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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 #27G (Special Update)

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


...MONDAY JUNE 26 2023 12:30 PM EDT...

The following is a special update on recent tropical activity in the Atlantic as I am currently on vacation. While on vacation I will continue to issue special updates on active disturbances or tropical cyclones when possible... meanwhile refer to the National Hurricane Center website hurricanes.gov (hurricanes dot gov) for up to the minute latest information on the Atlantic tropics.


Satellite image as of 1410Z June 26 showing current areas of interest (AOIs)… along with a simplified surface analysis of surface low pressures (Ls)… high pressure ridges (Hs)… and fronts (red lines) based on the NHC TAFB surface analysis at the time. Blue-dashed lines and Ls are used to mark the location of upper vorticity:


AREA OF INTEREST #10 (REMNANTS OF CINDY)… While moving northwestward into western Atlantic waters between the Lesser Antilles and Bermuda… Cindy has degenerated into a surface low without a fully-closed circulation as of 11 PM EDT yesterday (based on satellite scans of surface winds). The collapse of Cindy as a tropical cyclone is due to westerly shear imparted by the string of upper vorticity in the region which has pushed what remains of its thunderstorm activity well to the east of the surface low pressure center. Most of the global models (GFS… ECMWF… NAVGEM) continue to bring back Cindy as follows… therefore I am continuing with a track and intensity forecast in this update:

(1) The shearing cold core upper vorticity axis… due to prolonged isolation from high-latitude cold air… will begin to break up into dissipating upper vortices.

(2) The dissipating upper vortex in Cindy’s environment will give way to the more favorable low shear/upper outflow of the current warm core western Atlantic upper ridge cell… potentially allowing Cindy to make a comeback as a tropical cyclone.

(3) The current Great Lakes upper trough/surface frontal cyclone and northeastern US upper trough will combine into a large surface frontal system/ single upper trough that pushes toward the western Atlantic and Cindy. The upper trough will be amplified as to avoid excess westerly shear… instead potentially helping Cindy with its eastern divergence zone.  (4) The strong southerly upper flow on the east side of the upper trough and vigorous southerly flow on the west side of what will be a strong Atlantic surface (to be supported by ongoing convergence on the east side of the west Atlantic upper ridge cell) is expected to turn Cindy on a rapid northward acceleration toward Nova Scotia by day 4.


My updated forecast track is nudged westward based on Cindy’s current position relative to the previous forecast. I have also slightly lowered the intensity forecast as Cindy was not able to hang on to tropical cyclone status in the short-term and the sea-surface temperature profile that lies ahead is not conventionally conducive for tropical development. Between Cindy’s current position and 31N latitude water temps are at the 26+ deg C threshold needed for tropical development… and a rather narrow band of 26 deg C at 38N latitude has recently developed in association with the Gulf Stream (https://www.nhc.noaa.gov/sst/). However between 31N and 38N water temps are at a lukewarm 22 to 24 deg C which makes tropical development more questionable… but it may still happen with the help of the divergence on the east side of the incoming upper trough as noted above. I transition Cindy to non-tropical as it closes in on Nova Scotia at 40+ north latitude where water temps rapidly drop into the teens of deg C. Noting the GFS run in the computer model summary below is notably further southeast with Cindy’s track and stronger with Cindy’s strength. This is because the GFS continues to see Cindy re-generating under the supportive eastern divergence zone of the dissipating upper vortex in the region… with this re-generation position giving Cindy more time over warm water before it moves north into cooler water. However given the current more western position of Cindy… disregarding this solution while instead projecting Cindy to re-generate in split flow upper divergence between the northeast side of the dissipating upper vortex and southwest side of the western Atlantic upper ridge cell.


Regarding impacts:

(1) Interests in Bermuda should be aware of Cindy as it could get pushed very close to or over the island by the strong Atlantic surface ridge as it potentially re-strengthens. Timing for potential impacts (coastal surf… rain… wind) would be Wednesday or Thursday

(2) Interests in Nova Scotia and New Brunswick should also be aware of Cindy as it could make landfall as a vigorous frontal cyclone just after 4 days. In this scenario surf could also spread to the northeastern US coast during this timeframe.

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

0 Hr Position (1200Z Jun 26)… Remnant low located at 24N-62.5W

IOH 24 Hr Forecast (1200Z Jun 27)… Remnant low located at 27N-62.5W

IOH 48 Hr Forecast (1200Z Jun 28)… 45 mph maximum sustained wind tropical storm centered just south-southeast of Bermuda at 30N-64W

IOH 72 Hr Forecast (1200Z Jun 29)… 50 mph maximum sustained wind tropical storm centered just north-northwest of Bermuda at 33N-65.5W

IOH 96 Hr Forecast (1200Z Jun 30)… Frontal cyclone located offshore of western Nova Scotia centered at 40N-65.5W

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

Formation chance through 48 hours...near 0%

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


AREA OF INTEREST #11A tropical wave of low pressure in the central tropical Atlantic… currently near 11N-52W as of this writing… has been becoming better defined and organized over the last couple of days. This is probably the western of the two of the duplex of closely spaced tropical waves that emerged from western Africa a few days ago. In my previous posts I was tracking the eastern of the two waves as an area of interest for a period of time… but now I am initializing the wave near 11N-52W as a new area of interest due to the continuous organization of its thunderstorm activity. The wave has been thriving under the low shear and upper outflow of the central Atlantic tropical upper ridge cell that remains in the region… however I assign low odds of tropical cyclone formation as the wave only has 24 more hours in the favorable environment before it moves into westerly shear associated with the ongoing upper vorticity in the Caribbean and western Atlantic and because none of the global models develop this wave. Some north angle in the west track of this wave is anticipated due to the surface ridge weakness associated with ex-Cindy and the frontal system that will soon enter the Atlantic from the eastern US.


Regardless of tropical cyclone formation or not… periods of gusty winds and heavy rainfall appear more likely for the Lesser Antilles by late tomorrow and into Wednesday.

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

IOH 24 Hr Outlook (1200Z Jun 27)… 15% chance of tropical cyclone formation (east-southeast of Barbados near 12.5N-57.5W)

IOH 48 Hr Outlook (1200Z Jun 28)… 0% chance of tropical cyclone formation (eastern Caribbean Sea near 14.5N-63.5W)

******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM 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/)


0000Z (Jun 26) CMC Model Run...

**For Area of Interest #10… remnant trough of Cindy passes over Bermuda at 102 hours… accelerates north toward western Nova Scotia through 144 hours while transitioning into a non-tropical frontal low

**For Area of Interest #11… no development shown


0000Z (Jun 26) ECMWF Model Run...

**For Area of Interest #10… remnant trough of Cindy redevelops into a tropical depression over Bermuda at 78 hours… accelerates north into western Nova Scotia through 108 hours while transitioning into a non-tropical frontal cyclone… frontal cyclone continues north across New Brunswick through 120 hours

**For Area of Interest #11… no development shown


0600Z (Jun 26) GFS Model Run...

**For Area of Interest #10… the east end of Cindy’s remnant trough becomes a tropical depression near 27N-60.2W at 54 hours… strengthens into a compact hurricane while passing just east of Bermuda through 87 hours… hurricane located at 38N-63W at 120 hours

**For Area of Interest #11… no development shown


0000Z (Jun 26) NAVGEM Model Run...

**For Area of Interest #10… remnant trough of Cindy redevelops into a tropical depression near 27.5N-65W at 36 hours… center passes just west of Bermuda through 72 hours while it strengthens into a tropical storm… accelerates north into western Nova Scotia through 102 hours while transitioning into a non-tropical frontal cyclone… frontal cyclone continues north across New Brunswick and into southeastern Quebec

**For Area of Interest #11… no development shown

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