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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 #93

*******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.*********


...UPDATE...THURSDAY OCTOBER 3 2024 3:20 PM EDT...

The surface and upper air panels valid for 1320Z October 2... which were not previously included in the birdseye view chart below to ensure a timely release of the 1:15 AM EDT October 3 update... have now been added. In addition the following events have occurred since the 1:15 AM EDT update:

(1) Kirk continues to be a major category 3 hurricane in the open central Atlantic... with intensity oscillating between 120 and 125 mph maximum sustained winds.

(2) Tropical Storm Leslie... located southeast of Kirk... is only gradually developing so far while having reached 45 mph maximum sustained winds as of 11 AM EDT.


...THURSDAY OCTOBER 3 2024 1:15 AM EDT...

See remnants of Joyce… Hurricane Kirk… and tropical depression thirteen (recently upgraded to Tropical Storm Leslie) sections below for more information on currently or formerly active tropical cyclones currently positioned in the open parts of the Atlantic basin. In addition monitoring the following areas of interest:

(1) See area of interest #34 for a complex tropical disturbance which could develop within the next few days in southern Gulf of Mexico and surrounding land areas.

(2) See area of interest #37 section below for the western Atlantic frontal low that may acquire tropical characteristics while it moves east-southeast into Bermuda and vicinity.

(3) In about 4 to 5 days… the major upper trough forecast to recurve Kirk northeastward may produce another surface frontal low or cyclone with tropical characteristics to the south of Newfoundland… toward the 26 deg C warm water around 40N latitude. As such… will add another area of interest for the northwest Atlantic waters in future updates if necessary.


REMNANTS OF JOYCE... While its thunderstorms continued to remain sheared off to the northeast of its surface low pressure circulation... Joyce was downgraded to a remnant low by 11 PM EDT Sunday when the surface circulation no longer had a well-defined center. Ex-Joyce through 1200Z Monday was producing sheared-off thunderstorms... after which time the surface circulation and its associated surface convergence became too weak to kick off additional thunderstorms. Ex-Joyce has been moving slowly and erratically while remaining trapped between the western Atlantic deep-layer ridge and eastern Atlantic surface ridge... and as of this writing was positioned near 25N-51.5W. The remnant surface low... which continues to remain void of thunderstorms... appears close enough to Hurricane Kirk to the southeast such that the most likely future outcome is the remnant surface low begins to be pulled southward by the outer northwestern circulation of Kirk which will absorb it (or alternatively it entirely dissipates just before being absorbed by Kirk). This is my final statement on Joyce as it is no longer a tropical cyclone.


HURRICANE KIRK... While continuing west-northwest across the eastern and central tropical Atlantic over the last couple of days... Tropical Storm Kirk eventually became a hurricane but took a little longer to do so than I previously expected. This was due to a combination of lingering northerly shear on the east side of the regional tropical upper ridge and perhaps ingestion of dry Saharan air seen as a beige tint in true-color visible satellite imagery to the east and north of the hurricane. Kirk will soon be turning increasingly north into a large-scale mid-ocean ridge weakness induced by the combination of Ex-Joyce... the current northwest Atlantic frontal cyclone which has recently become re-enforced by the south part of an upper trough that recently departed the east Canada coast... and a currently developing west Atlantic frontal low that will be tracking toward the vicinity of Bermuda while supported by upper vorticity that is currently departing the eastern US. A complete north turn by 72 to 96 hours is expected around the east side of the Bermuda-area frontal low. My intensity forecast for this period of time has been lowered compared to the previous due to the lower initial intensity of Kirk. The southern base of the mid-latitude upper trough tied to the current northwest Atlantic frontal cyclone... the same feature that sheared apart Joyce... shifts east into Kirk's environment and potentially disrupts Kirk's northwestern outflow in the next 24 hours. Therefore my intensity forecast point through that time only calls for gradual intensification into a top-end category 1 hurricane. After that time the prolonged isolation from high-latitude cold air... combined with Kirk's thunderstorm latent heat release... should cause the disrupting upper vorticity to dissipate... allowing the eastward-shifting mid-latitude upper ridge currently over the western Atlantic to merge with the tropical upper ridge that Kirk was born under... resulting in a vast area of favorable low shear and upper outflow... albeit the latest model runs suggest some of this upper vorticity is still just southwest of Kirk at 48 hours so I do not quiet show category 3 major hurricane status at that time just yet. However by 72 hours I expect Kirk to firmly be a category 3... and I wouldn't be surprised if Kirk briefly touched category 4 between 72 and 96 hours. By 96 hours the upper vorticity tied to the Bermuda-area frontal low swings east into Kirk and begins to shear it... and so I show a loss of major (category 3+) status by that time. After 96 hours Kirk begins to accelerate northeastward on the east side of a strong amplified upper trough that materializes from the merger between (1) the aforementioned shearing upper vorticity near Kirk... (2) an upper trough that moves into the Atlantic from the northeastern US in 72+ hours while pivoting around the south side of the current central Canada deep-layer cyclone... (3) an eastern fracture of the current central Canada deep-layer cyclone which by late in the 5-day forecast period is a high-latitude upper trough positioned between Greenland and Canada. By 120 hours the shear level over Kirk should decrease as the flow on the east side of the strong amplified upper trough is less westerly and more southwesterly which would be more aligned with the track of Kirk... and as the faster forward speed of Kirk is more aligned with the upper southwesterly wind speed... so I show a slower weakening rate and hence keep Kirk as a category 2 hurricane from 96 to 120 hours. The weakening rate is also slowed due to the amount of supporting upper divergence on the east side of the amplified upper trough. The size of the upper divergence zone should also help Kirk's surface low pressure field grow in size. Note that Kirk is expected to reach waters below 26 deg C just before 120 hours... therefore expecting Kirk to complete transition into a large and powerful non-tropical frontal cyclone not long after 120 hours.


For now it appears there is a high likelihood of Kirk's remnant frontal cyclone generating swells that reach the shores of the Azores and the British Isles by early next week.


Update as of 1:15 AM EDT… the above forecast was completed around 1200Z Wednesday… since then Kirk quickly developed a sharp eye on satellite pictures and has rapidly intensified into a category 3 with 125 mph maximum sustained winds.

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

0 Hr Position (1200Z Oct 2)... 85 mph maximum sustained wind hurricane centered in the central tropical Atlantic at 18N-43W

IOH 24 Hr Forecast (1200Z Oct 3)... 95 mph maximum sustained wind hurricane centered in the central Atlantic at 20N-46W

IOH 48 Hr Forecast (1200Z Oct 4)... 110 mph maximum sustained wind hurricane centered in the central Atlantic at 22.5N-48W

IOH 72 Hr Forecast (1200Z Oct 5)... 125 mph maximum sustained wind major hurricane centered in the central Atlantic at 27N-50W

IOH 96 Hr Forecast (1200Z Oct 6)... 110 mph maximum sustained wind hurricane centered in the central Atlantic at 32N-50W

IOH 120 Hr Forecast (1200Z Oct 7)... 100 mph maximum sustained wind hurricane centered in the north Atlantic at 39.8N-42W

*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT*************************

Peak Strength (1200Z Oct 4)... 130 mph maximum sustained wind major hurricane centered in the central Atlantic at 22.7N-48.5W

5-Day Position (1200Z Oct 7)... 90 mph maximum sustained wind hurricane centered in the north Atlantic at 39.6N-42W


AREA OF INTEREST #36 (RECENTLY UPGRADED TO TROPICAL DERPESSION THIRTEEN)... The eastern Atlantic tropical wave of low pressure that has been southeast of Kirk spent Monday and today developing an increasingly independent and small area of thunderstorms... and as of 11 AM EDT was upgraded by the NHC to tropical depression thirteen. Over the five day forecast period the atmospheric features that will influence Kirk include the vast warm core upper anticyclone to the northwest that will be re-enforced by Kirk's thunderstorm latent heat release... the eastern Atlantic surface ridge to the north to be supported by convergence on the east side of the anticyclone... and upper vorticity currently to the northeast that will be pushed southwest toward this system by the anticyclone. The formation of the tropical depression was boosted by split flow upper divergence between the south tip of the upper vorticity and southeast side of the upper anticyclone... and based on the continuously improving appearance of this system on true-color visible satellite the small tropical depression could begin to strengthen briskly. Therefore my forecast below shows steady strengthening into a high-end tropical storm through 48 hours... as such the increasingly stronger/taller tropical cyclone only slowly progresses west in the next 24 hours (despite the presence of the steering eastern Atlantic surface ridge) while dragged by the south tip of the upper vorticity. And by 48 hours I show some north angle in the west drift as the steering south tip of the upper vorticity retrogrades southwest to a position northwest of this system. Due to isolation from high-latitude cold air... the south tip of the upper vorticity dissipates by 72 hours and I show more rapid intensification into a category 2 hurricane coupled with a less north and more west faster track around the eastern Atlantic surface ridge. The reasoning behind the faster intensification rate is the compact size of the storm which allows it to undergo more-rapid intensity fluctuations... and that the south tip of the upper vorticity might introduce some shear or outflow disruption in the 48-hour window... with these negative effects then going away by 72 hours.


For the end of the forecast period (96 to 120 hours)... this system then undergoes interaction with the main body of the upper vorticity which retrogrades southwest to a position just northwest of this system. As such the west forward speed around the eastern Atlantic surface ridge is once again slowed... with more north angle in the track. And while continuing to model this system as a small tropical cyclone subject to rapid intensity changes... I show abrupt weakening to a category 1 hurricane by 96 hours due to southerly shear imparted by the main body of upper vorticity... followed by rapid re-development back into a category 2 at 120 hours once the main body of the upper vorticity fades due to its prolonged isolation from high-latitude cold air.


Update as of 1:15 AM EDT… the above forecast was completed around 1200Z Wednesday… since then tropical depression thirteen was upgraded to Tropical Storm Leslie with 40 mph maximum sustained winds.

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

0 Hr Position (1200Z Oct 2)... 35 mph maximum sustained wind tropical depression centered in the eastern tropical Atlantic at 10.6N-29.1W

IOH 24 Hr Forecast (1200Z Oct 3)... 50 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 10.5N-30W

IOH 48 Hr Forecast (1200Z Oct 4)... 65 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 11.5N-32.5W

IOH 72 Hr Forecast (1200Z Oct 5)... 100 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 12N-36W

IOH 96 Hr Forecast (1200Z Oct 6)... 85 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 14.5N-37.5W

IOH 120 Hr Forecast (1200Z Oct 7)... 100 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 16N-40W

*****National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT*************************

5-Day Position (1200Z Oct 7)... 90 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 16.5N-41W


AREA OF INTEREST #34... Over the last couple of days a low-level spin that was near the northeast Yucatan peninsula has drifted west-southwest toward the northwestern corner of the peninsula and eastern Bay of Campeche while at the same time the Caribbean low-level spin that was east of Central America has moved north-northwest across the Cayman Islands and toward western Cuba… as the two low-level spins are cyclonically orbiting each other. Southern Caribbean upper vorticity has been pushed westward and overtop this complex dual-spin disturbance by the western Atlantic deep-layer ridge… with the cyclonic orbit between the two spins perhaps further enabled by the cyclonic flow of the overhead upper vorticity. Although the upper vorticity is suppressing upper outflow needed for thunderstorms… the upper vorticity is now small enough and continues to fade from its isolation from high-latitude cold air such that each of the two low-level spins is producing its own area of showers and thunderstorms. Still expecting over the next 2 to 3 days that  the two spins will merge near the north coast of the Yucatan peninsula. What happens beyond that time largely hinges on the current central Canadian frontal cyclone and its upper vorticity… in addition to the current upper vorticity over the eastern US. The latest forecast shown in the models has the tail end of the eastern US upper vorticity becoming a slow-moving cut-off feature over the south-central United States toward day 5 due to warm core upper ridging prevailing over the United States in the warm sector of the Canadian frontal cyclone... albeit some upper troughs pivot east across the US on the south side of the upper vorticity atop the Canadian frontal cyclone but are not strong enough to dislodge the upper ridging pattern over the US. Except for the CMC… the global models are shy to develop this area of interest while forecasting a broad tropical low that struggles to consolidate into a tropical cyclone. This could be due to the initial state of this area of interest which is already starting off with two maximum spins instead of one... followed by a potentially elongated area of upper divergence in the Gulf of Mexico toward days 4 and 5 (in association with the south-central US upper vorticity) that could cause this system to be elongated with multiple centers instead of circular with a single center. Another factor potentially going against development is possible shear imparted by the forecast south-central US upper vorticity. My current forecast strategy is to drift this system slowly northeast from the north coast of the Yucatan peninsula and into the southeastern Gulf of Mexico on days 4 and 5 in the flow ahead of the upper vorticity... and I continue to forecast less than 50% peak odds of tropical cyclone formation.


This complex disturbance has produced some periods of heavy rainfall across the Cayman Islands and Yucatan peninsula. Over the next few days additional periods of heavy rain are possible here… across western Cuba… the Florida Keys… and southern Florida peninsula. These areas may also see periods of gusty winds and coastal surf… even if this system ends up being a complex tropical disturbance with multiple centers instead of a tropical cyclone with a single center.

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

Formation chance through 5 days... 40% (southeastern Gulf of Mexico near 25N-85.5W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************

Formation chance through 48 hours... 0%

Formation chance through 7 days... 30%


AREA OF INTEREST #37 The divergence zone of upper vorticity currently departing the eastern United States is producing an offshore frontal low. Through 48 hours the upper vorticity and frontal low move east-southeast into the vicinity of Bermuda… the south angle in the track being aided by warm core upper ridging forecast to be over the United States. During this time the cyclonic flow of the frontal low and upper vorticity are likely to be vertically stacked… resulting in low vertical shear. Combined with warm waters this may allow this system to acquire thunderstorms and tropical characteristics. After 48 hours the upper vorticity continues east toward tropical cyclone Kirk… and the deep-layer cyclonic flow  on the west side of the upper vorticity and Kirk is forecast to cause this system to dive south then east into the central Atlantic from days 2 to 5. Upper convergence on the west side of the upper vorticity… followed by westerly shear induced by the south side of the major upper trough that will be recurving Kirk northeast… make tropical development of this area of interest unlikely in the 2 to 5 day window.


Regardless of tropical character or not… this system may produce periods of heavy rain… gusty winds… and coastal surf to Bermuda within the next couple of days.


Update as of 1:15 AM EDT… this outlook was was completed around 1800Z Wednesday… since then the surface frontal low has seen some reduction in shower and thunderstorm activity… if this continues will be lowering odds of tropical development in my next update.

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

Formation chance through 2 days... 30% (just east of Bermuda near 32N-62W)

Formation chance days 2 to 5… 0% (central Atlantic near 29N-59W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************

Not in the official outlook


...COMPUTER MODEL SUMMARY...

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


1200Z (Oct 1) CMC Model Run...

**For Tropical Storm Kirk... gains hurricane strength and gradually curves north to 35N-45W through 132 hours... subsequently turns east-northeast into the waters just northwest of the Azores through 168 hours

**For area of interest #34...current southern Gulf of Mexico broad tropical low develops a better-defined center in the Bay of Campeche by 102 hours... the broad tropical low reverses to an east-northeast track with the center positioned just north of the Yucatan peninsula by 168 hours

**For area of interest #36... tropical cyclone formation suggested near 11.2N-28.5W at 24 hours... while gaining hurricane strength continues west-northwest to 18N-48.5W through 168 hours


0000Z (Oct 2) CMC Model Run...

**For Hurricane Kirk... curves north to 34.5N-46W by 120 hours... subsequently curves east-northeast into the waters north of the Azores by 168 hours

**For area of interest #34... tropical cyclone formation suggested in the northeastern Bay of Campeche at 114 hours... while moving slowly east-northeast into the southeastern Gulf of Mexico through 168 hours gains hurricane strength

**For area of interest #36... tropical cyclone formation suggested near 10.5N-28.5W at 12 hours... while gaining hurricane strength continues west-northwest to 17.5N-51W through 168 hours

**For area of interest #37… dissipates east-southeast of Bermuda around 132 hours


0000Z (Oct 1) ECMWF Model Run...

**For Tropical Storm Kirk... gains hurricane strength and gradually curves north to 32N-51W through 138 hours... continues north-northeast to 43N-41W through 168 hours

**For area of interest #34... current southern Gulf of Mexico broad tropical low develops a better-defined center near 23.8N-89W by 108 hours... remains quasi-stationary at this location through 168 hours while becoming increasingly elongated southwest-to-northeast featuring multiple centers

**For area of interest #36... tropical cyclone formation suggested near 10.5N-26.5W at 24 hours... while gaining hurricane strength continues west-northwest to 17.5N-45W through 168 hours


0000Z (Oct 2) ECMWF Model Run...

**For Hurricane Kirk... curves north to 32N-49.5W through 108 hours... subsequently turns east-northeast into the waters north of the Azores through 168 hours

**For area of interest #34... through 126 hours gradually consolidates in the central Gulf of Mexico but still as a broad tropical low... from 126 to 168 hours becomes increasingly elongated southwest-northeast with multiple centers where northeast end of the system moves across the Florida peninsula and southwest end of the system located on north coast of the Yucatan peninsula

**For area of interest #36... tropical cyclone formation suggested near 10.5N-30W at 30 hours... while gaining hurricane strength increasingly curves north in its westward track and reaches 10.5N-45W through 168 hours

**For area of interest #37… dissipates east-southeast of Bermuda around 108 hours


1200Z (Oct 1) GFS Model Run...

**For Tropical Storm Kirk... gains hurricane strength and gradually curves north to 34.5N-47.5W through 132 hours... subsequently curves east-northeast into the waters north of the Azores through 168 hours

**For area of interest #34... current southern Gulf of Mexico broad tropical low develops a better-defined center just northwest of the Yucatan peninsula through 99 hours... afterwards drifts slowly east-northeast into the central Gulf of Mexico while becoming increasingly elongated southwest-to-northeast featuring multiple centers

**For area of interest #36... tropical cyclone formation suggested near 10.2N-28W by 21 hours... while gaining hurricane strength continues west-northwest to 19.8N-45W through 168 hours


0600Z (Oct 2) GFS Model Run...

**For Hurricane Kirk... curves north to 33N-49.5W through 105 hours... while transitioning into a rather large and powerful remnant frontal cyclone accelerates east-northeast into the waters north of the Azores and then moves toward the British Isles through 168 hours

**For area of interest #34... through 120 hours gradually consolidates in the north-central Gulf of Mexico but still as a broad tropical low... from 120 to 168 hours becomes increasingly elongated southwest-northeast with multiple centers where northeast end of the system moves across south Florida and the NW Bahamas and southwest end of the system located on north coast of the Yucatan peninsula

**For area of interest #36... tropical cyclone formation suggested near 10N-29W at 12 hours... while gaining hurricane strength increasingly curves north in its westward track and reaches 22.5N-44W through 168 hours

**For area of interest #37… dissipates east-southeast of Bermuda around 123 hours (possible tropical cyclone formation suggested beforehand and just east of Bermuda around 48 hours)


0600Z (Oct 2) NAVGEM Model Run...

**Not available at above-mentioned source

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