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 #78

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


...THURSDAY AUGUST 12 2021 11:07 PM EDT...

Tropical Depression Fred is re-organizing tonight… increasing the potential for tropical storm conditions in parts of Cuba and Florida in the coming days… see Fred section below for details. See area of interest sections below for an update on the pair of central Atlantic tropical waves of low pressure… the eastern of the two waves bears watching as it could develop further while moving into the northern Lesser Antilles… Virgin Islands… and Puerto Rico by Sunday and Monday.


Elsewhere...satellite imagery suggests a tropical wave has recently emerged from Western Africa but has lost thunderstorm activity while embedded in a dry Saharan air surge that spreads further south than recent such surges. Models insist that the next wave… the one currently over Western Africa (southwest Mali) with thunderstorms complexes currently on its east and west ends… will enter the Atlantic in about 48 hours (2 days). Due to the widespread tropical upper ridging forecast to persist over the eastern tropical Atlantic... a haven of low shear and upper outflow will be present for this wave to also potentially become an area of interest for tropical development as long as it does not ingest dry saharan air.


TROPICAL DEPRESSION FRED...More recent satellite image of Fred taken at 0230Z… black plus marks the center of circulation:

After a disrupting landfall 24 hours ago across Haiti and the Dominican Republic… Fred appears to be on the mend tonight. Earlier today Fred emerged from Haiti as a cloud swirl with scattered thunderstorms well east of the center due to westerly shear induced by the axis of west Atlantic upper vorticity. Tonight the thunderstorms have redeveloped in a smaller… stronger… and concentrated pattern just east of the center. Also noteworthy is the center essentially was fixed at the same place between 5 PM and 8 PM EDT… indicating a temporary halt in the west-northwest track as the center makes an attempt to regenerate toward the nearing thunderstorm complex. Due to the halt in track… my updated forecast track is adjusted south and east in the short-term but remains the same in the longer range. As the current frontal cyclone over eastern Canada departs and a surface ridge builds over the eastern US... the tail end of the front driven by the frontal cyclone is forecast to linger as a surface ridge weakness over the interior southeast US and to the south of that surface ridge with the support of the divergence zones of lingering upper vorticity over the eastern Gulf of Mexico and upper vorticity to be cut-off from the frontal cyclone’s upper vortex in the vicinity of Iowa. The forecast track philosophy is to bring Fred west-northwest and then northwest while aiming for the surface ridge weakness.


I have raised my intensity forecast… essentially agreeing with the NHC forecasting from yesterday while ironically as of this writing the NHC is now lower than my intensity forecasting. My upward adjustment is due to the observations of Fred re-organizing as noted in the previous paragraph… followed by a forecast reduction in wind shear as the latest GFS shows the lingering upper vorticity to be near the west Florida coast dissipating by 72+ hours. This seems plausible as Fred is already showing stronger thunderstorm activity whose latent heat release would help weaken the cool core upper vorticity.


The following land areas will have to watch for arrival of tropical storm conditions (gusty winds... heavy rain with flash flood potential... and coastal sea swells) in the coming days:

** Cuban interests should have finished preparing for possible tropical storm conditions by now. Fred has potential to regain tropical storm strength as it re-organizes while the center tracks parallel to and just offshore of the north Cuban coast from now thru tomorrow… near enough to allow the south side of Fred to bring possible tropical storm conditions.

**Interests in the southern Bahamian islands could see heavy rainfall from the northern outer bands of Fred from now through tomorrow.

**Interests across south Florida and the Florida Keys should now be preparing for possible tropical storm condition to arrive by Saturday.

**Interests across the northwest Florida peninsula coast are not likely to see tropical storm conditions if the current forecast track holds… however coastal sea swells and rip currents are still possible this weekend.

**Interests across the Florida panhandle… southwest Georgia and southern Alabama should be aware of Fred as it could bring tropical storm conditions in the region late this weekend and into Monday.

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

0 Hr Position (1800Z Aug 12)… 35 mph maximum sustained wind tropical depression centered offshore of the north coast of Cuba at 21.3N-75.3W

IOH 24 Hr Forecast (1800Z Aug 13)… 45 mph maximum sustained wind tropical storm centered between Cuba and Andros Island at 23N-78.8W

IOH 48 Hr Forecast (1800Z Aug 14)… 45 mph maximum sustained wind tropical storm centered over the Florida Keys at 24.5N-81.5W

IOH 72 Hr Forecast (1800Z Aug 15)… 50 mph maximum sustained wind tropical storm centered offshore of western Florida at 27.5N-83W

IOH 96 Hr Forecast (1800Z Aug 16)… 60 mph maximum sustained wind tropical storm centered offshore of the Florida panhandle at 29N-85.5W

IOH 120 Hr Forecast (1800Z Aug 17)… remnant low centered over west-central Alabama at 32.5N-87.5W


AREA OF INTEREST #1…The strong tropical wave of low pressure that has recently moved into the central tropical Atlantic from the eastern Atlantic continues its west-northwest march with little change as the thunderstorms remain limited on the east side of its low pressure spin due to dry Saharan air. The brisk west-northwest track suggests this system is being channeled into stronger east-southeasterly flow on the east side of the large tropical wave to the west associated with area of Interest #2… and the forecast track below is a continuation of the current track from the 1800Z position of the center of spin (which was at 15N-44W) for the first 72 hours. By 96 and 120 hours… 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 eastern Canadian frontal cyclone).


Due to a brief period in the afternoon when the thunderstorms on the west side were better organized… the NHC as of this writing has risen their peak development odds to 70% in their 5-day outlook. However I maintain 60% odds for now as the thunderstorm activity is not as organized as it was in the afternoon. By days 3 to 5 I taper down the odds of development due to likely westerly shear from a lingering patch of western Atlantic upper vorticity Forecast to be northeast of the Bahamas.


Interests in the northern Lesser Antilles… Virgin Islands… and Puerto Rico are encouraged to monitor the progress of this tropical wave as it is forecast to pass over or nearby by Sunday and Monday.

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

IOH 24 Hr Outlook (1800Z Aug 13)…60% chance of tropical cyclone formation (central tropical Atlantic near 16N-50W)

IOH 48 Hr Outlook (1800Z Aug 14)…60% chance of tropical cyclone formation (east of the northern Lesser Antilles near 17N-56W)

IOH 72 Hr Outlook (1800Z Aug 15)…50% chance of tropical cyclone formation (northern Lesser Antilles near 18N-62W)

IOH 96 Hr Outlook (1800Z Aug 16)…30% chance of tropical cyclone formation (just north of Puerto Rico near 19.5N-66W)

IOH 120 Hr Outlook (1800Z Aug 17)…10% chance of tropical cyclone formation (east of the eastern Bahamas near 21N-70W)


AREA OF INTEREST #2…The south side of the broad tropical wave of low pressure in the central tropical Atlantic just east of the Lesser Antilles… the same wave that was formerly tagged invest 92-L… has lost its southern low pressure spin that is spawned Wednesday afternoon. In addition the wave is essentially void of significant thunderstorm activity… and I have now cancelled this wave as an area of interest for tropical development. This is my planned final statement on this wave on this blog.

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

IOH 24 Hr Outlook (1800Z Aug 13)…0% chance of tropical cyclone formation (just west of the southern Lesser Antilles near 12N-62.5W)

...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 tropical depression Fred...loses closed circulation over the next 6 hours… re-established a closed circulation just west of the Florida Keys at 54 hours… regains tropical storm status at 72 hours near 27N-85W… makes landfall on the Florida panhandle just west of the Big Bend coast at 102 hours… inland remnant low located over the central AL/GA border at 120 hours.

**For area of interest #1… no tropical cyclone formation shown

**For area of interest #2… no tropical cyclone formation shown

**Strong tropical wave forecast to emerge from Western Africa at 48 hours... no tropical cyclone formation shown afterwards


1200Z ECMWF Model Run...

** For tropical depression Fred... loses closed circulation just west of the Florida Keys at 48 hours… makes landfall over western Florida panhandle at 96 hours without re-developing a closed circulation.

**For area of interest #1… forecast to become a tropical depression near 17.5N-56.2W at 48 hours… weakens to a remnant low while passing over the northern Lesser Antilles and Virgin Islands thru 72 hours

**For area of interest #2… no tropical cyclone formation shown

**Strong tropical wave forecast to emerge from Western Africa at 48 hours... no tropical cyclone formation shown afterwards

**Strong tropical wave forecast to emerge from Western Africa at 120 hours... center of broad low pressure spin passes over the Republic of Cabo Verde Islands at 144 hours.


1800Z GFS Model Run...

**For tropical depression Fred... loses closed circulation over the next 3 hours… regains closed circulation just south of the Florida Keys at 39 hours… loses closed circulation just northwest of Cuba at 60 hours… remnant low makes landfall on Florida panhandle at Big Bend coast at 99 hours

**For area of interest #1… develops a well-defined surface low just north of Puerto Rico at 90 hours… weakens back to a surface trough at a location east of the eastern Bahamas at 120 hours.

**For area of interest #2… no tropical cyclone formation shown


1200Z NAVGEM Model Run...

** For tropical depression Fred... loses closed circulation over the next 6 hours… regains closed circulation on north Cuban coast at 23N-80W at 30 hours… regains tropical storm status just west of the western Florida Keys at 48 hours… gains hurricane strength near 27.6N-85.5W at 72 hours… makes landfall over western Florida panhandle at 90 hours… inland but vigorous remnant low located over eastern Kentucky at 120 hours.

**For area of interest #1… no tropical cyclone formation shown

**For area of interest #2… no tropical cyclone formation shown

**Strong tropical wave forecast to emerge from Western Africa at 48 hours...quick tropical cyclone formation suggested offshore of west Africa near 14N-20W at 90 hours… cyclone weakens to a large broad tropical depression over the Republic of Cabo Verde Islands at 120 hours.

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