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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 2024 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #67

*******Note that forecast 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.*********


...WEDNESDAY AUGUST 14 2024 12:30 AM EDT...

See Tropical Storm Ernesto section below for information on impacts the storm is currently bringing to the northeastern Caribbean Islands... and future impacts expected across the southeastern Bahamas... Bermuda... and southeastern Canada in the days ahead.


Further east... monitoring tropical waves of low pressure following behind Ernesto as follows:

(1) An east-west elongated tropical wave of low pressure is currently analyzed by the NHC TAFB to be at 32W longitude and largely covered by dry Saharan air that has prevented its development. Based on satellite imagery... it appears the western part of the tropical wave has broken off into a separate wave near 12.5N-42.5W as of this writing that is also suppressed by an overhead inverted upper trough... albeit the separate wave is producing an area of thunderstorms on its southwest side. Over the next 72 hours the surface wave at 42.5W is forecast to move west-northwest toward Ernesto's surface ridge weakness and into the eastern Caribbean... although the suppressing inverted upper trough accelerates west and away from the surface wave the anticyclonic outflow of Ernesto drives a chunk of the current west Atlantic band of upper vorticity southward into the eastern Caribbean... therefore the surface wave is not expected to develop while suppressed by the upper vorticity that sags into the eastern Caribbean.

(2) Satellite imagery over Africa (https://www.goes.noaa.gov/FULLDISK/GMIR.JPG) shows a large tropical wave of low pressure is over far western Africa... and is about to emerge into the eastern tropical Atlantic within the next couple of days. The south and east sides of the wave have a broad area of thunderstorm squalls while the northwest side of the wave appears to be ingesting dry Saharan air... none of the models forecast this wave to develop in the Atlantic perhaps due to the dry air ingestion.


TROPICAL STORM ERNESTO… While stepping over the northern Lesser Antilles and then Virgin Islands… Ernesto has begun an early turn towards the north that should see the center pass just northeast of Puerto Rico overnight. Although the storm has a traditional large swirling appearance on visible satellite pictures… colorized infrared shows the strongest thunderstorms have congregated in a north-south axis straddling the center… with the far eastern and western parts of the circulation being void of thunderstorms perhaps while ingesting dry Saharan air that has been seen as a beige tint to the northwest and northeast of the storm. The north-south axis of thunderstorms has recently taken on a peculiar appearance with two circular bursts on either side of the center... making the axis appear as a peanut on colorized infrared pictures.


The north turn is being induced by the current west Atlantic surface ridge weakness generated by the divergence zone of the upper trough now moving into the Atlantic from eastern Canada... and because the turn has begun earlier I have shifted the forecast track east through 48 hours while now showing a north track along 68.8W longitude. Because Ernesto is now a stronger/taller tropical storm... the band of nearby cut-off upper vorticity to the northwest may have also played a role in the earlier north turn. The peculiar infrared satellite appearance noted in the prior paragraph and possibility of shear from the upper vorticity cause me to only show gradual strengthening into a category 1 hurricane through 24 hours. This is still higher than my previous forecast intensity for this timeframe as land interaction with the northeastern Caribbean Islands is already coming to an end with the earlier northward turn. Beyond that time the potentially shearing upper vorticity is still forecast to dissipate from prolonged isolation from high-latitude cold air... exposing Ernesto to a more favorable environment where its northern outflow is also enhanced by the southwesterly flow ahead of the western Atlantic upper trough. However this window of time comes to an end earlier... for the timeframe that is now 48 hours away... as the early north turn of Ernesto ends up bringing the storm into westerly shear on the south side of the upper trough sooner... the end result is my forecast intensity for the timeframe that is now 48 hours away is the same as previous despite the higher 24-hour projected intensity. Forecast track and intensity beyond 48 hours is quiet similar to the previous as follows... (1) Ernesto is dragged northeastward by the western Atlantic upper trough and associated surface ridge weakness from 48 to 72 hours while I forecast the storm to weaken from the trough's shear... (2) the upper trough and surface weakness then leave behind Ernesto in the 72 to 120 hour window... with the blocking surface ridge induced by the western convergence zone of the departing upper trough merging with the Atlantic surface ridge... creating a solid wall to the east of Ernesto that deflects the northeast track of the storm into a straight north angle. For this final part of the 5-day forecast... I have nudged my updated track more eastward to suggest the center passes just east of Bermuda as this is the emerging GFS... NAVGEM... ECMWF... and CMC consensus in the computer model summary section below... however even with this forecast track the western part of Ernesto's core would still bring dangerous hurricane conditions to the island if the current intensity forecast holds. The intensity forecast calls for strengthening into a major category 3 hurricane in the 72 to 120 hour window as whatever disrupting cool core upper vorticity left behind by the exiting western Atlantic upper trough and near Ernesto likely dissipates from Ernesto’s thunderstorm latent heat release… with the storm also overspread by a warm core upper ridge (low shear and outflow environment) in the warm sector of the next frontal system to approach from eastern North America. The storm is in its best upper air environment over the next five days at day 5 due to the aforementioned and expansive upper ridge... however I do not call for an intensity above minimal category 3 during that time as the storm closes in on lower oceanic heat content in the northwest Atlantic while nearing the 26 deg C sea-surface temperature isotherm.


Regarding impact to land areas:

(1) The northern Lesser Antilles have already seen the peak winds and heaviest rainfall from this event early on Tuesday... coastal surf should continue to fall as the storm pulls north and away.

(2) The Virgin Islands have seen the peak winds from this event in recent hours... wind and coastal surf should decline in the hours ahead as the storm pulls north and away. However several hours of heavy rainfall lie ahead as the thunderstorms on the south side of the circulation overspread the Virgin Islands later today.

(3) Eastern Puerto Rico may see tropical storm force winds in the next few hours... with winds and coastal surf beginning to decline later today as the storm then pulls north and away. Several hours of heavy rainfall... with flash flood and mudslide potential on mountainous terrain... lie ahead as the thunderstorms on the south side of the circulation overspread Puerto Rico later today.

(4) The potential for storm force winds to arrive on the northeast coast of the Dominican Republic has ended as the storm has made its early northward turn discussed above. However surf will reach the shores of the northeastern Dominican Republic and southeastern Bahamas today.

(5) Interests in Bermuda should also watch this system as by day 4 (Saturday) this system appears likely to move into the island as a potentially strong hurricane.

(6) Interests across southeastern Canada (Nova Scotia... Prince Edward Island... Newfoundland... Labrador... and southeastern Quebec) should also monitor the progress of Ernesto as it has potential to move into the region early next week as a strong and potentially dangerous weather system as follows... Ernesto by Sunday could become a major hurricane in the northwest Atlantic as discussed above... which would help keep the intensity of this system high as it transitions into a non-tropical frontal cyclone supported by the divergence zone of the next eastern North America upper trough that will be digging toward Ernesto by early next week.

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

0 Hr Forecast (0000Z Aug 14)... 65 mph maximum sustained wind tropical storm centered over the Virgin Islands at 18.4N-64.7W

IOH 24 Hr Forecast (0000Z Aug 15)... 80 mph maximum sustained wind hurricane centered in the western Atlantic at 23N-68.8W

IOH 48 Hr Forecast (0000Z Aug 16)... 95 mph maximum sustained wind hurricane centered in the western Atlantic at 27N-68.8W

IOH 72 Hr Forecast (0000Z Aug 17)... 85 mph maximum sustained wind hurricane centered south of Bermuda at 30N-65W

IOH 96 Hr Forecast (0000Z Aug 18)... 105 mph maximum sustained wind hurricane centered just northeast of Bermuda at 33N-64W

IOH 120 Hr Forecast (0000Z Aug 19)... 115 mph maximum sustained wind major hurricane centered in the northwest Atlantic at 37.5N-64W

*****National Hurricane Center (hurricanes.gov) official forecast as of 5 PM EDT**************************

Peak Strength (0600Z Aug 16)... 110 mph maximum sustained wind hurricane centered in the western Atlantic at 27.2N-67.9W

Landfall (1800Z Aug 17)... 105 mph maximum sustained wind hurricane centered over Bermuda at 32.7N-65.3W

5-Day Position (1800Z Aug 18)... 105 mph maximum sustained wind hurricane centered over the northwest Atlantic at 36.8N-64.1W


...COMPUTER MODEL SUMMARY...

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


1200Z (Aug 12) CMC Model Run...

**For Tropical Storm Ernesto… passes over the northern Lesser Antilles and just north of the Virgin Islands through 36 hours… passes just north of Puerto Rico at 42 hours… gradually turns north and strengthens into a strong hurricane with the center passing just west of Bermuda at 132 hours… hurricane then accelerates northeast to 40.5N-59.5W through 168 hours


1200Z (Aug 12) ECMWF Model Run...

**For Tropical Storm Ernesto… passes over the northern Lesser Antilles and Virgin Islands through 30 hours…passes just north of Puerto Rico at 42 hours… gradually turns north and strengthens into a strong hurricane with the center passing just west of Bermuda at 120 hours… hurricane then accelerates north-northeast to 38N-60.5W through 168 hours

**Vigorous tropical wave of low pressure emerges from western Africa at 60 hours and passes over the Republic of Cabo Verde Islands as a broad tropical low at 90 hours… gradually weakens back to a wave while moving into the central tropical Atlantic through 168 hours


1800Z (Aug 12) GFS Model Run...

**For Tropical Storm Ernesto… passes over the northern Lesser Antilles at 15 hours then strengthens into a compact strong tropical storm in the northeast corner of the Caribbean that moves into the south coast of Puerto Rico at 36 hours… after turning northwest across Puerto Rico gradually re-curves northeast while strengthening into a large and strong hurricane with the center passing just west of Bermuda at 132 hours… hurricane subsequently accelerates north toward western Nova Scotia through 168 hours

**Vigorous tropical wave of low pressure emerges from western Africa at 63 hours and slowly passes over the Republic of Cabo Verde Islands by 102 hours as a broad tropical low… shortly thereafter weakens back to a wave with no development shown in the long range


1800Z (Aug 12) NAVGEM Model Run...

**For Tropical Storm Ernesto… passes west-northwest across the northern Lesser Antilles… Virgin Islands… and Puerto Rico through 30 hours… subsequently curves north then northeast while becoming an intense hurricane with the center moving into Bermuda by 120 hours… hurricane continues accelerating northeast toward Newfoundland through 168 hours

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