BIRDSEYE VIEW POSTS

Since 2012 on the now retired Weather Underground blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at IOHurricanes@outlook.com 

 
 
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MY 2022 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #111

Updated: Sep 26

*******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 SEPTEMBER 25 2022 4:30 AM EDT...

Tropical Storm Ian continues churning in the Caribbean Sea. This system is expected to bring impacts from the Cayman Islands to parts of the southeastern United States in the days ahead while at risk of strengthening into a strong hurricane... see Ian section below for more details.


Tropical Storm Gaston survives with renewed upper air support while moving westward away from the Azores... see Gaston section below for more information.


Hermine weakens to a tropical depression offshore of northwestern Africa... see Hermine section below for more information.


In addition to the above systems... also monitoring multiple areas of interest as follows:

(1) See area of interest #33 section below for information on a tropical low pressure area expected to meander aimlessly in the eastern and central tropical Atlantic over the next few days. This feature also has potential to become a tropical cyclone.

(2) A tropical wave of low pressure has entered the far eastern tropical Atlantic from the west coast of Africa. Although it is producing a distinct area of thunderstorms... development is not anticipated as it competes for surface inflow with the broad circulation of Hermine.

(3) Another tropical wave of low pressure is currently over western Africa in the vicinity of 2.5W longitude. The additional above-mentioned wave just offshore of western Africa will be moving slowly while caught in weak steering in a broad low pressure area to expand around Hermine and its remnants (see area of interest #33 section below for the ingredients that will make that broad low pressure area). It is possible this wave will therefore catch up to the offshore wave... resulting in a broad disturbance offshore of Africa in a couple of days. And with Hermine expected to be dissipated by that time... this disturbance will have less competition to develop. Upper-level winds will also be favored for development as the tropical upper ridge with low shear and upper outflow persists in the region. Will add a new area of interest in this region if necessary in future updates.


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 #33 as the other numbers were used 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.


TROPICAL STORM GASTON...Due to an ongoing lack of thunderstorms... the shallow circulation of Gaston weakened further to 45 mph maximum sustained winds while exiting the western Azores on a westward turn... while steered by the stout Atlantic surface ridge to the north. Despite remaining over below-26 deg C waters... Gaston has found new life while aligning with the supportive eastern divergence zone of a north Atlantic upper trough that moved in from the west. Specifically the tropical storm has re-strengthened to 50 mph maximum sustained winds while featuring an impressive thunderstorm mass on the north side of its circulation. Models such as the GFS in prior days have been hinting at Gaston reviving in an interaction with this upper trough... however I did not pay much attention as the upper trough would soon speed southeastward over top and past Gaston such that I thought it wouldn't spend enough time with Gaston to help it. Also noting Gaston lifted a bit more north in its westward track... recovering to 38.6N latitude instead of staying further south at 38N. This is a sign that Gaston has regained a tall enough structure to couple with the upper southerly flow on the east side of the upper trough.


Due to a strong warm core north Atlantic upper ridge being pump up by the warm southerly flow on the east side of ex-Fiona's circulation... the upper trough interacting with Gaston will soon zoom southeastward and join the current western European upper trough in making a large upper trough/vortex feature to the southeast of Gaston. Because Gaston has angled northward it now looks to escape the unfavorable upper convergence zone that will setup on the northwest side of this feature. Instead while continuing westward around the stout Atlantic surface ridge... Gaston at 24 hours may find a pocket of supporting split flow upper divergence between the northwest corner of the upper trough/vortex feature and southwest quadrant of the north Atlantic upper ridge. By 48 hours... an additional cell of warm upper ridging will develop in the northwest Atlantic in the warm sector of the eastern US frontal system (same system expected to coax Ian northward toward the eastern Gulf of Mexico). This northwest Atlantic upper ridge will cut-off part of ex-Fiona's upper trough and send it toward Gaston... with additional split flow upper divergence possible over Gaston and in between the southerly flow ahead of this upper trough feature and northerly flow streaming into the upper trough/vortex to the southeast of Gaston. Convergence on the west side of this upper trough feature will expand the steering Atlantic surface ridge westward such that Gaston should not buckle further north at 48 hours. Given that Gaston could be in a pocket of split flow upper divergence through 48 hours... I have opted to now keep Gaston as a tropical storm for 48 more hours in my updated forecast. Strength-wise... I keep Gaston's current strength as this is a delicate situation where Gaston could either gain more strength or go on to weaken from here... and so it wouldn't surprise me if in 24 hours from now Gaston is stronger or weaker than what I forecast. This is because any deviation in the forecast track could cause Gaston to lose alignment with the pocket of split flow upper divergence and weaken... or alternatively Gaston manages to stay aligned with the pocket of upper divergence and strengthen further. After 48 hours... the northwest Atlantic upper ridge cell sends the upper trough feature from ex-Fiona further southeast... joining the sprawling upper trough/vortex feature southeast of Gaston. This should place Gaston below upper northeasterly convergent flow between the northwest side of the upper trough/vortex feature and southeast side of the northwest Atlantic upper ridge... with the convergent nature of the upper flow suppressing Gaston. Thus I project weakening at 72 hours. A slight south angle in the forecast track between 48 and 72 hours is shown as Gaston could bend more south while coupled to the upper northeasterly flow... just before it weakens to a shallow feature.


Any coastal swells being generated by Gaston at the Azores should gradually decline over the next day or so as Gaston continues its westward exit from the region.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (0000Z Sep 25)...50 mph maximum sustained wind tropical storm centered west-southwest of the western Azores at 38.6N-33.4W

IOH 24 Hr Forecast (0000Z Sep 26)...50 mph maximum sustained wind tropical storm centered in the eastern Atlantic at 38.9N-37.5W

IOH 48 Hr Forecast (0000Z Sep 27)...50 mph maximum sustained wind tropical storm centered in the central Atlantic at 38.9N-42W

IOH 72 Hr Forecast (0000Z Sep 28)...Remnant low centered at 37.5N-47.5W


TROPICAL STORM IAN...Ian remains a young tropical storm still gathering itself in the central Caribbean Sea. The surface swirl which initially lifted more northward toward Fiona's surface ridge weakness has reversed course and regenerated southwestward closer to its thunderstorms and associated latent-heat release driven upper outflow where surface pressures fell. As of 11 PM EDT... the re-generated surface circulation was reported by NHC aircraft reconnaissance to be elongated northwest-to-southeast. The thunderstorm canopy has evolved into a well-organized mid-level rotation which contains moderate instead of strong thunderstorms on infrared satellite as of this writing.


Just west of Ian is a patch of northwestern Caribbean upper vorticity. And several hundred miles to the northwest and over North America... an upper trough in the vicinity of Lake Superior and upper trough over western Canada are in the process of merging into a potent upper trough that will settle over the eastern US... the eastern divergence zone of which will generate a surface ridge weakness. Ian over the next 24 hours is expected to move northwest across the western Caribbean while pulled by the upper southerly flow on the east side of the patch of upper vorticity and also while moving toward the developing eastern US surface ridge weakness. A northward turn directly toward the weakness is then anticipated by 48 and 72 hours which should bring Ian across western Cuba and into the eastern Gulf of Mexico. Models then agree that the eastern US upper trough and associated surface ridge weakness lift northeastward and away... trapping Ian south of a potent surface ridge that build under the western convergence zone of the amplified departing upper trough. In addition the eastern US upper trough is expected to leave behind a cut-off trough over the southeastern US. For the eastern US upper trough... models now show the trough and associated surface ridge weakness not having as far south of a reach. Combined with the fact that Ian is already southwest of my previous forecast track due to the aforementioned center reformation... I have adjusted the long range track to be further south and west in the long range with Ian to be more influenced by the potent surface ridge that builds over the eastern US and less influenced by the upper trough and its surface ridge weakness to be located a little more toward the north and further from Ian. Ian's northward speed is expected to slow in the 4+ day timeframe...a combination of Ian being embedded in steering upper southerly flow ahead of the aforementioned leftover cut-off upper trough while the potent surface ridge resists Ian's northward progress. The total shift in the long range track is about 2.5 degrees longitude... aligning Ian's center to barrel northward toward the Florida panhandle instead of tracking into the Florida Keys and west coast of the Florida peninsula. However it is possible for the forecast track to shift again... for example the models change their mind and revert back to showing a more southward-digging eastern US upper trough... or if the current patch of upper vorticity west of Ian shunts the currently organized mid-level spin and thunderstorms further east which causes the still-formative surface center to regenerate again further east... in which case the forecast track would shift back east.


Regarding the intensity forecast... although Ian is currently on par with my previous forecast track the initial part of my updated intensity forecast is lowered. This is because Ian's southwestward regeneration places it closer to the patch of northwestern Caribbean upper vorticity such that the western outflow of Ian could be moreso blocked by this feature. This cold core upper vorticity feature should be dissipated by 48 hours while remaining cut-off from high-latitude cold air... and potential rapid strengthening of Ian is anticipated. I eventually do catch up to my previous intensity forecast and bring Ian to category 3 hurricane status for the timeframe that is now 72 hours away... because the eastern US upper trough and its shearing upper westerly winds are expected to be further north and away from Ian as discussed in the prior paragraph. My peak category 3 intensity is a notch lower than the NHC latest forecast which predicts category 4 as of this writing... as I am not ready yet to make that call with Ian still needing to get its act together by having the surface circulation consolidate and become more circular... and stay aligned with its currently-organized mid-level spin... and also Ian in the next 24 hours may have challenges while fighting with the northwest Caribbean patch of upper vorticity. My longer range weakening trend is notably slower as the updated forecast track reduces land interaction with the Florida peninsula... and as models have trended with a more amplified and further west version of the leftover cut-off upper trough over the southeast US such that the upper flow over Ian is more southerly... more aligned with the forecast track direction such that lower wind shear is implied. However some shear that weakens Ian slowly is anticipated as Ian slows down its northward speed and falls behind the upper southerly wind speed.


Regarding impacts to land areas:

(1) Because Ian re-generated southwestward over the last 24 hours... it remains on track to clear Jamaica despite some growth in the storm size. Coastal sea swells are possible for Jamaica over the next couple of days... especially if Ian strengthens as forecast.

(2) I recommend interests in the Cayman Islands should finish preparing for tropical storm to hurricane force conditions (heavy rain and wind with damage potential... coastal surf) to be completed by noon local time later today. Although the westward shift in the forecast track suggests a lower likelihood of wind impacts... reference the above forecast track discussion where a shift back east in the forecast track could still happen... remain on guard.

(3) Western Cuba will see tropical storm force conditions (heavy rain with flooding potential... gusty winds with some damage potential... and coastal surf) from Monday night to Tuesday night. Life-threatening coastal storm surge and wind is possible for the Isle of Youth and western Cuban mainland in the vicinity and west of the isle should Ian in fact intensify as currently forecast. I recommend preparations for Ian should be finished here by midday Monday.

(4) Coastal sea swells for Honduras... Belize... and especially Qunitana Roo province of the Yucatan peninsula due to the west shift in Ian's forecast track. Any additional west shift in the forecast track could expose northern Quintana Roo and Cancun to tropical storm force winds and heavy rainfall on Monday evening.

(5) Although the forecast track has shifted west... the Florida peninsula and Florida Keys should remain on-guard for a possible shift back east. Heavy rainfall with flash flooding potential will be a hazard regardless of the more west or east track... especially as the forward speed of Ian slows later in the forecast period. Coastal surf for the Keys and west coast of the peninsula is also expected regardless of a further west or east track. Tropical storm to hurricane force winds and more damaging coastal storm surge for the Keys and west half of the peninsula is possible if the forecast track shifts back east. Tropical storm force winds are possible for the east half of the peninsula should the forecast track shift back east. Timing of impacts is Tuesday and Wednesday... be ready to prepare if needed tomorrow night and Monday.

(6) The Florida panhandle should monitor the progress of Ian for tropical storm to hurricane force conditions to arrive in the Wednesday or Thursday timeframe (heavy rain... damaging wind potential... and coastal surf and storm surge). Due to the slow forward motion of the storm forecast... coastal surf and wind impacts could be prolonged... with significant flash flooding from a prolonged period of heavy rainfall possible.

(7) A prolonged period of heavy rainfall with significant flash flooding is also possible for Georgia and Alabama by Thursday. The southern parts of both states have potential to see tropical storm force with damage potential... however a more east track would aim the tropical storm conditions toward southern Georgia... and a more west track would aim the tropical storm conditions toward southern Alabama.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (0000Z Sep 25)...50 mph maximum sustained wind tropical storm centered south-southeast of Jamaica at 14.7N-77.7W

IOH 24 Hr Forecast (0000Z Sep 26)...60 mph maximum sustained wind tropical storm centered west-southwest of Jamaica and south of the Cayman Islands at 16.8N-81.5W

IOH 48 Hr Forecast (0000Z Sep 27)...90 mph maximum sustained wind hurricane centered south-southwest of the Isle of Youth of western Cuba at 19.5N-83W

IOH 72 Hr Forecast (0000Z Sep 28)...120 mph maximum sustained wind major hurricane centered just north of the western tip of Cuba at 22.5N-85W

IOH 96 Hr Forecast (0000Z Sep 29)...115 mph maximum sustained wind major hurricane centered in the eastern Gulf of Mexico at 26N-85W

IOH 120 Hr Forecast (0000Z Sep 30)...110 mph maximum sustained wind hurricane centered offshore of the Florida panhandle at 28.5N-85W


TROPICAL DEPRESSION HERMINE... Over the last 24 hours... Hermine which is located offshore of northwestern Africa looks increasingly less like a tropical cyclone and more like a typical mid-latitude broad and sheared surface low pressure area supported by the eastern divergence zone of broad upper troughing in the region. The NHC has downgraded Hermine to a tropical depression... and I am willing to debate if its even worth calling it a tropical depression at this point. As such I forecast Hermine to be downgraded into a remnant low in the next 24 hours due to ongoing southwesterly shear being applied by the upper troughing and also due to the water temps below 26 deg C which Hermine is now located over. The slight east lean in the forecast track that I have is due to the models showing the upper southerly flow switching to a more westerly direction over the next 24 hours.


The upper southerly flow is transporting Hermine's tropical moisture north-northeastward into the Canary Islands and into Morocco. The divergence on the east side of the upper troughing is also helping to make cloudiness and rainfall from this moisture. Unusual amounts of rain may occur in these areas with this setup over the next day or so... flash flooding cannot be ruled out.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (0000Z Sep 25)...35 mph maximum sustained wind tropical depression centered in the eastern Atlantic at 22.9N-20.3W

IOH 24 Hr Forecast (0000Z Sep 26)...Remnant low centered in the eastern Atlantic at 25N-19.5W


AREA OF INTEREST #33...The wandering tropical low pressure spin in the eastern Atlantic has lost thunderstorm activity. Based on a band of beige tint just to the northeast in true-color visible satellite (before sunset)... this appears to be due to ingestion of dry Saharan air. The west drift of this tropical low pressure has switched to a northward direction... a sign that this system is in the grip of the broad circulation of Hermine to the northeast. The upper trough currently interacting with Gaston... the shortwave upper trough over the eastern Azores... and the current western Europe upper trough are expected to merge into a substantial upper trough whose large eastern divergence zone will expand on the broad low pressure area associated with Hermine. My updated forecast track has an aimless north drift/stalling motion of the tropical low pressure of interest through 72 hours while this system is stuck in a saddle point of conflicting steering between the broad low pressure area ot the northeast and Atlantic surface ridge that has been trying to push this system west. The cold core substantial upper trough that will be generating the broad low pressure area to the northeast is expected to weaken by 96+ hours while remaining isolated from cold air thanks to the ongoing warm core north Atlantic upper ridge. The upper ridge will also break the weakening trough into a series of upper vortices that retrograde southwestward around the ridge. As the cold core upper trough and associated surface low pressure area to the northeast weakens... the Atlantic surface ridge will finally try to push this system west by 96+ hours. However a north angle is depicted in the developing west track as the surface ridge will develop a weakness to the northwest as a frontal system over the eastern US moves offshore. And should this system in fact becoming a stronger/taller tropical cyclone... the upper southwesterly flow ahead of one of the decaying upper vortices would also coax this system on a more northward track.


Due to this system's current lack of thunderstorms... I retain a low 30% peak odds of tropical cyclone formation in the 5-day forecast period. I currently do not expect a total defeat of this system from dry Saharan air as the broad low pressure area to the northeast may slow the westward transport of additional Saharan air toward this system... which is why I also did not lower the peak odds. However I have lowered the short-term odds.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (0000Z Sep 26)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-37W)

IOH 48 Hr Outlook (0000Z Sep 27)...20% chance of tropical cyclone formation (eastern tropical Atlantic near 13.5N-37W)

IOH 72 Hr Outlook (0000Z Sep 28)...30% chance of tropical cyclone formation (eastern tropical Atlantic near 13.5N-37W)

IOH 96 Hr Outlook (0000Z Sep 29)...30% chance of tropical cyclone formation (eastern troipcal Atlantic near 14.5N-38.5W)

IOH 120 Hr Outlook (0000Z Sep 30)...30% chance of tropical cyclone formation (central tropical Atlantic near 16N-41W)


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)


1200Z (Sep 24) CMC Model Run...

**For Tropical Storm Gaston... weakens to a remnant low near 38.5N-39.5W at 48 hours... remnant low weakens to a trough near 36N-45.5W at 78 hours.

**For Tropical Storm Ian... passes west of the Canary Islands at 60 hours... strengthens into a hurricane while moving over the west tip of Cuba at 78 hours... located in the eastern Gulf of Mexico at 26N-85.2W at 120 hours.

**For Tropical Depression Hermine... weakens to a remnant low at 18 hours near 22N-21.2W at 18 hours... remnant low turns west and weakens to a trough near 24N-24.5W at 54 hours.

**For area of interest #33... tropical low drifts north and then stalls near 14N-37.5W at 42 hours... the remnant trough of Hermine causes this system to resume a north-northeast drift at 84 hours... tropical low reaches 18N-36.5W at 126 hours.

**Tropical wave of low pressure emerges from western Africa at 126 hours... organizes into a small tropical low which reaches 12.5N-25W at 168 hours.


1200Z (Sep 24) ECMWF Model Run...

**For Tropical Storm Gaston... maintains strength through 24 hours while reaching 39.5N-35W at 24 hours... weakens to a remnant low afterwards with the remnant low moving west-southwest... the remnant low weakens to a trough near 36N-51W at 96 hours.

**For Tropical Storm Ian... passes just west of the Cayman Islands between 24 and 48 hours... strengthens into a hurricane which moves north across western Cuba just after 72 hours... center passes just west of the Florida Keys at 96 hours... center moves into Tampa Bay Florida at 120 hours.

**For Tropical Depression Hermine... continues north and reaches 25N-20W at 24 hours... weakens to a remnant low by 48 hours while stalling near 26N-20W... remnant low turns west and weakens to a trough near 26N-23.5W at 72 hours.

**For area of interest #33... tropical low drifts north and stalls near 13.8N-36W at 24 hours... after 72 hours the tropical low drifts north-northwest and weakens to a trough near 15.5N-39.8W at 120 hours.


1800Z (Sep 24) GFS Model Run...

**For Tropical Storm Gaston... begins to weaken at 33 hours while located near 38.5N-39W at 33 hours... weakening remnant low opens to a trough near 36N-48.5W at 78 hours.

**For Tropical Storm Ian... begins to briskly strengthen further to the southwest and and becomes a compact hurricane offshore of northeastern Honduras near 17N-81.8W at 39 hours... curves north-northwest and center reaches the west tip of Cuba at 72 hours... continues north-northwest with hurricane centered offshore of the Florida panhandle near 28.5N-85.5W at 120 hours.

**For Tropical Depression Hermine... weakens to a remnant low near 24.5N-19.8W at 30 hours... remnant low turns on a westward drift and opens to a trough near 25N-21.2W at 57 hours.

**For area of interest #33... tropical low remains generally stationary through 93 hours after which time it begins to drift north-northwest... reaches 26.2N-39.5W at 120 hours.


1800Z (Sep 24) NAVGEM Model Run...

**For Tropical Storm Gaston... weakens to a remnant low near 37N-38.8W at 42 hours... remnant low opens to a trough near 35.5N-37.5W at 66 hours

**For Tropical Storm Ian... strengthens to a hurricane west of the Cayman Islands at 48 hours... as a potentially intense hurricane the center passes between the west tip of Cuba and northeastern Yucatan peninsula at 66 hours... continues north-northwest across the central Gulf of Mexico with center reaching 27.5N-89W at 120 hours.

**For Tropical Depression Hermine... weakens to a remnant low near 24N-21W at 36 hours... opens to a trough near 25N-21W at 48 hours.

**For area of interest #33... tropical low remains generally stationary through 66 hours after which time it begins to drift northeast... tropical low dissipates near 15N-34.5W at 102 hours.

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