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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 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #60

Updated: Aug 23, 2023

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


...TUESDAY AUGUST 22 2023 3:50 PM EDT...

The Atlantic tropics remain quiet active with now four named systems lining the tropical latitudes of the Atlantic... see remnants of Emily (Area of Interest #25)... Tropical Storm Franklin... remnants of Gert... and Tropical Storm Harold sections below for more details. Note Franklin and Harold are impacting land areas... more information on impacts is provided in the respective sections below.


In addition... looking for possible development from other features as follows:

(1) See area of interest #23 section below for an update on the eastern Atlantic tropical wave of low pressure being monitored for development as it continues west-northwest into the central Atalntic in the days ahead.

(2) Computer models are mixed on possible development from tropical waves of low pressure to follow behind area of interest #23 by moving into the eastern Atlantic from Africa. There are no immediate concerns as satellite imagery does not currently show any organized tropical waves over Africa as of this writing.

(3) Some recent model runs suggest that the elongated area of upper vorticity northwest of Tropical Storm Franklin may produce a broad central or western Caribbean tropical low pressure area immediately to the southwest of Franklin in the days ahead... via the elongated divergence zone associated with the upper vorticity. Upper winds would also become more conducive over time for such a broad low pressure area as the upper vorticity retrogrades westward and away while pushed by the central US upper ridge... allowing for Atlantic tropical upper ridging with lower shear and upper outlfow to expand in the Caribbean. Will add an area of interest for the central or western Caribbean in future updates if necessary.


REMNANTS OF GERT... Over the last 24 hours Gert... located east of the northern Lesser Antilles... weakened to a tropical depression while moving westward closer to Tropical Storm Franklin's upper outflow which is shearing Gert's thunderstorms east of the center. As of 11 AM EDT the National Hurricane Center has downgraded Gert to a remnant low pressure as the sheared-off activity is now dissipating and the remaining cloud swirl is fading in visible satellite pictures. Impacts to the northern Lesser Antilles are expected to be negligble as the remnants are expected to dissipate in the hostile shear environment. This is my final statement on Gert on this blog as it is no longer a tropical cyclone.


TROPICAL STORM FRANKLIN... Over the last 24 hours Franklin has been interacting with a southwest-northeast tilted string of upper vorticity to the northwest which has recently become re-enforced as the central US upper ridge has pushed in more upper vorticity that was over the southeastern US. The upper vorticity has been producing westerly shear across Franklin which has pushed the thunderstorms to the east half of the circulation. The thunderstorm activity has been quiet robust... and as sometimes seen with sheared tropical cyclones the latent heat release and resultant warm core outflow of the thunderstorms tends to cause surface pressure falls and potential center reformations toward the thunderstorms. Indeed Franklin's track has had a hiccup within the last 24 hours where it stopped its westward progress and dipped south in such a center reformation. Franklin's surface center has at times been hard to define which may be an effect of the elongated divergence zone ahead of the upper vorticity trying to elongate Franklin's surface circulation. More recently it appears an upper divergence maximum has produced a smaller burst of thunderstorms to the west of the larger main area of thunderstorms... and visible satellite pictures show a better-defined northward-moving cloud swirl near the smaller burst. This is an indication that the anticipated northward turn toward Hispaniola (Haiti and the Dominican Republic)... caused by the developing western Atlantic surface ridge weakness as a cold front and upper trough enter the western Atlantic from eastern Canada... has begun.


Due to the southward hiccup in the recent track of Franklin noted in the prior paragraph... changes have occurred to the track guidance for Franklin in the last 24 hours which are reflected in my updated track forecast below. The previous forecast track was more toward the east while having Franklin crossing Hispaniola and then chase the western Atlantic upper trough and surface cold front. With the delayed passage across Hispaniola... it appears Franklin will initially be lifted northeastward through 72 hours by those features but then be left behind by them... creating an overall westward shift in the longer-range track guidance. After being left behind... their will be effectively no surface steering as a series of shortwave upper troughs and associated surface frontal depressions to push in from the northeastern United States will prevent the Atlantic surface ridge from re-building in the western Atlantic... while at the same time the frontal depressions stay too far to influence Franklin. So then we turn to the upper-levels for steering... espeically since Franklin is forecast to stay a sufficiently strong/tall feature to be pulled by upper-level winds during the 5-day forecast window. Indeed in the upper-levels the western Atlantic upper trough that leaves Franklin behind will also leave behind an upper vortex just to Franklin's north at 72 hours... with the forecast track below showing Franklin arcing northeastward and then northward around the east side of the vortex in the 72 to 120 hour window.


Regarding intensity... the initial more southward position places Franklin a little further away from the shearing upper vorticity to the northwest. Morever the upper vorticity is forecast to soon retrograde westward and away around the central US upper ridge and the shear affecting Franklin will relax over the next 48 hours... therefore I forecast Franklin to strengthen a little more before crossing Hispaniola. By 48 hours I anticipate Franklin to only slowly recover back to its pre-Hispaniola strength as it recovers from the land interaction with the mountanious terrain of Hispaniola... then thru 96 hours do not show any additional strengthening with the arrival of westerly shear on the south side of the upper vortex mentioned at the end of the prior paragraph. Models agree that Franklin's thunderstorm latent heat release will weaken the disrputive cool core upper vortex by 120 hours... and combined with the passage across an area of rather warm 30 deg C waters begin to show Franklin strengthen briskly. My intensity forecast between 96 and 120 hours calls for Franklin to therefore jump into category 1 hurricane status.


Regarding impact to land areas:

(1) Although the northward turn of Franklin into Hispaniola (Haiti and the Dominican Republic) was delayed... it is now underway. Preparations for possible flash flooding and mudslides from heavy rain... gusty winds with some damage potential... and coastal surf should be finished within the next few hours.

(2) For the eastern Bahamas... the forecast track of Franklin has shifted westward and tropical storm advisories are now in effect for gusty winds in addition to the coastal surf that was previously anticipated. Preparations for Franklin should be completed by tomorrow evening as conditions are forecast to deteriorate by Thursday.

(3) For Puerto Rico... the westward shift in the forecast track has reduced the potential for rainfall flooding.

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

0 Hr Position (1200Z Aug 22)... 50 mph maximum sustained wind tropical storm centered in the central Caribbean Sea at 15.5N-71.1W

IOH 24 Hr Forecast (1200Z Aug 23)... 60 mph maximum sustained wind tropical storm centered over the southern Haiti/Dominican Republic border at 18N-72W

IOH 48 Hr Forecast (1200Z Aug 24)... 60 mph maximum sustained wind tropical storm centered over the easternmost Bahamas at 21.2N-71.2W

IOH 72 Hr Forecast (1200Z Aug 25)... 60 mph maximum sustained wind tropical storm centered over the western Atlantic at 22.8N-69W

IOH 96 Hr Forecast (1200Z Aug 26)... 60 mph maximum sustained wind tropical storm centered over the western Atlantic at 24N-67W

IOH 120 Hr Forecast (1200Z Aug 27)... 85 mph maximum sustained wind hurricane centered over the western Atlantic at 26N-67W

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

Landfall (1200Z Aug 23)... 50 mph maximum sustained wind tropical storm centered over the south coast of the Dominican Republic at 18.3N-71.3W

5-day Position (1200Z Aug 27)... 80 mph maximum sustained wind hurricane centered in the western Atlantic at 27.1N-67.1W


TROPICAL STORM HAROLD... Plenty has happened with the Gulf of Mexico broad low pressure area... which was tagged by the NHC as potential tropical cyclone nine... over the last 24 hours. By 5 PM EDT yesterday it strengthened into tropical depression nine... and then by 2 AM EDT early today it strengthened further to Tropical Storm Harold with 45 mph maximum sustained winds while continuing west-northwestward nearing far southern Texas. Then just before landfall... at 10 AM EDT... the broad circulation of Harold consolidated northward toward a ball of thunderstorms and strengthened to 50 mph maximum sustained winds... with the center making landfall at this strength as of 11 AM EDT at Padre Island Texas. The impacts have been weighted toward the north side of the circulation as the brisk forward speed of the tropical storm limits winds on the south side of the surface circulation and enhances them on the north side... and also the thunderstorm activity has been lopsided to the north half of this system by ongoing light southerly shear imparted by upper vorticity over northern Mexico:

(1) Gusty winds have been occurring in a narrow swath on the north side of this system from a corridor spanning Corpus Christi along the coast... to inland areas in the vicnity of Alice and Freer. National Weather Service stations (weather.gov) showed that a peak gust to 59 mph occurred at 11:51 AM CDT at Corpus Christi... and as of this writing the weather station for Alice recently reported a peak gust to 37 mph. This narrow swath of gusty winds should subside within the next few hours as Harold weakens from landfall.

(2) Northern Tamaulipas in Mexico has been spared heavy rainfall due to the northward center reformation and ongoing light southerly shear keeping activity toward the north. However based on the latest satellite and radar presentation... combined with the forecast track... heavy rainfall with some flash flooding may reach northern Coahuila in Mexico in the next 24 hours. A swath of southern Texas may see incidents of flash flooding from heavy rainfall in the next 24 hours... with some heavy rain possibly reaching southwestern Texas.

(3) Coastal surf along the southern Texas coast... generated by the onshore flow on the north side of Harold... should subside over the next few hours as Harold continues marching quickly inland.


Harold will continue west-northwest inland across the Texas/Mexico border region while steered by the southwest edge of the current eastern North America surface ridge and central US upper ridge. Harold made landfall a little early as its tracking faster than the previous forecast track... my updated one shown below reflects the faster forward speed of Harold.


Update as of 2 PM EDT... Harold continues zooming west-northwest inland across far southern Texas and has weakened to 45 mph maximum sustained winds due to the landfall.

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

0 Hr Position (1200Z Aug 22)... 50 mph maximum sustained wind tropical storm centered on the far southern Texas coast at 27.1N-97.4W

IOH 24 Hr Forecast (1200Z Aug 23)... Dissipating remnant low centered over southwestern Texas at 30N-103.8W

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

Loss of Tropical Cyclone Status (1200Z Aug 23)... 25 mph maximum sustained wind remnant low centered just north of the western Texas/Mexico border at 29.5N-103.5W


AREA OF INTEREST #23... The eastern Atlantic tropical wave of low pressure continues to display a broad area of rotation which as of 1200Z was centered near 16N-32W. The updated forecast track points shown below are adjusted south and east due to the curernt position of the rotation center relative to the previous forecast. The westward forecast track has some northward angle overall as this system is forecast to move toward the surface ridge weakness caused by the remnants of Emily (Area of Interest #25). By 72+ hours ex-Emily and the western Atlantic frontal system/upper trough curving Emily northward are forecast to lift northeastward and away... around the amplified warm air mass upper ridge in the northwest Atlantic which will later progress toward the northeast Atlantic. However a northward angle in the forecast track is kept thru day 5 due to the likely influence of Franklin's surface circulation. Regarding odds of tropical cyclone formation... computer models have trended away from developing this system and the shower and thunderstorm activity in the circulation remains anemic... therefore I have lowered peak odds of tropical cyclone formation to below 50%. The NHC has also made a similar move in their recent tropical weather outlooks. I reserve peak odds of development to after 72 hours as the aforementioned warm air mass upper ridge pushes the south part of the current northeastern Atlantic upper trough toward this system in the next 48 hours... which will allow the southwest part of the upper trough to impart some northerly shear over this system in the short-term. By days 4 and 5 noting that this system will be approaching an upper trough that will also be interacting with ex-Emily (see Area of Interest #25... ex-Emily... section below for more info on this upper trough). However by then the cool core upper trough is forecast to be decaying due to prolonged isoaltion from high-latitude cold air. Thus only light southerly shear... which is not prohibitive to development... is anticipated from the decaying upper trough.

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

IOH 24 Hr Outlook (1200Z Aug 23)... 10% chance of tropical cyclone formation (eastern tropical Atlantic near 17N-37W)

IOH 48 Hr Outlook (1200Z Aug 24)... 10% chance of tropical cyclone formation (central tropical Atlantic near 18.5N-41W)

IOH 72 Hr Outlook (1200Z Aug 25)... 30% chance of tropical cyclone formation (central tropical Atlantic near 19.5N-45W)

IOH 96 Hr Outlook (1200Z Aug 26)... 40% chance of tropical cyclone formation (central Atlantic near 22.5N-50W)

IOH 120 Hr Outlook (1200Z Aug 27)... 40% chance of tropical cyclone formation (central Atlantic near 24N-55W)

******National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*****************************

Formation chance through 48 hours...10%

Formation chance through 7 days (168 hours)...40%


AREA OF INTEREST #25 (REMNANTS OF EMILY)... Tracking the remnants of Emily as upper winds could become more conducive for its redevelopment as this system curves north across the open central Atlantic in the next 72 hours... this marks the twenty-fifth tropical Atlantic area of interest tracked on this site this year. The large remnant cloud swirl of Emily has become tucked underneath bands of showers and thunderstorms being generated by upper divergence out ahead of the upper vorticity that is shearing Emily. A careful look at visible satellite animation around 1200Z shows a well-defined cloud swirl near 24N-46W underneath the bands of activity. Therefore I ascertain their remains a well-defined surface low pressure center to work with such that this system has a decent chance of regenerating into a tropical cyclone... and I am continuing to provide a specific track and intensity forecast as outlined below. Noting my updated track forecast points are shifted northward as the above-mentioned well-defined center is north of the previous forecast. The track forecast continues to show a northward turn around 50W longitude into a western Atlantic surface ridge weakness that will be kicked off by the arrival of the surface cold front and amplified upper trough now pushing in from eastern Canada. During the northward turn the current western Atlantic upper vorticity near 30N-60W will be kicked toward Emily as an amplified upper trough thru 48 hours whose eastern divergence zone potentially aids Emily. Its possible that Emily simply degenerates into an elongated north-south trough that becomes absored by the incoming cold front... as the upper trough will have an elongated upper divergence zone. Or alternatively Emily could re-generate into a tropical cyclone with the initial help from the upper trough... followed by arrival into more favorable warm core upper ridging with low shear and upper outflow associated with the warm surface southerly flow ahead of the incoming frontal system. Because the model consensus has trended toward no regenesis of Emily before it merges with the cold front... my updated forecast has a lower intensity and only calls for a short-lived tropical depression that then merges with the cold front. Note that after merging with the front... Emily is likely to last for a period of time while accelerating northeastward into the open north Atlantic as a non-tropical frontal low supported by the eastern divergence zone of the front's upper trough.

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

0 Hr Position (1200Z Aug 22)... Tropical low centered in the central Atlantic at 24N-46W

IOH 24 Hr Forecast (1200Z Aug 23)... Tropical low centered in the central Atlantic at 27.5N-50W

IOH 48 Hr Forecast (1200Z Aug 24)... Tropical low centered in the central Atlantic at 32N-50W

IOH 72 Hr Forecast (1200Z Aug 25)... 35 mph maximum sustained wind tropical depression centered in the central Atlantic at 39N-48.5W

IOH 96 Hr Forecast (1200Z Aug 26)... Frontal low centered in the north Atlantic at 48N-40W

******National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*****************************

Formation chance through 48 hours...10%

Formation chance through 7 days (168 hours)...30%


...COMPUTER MODEL SUMMARY...

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


0000Z (Aug 22) CMC Model Run...

**For Tropical Depression Gert... dissipates just northeast of the northern Lesser Antilles at 60 hours

**For Tropical Storm Franklin... through 48 hours weakens to a remnant trough while moving north-northwest to the southwest tip of Haiti... remnant trough subsequently moves into the eastern Bahamas through 66 hours with the northeast end of the trough rapidly regenerating into a tropical cyclone near 24.5N-69W through 96 hours... tropical cyclone strengthens while continuing north to 27.5N-69W through 120 hours

**For Tropical Storm Harold... makes landfall just north of the Texas/Mexico border just before 18 hours... inland remnants dissipate over north-central Mexico near 28N-104W just after 42 hours

**For area of interest #23... moves west-northwest to 22.5N-50W through 126 hours as a surface trough

**For area of interest #25... the remnants of Emily redevelop into a tropical cyclone near 32N-50W at 60 hours... through 126 hours rapidly accelertates north-northeastward while merging with cold front and transitions into a remnant frontal cyclone located at 53.5N-34W

**Tropical wave emerges from the west coast of Africa at 30 hours and passes south of the Republic of Cabo Verde Islands at 90 hours as a broad tropical low... broad tropical low reaches 14N-39W at 168 hours

**Additional strong tropical wave of low pressure emerges from the west coast of Africa at 168 hours

**Southwest part of Franklin's remnant trough combines with remnants of eastern Pacific tropical cyclone that moves north across Honduras to make a broad western Caribbean tropical low near 16.5N-84W by 78 hours... broad tropical low drifts northwestward into the Yucatan peninsula through 168 hours


0000Z (Aug 22) ECMWF Model Run...

**For Tropical Depression Gert... dissipates just northeast of the northern Lesser Antilles at 36 hours

**For Tropical Storm Franklin... weakens to a surface trough that lifts north into Haiti through 36 hours... trough re-organizes into a tropical low just east of the eastern Bahamas at 54 hours... tropical low re-strengthens into a tropical cyclone near 23.5N-66.2W at 108 hours... tropical cyclone lifts north to 24.5N-66.2W through 120 hours

**For Tropical Storm Harold... makes landfall just north of the Texas/Mexico border just after 12 hours... inland remnants dissipate over north-central Mexico near 29N-101.5W at just after 36 hours

**For area of interest #23... continues west-northwest to 23.5N-50W through 120 hours as a surface trough

**For area of interest #25... remnant low of Emily curves northward and becomes absorbed by cold front at 78 hours while located near 40N-47.5W

**Strong tropical wave emerges from western Africa at 144 hours and moves into the Republic of Cabo Verde Islands by 168 hours as a broad tropical low

**Western Caribbean tropical low develops at 96 hours near 16.5N-87.5W from the southwestern fracture of Franklin's remnant trough... tropical low drifts northward into the northern Yucatan peninsula by 126 hours after which time it becomes stationary... tropical low consolidates over the northeastern coast of the peninsula by 168 hours


0600Z (Aug 22) GFS Model Run...

**For Tropical Depression Gert... dissipates just northeast of the northern Lesser Antilles at 36 hours

**For Tropical Storm Franklin... lifts north into the south coast of Haiti through 30 hours after which times it weakens to a remnant trough arriving to the northwest coast of Haiti at 36 hours... trough re-organizes into a tropical low over the easternmost Bahamas at 48 hours and then a compact tropical cyclone just north of the easternmost Bahamas at 54 hours... as a strengthening tropical cyclone it curves east to 23N-68.5W through 96 hours... curves north to 25N-69W through 120 hours as a strengthening hurricane

**For Tropical Storm Harold... makes landfall just north of the Texas/Mexico border just before 9 hours... inland remnants continue west-northwest across the Texas/Mexico border region and dissipates over north-central Mexico near 30.5N-106.2W at 36 hours

**For area of interest #23... no development shown

**For area of interest #25... remnant low of Emily curves northward and merges with cold front at 84 hours while located near 41.5N-45W... continues northeastward as a remnant frontal cyclone that reaches 50.8N-33.5W at 120 hours


0600Z (Aug 22) NAVGEM Model Run...

**For Tropical Depression Gert... curves north and dissipates near 20.5N-60.5W at 42 hours

**For Tropical Storm Franklin... crosses northward through the Dominican Republic through 30 hours and begins strengthening by 48 hours while passing just east of the eastern Bahamas... curves east to 23N-66.2W through 90 hours while becoming a hurricane... subsequently bends north to 25.2N-69W through 120 hours

**For Tropical Storm Harold... makes landfall just north of the Texas/Mexico border at 12 hours... inland remnants continue west-northwest and dissipate over the western Texas/Mexico border near 30N-104.8W

**For area of interest #23... no development shown

**For area of interest #25... remnant low of Emily curves northward and merges with cold front at 84 hours while located near 40N-46W... as a frontal low continues northeastward and then eastward and reaches 47N-28.8W at 120 hours

**Tropical wave emerges from western Africa at 42 hours and passes just south of the Republic of Cabo Verde Islands at 96 hours as a tropical low... tropical low opens back to a wave around 40W longitude at 162 hours

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