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 #37

*******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 JULY 1 2021 3:08 PM EDT...

See Tropical Storm Elsa and multiple 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 eastern Caribbean Sea

(2) Area of interest #2...tropical wave of low pressure located east of Elsa in the eastern tropical Atlantic.

The largest concern at this time is Elsa...which will pass through the southern Lesser Antilles tomorrow and go on to potentially threaten Haiti...Jamaica...the Cayman Islands...Cuba...and possibly south Florida through this weekend and into next week.


Elsewhere...an upper vortex continues sliding southwest across the Gulf of Mexico while moving around amplifying upper ridging over the central US. A small upper ridge over the northwestern Caribbean Sea is expanding in the wake of the upper vortex. Showers and thunderstorms across the southern Gulf of Mexico...as well as the Florida peninsula and adjacent offshore western Atlantic waters are being generated by the southern and eastern divergence zones of the upper vortex and the outflow of the upper ridge. At this time there is no defined surface low pressure feature to declare an area of interest here...and the approach of the current eastern North America upper trough will increase upper southwesterly wind shear less conducive for tropical development by this weekend.


And finally...yet another distinct tropical wave of low pressure with strong thunderstorm clusters is over western 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...therefore awaiting to see future model runs or how organized the tropical wave becomes in the coming days before initiating yet another area of interest for this feature.


TROPICAL STORM ELSA...Over the last 24 hours...the vigorous and organized tropical low pressure spin in the central tropical Atlantic was upgraded to potential tropical cyclone five to allow for tropical storm watches and warnings to be raised in time for the southern Lesser Antilles...and then overnight the potential tropical cyclone developed a consolidated enough surface spin to be classified as tropical depression five and then Tropical Storm Elsa. If you thought the pace of last year's historic 2020 Atlantic Hurricane Season was unbeatable...think again...Elsa just beat Edouard of last year as the earliest fifth named storm on record in the Atlantic basin (Edouard was named on July 6 2020).


My updated forecast track is once again faster to the west than the previous as Elsa is moving about double the pace of a typical system in the deep tropical Atlantic. 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 norhtwest Atlantic upper ridge cell). The forecast track bends more north once Elsa enters the Caribbean Sea and rounds the southwest side of the Atlantic surface ridge. During the 5-day forecast period...the eastern North American upper trough and its surface cold front will finally make its way into the western Atlantic...eroding the west side of the Atlantic surface ridge and making the north angle in track increase with time. Once Elsa reaches the weakened west side of the surface ridge...the impressive forward speed of the tropical storm should also slow down by days 4 and 5.


Regarding intensity...the NHC as of this writing has chosen to keep a conservative intensity forecast that keeps Elsa below hurricane force over the next five days. In particular the NHC thinks Elsa is moving so fast to the west that the surface spin might outrun its thunderstorm canopy. Satellite imagery suggests Elsa is in fact on the cusp of outrunning its thunderstorm core while its surface swirl can be seen peeking out of the northwest edge of the thunderstorm core. This also makes Elsa's surface swirl prone to ingesting dry saharan air lurking to the northwest...therefore I have lowered the intensity forecast of Elsa overall compared to yesterday. However once Elsa slows down in the central Caribbean...I still ramp up the intensity toward major hurricane strength (category 3) by day 4 as the slower forward speed will allow the thunderstorm canopy to be aligned with the surface swirl...and as the western Atlantic upper vorticity is forecast to weaken continuosly which will allow the tropical upper ridging over the Caribbean to be large and expansive. This upper ridging's upper outflow...along with the very warm Caribbean water...will be quiet conducive for strengthening. This intensity forecast also assumes Elsa stays south of the northern Caribbean Islands...and with Elsa following the previous forecast track line thus far I do not expect this over the next 4 days. However by day 5 the current forecast track line takes Elsa into Cuba...and this is when I forecast a lower intensity below category 3.


For the Lesser Antilles:

**I recommend interests in Tobago... Grenada... Barbados... St Vincent and the Grenadines...St Lucia... and Martinique finish preparations for tropical storm conditions by tonight. Heavy rains and gusty winds with some damage potential will arrive by tomorrow afternoon and evening.

**Guadeloupe and Dominica to the north...and Trinidad to the south...could also see some gusty winds and heavy rains from the outer bands of Tropical Storm Elsa


For the western Dominican Republic...the forecast track outlined below could mean heavy rainfall with flash flooding potential from the northeastern bands of Elsa...to arrive by Sunday. Interests in Haiti...Jamaica...the Cayman Islands...and Cuba are encouraged to watch this system very carefully as there is potential for Elsa to be closing in on this region by Sunday and Monday as a potentially significant hurricane. Interests in south Florida should also begin closely watching the progress of Elsa as it could turn north into the region from Cuba by Wednesday at hurricane strength.

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

0 Hr Position (1200Z Jul 1)...40 mph maximum sustained wind tropical storm centered over the central tropcial Atlantic at 9.6N-50.2W

IOH 24 Hr Forecast (1200Z Jul 2)...50 mph maximum sustained wind tropical storm centered southeast of Barbados at 11.2N-58.2W

IOH 48 Hr Forecast (1200Z Jul 3)...65 mph maximum sustained wind tropical storm centered over the eastern Caribbean Sea at 14N-66W

IOH 72 Hr Forecast (1200Z Jul 4)...95 mph maximum sustained wind hurricane centered just south of southwestern Haiti at 17.5N-74W

IOH 96 Hr Forecast (1200Z Jul 5)...115 mph maximum sustained wind major hurricane centered over the southwest tip of eastern Cuba at 20N-77.5W

IOH 120 Hr Forecast (1200Z Jul 6)...100 mph maximum sustained wind hurricane centered over central Cuba at 22.5N-80W


AREA OF INTEREST #1...The previously vigorous tropical wave of low pressure that was crossing the Lesser Antilles is now in the eastern Caribbean Sea. After becoming disorganized with less activity through 1200Z this morning...the tropical wave is seeing some uptick in activity as of 1800Z this afternoon. Upper-level winds over this tropical wave will remain favorable for possible development in the short term as the western Atlantic upper vorticity continuously weakens...which will keep upper ridging with low shear and upper outflow intact over the wave. Thus I still keep low odds of development (5%) in my updated outlook below. The forward speed of the tropical wave will slow down and potentially bend more north as the west side of the steering Atlantic surface ridge weakens from the approach of the current eastern North America upper trough and its surface cold front. This will allow Elsa to catch up from the southeast. With Elsa potentially becoming a hurricane to the southeast...warm upper ridging to the southeast could be amplified by Elsa's thunderstorms. Coupled with the approach of the aforementioned upper trough to the northwest...southwesterly upper-level shearing winds over this tropical wave are likely to increase by day 3. This is where I end my outlook by dropping odds of development to 0%.


Regardless of additional development or not...this tropical wave has the potential to bring heavy rainfall and maybe gusty winds out ahead of Elsa and over Haiti...possibly the Dominican Republic (if the wave can maintain thunderstorm bands well northeast of its axis)...Jamaica...Cuba...and the Cayman Islands from tomorrow through this weekend.

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

IOH 24 Hr Outlook (1200Z Jul 2)...0% chance of tropical cyclone formation (just south of eastern Haiti near 17.5N-72W)

IOH 48 Hr Outlook (1200Z Jul 3)...5% chance of tropical cyclone formation (between Jamaica and eastern Cuba near 19N-77.5W)

IOH 72 Hr Outlook (1200Z Jul 4)...0% chance of tropical cyclone formation (just offshore of Cuba's southwest coast near 22N-82.5W)


AREA OF INTEREST #2...Its Deja Vu in the eastern tropical Atlantic...yet another tropical wave of low pressure appears to be organizing at a fairly quick pace in about the same area that Elsa's precursor tropical wave did a couple of days ago. This particular tropical wave appears to have its maximum spin at 7.5N-32W as of 1200Z earlier today. The good news here at least is that upper-level winds have potential to be progressively less favorable for development with time as some of the current upper vorticity in the central Atlantic gets pushed southwest and then west into the path of this wave by the current northwest Atlantic upper ridge cell. With the strong Atlantic surface ridge forecast to remain in place over the next five days...the forecast track shown below assumes this tropical wave will move at about the same brisk westward pace that Elsa did. Aligning this forecast track with the 0600Z GFS model run upper-level wind forecast...that will place this wave just east of the upper vorticity axis as the two move westward together in tandem from days 2 through 5. I have low 15% odds of development in the next 24 hours...followed by a gradual tapering down to 5% odds by the end of the 5-day forecast period as the upper vorticity axis potentially interferes with the upper outflow over the tropical wave. I am not yet comfortable with dropping longer term odds to 0% as only a slight change to the forecast track of the tropical wave or the upper vorticity axis could still give enough breathing room for the tropical wave's outflow and thunderstorms. It is also possible that the tropical wave maintains its current thunderstorm field whose latent heat release shrinks the cool core upper vorticity.

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

IOH 24 Hr Outlook (1200Z Jul 2)...15% chance of tropical cyclone formation (central tropical Atlantic near 8.5N-39W)

IOH 48 Hr Outlook (1200Z Jul 3)...10% chance of tropical cyclone formation (central tropical Atlantic near 9.5N-46W)

IOH 72 Hr Outlook (1200Z Jul 4)...5% chance of tropical cyclone formation (central tropical Atlantic near 10.5N-53W)

IOH 96 Hr Outlook (1200Z Jul 5)...5% chance of tropical cyclone formation (just east of the southern Lesser Antilles near 11.7N-59.8W)

IOH 120 Hr Outlook (1200Z Jul 6)...5% chance of tropical cyclone formation (eastern Caribbean Sea near 13N-66.8W)


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)


0000Z CMC Model Run...

**For Tropical Storm Elsa...crosses Barbados and the southern Lesser Antilles at 36 hours...passes over southwestern Haiti at 78 hours...weakens to a remnant low while moving northwest into eastern Cuba by 90 hours...remnant low turns north into the Florida Keys at 120 hours.

**For area of interest #1...tropical wave develops small/weak low pressure spin southwest of Jamaica at 48 hours...low pressure dissipates just offshore of Honduras at 72 hours.

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


0000Z ECMWF Model Run...

**For Tropical Storm Elsa...located in northeastern Caribbean Sea near 16.2N-65W at 48 hours...dissipates while moving across Haiti by 96 hours.

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

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


0600Z GFS Model Run...

**For Tropical Storm Elsa...intensifies into a hurricane by 24 hours while located at 13N-56W...crosses Barbados and the southern Lesser Antilles by 36 hours while still at hurricane strength...makes landfall over southeastern Jamaica while still at hurricane strength at 81 hours...crosses the Cayman Islands at hurricane strength at 102 hours...crosses western Cuba at hurricane strength at 120 hours.

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

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


0600Z NAVGEM Model Run...

**For Tropical Storm Elsa...crosses Barbados and the southern Lesser Antilles by 36 hours...makes landfall over the south coast of the Dominican Republic at 60 hours...emerges into the waters between Cuba and the eastern Bahamas at 78 hours...intensifies into a strong tropical storm while crossing the central Bahamas at 96 hours...becomes a strong hurricane by 120 hours while crossing 28N-75W 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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