top of page
Home: Text

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 

Home: Text
Home: Blog2
Search
  • Writer's pictureNCHurricane2009

MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #63

Updated: Aug 27, 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.**********


...UPDATE...FRIDAY AUGUST 25 2023 7:20 PM EDT...

The latest satellite imagery shows outer thunderstorm activity associated with Franklin has also reached the Dominican Republic. Because the grounds here have already been saturated by heavy rain from Franklin's earlier passage... there is a risk of flash flooding and/or mudslides over the next several hours if these trends continue.


...FRIDAY AUGUST 25 2023 5:50 PM EDT...

Tropical Storm Franklin is expected to strengthen into a strong western Atlantic hurricane and produce coastal surf for Bermuda... the US east coast from the mid-Atlantic to the northeast shoreline... and Atlantic Canada (Nova Scotia and Newfoundland) after this weekend. See Franklin section below for more information.


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

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

(2) See area of interest #25 section below for an update on the remnants of former Tropical Storm Emily moving northward in the open central Atlantic.

(3) See area of interest #26 section below for an update on the tropical low pressure which has become better defined in the western Caribbean... this feature is increasingly likely bring impacts to the northeastern Yucatan peninsula... far western Cuba... and the southeastern United States (parts of Florida... southeastern Georgia... and southern South Carolina) in the days ahead.

(4) See area of interest #27 section below for more information on a current central African tropical wave of low pressure which has some model support showing its development when it later moves into the eastern tropical Atlantic in a few days.


TROPICAL STORM FRANKLIN... Franklin has turned on an eastward drift to the north of the Caribbean islands while under the influence of upper vorticity that has been deposited to Franklin's north by the large-scale upper trough that is slowly entering the northwest Atlantic from eastern Canada. The size of the upper divergence region ahead of the upper vorticity appears to have expanded the size of Franklin's circulation... and the shear direction imparted by the upper vorticity has a more northwesterly component instead of a westerly component as the strongest thunderstorms are pushed to the southeast of the center. Aircraft recon data since 9:10 AM EDT today indicated Franklin has weakened to 50 mph maximum sustained winds from the shear... but also indicated that the center of rotation appears to be re-generating southeastward closer to the sheared off activity. Surface low pressure center reformations often occur in sheared tropical cyclones when the latent heat release generated warm core upper ridging and outflow of the sheared off thunderstorms drops surface pressures in the direction of the thunderstorms. My updated forecast track below is similar to the previous and nudged southward due to the center reformation. The upper vorticity is expected to soon consolidate into a vortex... with Franklin expected to arc northward and then northwestward through 72 hours around the northeastern side of the vortex. By 72 hours a frontal depression ejecting from the northeastern US will have arrived into Atlantic Canada while the western convergence zone of this depression's upper trough makes a small surface ridge over the northeastern US. Another frontal depression and its upper trough to approach from the Great Lakes region of North America during this same time appears it will be the system that finally accelerates Franklin northeastward into the high-latitude westerlies in the long range. However from 72 to 96 hours the forecast track is straight north as the passing small surface ridge to the north delays the eastward bend in the track. A northeastward acceleration between Bermuda and Nova Scotia is shown between 96 and 120 hours once the passing surface ridge gets out of the way.


My updated intensity forecast is nudged downward due to Franklin's initial lower intensity. Around or just after 24 hours... and thru 72 hours... Franklin is slated to take advantage of reduced westerly shear and also the divergence on the east side of the upper vortex such that I project the storm to ramp up into a category 2 hurricane. As Franklin lifts northward and away from the vortex between 72 and 96 hours... it will still be in a low shear environment as the upper trough to approach from the Great Lakes region will still be too far away to shear Franklin. At the same time the upper vortex will now be too far away to impede the southwestern outflow of the storm. Therefore at 96 hours I forecast Franklin to be a major category 3 hurricane... this would be the first major hurricane of the 2023 Atlantic season if this verifies. The southwesterly shear ahead of the approaching Great Lakes upper trough finally approaches between 96 and 120 hours... and weakening is shown during that timeframe.


Regarding impact to land areas:

(1) Over the next 24 hours the northeastern Caribbean islands (north shore of the Dominican Republic... Puerto Rico... Virgin Islands... and northern Lesser Antilles) are more likely to see coastal surf from Franklin due to the recent southeastward center reformation closer to the islands. Puerto Rico... the Virgin Islands... and the northern Lesser Antilles may also see heavy downpours from Franklin's sheared-off thunderstorm activity.

(2) Given the current forecast track and intensity of Franklin... Bermuda will be subjected to notable coastal surf by Monday and Tuesday. Interests in Bermuda should continue to monitor the progress of Franklin as any eastward shift in the track could place Bermuda under some gusty winds on the storm's east side.

(3) The mid-Atlantic and northeastern US coast are likely to see coastal surf from Franklin by early this upcoming week. Coastal surf will reach the shores of Atlanic Canada (Nova Scotia and Newfoundland) by Tuesday and Wednesday.

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

0 Hr Position (1200Z Aug 25)... 50 mph maximum sustained wind tropical storm centered north-northwest of Puerto Rico at 21.9N-68W

IOH 24 Hr Forecast (1200Z Aug 26)... 50 mph maximum sustained wind tropical storm centered over the western Atlantic at 23N-65.5W

IOH 48 Hr Forecast (1200Z Aug 27)... 75 mph maximum sustained wind hurricane centered over the western Atlantic at 25N-66.5W

IOH 72 Hr Forecast (1200Z Aug 28)... 100 mph maximum sustained wind hurricane centered west-southwest of Bermuda at 29.5N-69W

IOH 96 Hr Forecast (1200Z Aug 29)... 120 mph maximum sustained wind major hurricane centered west-northwest of Bermuda at 34N-69W

IOH 120 Hr Forecast (1200Z Aug 30)... 95 mph maximum sustained wind hurricane centered midway between Bermuda and Nova Scotia at 39N-63W

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

Peak Strength (1200Z Aug 28)... 110 mph maximum sustained wind hurricane centered west-southwest of Bermuda at 28.7N-69.4W

5-day Position (1200Z Aug 30)... 90 mph maximum sustained wind hurricane centered midway between Bermuda and Nova Scotia at 39N-63.6W


AREA OF INTEREST #23... The tropical wave of low pressure over the central Atlantic appears as an elongated north-south system with thunderstorm bursts in the vicnity of 21N-45W as of 1200Z. The elongation and also further north position of this system may suggest that it is trying to link with the elongated circulation of ex-Emily (Area of Interest #25) towards the north... especially as ex-Emily has been further south of previous forecasts. Therefore the updated forecast track has been adjusted northward accordingly on the diagnosis that the initial further north position of this system is attributed to ex-Emily being south of prior projections. Through 72 hours the forecast track of this system shows the current northwest heading bending north while steered in the flow between the southwest side of the Atlantic surface ridge and east side of what is forecast to be Hurricane Franklin. By 96 hours the steering picture gets muddy as this system gets trapped between a small surface ridge passing north of Franklin and the Atlantic surface ridge to the east. The models continue to forecast an upper trough fragment being left behind by the larger scale upper trough from eastern Canada now moving into the northwest Atlantic... to the east of Franklin's outflow and in this system's environment. The models resolve the 72 to 96 hour window by turning this system eastward with this upper trough fragment... while transitioning this system into a feature supported by the eastern divergence zone of the trough fragment. Between 96 and 120 hours the upper anticyclone of Franklin gets displaced eastward by wind shear which in turn displaces the upper trough fragment southward... and the blocking small surface ridge north of Franklin continues east and merges with the Atlantic surface ridge. Therefore the forecast track shown below returns to a northward drift in the flow between Franklin and the surface ridge for the end of the 5-day (120 hour) forecast period.


Regarding odds of tropical cyclone formation... the next obstacle this system will be dealing with will be the decaying upper trough to the west which previously interacting with ex-Emily. This cool core upper trough is decaying from prolonged isolation from high-latitude cold air... therfore southerly shear associated with the east side of the trough is not expected to be completely prohibitive to development... but still might provide disrpution over the next 48 hours. This system is not particularly well-organized at the moment and so I have dropped short-term odds of tropical cyclone formation to 0% for 24 hours and then to a low 20% for 48 hours. Because the model consensus for development is increasing for the 72+ hour window... I have raised tropical cyclone formation odds in this window to 50% in this update. This is because models continue to agree that the upper trough fragment that drops in to the east of Franklin's outflow and into this system's environment will be amplified enough to keep shear levels lower and aiding upper divergence higher. Note the brief dip in odds to 40% at 96 hours is associated with Franklin's outflow pushing the upper trough fragment eastward into this system while this system struggles to shift east into the Atlantic surface ridge... therefore the upper trough fragment may displace the thunderstorms of this system's toward the east. Odds of development improve again by 120 hours as the upper trough fragment is displaced southward due to Franklin's upper anticyclone getting displaced away from Franklin as noted at the end of the prior paragraph... allowing this system to start taking advantage of low shear and outflow beneath the anticyclone.

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

IOH 24 Hr Outlook (1200Z Aug 26)... 0% chance of tropical cyclone formation (central Atlantic near 25N-50W)

IOH 48 Hr Outlook (1200Z Aug 27)... 20% chance of tropical cyclone formation (central Atlantic near 28N-54W)

IOH 72 Hr Outlook (1200Z Aug 28)... 50% chance of tropical cyclone formation (central Atlantic near 31.5N-54W)

IOH 96 Hr Outlook (1200Z Aug 29)... 40% chance of tropical cyclone formation (central Atlantic near 31.5N-52.5W)

IOH 120 Hr Outlook (1200Z Aug 30)... 50% chance of tropical cyclone formation (central Atlantic near 33N-52.5W)

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

Formation chance through 48 hours...20%

Formation chance through 7 days (168 hours)...50%


AREA OF INTEREST #25 (REMNANTS OF EMILY)... The remnants of what was Tropical Storm Emily is in the open central Atlantic continuing northward in the southerly flow between the Atlantic surface ridge to the east and approaching cold front to the west. The low cloud motions on visible satellite animation suggest the remnant circulation remains elongated north-south in the vicnity of 34N-49W as of 1200Z... just to the south of a clump of shower and thunderstorm activity in the vicnity of 36N-47.5W. This position is south of the previous forecast... and my updated forecast in the outlook below is adjsuted accordingly. Because the circulation remains elongated... it is unlikely to regenerate into a tropical cyclone with well-defined center before it merges with the cold front. The elongated nature of ex-Emily's circulation also likely means it is more likely to lose its identity within the elongated surface vorticity of the cold front (instead of continuing on as a distinct non-tropical frontal low supported by the divergence zone of the front's upper trough). This is my planned final statement on this area of interest on this blog.

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

IOH 24 Hr Outlook (1200Z Aug 26)... 0% chance of tropical cyclone formation (north Atlantic near 42N-45W)

******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)...10%


AREA OF INTEREST #26... Over the last 24 hours the western Caribbean area of interest has notably changed with both its initial structure and the upper-level wind forecast in the models. First a better-defined tropical low pressure spin developed further north just offshore of eastern Honduras last evening insead of over Cenral America... resulting in a large north shift of the forecast track in my updated outlook below. Split flow upper divergence between the northeast corner of the southwestern Gulf of Mexico upper vortex and northwest extent of the regional tropical upper ridging has produced a surface trough in the southwestern Gulf that is attracting the western Caribbean tropical low northwestward on a path toward the northeastern Yucatan peninsula. Changes with the upper-level wind forecast centers around a former shortwave upper trough which has arrived to the United States eastern Gulf coastal region as a lobe of upper vorticity while it continues to revolve around the ongoing central US upper ridge... the models have varied on how to handle this upper vorticity. Comparing the state of the upper atmosphere this morning to what was predicted by yesterday's model runs indicates the lobe of upper vorticity is a little further west... which now allows it to stay further west while it chases the southwestern Gulf of Mexico upper vortex which is also moving around the central US upper ridge. By 96+ hours the lobe of upper vorticity merges with an upper trough moving through the Great Lakes region of North America... resulting in a lengthy upper trough spanning from the Great Lakes to the central Gulf of Mexico. The udpated forecast track in the outlook below calls for the tropical low to first drift northwest into the northeast corner of the Yucatan through 48 hours... followed by a north-northeast track across the eastern Gulf of Mexico and eventually the southeastern United States under the influence of the materializing lengthy upper trough... particularly as this system transitions into a feature supported by the eastern divergence zone of the lengthy trough.


Regarding odds of tropical cyclone formation... it appears odds of developemnt over the next 48 hours have notably increased as the western Caribbean tropical low pressure of interest has been organizing today with curved bands of thunderstorms across its northern semicircle while this system remains tucked under low shear and outflow beneath the regional tropical upper ridging ...by 48 hours I already ramp odds of development up to above 50%. By 72 hours I pull odds of development back down to the 50% mark as the materializing lengthy upper trough is more likely to produce disrputive westerly shear. By 96 hours most models now agree that a tropical cyclone should be in progress in the eastern Gulf of Mexico and so I ramp development odds back up to above 50%... but not quiet as high as today's 2 PM NHC outlook as models are still resolving the exact details of the lengthy upper trough... for instance the amount of shear this system will be experiencing is not yet clear. If the trough is further east and closer to this system then shear will be higher and less conducive for development... and vice versa if the trough is further west and further away. By 120 hours... increased land interaction with the southeastern United States and higher shear as the lengthy upper trough shifts east should make conditions more hostile for development... and I lower odds of development to 20% by then.


The potential for excess rainfall accumulations over Central America has ended with this system having already lifted northward and away. The Cayman Islands and the northwestern Bahamas are now unlikely to see notable impacts from this area of interest.


Interests in the northeastern Yucatan peninsula and far western Cuba should be aware that tropical cyclone impacts such as heavy rain... gusty winds... and perhaps coastal surf may develop over the next 48 hours. Interests across the Florida peninsula... the Florida Keys... the eastern Florida panhandle... southeastern Georgia... and southern South Carolina should be aware of this area of interest as tropical cyclone impacts could overspread the region in the 72+ hour window.

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

IOH 24 Hr Outlook (1200Z Aug 26)... 30% chance of tropical cyclone formation (northeast coast of the Yucatan peninsula near 20N-87.5W)

IOH 48 Hr Outlook (1200Z Aug 27)... 60% chance of tropical cyclone formation (northeast corner of the Yucatan peninsula near 20.5N-87.5W)

IOH 72 Hr Outlook (1200Z Aug 28)... 50% chance of tropical cyclone formation (southeastern Gulf of Mexico near 22.5N-85.5W)

IOH 96 Hr Outlook (1200Z Aug 29)... 70% chance of tropical cyclone formation (offshore of the west coast of the Florida peninsula near 27N-84.8W

IOH 120 Hr Outlook (1200Z Aug 30)... 20% chance of tropical cyclone formation (southern South Carolina coast near 32.5N-80.5W)

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

Formation chance through 48 hours...40%

Formation chance through 7 days (168 hours)...80%


AREA OF INTEREST #27... METEOSAT satellite image of Africa showing the position of a central Africa tropical wave of low pressure as of 1800Z:

Animation of METOESAT satellite imagery (https://tropic.ssec.wisc.edu/real-time/europe/movies/m7irn/m7irn_loop.html) shows a large tropical wave of low pressure is progressing westward over central Africa while moving from about 10N-12E to 10N-10E over the last day. Although the thunderstorm activity of the tropical wave is not particularly organized... regional tropical upper ridging covering the low-latitudes of Africa and eastern Atlantic with low shear and upper outflow is forecast to persist over the next several days and the models are in agreement on showing some development of this wave when it later moves into the eastern tropical Atlantic. Therefore the NHC has added this wave as another area of interest in their tropical weather outlook... this marks the twenty-seventh tropical Atlantic area of interest tracked on this site this year. The brisk westward forward speed in the outlook below is a reflection of the fact that the models want to bring this wave offshore in as soon as 3 to 4 days. I assign a low 10% odds of tropical cyclone formation by day 5 as the wave will have not had much time over water yet... and the models are consistent on this wave emerging from Africa as a large feature which will need time to consolidate. Noting the Republic of Cabo Verde Islands may see heavy rain and gusty winds from this system in about five days regardless of tropical cyclone formation or not.

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

IOH 24 Hr Outlook (1200Z Aug 26)... 0% chance of tropical cyclone formation (central Africa near 11N-3E)

IOH 48 Hr Outlook (1200Z Aug 27)... 0% chance of tropical cyclone formation (western Africa near 11.5N-4W)

IOH 72 Hr Outlook (1200Z Aug 28)... 0% chance of tropical cyclone formation (western Africa near 12N-11W)

IOH 96 Hr Outlook (1200Z Aug 29)... 0% chance of tropical cyclone formation (just offshore of Senegal near 12.5N-18W)

IOH 120 Hr Outlook (1200Z Aug 30)... 10% chance of tropical cyclone formation (just south of the Republic of Cabo Verde Islands near 13.5N-24W)

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

ormation chance through 48 hours...0%

Formation chance through 7 days (168 hours)...20%


...COMPUTER MODEL SUMMARY...

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


0000Z (Aug 25) CMC Model Run...

**For Tropical Storm Franklin... accelerates north-northwest to 30N-70W while strengthening into a hurricane... center of hurricane positioned west-northwest of Bermuda near 33.8N-69W at 120 hours

**For area of interest #23... tropical cyclone formation suggested near 28.5N-51W at 84 hours... tropical cyclone drifts west to 28N-53.5W at 120 hours

**For area of interest #25... the remnants of Emily transitions into a frontal low near 46.5N-43.5W at 72 hours... frontal low moves northeast to 56N-29W through 120 hours

**For area of interest #26... tropical low moves north-northwest to the north coast of the Yucatan peninsula through 60 hours... tropical cyclone formation over the southern Gulf of Mexico suggested near 24N-88.5W at 102 hours... tropical cyclone strengthens while moving into the northeastern Gulf of Mexico and reaches 28.5N-85.5W at 120 hours

**For area of interest #27... strong tropical wave of low pressure emerges from the west coast of Africa at 96 hours and by 120 hours organizes into a broad tropical low east-northeast of the Republic of Cabo Verde Islands near 17N-19.8W... tropical low passes just north of the islands through 150 hours with tropical cyclone formation suggested just northwest of the islands and near 18.8N-25.5W at 168 hours


0000Z (Aug 25) ECMWF Model Run...

**For Tropical Storm Franklin... drifts east-northeast to 23N-66W through 30 hours... accelerates north-northwest to 29N-69W through 84 hours while strengthening into a hurricane... hurricane passes west of Bermuda at 102 hours and accelerates north-northeast to 36N-66W through 120 hours

**For area of interest #23... tropical cyclone formation suggested near 29N-49.8W at 90 hours and continues strengthening as a compact tropical cyclone that reaches 29.8N-51W at 120 hours.

**For area of interest #25... the remnant low of Emily loses identity while merging with cold front while a seperate frontal low forms to the north near 45N-45W at 42 hours

**For area of interest #26... tropical low becomes better defined on the northeast coast of the Yucatan peninsula at 96 hours... while continuing north-northeast into the southeastern Gulf of Mexico tropical cyclone formation suggested near 24.5N-84.5W at 120 hours.

**For area of interest #27... strong tropical wave of low pressure emerges from the west coast of Africa at 78 hours and organizes into a broad tropical low just east of the Republic of Cabo Verde Islands at 108 hours... broad tropical low passes through the islands by 138 hours... center of broad tropical low reaches 16N-31W at 168 hours.


0600Z (Aug 25) GFS Model Run...

**For Tropical Storm Franklin... drifts east to 23N-66W through 24 hours... subsequently accelerates north-northwest to 29.5N-70W through 78 hours while strengthening into a hurricane and passes west of Bermuda by 93 hours... hurricane accelerates northeast to 37.5N-64W through 120 hours

**For area of interest #23... organizes into a compact tropical low near 30N-51.5W at 75 hours... tropical low drifts north to 31.5N-52.5W through 120 hours

**For area of interest #25... remnant low of Emily merges with cold front and loses identity near 37.5N-48W at 33 hours

**For area of interest #26... center of broad tropical low reaches northeast corner of the Yucatan peninsula through 72 hours... broad tropical low gradually consolidates into a tropical cyclone while moving north-northeast toward and then into the northwest coast of the Florida peninsula through 120 hours.

**For area of interest #27... strong tropical wave emerges from western Africa at 72 hours and moves across the Republic of Cabo Verde Islands as a broad tropical low by 114 hours... develops into a weak large tropical cyclone located near 15N-35W at 168 hours


0600Z (Aug 25) NAVGEM Model Run...

**For Tropical Storm Franklin... while strengthening into a large and intense hurricane moves north-northwest and then north-northeast to 30N-69W through 90 hours... center curves northeast and then east-northeast such that it passes just south of Bermuda at 120 hours.

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

**For area of interest #25... remnant low of Emily merges with cold front near 39.8N-48.8W at 36 hours... as a frontal low continues north and then east and then loses identity to larger frontal low developing just south of Iceland at 90 hours while located near 52N-34W

**For area of interest #26... center of broad tropical low reaches the northeast coast of the Yucatan peninsula by 48 hours and develops into a tropical cyclone just offshore of the northeast Yucatan coast at 66 hours... as a large and strengthening tropical cyclone continues north-northeast toward and then into the northwest coast of the Florida peninsula through 120 hours

**For area of interest #27... strong tropical wave emerges from western Africa at 72 hours and passes over the Republic of Cabo Verde Islands as a broad tropical low through 138 hours.

18 views0 comments

Comments


bottom of page