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 #38

*******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 12:17 AM EDT...


Please note that in addition to the land areas listed on the home page bulletins of this site…the western Bahamas could also see impact from Hurricane Elsa.


See Hurricane Elsa and pair of area of interest sections below for other areas being monitored for tropical development. These areas of interest include:

(1) Area of interest #1...tropical wave of low pressure located west of Elsa in the central Caribbean Sea…being cancelled as an area of interest

(2) Area of interest #2...tropical wave of low pressure located far east of Elsa in the central tropical Atlantic that could pass over the southern Lesser Antilles…northern Venezuela…and Aruba Bonaire and Curacao by the early to middle part of next week. Risk of development is low at this time.

The largest concern at this time is Elsa...which will pass through or near Haiti...the Dominican Republic…Jamaica...the Cayman Islands...Cuba...the western Bahamas…and parts of the southeast US over the coming days.


Elsewhere...yet another distinct tropical wave of low pressure with strong thunderstorm activity is emerging from the west coast of Africa. Upper-level winds in the eastern tropical Atlantic could be conducive for its development as an expansive upper ridge cell is expected to persist over the eastern tropical Atlantic. The model runs captured in the computer model summary section of this update did not forecast this wave to develop. The wave however is more organized than yesterday…therefore it could emerge as another area of interest for tropical development.


HURRICANE ELSA...Over the last 36 hours and since my last full update on the Atlantic tropics…Elsa has already attained category 1 hurricane strength while zipping quickly west-northwest through the southern Lesser Antilles this past morning and early afternoon. Since then Elsa stopped strengthening past 85 mph max sustained winds…and colorized infrared satellite suggests an eye-type dimple leaned to the west side of its central thunderstorm core. This suggests Elsa’s surface spin is moving so fast to the west that it may be trying to outrun its thunderstorm canopy. This could very well keep the largest amount of thunderstorm latent heat release and resultant upper outflow not quiet aligned with the surface center such that the surface center may not be able to drop its surface pressure further…so it’s conceivable Elsa maintains strength or even weakens in the next 24 hours. But this is the same statement made about Elsa yesterday and yet it managed to wrap thunderstorms symmetrically around the surface center strengthen earlier today…so it is also possible that Elsa strengthens some more on its way to the south Haiti coast in the next 24 hours. So out of caution…I show Elsa reaching high end category 1 strength by 24 hours (note as of the 11 PM EDT advisory that just came in…Elsa slightly weakened to 80 mph max winds…the intensity forecast shown below may need a downward adjustment if this continues overnight).


Yet again…my updated forecast track is faster to the west-northwest due to Elsa’s current position and 30 mph current forward speed. This is explained by the steering Atlantic surface ridge being strong and far south enough (while supported by a southern-located upper convergence zone that has setup between the north side of the tropical upper ridging in the region and south side of the northwest Atlantic upper ridge cell). The forecast track after 24 hours bends north with time and slows down once Elsa reaches 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. By the end of 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 Cuba and Florida…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 120 hours. Because Elsa has tracked a little further north…the global models (except the GFS) have trended more toward the north and east on a path into Haiti…eastern Cuba…and near the western Bahamas and toward the east side of the Florida peninsula…which is where I placed my updated forecast track tonight.


Based on tonight’s GFS model upper-level wind runs…Elsa will be underneath expansive upper ridging with low shear and upper outflow over the next five days…with the upper vorticity over the Gulf and southeast US not cutting too much into Elsa’s outflow from the west. That appears to be why all the global models (excepts the ECMWF) tend to recover Elsa’s strength in appreciable fashion after dramatically weakening it over Haiti and eastern Cuba. My updated intensity forecast below therefore shows Elsa’s strength oscillating up and down in the strong tropical storm to category 1 hurricane range among multiple land interaction episodes. This is lower than my previous intensity forecasts due to the increased land interaction along my latest forecast track…but still higher than the NHC forecast as of this writing. I also do not expect a sudden collapse of Elsa as the models show when Elsa passes Haiti…as the track appears en route to pass over narrower sections of Haiti’s southern peninsula and eastern Cuba.


With these forecast updates:


(1) Impacts in the Lesser Antilles have come to an end for a few hours now. Coastal sea swells may radiate outward toward Puerto Rico and the Virgin Islands overnight.

(2) For the Dominican Republic…heavier rainfall totals are likely the further west you go…with flash flooding and mudslides being a possible hazard. Tropical storm conditions (gusty winds with some damage potential and coastal sea swells) are likely in 24 hours (Saturday night) over the southwest part of the country. Preparations should be finished by tomorrow morning or early afternoon at the latest.


(3) For Haiti…hurricane force winds and storm surge are likely in the southern part of the country by 24 hours (Saturday night)…tropical storm force winds are likely in the northern part of the country as well. Preparations should be finished by tomorrow morning or early afternoon at the latest. Flash flooding rains and mudslides are also possible hazards.


(4) For Jamaica…the forecast track will likely place the island under tropical storm conditions under Elsa’s west side by 24 hours (Saturday night into early Sunday)…but in case the track wobbles more west Jamaica should still prepare for possible hurricane force conditions. Preparations should be finished by tomorrow morning or early afternoon at the latest. Flash flooding rains are also possible hazards.


(5) For the Cayman Islands…the forecast track could place the region under tropical storm conditions under Elsa’s west side by Sunday. Prepare now for possible tropical storm conditions.

(6) Cuba could experience tropical storm to hurricane force conditions by Saturday afternoon and into Sunday. Now is the time to prepare. At this time it appears such conditions are likely toward the east part of the country…but only a slight change in the track’s angle could bring these conditions to the west side of the country.


(7) The western Bahamas could see tropical storm force conditions by Monday. 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.

(8) The Florida peninsula and Keys could see tropical storm force to hurricane force conditions by Monday and Tuesday. 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…to avoid last minute crowding especially if you have not been vaccinated against the COVID-19 virus.


(9) 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 below holds…that would affect Georgia and the Carolinas…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 3)…85 mph maximum sustained wind hurricane centered over the eastern Caribbean Sea at 14.4N-65.1W

IOH 24 Hr Forecast (0000Z Jul 4)…95 mph maximum sustained wind hurricane centered over southwestern Haiti at 18N-74.2W

IOH 48 Hr Forecast (0000Z Jul 5)…65 mph maximum sustained wind tropical storm centered over eastern Cuba at 20.8N-76.2W

IOH 72 Hr Forecast (0000Z Jul 6)…90 mph maximum sustained wind hurricane centered between Andros Island and southeast Florida at 24.5N-79.5W

IOH 96 Hr Forecast (0000Z Jul 7)…75 mph maximum sustained wind hurricane centered over east-central Florida at 27N-80.2W

IOH 120 Hr Forecast (0000Z Jul 8)…90 mph maximum sustained wind hurricane making landfall over the southern tip of South Carolina at 32.3N-80.2W


AREA OF INTEREST #1...The previously vigorous tropical wave of low pressure moving westward across the Caribbean Sea and ahead of what is now Hurricane Elsa has significantly weakened…only producing scattered thunderstorms in the vicinity of Jamaica tonight. This is probably attributed to the fact the wave is moving slower than Elsa while reaching the weakening west extent of the steering Atlantic surface ridge (the ridge is weakening here due to the approach of the eastern North America upper trough and surface cold front)…resulting in Elsa catching up to the wave and stealing some of its surface inflow needed to fuel showers and thunderstorms. This tropical wave is no longer likely to produce notable weather…and this is my final statement on this tropical wave on this blog.

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

IOH 24 Hr Outlook (0000Z Jul 4)…0% chance of tropical cyclone formation (south of the Cayman Islands near 17.5N-80W)


AREA OF INTEREST #2...The vigorous tropical wave of low pressure in the central tropical Atlantic…located well east of what is now Hurricane Elsa…has been disrupted by central Atlantic upper vorticity that has been pushed into its path by the current northwest Atlantic upper ridge cell. This resulted in a disorganization and then loss of much of the thunderstorms early today. However as of this afternoon and evening…the wave has managed to develop a curious small area of rotation with an organized curved band of thunderstorms near 5N-40W. This area is located in a more favorable upper wind environment to the southeast of the upper vorticity…in touch with upper ridging to the east that is promoting outflow and low shear. Therefore I have continued this wave as an area of interest for tropical development for now.


The tropical wave is being steered west by the strong Atlantic surface ridge forecast to remain in place over the next five days. The wave has been moving a bit slower than I previously forecasted…which will also help keep some distance between the wave and less favorable central Atlantic upper vorticity…especially as the upper vorticity also continues west out ahead of the wave while pushed around by the northwest Atlantic upper ridge cell. By the middle and end of the 5-day forecast period…the central Atlantic upper vorticity will join with lingering western Atlantic upper vorticity. However all of this upper vorticity will still continue west and keep some distance from the wave while pushed around by another high-latitude upper ridge cell to develop in the warm sector of the next frontal system/upper trough to slide across north-central and northeastern North America. The end result is this tropical wave remains in a potentially favorable low shear/upper outflow environment to the southeast of the upper vorticity thru the forecast period. I have assigned low 10% odds of development to wait and see if the current small area of rotating thunderstorms persists….and also because none of the global models develop this wave in today’s runs.

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

IOH 24 Hr Outlook (0000Z Jul 4)…10% chance of tropical cyclone formation (central tropical Atlantic near 7N-46W)

IOH 48 Hr Outlook (0000Z Jul 5)…10% chance of tropical cyclone formation (central tropical Atlantic near 8N-52W)

IOH 72 Hr Outlook (0000Z Jul 6)…10% chance of tropical cyclone formation (east of Trinidad and northeastern Venezuela near 9N-58W)

IOH 96 Hr Outlook (0000Z Jul 7)…10% chance of tropical cyclone formation (southeastern Caribbean Sea just east of Venezuela’s offshore islands at 11N-64W)

IOH 120 Hr Outlook (0000Z Jul 8)…10% chance of tropical cyclone formation (just north of Aruba near 12.8N-70W)


...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 Hurricane Elsa...quickly weakens while moving northwest into Haiti by 36 hours…remnant low moves over eastern Cuba by 54 hours…remnant low regains tropical storm status over the northwest Bahamas at 84 hours…regains hurricane strength by the time it makes landfall over Cape Fear North Carolina at 114 hours…slides northeast across the North Carolina Outer Banks by 120 hours.

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

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


1200Z ECMWF Model Run...

**For Hurricane Elsa...quickly weakens while moving northwest into Haiti after 24 hours…remnant low moves over eastern Cuba by 48 hours…remnant low does not regenerate into a tropical cyclone while moving parallel to southeast US coast by 72 hours.

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

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


1800Z GFS Model Run...

**For Hurricane Elsa...reaches the south coast of Haiti by 27 hours and weakens and also shrinks in size into a compact tropical storm….compact tropical storm wobbles westward into eastern Jamaica by 45 hours…turns north toward eastern Cuba by 54 hours while weakening to a remnant low…remnant low slides northwest across central and western Cuba through 72 hours…remnant low regenerates into a tropical depression west of the Florida Keys by 93 hours…regains tropical storm strength near 26N-84W at 102 hours…regains hurricane strength while making landfall on the Big Bend of the Florida panhandle coast at 117 hours.

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

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

1200Z NAVGEM Model Run...

**For Hurricane Elsa...weakens to a tropical storm while crossing Haiti by 30 hours…emerges from Haiti and slides west-northwest into eastern Cuba as a remnant low by 42 hours…remnant low regains tropical storm status between Cuba and the western Bahamas at 66 hours…moves north across the western Bahamas by 78 hours…regains hurricane strength offshore of Georgia near 30N-80W at 108 hours…makes landfall at hurricane strength on the South Carolina coast at 120 hours.

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

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

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