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 #42 (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.**********


...TUESDAY JULY 6 2021 6:35 PM EDT...

Satellite image as of 2100Z. 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:

Note that the weekend edition posts (without the computer model summary and above-style charts created by mobile phone) will continue this week as I am currently on vacation.


See Tropical Storm Elsa section below for additional details on the storm. Elsewhere…a tropical wave of low pressure passing over northeast Venezuela…Trinidad…and Tobago has seen some increase in thunderstorms while pulling away from the dry Saharan air layer. However the wave is not likely to develop in the southern Caribbean as it catches up to suppressive upper vorticity in the west Atlantic to become trapped stationary by warm west Atlantic upper ridging to be re-enforced by Elsa’s thunderstorm latent heat release.


TROPICAL STORM ELSA...While offshore of southwest Florida and in a southwesterly shear environment ahead of upper vorticity over the southeast US and northern Gulf of Mexico…Elsa has been able to strengthen while developing a persisting thunderstorm mass over and east of its surface center aided by the divergent nature of the upper flow. As a result Elsa is just below hurricane force with 70 mph max sustained winds as of this writing. See special update #41A available on the home page of this site for more technical information on the evolution of Elsa since it emerged from Cuba early today.


Elsa is slightly southwest of my previous forecast track…so my updated one is adjusted accordingly. For the remainder of its life…Elsa will continue north and then northeast in deep-layer southerly flow around the west side of the Atlantic surface ridge and upper southwesterly flow ahead of the upper vorticity over the southeast US…with this upper flow regime to be re-enforced by the arrival of the next upper trough currently positioned over Central North America.


Due to the recent strengthening of Elsa…my updated intensity forecast is nudged upward. It appears the strongest of the southwesterly shear is off to the west such that instead of weakening…Elsa is able to take advantage of upper divergence on the east side of the southeast US upper vorticity…and as such will later take advantage of upper divergence ahead of the incoming upper trough from central North America. My updated intensity forecast assumes Elsa could make landfall in the northwest Florida peninsula tonight as a category 1 hurricane with max sustained winds as high as 80 to 85 mph…thus weakening to a 50 mph max sustained wind tropical storm from the landfall by the time it moves into southeast Georgia by this time tomorrow. While the center moves across the eastern Carolinas and southeast Virginia…I have updated my forecast to show Elsa as a low-end tropical storm supported by the forecast divergent nature of the upper flow…with the tropical storm force winds occurring on coastal regions while land friction keeps winds more on the breezy side over land. By 72 hours…the center of Elsa is forecast to be over cooler waters just offshore of the northeast US…and the cold front associated with the incoming central North America upper trough will overspread Elsa…thus I forecast transition into a non-tropical frontal cyclone at that time. However the frontal cyclone will maintain vigor with the support of the divergent nature of the upper flow.

With these forecast updates:


(1) The western Bahamas and western Cuba may see coastal sea swells and perhaps additional locally heavy rain from a stray outer band generated by Elsa through the rest of today.


(2) The Florida Keys have been raked with tropical storm force winds all morning…gusts to tropical storm force are still occurring. Tropical storm force winds will soon wind down…but coastal sea swells and additional heavy rain from outer bands will linger for the rest of today


(3) Coastal storm surge will remain a concern for the western part of the Florida peninsula for the rest of today. Tropical storm force winds (below hurricane force) are expected across the Port Charlotte region soon as the center with strongest winds will pass offshore. Tropical storm force winds to category 1 hurricane force winds are expected to arrive in the hurricane warning region from Tampa Bay and vicinity northward to the Steinhatchee River. Tropical storm force winds (below hurricane force) are likely inland from the Steinhatchee River…across Lake City and Live Oak regions…and into the eastern Florida/Georgia border region. The prior preparation for tropical storm conditions should encompass the new potential for category 1 hurricane force winds…it just means that now more people could see some wind damage and power outages.


(4) The east side of the Florida peninsula could still see sea swells and rip currents and some breezy winds today.


(5) All of the Florida peninsula could see heavy rains with flash flooding potential today.


(6) Interests in the Florida panhandle could still see coastal sea swells today. The heaviest rainfall will likely stay to the east due to the shearing upper southwesterly winds over Elsa.


(7) Interests inland over southeast Georgia could see tropical storm force winds from Elsa by early tomorrow (Wednesday) as Elsa rakes time to weaken after its north Florida landfall. Prepare now for possible isolated damage and power outages. Heavy rain with possible flash flooding is also another hazard to consider here.

(8) For coastal Georgia and the coastal Carolinas…on Wednesday (tomorrow) and Thursday Elsa could retain tropical storm force winds even if the center never quiet makes it back over water after its north Florida landfall…as Elsa could get aided by the divergent nature of the shearing upper southwesterly flow as we are currently seeing. I recommend interests along the coastal areas of Georgia and the Carolinas to begin preparing for possible tropical storm force winds and coastal sea swells. Inland areas in the eastern Carolinas could also see breezy winds with more isolated damage potential. Heavy rain with possible flash flooding is also another hazard to consider here.

(9) Interests across the northeastern US coastal region should monitor the progress of Elsa as the following hazards may occur by late Thursday through Friday as the tropical storm transitions into a potentially vigorous remnant frontal cyclone:

**Heavy rainfall from eastern Virginia to Maine

**Gusty winds with some damage potential from coastal Virginia to coastal Massachusetts

**Coastal sea swells from coastal Virginia to coastal Maine

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

0 Hr Position (1800Z Jul 6)…70 mph maximum sustained wind tropical storm centered offshore of southwest Florida at 25.4N-83W

IOH 24 Hr Forecast (1800Z Jul 7)…50 mph maximum sustained wind tropical storm centered over the Florida/Georgia border at 31.2N-82.5W

IOH 48 Hr Forecast (1800Z Jul 8)…40 mph maximum sustained wind tropical storm centered over northeastern North Carolina at 35.5N-77.6W

IOH 72 Hr Forecast (1800Z Jul 9)…Frontal cyclone centered just south of Massachusetts…Connecticut…Rhode Island…and Long Island New York at 39.8N-72.5W

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