*******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.**********
...SUNDAY JUNE 25 2023 11:00 AM 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 0930Z June 25 showing Tropical Storm Cindy and other 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 line is used to mark the location of upper vorticity axis:
REMNANTS OF BRET… Satellite image of Bret when it was still a tropical storm while passing just north of the ABC Islands and northwestern Venezuela at 1350Z June 24:
Over the last 36 hours Bret has moved at a rather quick west-southwest pace across the southern Caribbean… with the center as of midday yesterday passing just north of the ABC Islands (Aruba Bonaire and Curacao). This track took Bret into the western side of the current eastern Caribbean upper vorticity where northwesterly shear and suppressing upper convergence was expected to quickly dissipate Bret. Instead while passing by the ABC Islands aircraft recon found Bret hanging on as a minimal tropical storm (40 mph max sustained winds) while satellite imagery showed thunderstorm bursts trying to cover Bret’s center in the sheared environment. These bursts brought rainfall for the ABC islands as well as northwestern Venezuela and Guajira peninsula region of northern Colombia. The south angle in Bret’s track perhaps allowed it to reach an upper divergence environment between northwesterlies on the southwest corner of the the upper vorticity and northeasterlies at the southeast corner of the current western Caribbean upper ridge… with the divergence helping to make the thunderstorm bursts. However Bret did finally lose its closed surface circulation and was downgraded to a remnant surface trough of low pressure as of 5 PM EDT yesterday in a worsening upper air environment… as the eastern Caribbean upper vorticity is approaching what’s left of Bret from the east while it gets pushed around an amplified west Atlantic upper ridge cell. The encroaching upper vorticity is making the upper winds more westerly and hence more severely shearing Bret while more opposed to Bret’s westward heading. This is my final statement on Bret on this blog as it is now a remnant surface trough instead of a tropical cyclone.
TROPICAL STORM CINDY… Satellite image of Cindy at peak strength on June 24 2330Z. The center of circulation was on the west edge of the thunderstorm burst colored in red and orange:
Over the last 36 hours Cindy has accelerated northwestward across the central tropical Atlantic… the net effect of the current Atlantic surface ridge trying to push Cindy west-northwestward and southwest-northeast tilted string of upper vorticity located ahead whose southwesterly flow is trying to push Cindy northeastward. The conflicting direction between the surface and upper flows means the upper southwesterly flow is also shearing the thunderstorms to the east of Cindy’s center. The storm managed to reach a peak of 60 mph maximum sustained winds yesterday before moving into the heart of the southwesterly shear environment which has caused it to recently weaken to 50 mph max sustained winds. The models agree on Cindy dissipating due to the shear in the short-term. For the longer-term… the other global models have come into agreement with what the GFS model has been showing as follows:
(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 warm core western Atlantic upper ridge cell… potentially allowing Cindy to make a comeback as a tropical cyclone.
(3) The current central US upper trough/surface frontal cyclone and eastern 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 a rapid northward acceleration toward Nova Scotia by day 5.
The CMC and ECMWF wait till Cindy is accelerating across cooler waters and toward Nova Scotia before re-developing Cindy with the support of the incoming amplified upper trough… suggesting re-development as a non-tropical frontal cyclone instead of a tropical one. The GFS continues to show Cindy getting a head start in its re-development while still over warm waters… by showing Cindy getting enhanced in the eastern divergence zone of the dissipating upper vortex in the region… followed by eventual transition to non-tropical once Cindy vaults northward into cooler waters. My forecast strategy is to maintain Cindy as a tropical cyclone from now through day 4… then show the transition to non-tropical by day 5… while showing Cindy hanging on as a tropical depression in the current short-term shear environment and then re-strengthening it once the shear diminishes. I have a higher re-strengthening rate given the models have been joining the GFS overall with some kind of long-term re-strengthening. Noting as of this writing the NHC official forecast dissipates Cindy in the short-term… but acknowledges in their advisory discussions that Cindy could re-strengthen in the long range.
(1) The northern Lesser Antilles may see coastal surf from Cindy over the next day.
(2) 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
(3) Interests in Nova Scotia should also be aware of Cindy as it could make landfall as a vigorous frontal cyclone just after 5 days. In this scenario surf could also spread to the northeastern US coast during this timeframe.
Update as of 11 AM EDT… Cindy has weakened further to 45 mph maximum sustained winds
0 Hr Position (0600Z Jun 25)… 50 mph maximum sustained wind tropical storm centered at 20.3N-57.2W
IOH 24 Hr Forecast (0600Z Jun 26)… 35 mph maximum sustained wind tropical depression centered at 24N-60W
IOH 48 Hr Forecast (0600Z Jun 27)… 35 mph maximum sustained wind tropical depression centered at 27N-61W
IOH 72 Hr Forecast (0600Z Jun 28)… 50 mph maximum sustained wind tropical storm centered just southeast of Bermuda at 30N-63W
IOH 96 Hr Forecast (0600Z Jun 29)… 60 mph maximum sustained wind tropical storm centered just north of Bermuda at 33N-65W
IOH 120 Hr Forecast (0600Z Jun 30)… Frontal cyclone located offshore of western Nova Scotia centered at 40N-65W
******National Hurricane Center (hurricanes.gov) official forecast as of 11 AM EDT***************************
Loss of Tropical Cyclone Status (0000Z Jun 27)… Dissipation well south-southeast of Bermuda
AREA OF INTEREST #9… The tropical wave of low pressure in the eastern tropical Atlantic has continued westward and is now at 35W longitude as of this writing. The wave has lost its well-defined cloud cluster while becoming masked in regional dry Saharan air encroaching from the north and the models continue to not develop this wave. I have dropped odds of tropical cyclone formation to 0% in this update… and plan this to be my final statement on this area of interest on this blog.
IOH 24 Hr Outlook (1200Z Jun 26)… 0% chance of tropical cyclone formation (central tropical Atlantic near 9N-41W)
******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 25) CMC Model Run...
**For Tropical Storm Cindy… after passing northeast of the northern Lesser Antilles over the next 18 hours it weakens to a remnant trough near 24N-63W at 36 hours
**For Area of Interest #9… no development shown
**Tropical wave emerges from west coast of Africa at 78 hours… tropical cyclone formation suggested at 9.8N-42.5W at 162 hours
0000Z (Jun 25) ECMWF Model Run...
**For Tropical Storm Cindy… after passing northeast of the northern Lesser Antilles over the next 18 hours it weakens to a remnant trough near 26N-62.5W at 60 hours
0000Z (Jun 25) GFS Model Run...
**For Tropical Storm Cindy… weakens to a remnant low while passing northeast of the northern Lesser Antilles over the next 18 hours… regains tropical cyclone status east-southeast of Bermuda near 30.5N-61.5W at 99 hours which accelerates northward toward Nova Scotia through 144 hours while transitioning into a non-tropical frontal cyclone over cooler waters
0000Z (Jun 25) NAVGEM Model Run...
**For Tropical Storm Cindy… passes just northeast of the northern Lesser Antilles over the next 12 hours… gains intense hurricane strength while passing just east of Bermuda through 96 hours… accelerates northward toward Nova Scotia through 126 hours while transitioning into a non-tropical frontal cyclone over cooler waters