*******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.**********
...FRIDAY SEPTEMBER 9 2022 5:47 AM EDT...
Danielle while over the cool north Atlantic has finally transtioned into a non-tropical remnant frontal cyclone... see remnants of Danielle section below for more informaion. See Hurricane Earl and area of interest #27 to #29 sections below for updates on additional tropical systems being closely monitored in the Atlantic basin.
Elsewhere... the upper trough currently approaching Hurricane Earl from eastern Canada is expected to amplify into an upper vortex at a further north location. This closes the opportunity for the vortex to produce a subtropical disturbance east of Bermuda and separate from Earl. For the upper vortex currently consolidating in the western Gulf of Mexico... there are no signs of an organized subtropical disturbance developing in the central Gulf and beneath the supportive eastern divergence zone of the vortex.
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 #29 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.
REMNANTS OF DANIELLE... In the cool waters of the open north Atlantic... Hurricane Danielle at last has lost its thunderstorm core and associated warm core... completing transition into a still strong non-tropical remnant frontal cyclone now supported by the eastern divergence zone of the incoming upper vortex to the west. In the next 24 hours ex-Danielle is expected to undergo a counter-clockwise loop turn in a fujiwhara interaction with the frontal low to the west (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. After 24 hours... the upper ridge to the northwest approaching from southern Greenland is expected to push the upper vortex and ex-Danielle east-southeastward into the northeast Atlantic waters north of the Azores and offshore of Portugal and Spain's west coast by day 4. The erratic counter-clockwise loop turn followed by the east-southeast turn will prolong coastal sea swells for the Azores to a few days. By day 4 ex-Danielle will be weakening while having whirled beneath the center of the overhead upper vortex where there is a lack of supporting upper divergence... however ex-Danielle will need time to spin down from its current strength. As such... model runs suggest that ex-Danielle will still be strong enough to push coastal sea swells into the west coast of Portugal and Spain by day 4. Because Danielle is no longer a tropical system... this is my final statement on Danielle on this blog... and statements regarding the impacts of ex-Danielle in the days ahead will be carried on the home page bulletins of this site.
HURRICANE EARL... As expected... the center of Hurricane Earl has passed just southeast of Bermuda. The northwest quadrant of the hurricane has overspread the island with tropical storm force gusts... heavy rain bands... and coastal sea swells. The strongest gust logged by the Bermuda weather service was 50 mph at 22:45 local time late Thursday (weather.bm/observations.asp). Just before making its closest pass to Bermuda... Earl reached a peak category 2 strength of 105 mph maximum sustained winds with the hurricane more recently weakening to category 1 90 mph maximum sustained winds. The lower than expected intensity of Earl is likely due to the disorganized eye which has been and continues to be large and ragged. The amount of thunderstorm bands southwest of the eye is less relative to northeast of the eye... suggesting some light southwesterly shear out ahead of the upper trough approaching from eastern Canada that may have also dampened Earl's intensity. Over the next 24 hours the shear is expected to relax as northerly flow on Earl's northwest quadrant will pull cool air associated with the trough southward... helping the trough amplify into an upper vortex featuring 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 re-intensification of the hurricane is anticipated. Given Earl's current lower intenisty... my udpated intensity forecast no longer calls for Earl to become a major hurricane during this timeframe and instead now simply calls for Earl to re-acquire category 2 105 mph maximum sustained winds. Also noting that as of this writing the NHC intensity forecast is lowered and now barely brings Earl to category 3. Although the favorable interaction with the amplifying upper trough/vortex persists through 48 hours... the hurricane will be moving into waters below 26 deg C and therefore a gradual weakening rate is shown from 24 to 48 hours. By day 3 transition to a still strong non-tropical frontal cyclone is expected to be completed while the storm remains over cooler water.
Models have converged on a more north position of the amplifying upper trough/vortex... allowing Earl to travel more north and less eastward into the waters just offshore of Newfoundland by 48 hours instead of Earl recurving eastward out to sea in the mid-latitude westerlies. While whirling to a position beneath the upper trough/vortex... Earl is expected to meander just offshore of Newfoundland between 48 and 72 hours. The short-term track forecast is nudged north and east due to the current initial position of the hurricane... with the 48 and 72 hour portion of the track adjusted notably closer to Newfoundland in lieu of the latest model consensus. In the longer range as the upper trough/vortex shifts east as a typical mid-latitude feature... the remnant frontal cyclone of Earl is also expected to shift east while also beginning to weaken while trapped beneath the center/axis of the upper trough/vortex where upper divergence is lacking.
Regarding impact to land areas:
(1) For Bermuda... tropical storm conditions and coastal sea swells are expected to decrease today as the hurricane continues moving northeastward and away from the island.
(2) The medium-range forecast track for Earl and its remnant frontal cyclone has shifted closer to Newfoundland. Strong coastal sea swells for Newfoundland... with gusty winds over southeastern Newfoundland... are expected for a prolonged period on Sunday and Monday as the storm motion meanders. I recommend interests in southeastern Newfoundland use today and Saturday to prepare for likely gale force conditions.
(3) Given the shift in the medium and long term forecast track for Earl and its remnant frontal cyclone... ex-Earl is no longer expected to add to ex-Danielle's northeast Atlanitc and Azores coastal sea swells.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 9)... 90 mph maximum sustained wind hurricane centered just southeast of Bermuda at 31.3N-63.7W
IOH 24 Hr Forecast (0000Z Sep 10)... 105 mph maximum sustained wind hurricane centered in the open central Atlantic at 36N-57.5W
IOH 48 Hr Forecast (0000Z Sep 11)... 85 mph maximum sustained wind hurricane transitioning into a remnant frontal cyclone while centered just southeast of Newfoundland at 45N-51W
IOH 72 Hr Forecast (0000Z Sep 12)... Non-tropical remnant frontal cyclone centered just southeast of Newfoundland at 45N-51W
AREA OF INTEREST #27...The vigorous tropical wave of low pressure that has recently moved west-northwest into the central Atlantic continues to feature a broad low pressure spin. The center of rotation continued to consolidate further to the northwest than I previously anticipated while now located near 19.5N-43.5W as of this writing. The west-northwest track is expected to continue while this system angles toward the surface ridge weakness currently being produced by Hurricane Earl. This weakness will remain open as the upper trough to interact with Earl will have a large eastern divergence zone that will keep surface pressures low to the south of Earl. As such by the later part of the forecast period... a complete north turn into the ridge weakness is expected.
Regarding the favorability for tropical cyclone formation of this disturbance... that picture has continued to become murky due to the nearby shearing upper trough to the west which is pushing the strongest thunderstorm activity to the northeast of the swirl center of rotation of this disturbance. Although the upper trough has recently amplified into a vortex due to the strong outflow of Hurricane Earl... the shear remains elevated and disruptive as this system is too close to the upper vortex. While citing satellite scans of surface wind... the NHC in their tropical weather outlook on Thursday noted that the circulation of this disturbance has developed tropical storm force winds in the thunderstorm activity sheared off to the northeast of the center... however this system is not upgraded to a tropical storm as the thunderstorm activity is displaced too far from the center. Over the next 24 hours the shear levels will remain the same... and it would not surprise me if an abruptly-forming thunderstorm flare near the center upgrades this system to a tropical storm. As a result I keep 60% odds of tropical cyclone formation for the short-term (noting the NHC has recently lowered odds of development to 40% as of this writing... I am just not there quiet yet). After 24 hours... I trim down odds of development as the forecast track brings this system even closer to the shearing upper southwesterlies associated with the nearby upper vortex... with the southwesterlies then maintained by the south side of the upper trough interacting with Earl which will absorb the upper vortex. My ramp-down rate in this update is faster as I have made another north and west adjustment even closer to the shearing upper southwesterlies due to the the current position of the center of rotation. The faster ramp-down rate brings development odds to 0% by 96 hours... and this is when the updated outlook below is ended.
IOH 24 Hr Outlook (0000Z Sep 10)...60% chance of tropical cyclone formation (central Atlantic near 21N-48.5W)
IOH 48 Hr Outlook (0000Z Sep 11)...20% chance of tropical cyclone formation (central Atlantic near 22.5N-52.5W)
IOH 72 Hr Outlook (0000Z Sep 12)...15% chance of tropical cyclone formation (central Atlantic near 26.5N-52W)
IOH 96 Hr Outlook (0000Z Sep 13)...0% chance of tropical cyclone formation (central Atlantic near 31N-50W)
AREA OF INTEREST #28...The center of rotation associated with the tropical wave of low pressure currently in the far eastern tropical Atlantic is located near 8.5N-24W as of this writing. The rotation currently lacks thunderstorm activity with only one band currently present west of the center... and a swirl of low clouds defining the remainder of the circulation. This disturbance is expected to continue steadily westward across the eastern tropical Atlantic and around the south side of the current eastern Atlantic surface ridge. The forecast track points are adjusted westward to account for the current position of the center of rotation. In the longer range as Earl and its eventual remnant cyclone eventually weaken... the associated surface ridge weakness closes by days 4 and 5 which should allow this system to continue westward.
Regarding development potential...this disturbance will be in an environment of low shear and upper outflow beneath the tropical upper ridge in the region. However given the reduction of the thunderstorm activity in the circulation over the last 24 hour or so... perhaps a sign of the negative effects of the dry Saharan air lurking to the north... and a reduction in computer model support showing development... I have lowered my peak odds of tropical cyclone formation to 40%. However this remains above the NHC tropical weather outlook for this system as of this writing as the swirl of clouds defining the circulation remains well-defined.
IOH 24 Hr Outlook (0000Z Sep 10)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 9.5N-28.5W)
IOH 48 Hr Outlook (0000Z Sep 11)...25% chance of tropical cyclone formation (eastern tropical Atlantic near 10N-33.5W)
IOH 72 Hr Outlook (0000Z Sep 12)...35% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-38.5W)
IOH 96 Hr Outlook (0000Z Sep 13)...40% chance of tropical cyclone formation (central tropical Atlantic near 11N-43.5W)
IOH 120 Hr Outlook (0000Z Sep 14)...40% chance of tropical cyclone formation (central tropical Atlantic near 11.5N-48.5W)
AREA OF INTEREST #29... Satellite image highlighting a central Africa tropical wave of low pressure expected to move into the eastern tropical Atlantic in 4 to 5 days... image taken at 0600Z:
Satellite imagery suggests a tropical wave of low pressure is currently located over central Africa in the vicinity of 10.5N-10E. Model runs insist that once this tropical wave reaches the eastern tropical Atlantic that it has development potential. In addition the tropical upper ridge in the region featuring favorable low shear and upper outflow is expected to persist. Therefore I have added this tropical wave as an area of interest for Atlantic tropical development for the days ahead. I have set low 10% odds of development for day 5 as the wave will have just entered the eastern tropical Atlantic...and it is generally rare for tropical cyclone to occur in the first 24 hours of an African wave's entry into water. Odds could be raised in future updates as the 5-day forecast range will have a longer span over water... especially if models continue to suggest development potential with this wave.
IOH 24 Hr Outlook (0000Z Sep 10)...0% chance of tropical cyclone formation (central Africa near 10.5N-5E)
IOH 48 Hr Outlook (0000Z Sep 11)...0% chance of tropical cyclone formation (western Africa near 10.5N-1W)
IOH 72 Hr Outlook (0000Z Sep 12)...0% chance of tropical cyclone formation (western Africa near 11N-7W)
IOH 96 Hr Outlook (0000Z Sep 13)...0% chance of tropical cyclone formation (western Africa near the eastern tropical Atlantic coast near 11N-13W)
IOH 120 Hr Outlook (0000Z Sep 14)...10% chance of tropical cyclone formation (offshore of western Africa near 11.5N-19W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Sep 8) CMC Model Run...
**For Hurricane Earl... passes just southeast of Bermuda between 12 and 18 hours... afterwards accelerates northeast and reaches 46N-44W at 120 hours as a remnant frontal cyclone
**For area of interest #27... tropical low dissipates near 24N-52.5W at 66 hours
**For area of interest #28... tropical wave gradually coalesces into a tropical low which reaches 18N-52.5W at 168 hours.
**For area of interest #29... tropical wave emerges from west coast of Africa at 96 hours and organizes into a tropical low shortly thereafter... tropical cyclone formation suggested south of the Republic of Cabo Verde Islands at 132 hours... tropical cyclone located at 15.5N-34W at 168 hours.
1200Z (Sep 8) ECMWF Model Run...
**For Hurricane Earl... passes just southeast of Bermuda in next 24 hours...afterwards accelerates northeast and reaches 45N-43W at 120 hours as a remnant frontal cyclone
**For area of interest #27... tropical low dissipates near 23N-51W at 48 hours
**For area of interest #29... tropical wave emerges from west coast of Africa at 96 hours... organizes into a tropical low south of the Republic of Cabo Verde Islands at 120 hours... tropical low located at 14N-36.5W at 168 hours
0000Z (Sep 9) GFS Model Run...
**For Hurricane Earl... passes just southeast of Bermuda at 6 hours... afterwards accelerates northeast and reaches 46.2N-40.2W at 120 hours as a remnant frontal cyclone
**For area of interest #27... tropical low weakens to a trough near 20N-47.5W at 21 hours... trough dissipates near 25N-52W at 48 hours.
**For area of interest #29... tropical wave emerges from west coast of Africa at 93 hours... organizes into a tropical low near 12N-22.5W at 111 hours... however no development suggested in long term as tropical low later dissipates.
1800Z (Sep 8) NAVGEM Model Run...
**For Hurricane Earl... passes just southeast of Bermuda at 6 hours... afterwards accelerates northeast and reaches 44.5N-41W at 120 hours as a remnant frontal cyclone
**For area of interest #27... tropical low dissipates near 22.5N-51W at 60 hours
**For area of interest #29... tropical wave emerges from west coast of Africa at 102 hours and organizes into a tropical low shortly thereafter... develops into a tropical depression while moving into the Republic of Cabo Verde Islands at 150 hours... depression located over the northwestern islands at 168 hours.