*******Note that forecasts 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 SEPTEMBER 4 2022 5:59 AM EDT...
September continuing on a more active note for the 2022 Atlantic Hurricane Season with Hurricane Danielle persisting in the open north Atlantic... and with the potential for Tropical Storm Earl to become the second hurricane of the season while situated between the northern Caribbean islands and Bermuda in the days ahead.
Elsewhere and over western Africa... a pair of tropical waves of low pressure have continued west... with the western of the two recently emerging from the west coast of Africa while the eastern of the two has become less defined on satellite pictures over the last 24 hours. Model support showing some development of the western wave continues... see area of interest #27 section below for more information.
New to this site this year... I will be sequentially numbering up areas of interest for possible Atlantic tropical development. In this scheme... will reset back to #1 at the start of next year (January 2023). The current area of interest in this blog post is designated #27 as the other twenty-six were mentioned in previous birdseye view posts. This scheme is to reduce confusion as Atlantic tropical activity increases during the peak of the hurricane season... when multiple simultaneous areas of interest begin and end which previously required shuffling around the area of interest numbers from update to update.
HURRICANE DANIELLE...Over the last 24 hours... Danielle’s small ring of thunderstorms around its original small eye became open and the hurricane was downgraded to a maximal tropical storm of 70 mph maximum sustained winds. Meanwhile outer bands of thunderstorm activity redeveloped which have recently coalesced into a single ring around a now larger-diameter eye... and as of 11 PM EDT Danielle was re-upgraded to a 75 mph maximum sustained wind hurricane. The stationary hurricane is persisting off of its warm core anticyclonic upper outflow tucked just east of the parent upper vorticity that triggered the pre-cursor circulation of Danielle. The eastern divergence zone of the parent upper vorticity is also likely playing a role in supporting Danielle.
The fact that Danielle has struggled to gain additional strength in the last 24 hours could be a reflection of not so favorable thermodynamic conditions caused by the hurricane being parked over marginally warm waters. The water temperatures in the area may also be cooling due to the stationary hurricane’s winds upwelling cooler water beneath the sea surface. While the NHC as of this writing elects to show possible additional strengthening... my updated intensity forecast below no longer calls for such strengthening.
By day 2... the southern fracture of the current northwest Atlantic upper trough is expected to near Danielle in a weak state with two fragments. However by day 3 these two fragments and the parent upper vorticity of Danielle are still expected to coalesce into an amplified upper trough with Danielle interacting with the east side of the amplified trough. And by day 4 the amplified upper trough becomes re-enforced as the current eastern Canada upper trough approaches and merges with it. In the interaction with the amplified upper trough... Danielle is expected to finally move northeast in 2+ days. The amplified nature of the trough will allow Danielle to get the benefits of upper divergence on the east side of the trough without excess wind shear. Therefore as Danielle moves into waters below 26 deg C at 48+ hours... the supportive divergence zone of the trough will keep Danielle's weakening rate slow. The large size of the upper divergence zone should also cause Danielle to expand in size by creating an outer non-tropical low pressure circulation around Danielle's tropical core. The tropical warm core will eventually fade over cooler water... but the process could take some time due to the low shear environment that would be unable to push the thunderstorms away from the center. But once that process is completed... Danielle will be a large and still strong non-tropical frontal cyclone heading towards the northeast Atlantic. I currently expect the transition to non-tropical to be completed by day 4.
Also noting in the latest model data that the initial upper trough that sets up by day 3 is not quiet as amplified as previously shown... resulting in a less north and more east track. The more east position keeps Danielle a little more isolated from the approaching east Canada upper trough such that Danielle’s west side is not able to pull as much cold air associated with the trough southward. This keeps this upper trough also less amplified by day 4 and beyond such that the longer range track stays more east and less north. As a result the longer range forecast track below is adjusted accordingly... and Danielle’s remnant frontal cyclone now has increased potential to bring coastal sea swells to the Azores by Wednesday.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 4)... 75 mph maximum sustained wind hurricane centered at 38.1N-45W
IOH 24 Hr Forecast (0000Z Sep 5)... 75 mph maximum sustained wind hurricane centered at 38.5N-44W
IOH 48 Hr Forecast (0000Z Sep 6)... 70 mph maximum sustained wind tropical storm centered at 40.5N-43W
IOH 72 Hr Forecast (0000Z Sep 7)... 65 mph maximum sustained wind tropical storm gradually transitioning into a frontal cyclone while centered at 43N-40W
IOH 96 Hr Forecast (0000Z Sep 8)... Non-tropical remnant frontal cyclone centered at 46N-37W
TROPICAL STORM EARL... The tropical storm tracking west-northwest just north of the northeastern Caribbean islands has only slowly strengthened to 50 mph maximum sustained winds due to ongoing westerly shear being imparted by upper vorticity lingering to the west. Although a surface ridge is present over Nova Scotia and north of Earl... the tropical storm is likely to bend north in track while strong/tall enough to be steered by the east side of the lingering upper vorticity. Although the latest model data now suggests all of the south part of the current eastern Canada upper trough will now remain trapped over the southern US by a building upper ridge over North America... the north part of this trough is expected to generate a frontal cyclone to the west of Danielle that would draw Earl on a more northeast track. The updated forecast track is adjusted in the short term due to the current storm position being just southwest of the prior forecast track. The longer range track once again shows a slower forward speed as the north part of the approaching eastern Canada upper trough could now stay too far north of Earl to accelerate the forward speed of the storm.
Even though Earl is a tad stronger than in my prior intensity forecast... my updated one below remains unchanged as Earl does not appear to be in a hurry to intensify due to ongoing westerly wind shear. There is an opportunity for some strengthening in the next 24 hours as the shearing upper vorticity continues to weaken while remaining cut-off from high-latitude cold air. Westerly shear may make a little resurgence across the western Atlantic by day 2 as the shearing upper vorticity ingests the vorticity currently just offshore of the Carolinas and some of the vorticity associated with the southern fracture of the current northwest Atlantic upper trough. The forecast intensity thus takes a dip during this time. By 4+ days the shearing upper vorticity is expected to then re-weaken while again remaining cut-off from high-latitude cold air... with strengthening of Earl forecast during that timeframe. Also noting that models now agree on Earl becoming a hurricane by day 5.
Regarding impact to land areas... the center of Earl on its current track will continue to pass just north of the northeastern Caribbean islands. Therefore impacts to the northern Lesser Antilles… Virgin Islands... Puerto Rico... north coast of the Dominican Republic... and also the Bahamas and Bermuda will likely be limited to coastal sea swells from now through the middle of this upcoming week.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 4)... 50 mph maximum sustained wind tropical storm centered just north of the Virgin Islands at 19.5N-64.2W
IOH 24 Hr Forecast (0000Z Sep 5)... 60 mph maximum sustained wind tropical storm centered northeast of the Dominican Republic at 20.8N-67.5W
IOH 48 Hr Forecast (0000Z Sep 6)... 50 mph maximum sustained wind tropical storm centered in the western Atlantic at 23N-67.5W
IOH 72 Hr Forecast (0000Z Sep 7)... 50 mph maximum sustained wind tropical storm centered in the western Atlantic at 26N-67.5W
IOH 96 Hr Forecast (0000Z Sep 8)... 60 mph maximum sustained wind tropical storm centered south of Bermuda at 28N-64.5W
IOH 120 Hr Forecast (0000Z Sep 9)... 80 mph sustained wind hurricane centered southeast of Bermuda at 29N-62W
AREA OF INTEREST #27...A tropical wave of low pressure has recently emerged from the west coast of Africa with some signs of rotation in its cloudiness... with the center of rotation just offshore of Senegal near 12.5N-17.5W. The wave has featured limited shower and thunderstorm activity occurring only in small pockets over the last day or so... however computer model support suggesting some development of this wave has also persisted over the last couple of days. As a result the National Hurricane Center has added this wave as an area of interest for tropical development in their 5-day tropical weather outlook. This marks the twenty-seventh area of interest for Atlantic tropical development I have covered on this blog this year.
Regarding the track... this system will continue west around the south side of the Atlantic surface ridge over the next few days. Some north angle in the track is also anticipated as the fading remnants of area of interest #23 to the northwest and an intensifying Tropical Storm Earl create a surface ridge weakness during the forecast period. Atmospheric conditions are favorable for development over the next four days as the tropical upper ridge in the region... featuring low shear and upper outflow... is expected to persist. By day 5 a south fragment of the upper trough to interact with Danielle is expected to near the environment of this system which could impart some southerly wind shear. I assign only low 10% peak odds of tropical cyclone formation despite some of the above mentioned model support as I am uncertain about the thermodynamic favorability of the environment as evidenced by dry saharan air lurking just to the north in combination with only scattered pockets of thunderstorms currently present with the wave (note the NHC peak odds of development are 20% as of this writing). This could be yet another disturbance that does not succeed in developing due to dry air mass conditions that have been prevalent in this region of the Atlantic over the last several days. I trim odds of development down to a slimmer 5% margin by day 5 due to possible wind shear developing as mentioned above.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 5)...0% chance of tropical cyclone formation (southeast of the Republic of Cabo Verde Islands at 12.5N-22W)
IOH 48 Hr Outlook (0000Z Sep 6)...0% chance of tropical cyclone formation (southwest of the Republic of Cabo Verde Islands at 13N-26W)
IOH 72 Hr Outlook (0000Z Sep 7)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 14N-31W)
IOH 96 Hr Outlook (0000Z Sep 8)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 15N-36W)
IOH 120 Hr Outlook (0000Z Sep 9)...5% chance of tropical cyclone formation (central tropical Atlantic near 16.5N-41W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 3) CMC Model Run...
**For Hurricane Danielle... begins moving northeast at 42 hours... passes well north of the Azores while reaching 46.5N-30.5W at 120 hours
**For Tropical Storm Earl... reaches 22.8N-67.5W at 60 hours... turns north and reaches hurricane strength near 24N-67.5W at 102 hours... reaches 25.2N-65W at 120 hours
**For area of interest #27...Tropical wave emerges from west coast of Africa at 24 hours... develops into a tropical low just offshore of Senegal at 36 hours... tropical low passes through the Republic of Cabo Verde Islands at 60 hours... tropical cyclone formation suggested near 17N-29W at 72 hours... tropical cyclone located near 19.5N-41W at 120 hours
1200Z (Sep 3) ECMWF Model Run...
**For Hurricane Danielle... begins moving northeast at 48 hours... passes well north of the Azores while reaching 45N-31W at 120 hours
**For Tropical Storm Earl... reaches 21.5N-67.5W at 48 hours... turns north then northeast and reaches 25N-66W at 120 hours as a potential hurricane
**For area of interest #27... tropical wave emerges from west coast of Africa at 24 hours... organizes into a tropical low near 16N-37W at 96 hours... tropical low reaches 20N-42.5W at 120 hours
0000Z (Sep 4) GFS Model Run...
*For Hurricane Danielle... begins moving northeast at 24 hours... passes well north of the Azores while reaching 47.5N-25W at 120 hours
**For Tropical Storm Earl... reaches 21N-66W at 27 hours... turns north and becomes a hurricane near 25N-66W at 60 hours... located southeast of Bermuda near 28.5N-63W at 120 hours as a potentially intense hurricane
**For area of interest #27... no development shown
1800Z (Sep 3) NAVGEM Model Run...
**For Hurricane Danielle... begins moving north at 24 hours... located south-southeast of Greenland near 54N-40W at 120 hours
**For Tropical Storm Earl... located at 20.5N-66W at 24 hours... turns north and becomes a hurricane near 24N-68W at 78 hours... turns east and reaches 25N-65W at 120 hours as a potentially intense hurricane
**For area of interest #27... tropical wave emerges from west coast of Africa at 24 hours... organizes into a tropical low soon after which passes over the southern Republic of Cabo Verde Islands at 54 hours... tropical cyclone formation suggested near 16.5N-40W at 120 hours
**Tropical wave emerges from west coast of Africa at 150 hours... organizes into a tropical low soon after which is located just east of the Republic of Cabo Verde Islands at 168 hours