*******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.**********
...WEDNESDAY SEPTEMBER 7 2022 2:40 AM EDT...
The potential for an early to mid September outbreak of Atlantic tropical cyclones is increasing due to Hurricanes Danielle and Earl currently in progress... and a pair of organizing tropical waves in the eastern tropical Atlantic/western coastal Africa region designated as areas of interest #27 and #28 on this blog post. See the respective sections below for an update on each of these systems and the land areas to be affected. In addition to the pair of tropical waves... an additional three areas of interest could emerge over the next week and contribute to the tropical cyclone outbreak as follows:
(1) The upper trough currently pushing into central Canada is expected to interact with Hurricane Earl by this weekend. In this initial interaction the south side of the upper trough could amplify further due to northerly flow on the northwest quadrant of Earl pulling the upper trough's cool air southward. The south side of the upper trough could then be amplified further into a cut-off upper vortex situated just east of Bermuda as the current sprawling and amplified upper ridge over the United States pushes into the western Atlantic. Some of the latest model runs suggest the divergent east side of the cut-off upper vortex could trigger a surface low pressure... with wind shear beneath the vortex being low enough to allow the surface low to acquire tropical characteristics. Should models continue to suggest this possible subtropical system... will declare an associated area of interest in my next update. Of note... such a subtropical system could produce another round of coastal sea swells for Bermuda this weekend not long after Hurricane Earl affects the island.
(2) The cut-off upper vorticity currently over the southern United States is likely to be pushed into the western Gulf of Mexico by Friday and this weekend due to the current sprawling upper ridge building over the United States. The divergent east side of this upper vorticity may trigger a subtropical disturbance in the central or western Gulf of Mexico during this timeframe. Will consider adding an area of interst in this region in future updates if necessary.
(3) Some model runs suggest that in approximately one week from today... an additional organized tropical wave of low pressure could emerge from the west coast of Africa into the eastern tropical Atlantic. This wave's emergence into the tropical Atlantic waters will be within the 5-day forecasting range in a couple of days from now... upon which time wave could be added as yet another area of interest.
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 areas of interest in this blog post is designated #27 and #28 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... The upper vorticity west of Hurricane Danielle over the last 36 hours has coalesced into an amplified upper trough that has begun to pull the once stationary hurricane northeastward. The trough has not been able to knock away the warm core anticyclonic outflow over the hurricane as the trough is not able to exert shear due to its amplified nature. As a result the symmetric ring of thunderstorms around Danielle's eye and associated outflow has persisted while the hurricane has moved into waters below 26 deg C. The effect of the cooler water however is pronounced as the intensity of the thunderstorm ring has relaxed... and Danielle has faded to a minimal category 1 strength of 75 mph maximum sustained winds.
Over the next 48 hours the amplified upper trough west of Danielle will become re-enforced by the current trough approaching from eastern Canada. The ongoing 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 despite being over cool waters... 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 in the open north Atlantic. Due to the currently intact thunderstorm ring around Danielle's eye... I have delayed my forecast transition to non-tropical by 24 more hours in this update. Note Danielle has potential to bring coastal sea swells to the Azores by later today.
For the timeframe after 48 hours...the model solutions over the last day have changed their long term evolution of the upper trough interacting with Danielle. The block of upper ridging currently over eastern Canada... occurring in the warm sector of the current frontal system moving into central Canada... is more amplified than previously thought which will cause the upper trough interacting with Danielle to amplify further into a cut-off upper vortex. The eastern divergence zone of the forming upper vortex generates a frontal low just west of the remnant frontal cyclone of Danielle... with ex-Danielle subseuqently now forecast to undergo a counter-clockwise loop turn in a fujiwhara interaction with the frontal low (ex-Danielle is also expected to absorb the frontal low in the interaction). The counter-clockwise loop will also be induced by the steering flow around the upper vortex. Once the upper ridge over eastern Canada shifts into the far north Atlantic... the ridge is expected to push the upper vortex and ex-Danielle east-southeastward into the northeast Atlantic waters north of the Azores by day 5. The erratic counter-clockwise loop turn followed by the east-southeast turn will prolong the period of coastal sea swells for the Azores to a few days.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 7)... 75 mph maximum sustained wind hurricane centered at 42.7N-39.3W
IOH 24 Hr Forecast (0000Z Sep 8)...70 mph maximum sustained wind tropical storm transitioning into a non-tropical frontal cyclone while centered at 46N-34W
IOH 48 Hr Forecast (0000Z Sep 9)...Non-tropical remnant frontal cyclone centered at 50N-33.5W
TROPICAL STORM EARL (RECENTLY UPGRADED TO HURRICANE EARL)... While drifting northward away from Puerto Rico and in the general direction of Bermuda... Earl spent much of the last 36 hours as a strong tropical storm oscillating between 65 and 70 mph maximum sustained winds. The struggle for additional strengthening during that time was attributed to light westerly shear imparted by lingering upper vorticity to the west. As of this evening as the upper vorticity weakens further while remaining cut-off from high-latitude cold air... the shear is abating as noted by the thunderstorm activity once lopsided to the east side of the circulation now becoming better aligned with the center of rotation while also becoming better organized. Aircraft reconnaissance has also indicated that as of 8 PM EDT Earl is now a category 1 hurricane of 80 mph maximum sustained winds. The weakening upper vorticity to the west is also inducing the slow northward drifting track of the new hurricane. The upper trough currently entering the northwest Atlantic from eastern Canada will also pass too far north to accelerate Earl's forward speed. At 72+ hours the upper trough currently over central Canada will be far south enough by the time it approaches the hurricane to finally jettison Earl northeastward into the open north Atlantic. A westerly upper-level wind jet to setup between this upper trough and south side of what will be ex-Danielle's upper vortex should curve the track of Earl more eastward by day 5. Noting the current position of Earl is southwest of my previous forecast track... and the updated one is adjusted in that direction. The westward component of the adjustment brings Earl closer to Bermuda on Thursday... raising the potential for tropical storm force winds over the island to be induced by the northwest quadrant of the hurricane. Bermuda is under a tropical storm watch as of this writing.
Regarding intensity... potentially brisk strengthening into a category 2 hurricane is possible in the next 24 hours as wind shear continues to relax as noted in the above remarks. Some shear may redevelop on day 2 as the current central Canadian upper trough approaches Earl... and the intensification rate in my forecast below is slowed during that time. On day 3 the shear could relax as northerly flow on Earl's northwest quadrant could pull cool air associated with this trough southward... resulting in a more amplified upper trough with less shear and more upper divergence on its east side. This divergence could also aid Earl while the hurricane is still over warm water... therefore my forecast rate of intensification is ramped up from day 2 to 3. Although the favorable interaction with the amplified upper trough persists through day 4... the hurricane will be fast approaching cooler waters on its accelerating northeast track and therefore a gradual weakening rate is shown from day 3 to 4. By day 5 transition to a still strong non-tropical frontal cyclone is expected to be completed while the storm moves across waters below 26 deg C. Due to Earl's signs of already becoming well-organized over the last few hours... I have raised my intensity forecast to be slightly above the 11 PM EDT NHC intensity forecast. In other words... I think Earl now has potential to peak as a minimal category 4 hurricane on day 3.
Regarding impact to land areas:
(1) Any coastal sea swells on the shores of the northern Lesser Antilles... Puerto Rico... the Virgin Islands... north coast of the Dominican Republic... and the Bahamas should decrease over the next 24 hours as the hurricane continues drifting northward away from these land areas.
(2) Coastal sea swells are expected to increase to strong levels on the shores of Bermuda through Thursday... afterwards decreasing as the hurricane accelerates northeastward and away. The latest forecast track increases potential for the northwest side of Hurricane Earl to bring tropical storm force winds and heavy rainfall to the island also on Thursday. Use today (Wednesday) to prepare for tropical storm conditions.
(3) On the current forecast track... what is forecast to be the remnant frontal cyclone of Earl has potential to add to ex-Danielle's coastal sea swells to the Azores in approximately five days.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 7)... 80 mph maximum sustained wind hurricane centered in the western Atlantic at 24.8N-65.8W
IOH 24 Hr Forecast (0000Z Sep 8)... 105 mph maximum sustained wind hurricane centered south of Bermuda at 27.5N-65.8W
IOH 48 Hr Forecast (0000Z Sep 9)... 115 mph maximum sustained wind major hurricane centered just south- southeast of Bermuda at 30N-64W
IOH 72 Hr Forecast (0000Z Sep 10)... 130 mph maximum sustained wind major hurricane centered in the open central Atlantic at 35N-58W
IOH 96 Hr Forecast (0000Z Sep 11)... 110 mph maximum sustained wind hurricane cnetered in the open north Atlantic near 40.5N-50W
IOH 120 Hr Forecast (0000Z Sep 12)... Non-tropical remnant frontal cyclone centered at 50N-33.5W
AREA OF INTEREST #27...The tropical wave of low pressure that continues moving west-northwest across the eastern tropical Atlantic has passed just southwest of the Republic of Cabo Verde Islands... and continues to become better organized while developing a low pressure center (near 14N-30W as of 0000Z earlier tonight) with thunderstorm bands becoming increasingly apparent around the center. The west-northwest track is expected to continue while this system angles toward the surface ridge weakness currently being produced by Hurricane Earl... with this weakness staying open through day 5 by the potential subtropical system that could become established just east of Bermuda noted in the intro section of this birdseye view post. The north angle in the track of this system has potential to increase by day 5 while nearing the weakness. Atmospheric conditions are favorable for development over the next 24 hours as the tropical upper ridge in the region... featuring low shear and upper outflow... is expected to persist. The atmospheric favorability becomes a little more murky by 48 hours as the south part of the current upper trough interacting with Hurricane Danielle becomes pushed east-southeast toward this system by the warm core upper outflow of Hurricane Earl. Models such as the CMC and GFS suggest shear from this upper trough fragment could weaken this system in the long range. The ECMWF paints a different picture and suggests continuous strengthening of this system through day 5 as the upper trough fragment is amplified by Hurricane Earl's strong warm core anticyclone into a cut-off upper vortex... which in fact would only result in a slight amount of wind shear over this system. The shear could even relax by day 5 as the upper vortex retrogrades northwest toward the upper vortex of the aforementioned potential subtropical system that would be near Bermuda.
Due to Earl forecast to become a strong hurricane... I think the ECMWF solution has some credibility and therefore only slightly dip odds of tropical cyclone formation in the 2 to 4 day range. Odds are higher in the next 24 hours due to the current low shear enviroment... and again are higher at day 5 as shear potentially relaxes with the upper vortex potentially retrograding northwestward and away. I assign 65% peak odds of development... slightly higher than the NHC as of this writing due to the increased organization of this system.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 8)...65% chance of tropical cyclone formation (eastern tropical Atlantic near 15N-35W)
IOH 48 Hr Outlook (0000Z Sep 9)...60% chance of tropical cyclone formation (central tropical Atlantic near 16.5N-41W)
IOH 72 Hr Outlook (0000Z Sep 10)...60% chance of tropical cyclone formation (central tropical Atlantic near 17.5N-45W)
IOH 96 Hr Outlook (0000Z Sep 11)...60% chance of tropical cyclone formation (central tropical Atlantic near 19.5N-50W)
IOH 120 Hr Outlook (0000Z Sep 12)...65% chance of tropical cyclone formation (central Atlantic near 23N-51W)
AREA OF INTEREST #28...The tropical wave of low pressure that was over western Africa and to the east of area of interest #27... last mentioned in birdseye view post #92 on the home page of this site... has since become markedly better defined with its own cluster of thunderstorms over the last 36 hours or so. The organization of the clouds and pockets of thunderstorms as the wave now exits the west coast of Africa suggests the tropical wave is developing a center of rotation near 10N-15W. In addition computer model support suggesting some development of this wave is emerging. Therefore this wave has now earned itself area of interest status in the NHC tropical weather outlook... and this is now the twenty-eighth tropical area of interest I have monitored in the Atlantic basin on this site this year.
The tropical wave is expected to continue steadily westward across the eastern tropical Atlantic and around the south side of the current eastern Atlantic surface ridge... in an environment of low shear and upper outflow beneath the tropical upper ridge in the region. In combination with the wave appearing to already develop a low pressure center near 10N-15W as of this writing... and with area of interest #27 to the west-northwest moistening out the dry Saharan air in the region... I have already assigned a peak of 50% odds of tropical cyclone formation for the 5-day forecast period (note that this is higher than the NHC's current 20% as of this writing).
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Sep 8)...25% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-18.5W)
IOH 48 Hr Outlook (0000Z Sep 9)...35% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-22W)
IOH 72 Hr Outlook (0000Z Sep 10)...45% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-26W)
IOH 96 Hr Outlook (0000Z Sep 11)...50% chance of tropical cyclone formation (eastern tropical Atlantic near 11N-31W)
IOH 120 Hr Outlook (0000Z Sep 12)...50% chance of tropical cyclone formation (eastern tropical Atlantic near 11.5N-36W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 6) CMC Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 46.2N-34W at 42 hours... while undergoing a fujiwhara interaction with and absorbing adjacent frontal low to the west the remnant frontal cyclone undergoes a counter-clockwise loop... at end of the interaction the remnant frontal cyclone weakens to a frontal low and moves east-southeast with the frontal low reaching 45N-27.5W at 120 hours.
**For Tropical Storm Earl... moves north and reaches 25.5N-66W at 36 hours where it reaches hurricane strength... passes just southeast of Bermuda at 72 hours... afterwards rapidly accelerates northeast to 43N-49W at 120 hours where it transitions into a remnant frontal cyclone.
**For area of interest #27... tropical cyclone formation suggested near 18N-37.5W at 42 hours... weakens to a remnant low near 19.5N-46W at 72 hours... remnant low curves northward toward Earl and reaches 29N-50W at 120 hours.
**For area of interest #28... tropical wave organizes into a tropical low near 10N-23W at 66 hours... tropical low located near 16.5N-40.5W at 168 hours
**Tropical wave emerges from west coast of Africa at 144 hours... organizes into a tropical low just southeast of the Republic of Cabo Verde Islands at 168 hours.
1200Z (Sep 6) ECMWF Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 48N-34W at 48 hours... while undergoing a fujiwhara interaction with and absorbing adjacent frontal low to the west the remnant frontal cyclone undergoes a counter-clockwise loop... at end of the interaction the remnant frontal cyclone moves east-southeast and reaches 41.5N-20W at 120 hours.
**For Tropical Storm Earl... moves north and reaches 25N-65.5W at 24 hours where it reaches hurricane strength... passes just southeast of Bermuda between 48 and 72 hours... afterwards rapidly accelerates northeast to 45N-45W at 120 hours where it transitions into a remnant frontal cyclone.
**For area of interest #27... tropical cyclone formation suggested near 18N-40W at 48 hours... curves northward toward Earl and becomes a compact hurricane near 32N-50W at 120 hours
**For area of interest #28... tropical cyclone formation suggested near 17.5N-45W at 168 hours
**Tropical wave emerges from west coast of Africa between 120 and 144 hours... tropical cyclone formation suggested just south of the Republic of Cabo Verde Islands at 168 hours.
**Upper trough that interacts with Earl at 96 to 120 hours deposits a cut-off upper vortex and associated surface frontal cyclone southwest of Earl and near 37.5N-58W... frontal cyclone transitions to tropical cyclone that moves east-northeast and reaches 39.5N-49W at 168 hours
1800Z (Sep 6) GFS Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 48.5N-31.5W at 48 hours... while undergoing a fujiwhara interaction with and absorbing adjacent frontal low to the west the remnant frontal cyclone undergoes a counter-clockwise loop... at end of the interaction the remnant frontal cyclone moves east-southeast and reaches 44N-19.5W at 120 hours.
**For Tropical Storm Earl... moves north and reaches 26N-65.5W at 21 hours where it reaches hurricane strength... passes just southeast of Bermuda at 57 hours... afterwards rapidly accelerates northeast to 43N-41W at 120 hours where it transitions into a remnant frontal cyclone.
**For area of interest #27... tropical cyclone formation suggested near 17.5N-38W at 39 hours... weakens to a tropical low near 18.5N-46.5W at 75 hours... remnant low dissipates near 24.5N-53W at 120 hours
**For area of interest #28... tropical wave organizes into a tropical low near 10N-20W at 57 hours... tropical low located near 12N-33W at 120 hours
**Upper trough that interacts with Earl at 93 hours deposits a cut-off upper vortex and associated surface frontal low southwest of Earl and near 34N-61.5W... frontal low strengthens further and becomes a subtropical cyclone beneath the cut-off upper vortex while located near 34.5N-59W at 120 hours...
1800Z (Sep 6) NAVGEM Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 46N-33.5W at 36 hours... while undergoing a fujiwhara interaction with and absorbing adjacent frontal low to the west the remnant frontal cyclone undergoes a counter-clockwise loop... at end of the interaction the remnant frontal cyclone moves east-southeast and reaches 44N-23W at 120 hours.
**For Tropical Storm Earl... moves north and reaches 28N-65W at 36 hours where it reaches hurricane strength... passes just southeast of Bermuda at 54 hours... afterwards rapidly accelerates northeast to 41.8N-42.5W at 120 hours where it transitions into a remnant frontal cyclone.
**For area of interest #27... tropical low moves west-northwest then northwest and weakens to a surface trough near 22.5N-28.5W at 102 hours... remnant trough dissipates soon after.
**For area of interest #28... tropical wave organizes into a tropical low near 11N-24W at 60 hours... tropical low located at 13.5N-34W at 120 hours.
**Tropical wave emerges from west coast of Africa at 144 hours... organizes into a tropical depression just southeast of the Republic of Cabo Verde Islands at 168 hours.