*******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.**********
...MONDAY SEPTEMBER 5 2022 8:57 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 and also the strongest hurricane of the season thus far while passing just southeast of Bermuda later this week. See Danielle and Earl sections below for an update on both active storms. Elsewhere... see area of interest #27 section below for an update on the tropical wave in the eastern tropical Atlantic which is showing signs of increased thunderstorm activity and organization this morning.
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... Danielle has proceeded to strengthen further to a stronger category 1 hurricane featuring 90 mph maximum sustained winds over the last several hours while the ring of thunderstorms around the large eye thickened and had higher intensity on colorized infrared satellite pictures. The 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 a few days ago. The eastern divergence zone of the parent upper vorticity is also likely playing a role in supporting Danielle. As of late the thunderstorm ring has become more ragged and weaker... a sign that the marginally warm water temperatures in the region are beginning to affect Danielle. The water temperatures in the area may also be cooling as the slow-moving hurricane’s winds potentially upwell cooler water beneath the sea surface. My updated intensity forecast is adjusted to reflect the current higher intensity of the hurricane... and only shows weakening going forward given the above observations.
To the west of Danielle is not only the parent upper vorticity that triggered the pre-cursor circulation of the hurricane... but also upper vorticity associated with the remnants of a former northwest Atlantic upper trough. Danielle is beginning to move northeast under the influence of these upper vorticity features... and over the next couple of days these features will also merge into an amplified upper trough with Danielle to interact with the east side of the amplified trough. And by day 3 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 move increasingly faster to the northeast with time. 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... 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 3. Note Danielle’s remnant frontal cyclone has 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 (0600Z Sep 5)... 90 mph maximum sustained wind hurricane centered at 39.6N-44.4W
IOH 24 Hr Forecast (0600Z Sep 6)... 80 mph maximum sustained wind hurricane centered at 41N-42.5W
IOH 48 Hr Forecast (0600Z Sep 7)... 70 mph maximum sustained wind tropical storm gradually transitioning into a frontal cyclone while centered at 43.5N-39W
IOH 72 Hr Forecast (0600Z Sep 8)... Non-tropical remnant frontal cyclone centered at 46.5N-35W
TROPICAL STORM EARL... The tropical storm that has been tracking west-northwest just north of the northeastern Caribbean islands has recently made a sharp north turn despite the presence of surface ridging over eastern North America. This is due to Earl being strong/tall enough to be influenced steering-wise by the east side of the lingering upper vorticity to the west. The shear imparted by the upper vorticity also continues to keep the strongest thunderstorms lopsided to the east side of Earl's circulation. The early part of my updated track forecast is shifted east to reflect Earl's early north turn... however remains the same in the longer range with no change in the overall steering pattern in the lastest forecast model data. This data continues to show the south part of the current eastern Canada upper trough being trapped over the southern US by a building upper ridge over North America... and shows the north part of this trough eventually generating a frontal low to the west of Danielle that would draw Earl on a more northeast track. For the next 96 hours the forecast track has a slow forward speed as the north part of the approaching eastern Canada upper trough is expected to stay too far north of Earl to accelerate the forward speed of the storm. However by 120 hours the next upper trough to approach Earl from Canada will be far south enough to finally accelerate the storm's forward speed.
Regarding the intensity forecast... my updated one shows Earl a little stronger in the short-term as the early north turn of the storm keeps it a little further away from the strongest shear associated with the lingering upper vorticity to the west. Strengthening is anticipated at 72+ hours as the upper vorticity finally weakens while continuing to remain cut-off from high-latitude cold air. Noting that the NHC forecast as of this writing brings Earl to category 3 by day 5. I currently go with a lower but still strong category 2 intensity for that timeframe as I anticipate some shear on day 4 from the second Canadian upper trough to approach Earl late in the forecast period. This shear could relax by day 5 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... which is why I do agree on Earl at least becoming a category 2.
Regarding impact to land areas... for the next 72 hours the primary impact is expected to be coastal sea swells for the northern Lesser Antilles... Virgin Islands... Puerto Rico... north coast of the Dominican Republic... and also the Bahamas and Bermuda. Earl will be passing just southeast of Bermuda on the latest forecast track later this week... and interests here should monitor the progress of this storm as any shift in the forecast track to the north or west would add heavy rainfall and gusty winds to the list of impacts.
0 Hr Position (0600Z Sep 5)... 50 mph maximum sustained wind tropical storm centered northeast of the Dominican Republic at 20.9N-65.3W
IOH 24 Hr Forecast (0600Z Sep 6)... 60 mph maximum sustained wind tropical storm centered in the western Atlantic at 23.5N-65.3W
IOH 48 Hr Forecast (0600Z Sep 7)... 60 mph maximum sustained wind tropical storm centered in the western Atlantic at 26.5N-65.3W
IOH 72 Hr Forecast (0600Z Sep 8)... 70 mph maximum sustained wind tropical storm centered south of Bermuda at 28.5N-64W
IOH 96 Hr Forecast (0600Z Sep 9)... 90 mph maximum sustained wind hurricane centered southeast of Bermuda at 29.5N-61.5W
IOH 120 Hr Forecast (0600Z Sep 10)... 100 mph maximum sustained wind hurricane centered in the open central Atlantic at 35N-57.5W
AREA OF INTEREST #27...A tropical wave of low pressure continues pulling westward and away from the west coast of Africa in the far eastern tropical Atlantic. Although the NHC TAFB surface analysis has the wave axis at 25W longitude... it is clear the area of rotation and thunderstorms is just east of the axis near 12.5N-22W... or just southeast of the Republic of Cabo Verde Islands. 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 three days as the tropical upper ridge in the region... featuring low shear and upper outflow... is expected to persist. By day 4 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. However the shear even through day 5 is not expected to be hostile as this trough fragment begins to move northwest and out of the way while heading toward an amplifying upper trough that is expected to be interacting with Earl during that time.
Due to the increase in the thunderstorms associated with the tropical wave's area of rotation... I agree with the NHC on raising peak odds of tropical cyclone formation. As of 8 AM EDT the NHC increased peak odds of development to 40%. I am at a slightly more cautious 30% in this update due to dry Saharan air that lurks just to the north and west of this system. Over the last several days this part of the Atlantic has not been a good host for tropical development due to dry air conditions. I trim odds of development back down to 15% at days 4 and 5 in anticipation of increased wind shear as discussed above.
IOH 24 Hr Outlook (0600Z Sep 6)...5% chance of tropical cyclone formation (southwest of the Republic of Cabo Verde Islands at 13N-26W)
IOH 48 Hr Outlook (0600Z Sep 7)...15% chance of tropical cyclone formation (eastern tropical Atlantic near 14N-31W)
IOH 72 Hr Outlook (0600Z Sep 8)...30% chance of tropical cyclone formation (eastern tropical Atlantic near 15N-36W)
IOH 96 Hr Outlook (0600Z Sep 9)...15% chance of tropical cyclone formation (central tropical Atlantic near 16.5N-41W)
IOH 120 Hr Outlook (0600Z Sep 10)...15% chance of tropical cyclone formation (central tropical Atlantic near 17.5N-46W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 4) CMC Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 50N-26W at 120 hours
**For Tropical Storm Earl... reaches 21.5N-67.5W at 24 hours... turns north and reaches hurricane strength near 24.5N-68W at 66 hours... located just south of Bermuda at 120 hours as a potentially intense hurricane
**For area of interest #27... no development shown
**Tropical wave emerges from west coast of Africa at 72 hours... through 120 hours evolves into a broad tropical low south of the Republic of Cabo Verde Islands.
1200Z (Sep 4) ECMWF Model Run...
**For Hurricane Danielle... moves northeast and then eastward with remnant frontal cyclone reaching 44.5N-20.5W at 120 hours
**For Tropical Storm Earl... reaches 21.5N-66W at 24 hours while becoming a compact hurricane... reaches 29N-64.5W at 120 hours.
**For area of interest #27... tropical cyclone formation suggested near 23N-44W at 120 hours
1800Z (Sep 4) GFS Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 52.5N-30W at 120 hours
**For Tropical Storm Earl... becomes a compact hurricane near 22.8N-66W at 30 hours... passes just southeast of Bermuda at 105 hours as a larger and potentially intense hurricane... located at 32.5N-59.5W at 120 hours
**For area of interest #27... tropical wave evolves into tropical low near 14.5N-32.5W at 60 hours... tropical low reaches peak strength near 18N-39.8W at 93 hours... tropical low weakens back to a wave near 17.5N-45.5W at 123 hours
1800Z (Sep 4) NAVGEM Model Run...
**For Hurricane Danielle... moves northeast with remnant frontal cyclone reaching 51N-26W at 120 hours
**For Tropical Storm Earl... reaches hurricane strength near 24.5N-66.5W at 60 hours... passes just southeast of Bermuda at 108 hours as a larger and potentially intense hurricane... located at 32.5N-60W at 120 hours
**For area of interest #27... organizes into a tropical low near 13N-31W at 60 hours... tropical low located near 16N-45W at 120 hours
**Tropical wave emerges from west coast of Africa at 102 hours... organizes into a tropical low soon after which becomes a tropical cyclone near 15.5N-29W at 150 hours... tropical cyclone located at 17N-31.5W at 168 hours