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 #41 (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 JULY 5 2021 5:34 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 0600Z:

GFS Model Upper-Level Winds 0600Z:

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…tropical waves of low pressure in the eastern and central tropical Atlantic have not shown signs of development while capped by dry Saharan air…and none of the global models forecast tropical development in the Atlantic basin for the next few days.


TROPICAL STORM ELSA...Overnight last night and while approaching central Cuba…Elsa managed to strengthen to 65 mph maximum sustained winds. As the center approached its Cuba landfall early this afternoon…the storm weakened back to 60 mph max sustained winds (as of the recent 5 PM EDT advisory the NHC has assumed the landfall has weakened Elsa further to 50 mph max sustained winds). In addition to land interaction…some of the weakening maybe attributed to upper vorticity from last week lingering over the southeast Gulf of Mexico whose upper southwesterly flow might be lightly shearing Elsa and also choking some of the western outflow of the storm.


My previous forecast had Elsa’s center midway between Cuba and the Florida Keys by late this afternoon. However…with Elsa still further south and over Cuba…my updated forecast track below is adjusted southward accordingly….which gives just a little more time before conditions deteriorate across the Florida Keys and peninsula. The north turn across central Cuba and toward the west side of the Florida peninsula is the net effect of the northwest push of the eastern US and Atlantic surface ridges…coupled with the fact Elsa is strong/tall enough to feel the effects of the upper southwesterly flow setting up across the eastern Gulf of Mexico out ahead of the SE Gulf upper vorticity (mentioned in the prior paragraph) and upper vorticity being left behind over the southeast US/northern Gulf. My forecast track line continues takes Elsa across much of the west Florida peninsula coast through 24 hours…and then inland across the eastern US by 48 and 72 hours. The GFS in recent days had previously been west of this forecast track line while overdoing the land interaction with Jamaica and having a weakened/shallow system that gets pushed more west by the surface flow around the aforementioned surface ridges. Today the GFS understands Elsa will remain intact and has a stronger storm and more east track in line with my and the NHC’s general forecast idea. The ECMWF since yesterday has followed suit by showing an intact system…and now the two models basically agree on track. However I think the ECMWF pushes Elsa too far east in the long range which allows Elsa to re-strengthen over the coastal Carolina region while tapping into warm Gulf Stream water. At this time I do not see enough of an eastward angle in the forecast upper southwesterly flow to agree with the ECMWF…so for now I am basically in agreement with the GFS.


My updated intensity forecast is slightly raised as the 1200Z GFS and ECMWF show Elsa gaining strength over the far eastern Gulf of Mexico (over the Florida Keys and just offshore of the Florida peninsula west coast) despite the shearing effects of the upper southwesterly flow. My updated forecast assumes Elsa may re-strengthen as high as 65 to 70 mph max sustained winds as it moves into the Florida Keys late tonight and early tomorrow…as Elsa has a fairly healthy structure on both true-color and colorized infrared satellite channels. Then as Elsa’s center moves by Port Charlotte on the Florida west coast and more into the shearing upper southwesterly flow by tomorrow afternoon…I assume it will weaken to 60 mph max sustained winds. I then forecast Elsa to weaken to an inland tropical depression over the southeast US by 48 hours…and then by 72 hours transition into a remnant frontal low moving toward the northeast US coastal region while supported by the divergent east side an approaching SW to NE tilted upper trough to be associated with the next cold front currently seen moving across the central US and central Canada.


With these forecast updates:


(1) For the Cayman Islands…the tropical storm wind field passed to the north. However the islands have been buried in Elsa’s southern rain bands…with the heavy rain likely coming to an end at this point based on the latest satellite imagery.


(2) Cuba is experiencing tropical storm force conditions and coastal sea swells across central part of the country. Heavy rains with flash flooding potential will continue across western and central parts of the country through tonight.


(3) The western Bahamas will not see direct impact from Elsa…however coastal sea swells and locally heavy rain from a stray eastern band generated by Elsa remains possible through tomorrow.


(4) The Florida peninsula and Keys will see tropical storm force conditions by tomorrow…I recommend preparations should have finished by now in the Florida Keys and south half of the Florida peninsula. Elsa has taken a little longer to turn to the north…so the north half on the Florida peninsula has till tomorrow morning at the latest to finish preparing. The current forecast track would bring the strongest winds and coastal storm surge across the Keys and along much of the peninsula west side. The east side could still sea swells and rip currents. All of the peninsula could see heavy rains with flash flooding potential.


(5) Interests in the Florida panhandle and along the Georgia and Carolina coasts should still follow Elsa’s progress as impacts are possible late tomorrow and Wednesday. However the potential for tropical storm force winds at these locations is low as the current forecast track line continues to hold…but coastal sea swells…rip currents…and heavy rainfall will be possible hazards with the current forecast track.

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

0 Hr Position (1800Z Jul 5)…60 mph maximum sustained wind tropical storm making landfall over central Cuba at 22.2N-81.6W

IOH 24Hr Forecast (1800Z Jul 6)…60 mph maximum sustained wind tropical storm centered offshore of Port Charlotte Florida at 26.5N-82.5W

IOH 48 Hr Forecast (1800Z Jul 7)…35 mph maximum sustained wind tropical depression centered inland over southeastern Georgia at 31.2N-82W

IOH 72 Hr Forecast (1800Z Jul 8)…Remnant low transitioning into a non-tropical frontal low centered over the eastern North Carolina/Virginia border at 36.5N-77.3W

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