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 #71

Updated: Sep 8, 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...THURSDAY SEPTEMBER 7 2023 10:00 PM EDT...

The following recent events have occurred across the Atlantic tropics:

(1) As of 5 PM EDT... Hurricane Lee is now a major category 4 hurricane with 130 mph maximum sustained winds. No changes to my intensity forecast below which accounts for Lee becoming a category 5 hurricane overnight.

(2) As of 5 PM EDT... Tropical Depression Fourteen is now Tropical Storm Margot.

(3) Satellite imagery shows a tropical wave of low pressure over western Africa... now approaching the west coast of Africa... has become better defined and organized. If these trends continue... will add it as another area of interest by my next full update on the Atlantic tropics.


...THURSDAY SEPTEMBER 7 2023 4:30 PM EDT...

The Atlantic tropics are expected to remain active over the next several days... see the sections below all current active tropical cyclones and areas of interest. The largest concern in the Atlantic basin is Hurricane Lee which is expected to be an intense hurricane near the northeastern Caribbean Islands by this weekend.


In addition to the current areas of interest listed below... some model runs insist that an additional strong troipcal wave of low pressure may emerge from western Africa behind TD Fourteen in about two days. Current METEOSAT satellite imagery (https://www.goes.noaa.gov/f_meteo.html) does not yet show a well-defined robust tropical wave trackable over Africa at this time... however should this change another area of interest may need to be added in future updates.


HURRICANE LEE... Over the last 36 hours Tropical Storm Lee in the central tropical Atlantic has spent its time rapidly organizing and intensifying into what is now a category 2 hurricane with 105 mph maximum sustained winds as of 11 AM EDT. For the next 96 hours Lee is expected to continue west-northwest across the Atlantic tropics while pushed around the recovering the Atlantic surface ridge being built by the western convergence zone of the current northeast Atlantic upper vortex... with the northward angle in track associated with the gradual rate of recovery of the ridge... the ongoing surface ridge weakness associated with ex-Idalia near Atlantic Canada... and as the current eastern US surface frontal system pushes offshore after ex-Idalia dissipates. Lee has moved north of my previous forecast track and so my updated one is adjsuted accordingly. Also noting the model guidance has shifted more north and slower to the west overall... however for the middle of the 5-day forecast period I tend to be southwest of the model guidance as the southerly flow of the eastern US surface frontal system and its associated upper troughing appear too far west of Lee in the model fields for me to agree to a more northeast position of the hurricane. By the end of the 5-day period... the current upper troughs over the Great Lakes and western Canada will have merged into a broad trough over the eastern US that pushes the surface frontal system over the eastern US offshore and north of Lee... helping to create a surface ridge weakness to turn the hurricane north. In the upper layers the north turn of the hurricane will be aided as Lee will be near upper southwesterly flow ahead of the broad trough over the eastern US... and the latest model guidance has trended toward the broad trough being tilted southwest-northeast such that the upper flow is more westerly and less southerly which would explain the more north and less west track in the latest long-range model guidance. Thus from 96 to 120 hours my track forecast below turns the hurricane north.


As far as intensity... Lee has strengthened faster than my previous intensity projection. Through 72 hours Lee will be under expansive tropical upper ridging with low shear and upper outflow and sea surface temperatures in Lee's path are at an unusually warm 29 to 30 deg C for this region of the Atlantic. The NHC official forecast as of 11 AM EDT now calls for a category 5 hurricane by 36 hours. I do agree that Lee will become a category 5... but sooner and within the next 24 hours due to the healthy structure of the hurricane which featuers a small eye an symmetric thunderstorm field and as the nearby patch of 30 deg C waters in Lee's path has expanded in size (https://www.nhc.noaa.gov/sst/). By 48 hours I anticipate a high likelihood of Lee undergoing an eye wall replacement cycle and project category 4 status... and by 72 hours I forecast a second category 5 peak stronger than the first after the eye wall replacement cycle finishes. For the 96 to 120 hour period I project a gradually weakening category 4 hurricane while Lee's western outflow potentially becomes obstructed by the southwesterlies ahead of the broad upper trough to be positioned over the eastern US. 


Regarding impact to land areas... expect wide-reaching surf from this powerful hurricane to reach the northern Lesser Antilles... Virgin Islands... Puerto Rico... the north shores of Haiti and the Dominican Republic... the Bahamas... and Bermuda by this weekend and into early next week. If Lee does track more south in the middle of the 5-day forecast period as discussed above... some gusty winds and heavy rainfall cannot be ruled out for the northern Lesser Antilles this weekend. Interests in Bermuda should carefully monitor Lee as the latest steering patterns setting up in the long range model guidance suggest the powerful hurricane  drifting north toward the area.

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

0 Hr Position (1200Z Sep 7)... 105 mph maximum sustained wind hurricane centered in the central tropical Atlantic at 16.4N-50W

IOH 24 Hr Forecast (1200Z Sep 8)... 160 mph maximum sustained wind major hurricane centered in the central tropical Atlantic at 17.5N-55W

IOH 48 Hr Forecast (1200Z Sep 9)... 150 mph maximum sustained wind major hurricane centered northeast of the northern Lesser Antilles at 19N-58W

IOH 72 Hr Forecast (1200Z Sep 10)... 170 mph maximum sustained wind major hurricane centered north of the northern Lesser Antilles at 21N-62W

IOH 96 Hr Forecast (1200Z Sep 11)... 150 mph maximum sustained wind major hurricane centered in the western Atlantic at 22.5N-66W

IOH 120 Hr Forecast (1200Z Sep 12)... 145 mph maximum sustained wind major hurricane centered in the western Atlantic at 25N-66W

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

Peak Strength (0000Z Sep 9)... 160 mph maximum sustained wind major hurricane centered in the central tropical Atlantic at 19.2N-56.1W

5-day Position (1200Z Sep 12)... 140 mph maximum sustained wind major hurricane centered in the western Atlantic at 23.6N-66W


TROPICAL DEPRESSION FOURTEEN... The rotating tropical wave of low pressure that recently passed through the Republic of Cabo Verde Islands has consolidated into tropical depression fourteen now centered just west of the islands. This system is notably north and west of my previous forecast track and my updated one is adjusted accordingly. A faster turn towards the west is anticipated in the short-term as this system encounters the same recovering Atlantic surface ridge that Hurricane Lee is moving under the influence of. Afterwards this system will be strong/tall enough to turn north along 40W longitude under the influence of upper southerlies on the east side of the central Atlantic upper vortex. Between 72 and 96 hours... even though the latent heat release of this system's thunderstorms may weaken the cold core upper vortex as noted in the current model guidance... I keep the forecast track straight north along 40W longitude as a surface trough/front passing to the north... associated with what will be the eastern divergence zone of the southern fragment of the current western Atlantic upper trough... may help to attract this system. From 96 to 120 hours I currently forecast that the southerly flow on the east side of the incoming upper trough fragment will help keep this system moving straight north along 40W longitude. For intensity... this system has developed into a tropical cyclone a little faster than I previously anticipated and so my updated intensity forecast is increased. The majority of the previous model guidance suggested this system would become excessively broad and stay weak without a well-defined center needed for focused thunderstorms while absorbing ex-Katia to the north while also becoming expanded in size by the divergence zone of the central Atlantic upper vortex. However the current model guidance has caught on to the fact that this system... already being a tropical cyclone... has a well-defined core developing and now depicts a stronger system in their projection... and this is another reason to increase my intensity forecast. I slow the intensification rate between 48 and 72 hours as this system gets disrupted by the central Atlantic upper vortex... but return to a higher rate of development by 72+ hours as the latent heat release of this system potentially punches out the upper vortex as noted above. Noting that by 120 hours this system maybe reaching its peak intensity as it potentially struggles with shear to be imparted by the incoming above-mentioned upper trough fragment arriving from the western Atlantic.


Noting that weather conditions are improving across the Republic of Cabo Verde Islands as this system is pulling westward and away... no tropical storm advisories were issued here.

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

0 Hr Position (1200Z Sep 7)... 35 mph maximum sustained wind tropical depression centered just west of the Republic of Cabo Verde Islands at 15.7N-26.4W

IOH 24 Hr Forecast (1200Z Sep 8)... 50 mph maximum sustained wind tropical storm centered in the eastern tropical Atlantic at 17.5N-31.5W

IOH 48 Hr Forecast (1200Z Sep 9)... 75 mph maximum sustained wind hurricane centered in the eastern tropical Atlantic at 18.5N-36.5W

IOH 72 Hr Forecast (1200Z Sep 10)... 80 mph maximum sustained wind hurricane centered in the central Atlantic at 22N-40W

IOH 96 Hr Forecast (1200Z Sep 11)... 95 mph maximum sustained wind hurricane centered in the central Atlantic at 26N-40W

IOH 120 Hr Forecast (1200Z Sep 12)... 105 mph maximum sustained wind hurricane centered in the central Atlantic at 30N-40W

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

5-day Position (1200Z Sep 12)... 90 mph maximum sustained wind hurricane centered in the central Atlantic at 30.2N-42.7W


AREA OF INTEREST #33 (REMNANTS OF FRANKLIN)... The remnant frontal cyclone of Franklin in the northeast Atlantic has swung northeastward and northward across the east side of the overhead upper vortex. For some time the cold temps and eastern divergence zone of the vortex did help ex-Franklin build showers and thunderstorms… however as of 1800Z today ex-Franklin arrived to even cooler 20 deg C waters near 47N-16.5W and no longer has shower and thunderstorm activity. Going forward the models now show the eastern divergence zone of the vortex spinning up another frontal low offshore of Portugal… with this frontal low throwing ex-Franklin southward for the remainder of its lifespan. Even though this will translate to arrival back to warmer waters… the models show ex-Franklin dissipating under the western convergence zone of the upper vortex. Therefore subtropical development of ex-Franklin is no longer anticipated… and this is my final statement on ex-Franklin on this blog.


Note that coastal surf from ex-Franklin has ended for further south locations such as the Azores and Canary Islands… and any surf reaching the shores of Western Europe will soon end as ex-Franklin weakens and dissipates.

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

IOH 24 Hr Outlook (1800Z Sep 8)... 0% chance of subtropical cyclone formation (northeast Atlantic near 45.5N-19.5W)

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

Formation chance through 48 hours...0%

Formation chance through 7 days (168 hours)...0%


...COMPUTER MODEL SUMMARY... 

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


0000Z (Sep 7) CMC Model Run...

**For Hurricane Lee... reaches 24N-66.5W at 120 hours as an intense hurricane.

**For Tropical Depression Fourteen... passes over the southern Republic of Cabo Verde Islands thru 6 hours as a tropical low with tropical cyclone formation suggested near 15.5N-29W at 30 hours... as a strengthening compact tropical cyclone reaches 19.5N-40W at 84 hours after which time it turns north... reaches 26N-42W at 120 hours as a hurricane

**For Area of Interest #33... ex-Franklin circles around periphery of overhead upper vortex and begins to weaken near 46.5N-18W at 42 hours while reaching the northwestern convergence zone of the vortex... dissipates north of the Canary Islands through 120 hours.

**Additional tropical wave emerges from west coast of Africa at 60 hours... tropical cyclone formation suggested near 13N-37.5W at 162 hours


0000Z (Sep 7) ECMWF Model Run...

**For Hurricane Lee... reaches 23N-64W at 120 hours as an intense hurricane.

**For Tropical Depression Fourteen... tropical cyclone formation just west of the southern Replublic of Cabo Verde Islands at 12 hours... tropical cyclone reaches 21.5N-40.2W at 84 hours after which time it begins to turn north... tropical cyclone reaches 27.5N-42W at 120 hours as a hurricane

**For Area of Interest #33... ex-Franklin circles around periphery of overhead upper vortex and begins to weaken near 46.5N-18.5W at 42 hours while reaching the northwestern convergence zone of the vortex... dissipates north of the Canary Islands through 114 hours. 


0600Z (Sep 7) GFS Model Run...

**For Hurricane Lee... reaches 23N-64.5W at 120 hours as an intense hurricane.

**For Tropical Depression Fourteen... tropical cyclone formation just west of the southern Replublic of Cabo Verde Islands at 3 hours... reaches 20N-36.5W at 57 hours as a compact hurricane after which time it more sharply turns north... reaches 29.5N-41W as an intense hurricane by 120 hours.

**For Area of Interest #33... ex-Franklin circles around periphery of overhead upper vortex and begins to weaken near 36N-19.8W at 39 hours while reaching northwestern convergence zone of the vortex... dissipates north of the Canary Islands through 114 hours.

**Additional tropical wave of low pressure emerges from wesat coast of Africa at 66 hours... located near 13N-39W as a tropical low at 165 hours


0600Z (Sep 7) NAVGEM Model Run...

**For Hurricane Lee... reaches 23N-63W as 120 hours as an intense hurricane. 

**For Tropical Depression Fourteen... reaches 19.8N-40.2W at 96 hours after which time it turns north... located at 21N-40.5W at 120 hours as a broad tropical storm

**For Area of Interest #33... ex-Franklin circles around periphery of overhead upper vortex and begins to weaken near 47.5N-18W at 42 hours while reaching the northwestern convergence zone of the vortex... while turning southeastward ex-Franklin weakens to a trough west-southwest of Portugal by 120 hours.

46 views0 comments

Comments


bottom of page