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 #39 (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.**********


...SATURDAY JULY 3 2021 11:15 PM EDT...

Satellite image as of 0230Z. 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 Tropical Storm Elsa section below for additional details on the storm. See area of interest #1 section below for an update on the central Atlantic tropical wave of low pressure.


Elsewhere...yet another distinct tropical wave of low pressure has recently emerged from the west coast of Africa and into the eastern tropical Atlantic. Upper-level winds in the eastern tropical Atlantic could be conducive for this wave’s development as an expansive upper ridge cell is expected to persist in the region. Although the wave has developed a low pressure cloud swirl…it has lost thunderstorms in the last 24 hours due to dry Saharan air and none of the recent model runs develop it. Therefore I have not added it as an area of interest for tropical development.


TROPICAL STORM ELSA...Over the last 24 hours and since my last full update on the Atlantic tropics…Elsa has weakened from a hurricanes to a top-end tropical storm with 70 mph max sustained winds while racing west-northwest toward the southern Dominican Republic and Haiti. The center has just dodged landfall by taking a more west and less north angle in track and thus missing the southwest peninsula of Haiti. That does not mean Elsa had no impact here…as heavy rainfall with flash flooding and mudslide potential and tropical storm force winds and coastal sea swells spread over the southwest Dominican Republic earlier today…and these conditions are still ongoing over the southern Haitian peninsula.


My updated forecast track is adjusted west given the more west angle in track that has been ongoing over the last few hours. Elsa’s fast speed is finally diminishing as well as the tropical storm finally feels the effects of the weakening west side of the steering surface ridge. This part of the ridge is weakening as the eastern North American upper trough and its surface cold front is moving into the west Atlantic. During the 5-day forecast period…the upper trough will leave behind upper vorticity over the northern Gulf of Mexico and southeast US…and the remainder of the upper trough and surface front will be leaving the region and allowing the steering surface ridge to somewhat rebuild ahead of the next frontal system to slide across north-central and northeastern North America. That leaves Elsa to be pushed more west by the recovering west side of the surface ridge and move towards central Cuba and Florida Keys…but at the same time Elsa will likely be strong/tall enough to be pulled north by the lingering upper vorticity over the southeast US/northern Gulf such that the track should be completely due north by 72 and 96 hours. With the west adjustment…that places the forecast track line in my updated forecast through much of the west Florida peninsula coast…and then inland across the eastern US by 96 and 120 hours. However the forecast track can still shift again from any shorter-term wobbles of the center…or if the center reforms east into the strongest thunderstorms.


The strongest thunderstorms have been east of the surface center…especially over the last 24 hours as the surface steering flow was strong enough to push the surface center to the west side of the central thunderstorm canopy. With Elsa slowing down as discussed in the previous paragraph…this should allow the surface center and strongest thunderstorms to finally stack. And with an impressive and expanding thunderstorm mass over and east the surface center that covers the southern Haitian peninsula as seen in the latest satellite pictures…Elsa is in danger of regaining its former category 1 hurricane strength in the next 24 hours…and this is what I forecast. I show a slightly lower but still hurricane force intensity when Elsa nears the Florida Keys and peninsula by 48 hours due to forecast land interaction with central Cuba (I keep hurricane strength by that point as Elsa would cross over a narrow swath of Cuba if the forecast track holds). The west adjusted forecast track moves Elsa closer into southwesterly shear ahead of the forecast lingering upper vorticity over the southeast US/northern Gulf…and also ahead of the SW to NE tilted upper trough associated with the next frontal system to slide over north-central/NE North America…thus I forecast Elsa to weaken to a tropical storm as it slides along the west Florida peninsula coast. I forecast Elsa to weaken to an inland tropical depression over the southeast US by 96 hours…and then by 120 hours transition into a remnant frontal low moving toward the northeast US coastal region while supported by the divergent east side of the SW to NE tilted upper trough.


With these forecast updates:


(1) For Haiti…expect additional heavy rainfall with flash flooding and mudslide potential over the southern peninsula tonight…with tropical storm force winds and coastal sea swells.


(2) For Jamaica…preparations for Elsa should have been completed by now. If the current track continues…expect the center to pass over or near the north coast tomorrow…bringing tropical storm force to hurricane force conditions. Flash flooding rain is also another possible hazard.


(3) For the Cayman Islands…the forecast track could place the region under tropical storm conditions under Elsa’s west side by late tomorrow (Sunday). Preparations should be completed by tomorrow (Sunday) morning.


(4) Cuba will likely experience tropical storm to hurricane force conditions tomorrow over the southeast part of the country toward the south coast…and the central part of the country. Only a slight change in the track’s angle could also bring these conditions to the west side of the country. Preparations on the east side of the country should have been completed by now….and for the central and western parts I recommend preparations finish by tomorrow morning.


(5) The western Bahamas are less likely to see tropical storm force conditions on Monday. However I recommend that now is the time to gather storm preparation supplies early and be ready to prepare in case watches/warnings are issued in the next day or so in the small chance that Elsa’s forecast track shifts back east.


(6) The Florida peninsula and Keys will likely see tropical storm force to hurricane force conditions on Monday and Tuesday. I recommend that now is the time to prepare. It is hard to say where exactly the worst conditions will be as the forecast track error could be as wide as the peninsula. The current forecast track would bring the strongest winds across the Keys and along much of the peninsula west side. A marginal shift east would keep Elsa’s strongest winds along the east side of the peninsula. And a slight shift east would bring Elsa’s center over land…with the worst winds over south Florida (and not as much wind over north Florida) as an inland track would potentially weaken Elsa faster due to land interaction. Wind is not the only hazard…heavy rains with flash flooding potential and coastal storm surge and sea swells are also a concern.


(7) Interests in the Florida panhandle and along the Georgia and Carolina coasts should follow Elsa’s progress as impacts are possible in the Tuesday/Wednesday timeframe (if the track forecast undergoes a marginal shift to the east…that would affect coastal Georgia and the Carolinas more strongly as Elsa would spend less time over land and have a higher strength than shown in the forecast below. If the track shifts more west then that would affect the Florida panhandle)

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

0 Hr Position (0000Z Jul 4)…70 mph maximum sustained wind tropical storm centered just offshore of southwestern Haiti at 17.8N-74.7W

IOH 24 Hr Forecast (0000Z Jul 5)…85 mph maximum sustained wind hurricane centered offshore of central Cuba at 20.1N-78.8W

IOH 48 Hr Forecast (0000Z Jul 6)…80 mph maximum sustained wind hurricane centered over the Florida Keys at 24.5N-81.2W

IOH 72 Hr Forecast (0000Z Jul 7)…60 mph maximum sustained wind tropical storm centered inland just northeast of Tampa Bay Florida at 28N-82.2W

IOH 96 Hr Forecast (0000Z Jul 8)…30 mph maximum sustained wind tropical depression centered inland over the eastern part of the South Carolina/Georgia border at 32.5N-81.2W

IOH 120 Hr Forecast (0000Z Jul 9)…Remnant frontal low centered over the Virginia/Maryland border at 38.2N-77W


AREA OF INTEREST #1…The tropical wave of low pressure in the central tropical Atlantic has gradually lost its defined low-latitude spin…and what remains of its distinct thunderstorm activity has gradually dwindled while ingesting dry Saharan air lurking to the north. Therefore I am canceling this tropical wave as an area of interest for tropical development…and plan this to be my final statement on this wave on this blog unless it later redevelops thunderstorm activity in the coming days.

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

IOH 24 Hr Outlook (0000Z Jul 5)…0% chance of tropical cyclone formation (central tropical Atlantic near 8N-52W)

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