hr Forecast (0000Z Aug 19)… remnant low centered over western Tennessee at 36N-88W


TROPICAL DEPRESSION GRACE… The NHC recon aircraft data has continued to find that Grace has an oblong circulation where the north-south position of the storm has been hard to find. Grace has essentially been more like a strong tropical wave than a bonafide tropical cyclone… which could be why it has weakened to a tropical depression even before interacting with the Dominican Republic land mass. The thunderstorm activity is becoming displaced southeast of the NHC’s estimated center… this could be a sign of resistance (start of westerly shear) from the west Atlantic upper vorticity string. Some of this unfavorable upper vorticity string is forecast to shift southwest into Grace’s path due to the strength of the west Atlantic upper ridge. And combined with land interaction with Haiti and the Dominican Republic… I now forecast Grace to weaken to a tropical wave in the next 24 hours… which is something many of the global models now agree upon. If indeed Grace does become a wave… we may still have to watch for its regenesis in the Gulf of Mexico in the coming days if the north side of the wave takes advantage of better upper winds (upper ridging with low shear and upper outflow) located north of the upper vorticity string.


Regarding impacts… the primary concern is for heavy rains with flooding potential across Haiti and the Dominican Republic over the next 24 hours… and potentially beyond that timeframe for the Cayman Islands… Jamaica… and Cuba if Grace later on begins to take advantage of better upper winds as mentioned at the end of the previous paragraph.

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

0 Hr Position (0000Z Aug 16)… 35 mph maximum sustained wind tropical depression centered just southeast of the Dominican Republic at 17.3N-68.6W

IOH 24 Hr Forecast (0000Z Aug 17)… Tropical wave located over and south of Haiti at 72.6W


AREA OF INTEREST #1 (RECENTLY UPGRADED TO TROPICAL DEPRESSION EIGHT)… The tropical low pressure northeast of Bermuda has recently strengthened to tropical depression eight. The center of low pressure spin is located at 33.2N-62.7W with the thunderstorm activity remaining a bit displaced to the south of the center due to light northerly shear induced by the east edge of the upper ridging.


The forecast track of this system is expected to be a slow anti-cyclonic loop around the island of Bermuda while pushed around by the eastern US surface ridge as that ridge moves offshore into the northwest Atlantic. The slow speed in the track is due to the drag of the Atlantic surface ridge to the east which will try to oppose the force applied by the nearing eastern US surface ridge. By 120 hours the upper vorticity over the north-Central US will be heading into the northwest Atlantic… creating a surface ridge weakness that should

carry this system northeast and out to sea. By days 2 to 4… I forecast a ramp up to Hurricane strength as the upper ridging is forecast to shift east over this system which will help end the shear and produce an excellent upper outflow environment. Weakening is shown by day 5 due to an increase is shear from the aforementioned upper vorticity to enter the northwest Atlantic.


Interests in Bermuda should now be preparing for gusty winds and coastal sea swells as the chances for tropical storm conditions is high over the next 48 hours.

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

0 Hr Position (0000Z Aug 16)…30 mph maximum sustained wind tropical depression centered just northeast of Bermuda at 33.2N-62.7W

IOH 24 Hr Forecast (0000Z Aug 17)…35 mph maximum sustained wind tropical depression centered just southeast of Bermuda at 32N-64.5W

IOH 48 Hr Forecast (0000Z Aug 18)…50 mph maximum sustained wind tropical storm centered just southwest of Bermuda at 32N-66W

IOH 72 Hr Forecast (0000Z Aug 19)…70 mph maximum sustained wind tropical storm centered west-southwest of Bermuda at 32N-67.5W

IOH 96 Hr Forecast (0000Z Aug 20)…85 mph maximum sustained wind hurricane centered in the western Atlantic near 34N-69W

IOH 120 Hr Forecast (0000Z Aug 21)… 70 mph maximum sustained wind tropical storm centered in the northwestern Atlantic near 36.5N-65W

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