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 #118

Updated: Oct 4

*******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 OCTOBER 2 2022 5:05 PM EDT...

The Atlantic tropics remain active as we move into early October... with multiple areas of interest being monitored for signs of future tropical development:

(1) See area of interest #34 section below for an update on the tropical disturbance in the eastern Atlantic.

(2) The previously dormant tropical wave of low pressure in the central tropical Atlantic has quickly developed and become better organized while finding an area of favorable upper-level winds... see area of interest #35 section below for more information.

(3) The broad frontal low pressure area currently offshore of the United States mid-Atlantic coast has absorbed the remnants of Ian. A frontal cyclone is expected to develop within the broad low pressure area and potentially acquire tropical characteristics... see area of interest #36 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 areas of interest in this blog post are designated #34 to #36 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.


AREA OF INTEREST #34...Continuing to monitor the eastern Atlantic for signs of tropical development as follows:


Warm southerly flow ahead of the current broad frontal low pressure system offshore of the mid-Atlantic United States is expected to maintain the current amplified upper ridge over the western Atlantic. In turn the amplified upper ridge is expected to send the current north Atlantic upper trough southeastward into the eastern Atlantic where it will then be cut-off from the mid-latitude westerlies by the upper ridge. At the surface...a tropical wave of low pressure currently passing 30W longitude and an additional tropical wave approaching from far western Africa appear to be merging into a broad tropical low pressure area in the vicinity of 10N-25W. The eastern divergence zone of the aforementioned eastern Atlantic cut-off upper trough is expected to weaken the south side of the steering Atlantic surface ridge such that the broad tropical low pressure area is expected to float northwestward instead of continuing westward. The broad tropical low is also itself expected to transition into a system supported by the eastern divergence zone of the cut-off upper trough. I have lowered short-term odds of tropical cyclone formation as the broad system will need time to consolidate. However I maintain longer term odds of 50% odds as there remains some computer model support showing development of this system. This is lower than the NHC's 70% as of this writing as some southwesterly shear to be induced by the cut-off upper trough and the potential that the broad system never consolidates are negative factors for this area of interest.

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

IOH 24 Hr Outlook (1200Z Oct 3)...0% chance of tropical cyclone formation (eastern tropical Atlantic near 11N-27W)

IOH 48 Hr Outlook (1200Z Oct 4)...10% chance of tropical cyclone formation (eastern tropical Atlantic near 12.5N-30W)

IOH 72 Hr Outlook (1200Z Oct 5)...40% chance of tropical cyclone formation (eastern tropical Atlantic near 15.5N-31W)

IOH 96 Hr Outlook (1200Z Oct 6)...50% chance of tropical cyclone formation (eastern tropical Atlantic near 18N-32.2W)

IOH 120 Hr Outlook (1200Z Oct 7)...50% chance of tropical cyclone formation (eastern Atlantic near 20N-35W)


AREA OF INTEREST #35...The cool core central Atlantic string of upper vorticity has decayed into a vortex near 22.5N-51.5W and a remnant area of upper vorticity in the central Caribbean while remaining cut-off from high-latitude cold air thanks to the building western Atlantic upper ridge (see area of interest #34 section on what is bolstering the upper ridge). Once the remnant area of Caribbean upper vorticity dissipates... a northern Caribbean upper ridge axis is expected to solidify... resulting in an area of split flow upper divergence between the southeast side of the upper ridge axis and southwest side of the aforementioned central Atlantic upper vortex. The once dormant central Atlantic tropical wave of low pressure was expected to later become enhanced by the split flow upper divergence... instead the wave has markedly becomes enhanced over the last 24 hours as the southeast side of the upper vortex is enhancing the poleward upper outflow of the wave. The tropical wave currently features widespread thunderstorm squalls sufficiently organized to suggest that a low pressure spin is developing near 10N-47.5W. The tropical wave has been introduced into the NHC tropical weather outlook... and this marks the thirty-fifth Atlantic tropical area of interest I have tracked on this blog this year.


The forecast track in the outlook below suggests a slight northward angle in track toward the surface ridge weakness associated with area of interest (AOI) #36. By day 5 the ridge weakness closes as the low pressure area associated with AOI #36 lifts out to the northeast... and the forecast track of this system is therefore bent more westward by the end of the 5-day forecast period. I already suggest short-term elevated 25% odds of tropical cyclone formation due to the brisk progress the tropical wave has made in organizing. However the odds are capped at the 25% mark through 48 hours as the tropical wave moves toward the south side of the aforementioned upper vortex where it may encounter some shear or northern upper outflow suppression. At 72+ hours I raise development odds to 40% and then 50% as the wave encounters split flow upper divergence in the eastern Caribbean as remarked in the previous paragraph. Note these development odds are higher than the NHC's current 30% as I am giving weight to the currently healthy development that tropical wave has already exhibited. However I have not selected odds above 50% in this update as not all models agree on developing the wave in the 5-day window... for example the ECMWF and CMC wait to develop the wave toward day 7 as it nears Central America.


Regardless of tropical cyclone formation or not... chances have increased for heavy rainfall and gusty winds for the southern Lesser Antilles for late Tuesday and into Wednesday.

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

IOH 24 Hr Outlook (1200Z Oct 3)...25% chance of tropical cyclone formation (central tropical Atlantic near 11N-52W)

IOH 48 Hr Outlook (1200Z Oct 4)...25% chance of tropical cyclone formation (east of the southern Lesser Antilles near 12N-57W)

IOH 72 Hr Outlook (1200Z Oct 5)...40% chance of tropical cyclone formation (southern Lesser Antilles near 13N-61.5W)

IOH 96 Hr Outlook (1200Z Oct 6)...50% chance of tropical cyclone formation (eastern Caribbean Sea near 14N-65.5W)

IOH 120 Hr Outlook (1200Z Oct 7)...50% chance of tropical cyclone formation (central Caribbean Sea near 14.5N-69.5W)


AREA OF INTEREST #36...A southward-digging upper trough over eastern Canada and upper trough over the eastern United States have merged... with the large-scale eastern divergence zone of the merged upper trough resulting in a broad frontal low pressure area currently located just offshore of the United States mid-Atlantic coast. Ian's remnant low which had been hanging out near the North Carolina/Virginia border has lost its identity within the west side of the broad frontal low pressure. The warm sector of another frontal low pressure to transit rapidly east from its current northwestern Canada position will build a southern Canadian upper ridge that passes north of the upper trough... with this upper ridge now forecast to cut-off the southern part of the United States upper trough into a vortex in the vicinity of the North Carolina/Virginia border over the next 48 hours. In turn increasing divergence on the east side of the materializing upper vortex is forecast to generate a surface frontal cyclone just offshore of the US mid-Atlantic region. From 48 to 72 hours the frontal cyclone is expected to then whirl in a counter-clockwise loop arc and into the center of the upper vortex as a maturing frontal cyclone typically does. Due to the de-stabilizing cold temperatures of the upper vortex (200 mb heights near 1200 dekameters) and close proximity of the warm Gulf stream waters in the vicinity of Cape Hatteras and points south... there is potential for the frontal cyclone to build thunderstorms and acquire tropical characteristics around the 72-hour mark. Therefore I have initiated yet another area of interest in the region... and this marks the thirty-sixth tropical area of interest I have tracked on this blog this year.


For the 72-hour window...I set odds of subtropical cyclone formation at a low 20% as the ECMWF and NAVGEM models suggest the frontal cyclone remains oblong instead of circular which will prevent a well-defined center needed for subtropical cyclone status. Also the window for subtropical development is short lived as soon after... by 96 hours... the overhead upper vortex begins to race to the northeast which will ultmately leave behind the frontal cyclone and cause it to weaken beneath the western convergent side of the departing upper vortex. Note the forecast track has the frontal cyclone accelerate east-southeast under the west-northwesterly flow of the southwest quadrant of the departing upper vortex...and also the southwest quadrant of a new broad frontal low to be generated by the eastern divergent side of the departing upper vortex. The acceleration of the upper vortex is expected as mid-latitude upper westerly flow in the region markedly increases with the approach of the current northwest US upper vortex and the next southward digging upper trough to approach from western Canada.


Regardless of whether or not the forecast frontal cyclone acquires tropical chracteristics... the tight pressure gradient between the north side of the frontal cyclone and south side of ongoing surface ridging to the north will prolong coastal surf for the North Carolina and mid-Atlantic United States coast through the middle part of this week. As the frontal cyclone whirls closer to shore through 48 and 72 hours... expect gusty winds with some damage potential across Delaware... southeastern coastal Maryland... southeastern coastal Virginia... and the northern North Carolina coast in the Monday (tomorrow) to early Wednesday timeframe.

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

IOH 24 Hr Outlook (1200Z Oct 3)...0% chance of subtropical cyclone formation (offshore of the mid-Atlantic United States near 37N-73W)

ION 48 Hr Outlook (1200Z Oct 4)...0% chance of subtropical cyclone formation (offshore southeastern Maryland and Delaware near 37N-73.5W)

IOH 72 Hr Outlook (1200Z Oct 5)...20% chance of subtropical cyclone formation (offshore of the North Carolina/Virginia border near 36.2N-74W)

IOH 96 Hr Outlook (1200Z Oct 6)...0% chance of subtropical cyclone formation (western Atlantic near 35N-70W)


...COMPUTER MODEL SUMMARY...

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


0000Z (Oct 2) CMC Model Run...

**For area of interest #34... tropical wave organizes into tropical low near 13N-27.5W at 48 hours... tropical low moves northwest and then west-northwest and reaches 16.5N-34W at 120 hours.

**For area of interest #35... tropical wave becomes more amplified as it crosses 65.5W longitude in the eastern Caribbean at 90 hours... organizes into a tropical low located just offshore of northern Nicaragua at 168 hours.

**For area of interest #36... frontal cyclone materializes just offshore of northeastern North Carolina near 35.5N-74W at 54 hours... remains in this vicinity through 84 hours while undergoing a small counter-clockwise loop... while establishing a more circular center becomes a potential eastward-shifting subtropical storm near 35.5N-73W at 90 hours... the eastward accelerating circulation weakens to a remnant low located near 36N-65.5W at 120 hours


0000Z (Oct 2) ECMWF Model Run...

**For area of interest #34... tropical wave organizes into tropical low south-southwest of the Republic of Cabo Verde Islands near 11.5N-25.2W at 48 hours... tropical low weakens to a trough near 18.8N-36W at 120 hours.

**For area of interest #35...tropical wave organizes into a broad tropical low east of Nicaragua and near 13N-80W at 168 hours.

**For area of interest #36... frontal cyclone materializes just offshore of the Delaware/Maryland border near 37.8N-74.5W at 72 hours... frontal cyclone subsequently weakens to a remnant low while shifting southeastward and reaches 35.2N-73.5W at 96 hours.


0600Z (Oct 2) GFS Model Run...

**For area of interest #34... tropical wave organizes into tropical low near 11.5N-26.5W at 42 hours... tropical cyclone formation suggested near 13N-30W at 57 hours... turns north and reaches peak strength as a high-end compact tropical storm near 18N-30W at 87 hours... after peak strength turns north-northwest with remnant low reaching 22.5N-32.5W at 120 hours

**For area of interest #35... tropical cyclone formation suggested near 11N-52W at 45 hours... weakens to a remnant low near 11.5N-55W at 60 hours... remnant low weakens to a remnant wave while crossing the southern Lesser Antilles at 96 hours.

**For area of interest #36... frontal cyclone materializes just offshore of northeastern North Carolina near 35.5N-74W at 39 hours... undergoes a small counter-clockwise loop which brings the frontal cyclone center close to the southeast Virginia coast through 63 hours... while establishing a more circular center potentially becomes a subtropical cyclone centered near the southeast Virginia coast through 69 hours... the potential subtropical cyclone weakens to a remnant low while drifting southward to the waters just offshore of Cape Hatteras North Carolina through 81 hours... remnant low turns southeast and dissipates near 33N-73.5W at 93 hours.


0600Z (Oct 2) NAVGEM Model Run...

**For area of interest #34... tropical wave organizes into a tropical low near 11N-28.5W at 42 hours which proceeds northwest... tropical cyclone formation suggested near 15N-31W at 78 hours... tropical cyclone weakens back to a remnant low which reaches 19.5N-35.2W at 120 hours.

**For area of interest #35... tropical wave amplifies into a tropical low over Barbados at 84 hours... tropical low gradually organizes into a tropical depression which reaches the waters just south of the Dominican Republic at 168 hours.

**For area of interest #36... broad frontal low currently located offshore of the mid-Atlantic United States takes a counter-clockwise loop turn while strengthening into a frontal cyclone located near 37N-73W at 54 hours... frontal cyclone weakens to a remnant low while located near 35N-69W at 102 hours.

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