BIRDSEYE VIEW POSTS

Since 2012 on the Weather Underground (www.wunderground.com) 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 via Disqus on Weather Underground at www.wunderground.com/cat6. You can see my Disqus feed at this link for my latest comments. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
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MY 2019 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #155

*******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.**********


...SUNDAY OCTOBER 13 2019 10:22 PM EDT...

See Tropical Storm Melissa section below for the only active tropical cyclone in the Atlantic basin. See area of interest sections below for all areas being monitored for tropical cyclone formation.


Elsewhere...the broad western Atlantic surface trough of low pressure northeast of Puerto Rico is currently disorganized while becoming disrupted by upper vorticity from the upper trough over Melissa...with another round of disruption in the next couple of days to come from upper vorticity from the current central North America upper vortex to get cut off by amplifying Gulf of Mexico upper ridging. Before considering this an area of interest for development...will have to see how it survives the disruption first.


In addition...the frontal low in the western Gulf of Mexico has not developed thudnerstorm activity while moving into south Texas and east-central Mexico...no concerns here.


TROPICAL STORM MELISSA...Melissa in the northwest Atlantic has made the transition to fully tropical status as of yesterday while exhibiting warm core anticyclonic upper outflow in its thunderstorms beneath the larger scale of upper trough it is embedded under. The instability for Melissa's thunderstorms continues to be aided by the cold upper air temperatures of the upper trough. The deep-layered frontal cyclone over central North America continues to swing the upper trough east-northeastward...and likewise Melissa's track is following suit. Melissa has continued weakening while losing touch with the divergence zone on the east side of the upper trough...with this zone producing a new frontal low just northeast of Melissa. By 24 hours upper vorticity currently between Greenland and Canada will produce a much stronger frontal cyclone southeast of Greenland...therefore in the next day or so Melissa will continue to be dragged eastward-northeastward out to sea while channeled on the north side of the current Atlantic subtropical surface ridge...and toward the aforementioned frontal low and frontal cyclone to the northeast. I have adjusted the forecast track eastward due to Melissa's current position. I forecast Melissa to dissipate into a remnant low in the next 24 hours as the overhead upper trough loses its definition to the much colder upper vortex over central North America and upper vorticity diving from Greenland/Canada...which will place Melissa in a more hostile upper westerly shear environment.

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

0 Hr Position (1800Z Oct 13)...40 mph maximum sustained wind tropical storm centered at 39.9N-58.8W

IOH 24 Hr Forecast (1800Z Oct 14)...Remnant low south of Newfoundland centered at 41N-52W


AREA OF INTEREST #1...A broad tropical low pressure with showers and thunderstorms in the southern Caribbean region continues persisting under upper outflow heading into a small upper vortex to the east and northwestern Caribbean upper trough that cut-off from the much larger upper trough over Tropical Storm Melissa. The latent heat release of these thunderstorms is also locally bolstering warm core upper ridging between the vortices...which is also helping the upper outflow. After 24 hours...the northwestern Caribbean upper trough is expected to dissipate in the midst of warm Gulf of Mexico upper ridging that will keep upper winds favorable for tropical development...and surface ridging is expected to persist over the southern US during the next 96 hours to steer this disturbance west across Central America and southeastern Mexico (the surface ridging will be bolstered by upper convergence in the wake of the upper vortex supporting the current central Canada frontal cyclone...and another upper trough and surface front at 48 to 72 hours to merge with the frontal cyclonic system from the west will pass too far north with yet another surface ridge to quickly build in its wake such that a major northward turn of this disturbance is unlikely during the next 96 hours). I have raised my odds of tropical cyclone formation due to the more northward position of the thunderstorms which increases the odds of an offshore circulation consolidating over the northwestern Caribbean and/or Bay of Campeche in the coming days...but the odds are still low due to a high probability of land interaction and also due to lackluster support in today's model runs. The odds are briefly dipped to a minimum of 0% at 72 hours due to land interaction with the Yucatan peninsula that will keep the entire disturbance over land. By 120 hours...a frontal system over the western US will likely turn this disturbance northward across the western Gulf of Mexico at a position just offshore of Veracruz. Odds are not raised between 96 and 120 hours as the other frontal system passing by to the north in 48 to 72 hours will leave behind a cut-off upper trough that could increase wind shear during this time. Regardless of tropical cyclone formation...in the coming days heavy rainfall with possible flash flooding may occur in the land areas mentioned in the outlook below.

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

IOH 24 Hr Outlook (1800Z Oct 14)...5% chance of tropical cyclone formation (Nicaragua...Honduras...northwestern Caribbean Sea)

IOH 48 Hr Outlook (1800Z Oct 15)...15% chance of tropical cyclone formation (northwestern Caribbean...western Honduras...and just east of Belize)

IOH 72 Hr Outlook (1800Z Oct 16)...0% chance of tropical cyclone formation (western Yucatan peninsula of southeastern Mexico...northern Guatemala...and eastern Bay of Campeche)

IOH 96 Hr Outlook (1800Z Oct 17)...10% chance of tropical cyclone formation (southeastern Mexico...Bay of Campeche)

IOH 120 Hr Outlook (1800Z Oct 18)....10% chance of tropical cyclone formation (just offshore of Veracruz near 22N-96.5W)


AREA OF INTEREST #2...The active tropical wave currently emerging from western Africa into the Atlantic tropics is showing signs of an organizing low pressure spin...and upper winds initially will be favorable for tropical development due to persistent eastern tropical Atlantic upper ridging with low shear and upper outflow. Therefore I have notably raised the odds of tropical cyclone formation compared to my previous outlooks...and interests in the Republic of Cabo Verde Islands should watch this tropical wave as it could move into the islands as a tropical depression or storm in 48 through 72 hours. I have nudged my forecast track eastward due to the current position of the tropical wave...and due to a higher chance this disturbance becomes a tropical cyclone tall enough to be dragged northward by a cut-off upper trough to be left behind by the large northeastern Atlantic upper trough. I drop the odds of development to 0% by 96 hours due to increasing southwesterly shear while the disturbance nears the cut-off upper trough. I do not have odds of development above 40% at the present time due to today's GFS and NAVGEM models not showing development (only the CMC and Euro show development today)...and because of dry saharan air to the west that lies over the Republic of Cabo Verde Islands.

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

IOH 24 Hr Outlook (1800Z Oct 14)...40% chance of tropical cyclone formation (just east of the Republic of Cabo Verde Islands near 15N-19W)

IOH 48 Hr Outlook (1800Z Oct 15)...40% chance of tropical cyclone formation (over the southeastern Republic of Cabo Verde Islands near 16N-22W)

IOH 72 Hr Outlook (1800Z Oct 16)...20% chance of tropical cyclone formation (over northwestern Republic of Cabo Verde Islands near 17N-25W)

IOH 96 Hr Outlook (1800Z Oct 17)...0% chance of tropical cyclone formation (west-northwest of the Republic of Cabo Verde Islands near 17.5N-28.5W)


AREA OF INTEREST #3...The eastern Atlantic tropical wave previously removed as an area of interest on this blog...in post #152...due to ingestion of dry saharan air has made a comeback in the central tropical Atlantic while escaping the dry air as it has displayed a low pressure spin yesterday and today...as a result it is now in the National Hurricane Center tropical weather outlook. Currently the thunderstorm activity is disorganized due to southwesterly shear from the large upper vortex in the central Atlantic...but this upper vortex is forecast to diminish during the forecast period while staying isolated from mid-latitude upper troughs. As this tropical wave nears the Lesser Antilles in 72 to 120 hours...it could become quiet active as it interacts with the eastern divergence zone of a forecast sharp upper trough. This upper trough is expected to come together from upper vorticity from the upper trough over Melissa and current central North America upper vortex getting cut off by amplifying Gulf of Mexico upper ridging. Due to the sharp nature of the upper trough...wind shear over the tropical wave is expected to be low...and the upper trough will likely curve this system north should it quickly develop into a strong/tall enough tropical cyclone. In addition a northward turn of this tropical disturbance will be induced in the low-levels as a frontal system to sweep across the US in 48 to 72 hours moves into the western Atlantic by the end of the forecast period and creates a surface ridge weakness. Despite the increasingly favorable upper wind outlook...I only have peak odds of development at 30% through 120 hours due to the current lackluster computer model support.

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

IOH 24 Hr Outlook (1800Z Oct 14)...0% chance of tropical cyclone formation (tropical Atlantic near 10.5N-48W)

IOH 48 Hr Outlook (1800Z Oct 15)...5% chance of tropical cyclone formation (tropical Atlantic near 11N-53W)

IOH 72 Hr Outlook (1800Z Oct 16)...20% chance of tropical cyclone formation (east of the Lesser Antilles near 13N-57W)

IOH 96 Hr Outlook (1800Z Oct 17)...30% chance of tropical cyclone formation (just east of the northern Lesser Antilles near 17N-59W)

IOH 120 Hr Outlook (1800Z Oct 18)...40% chance of tropical cyclone formation (just northeast of the northern Lesser Antilles near 20N-61W)

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