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 #157

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


...TUESDAY OCTOBER 15 2019 3:28 PM EDT...

The active tropical wave emerging from Africa becomes an unusual far east Atlantic tropical depression for October moving into the Republic of Cabo Verde Islands...see tropical depression fifteen section below for details. 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...and is being disrupted by upper vorticity from the current eastern Canada upper vortex getting cut off by amplifying Gulf of Mexico upper ridging. Because upper-level winds will be much more favorable to area of interest #2 approaching from the southeast...I suspect this disturbance will not develop while getting absorbed by the area of interest in about 48 to 72 hours.


TROPICAL DEPRESSION FIFTEEN...The active tropical wave that has recently emerged from Africa has strenghtened into tropical depression fifteen as of yesterday afternoon...and is currently centered close to the southeastern Republic of Cabo Verde Islands. However weather conditions over the islands have remained quiet due to light southwesterly shear ahead of a cut-off upper trough keeping the thunderstorms of the depression off to the east of the center...thus preventing the depression so far from moistening away the dry saharan air over the islands. This has also prevented the depression from strengthening into a tropical storm...but still watching for this possiblity as a small circular thunderstorm burst has been recently developing just east of the center as of 1740Z. However my intensity forecast by 24 hours no longer shows a tropical storm as the northwestward track of this system will take it closer to the stronger southwesterly shearing winds of the cut-off upper trough...a combination of being tall enough to be steered northward by the upper trough and the westward push of the Atlantic surface subtropical ridge. I forecast the stronger shear weakening the tropical depression into a remnant trough of low pressure by 48 hours...with the surface trough likely turning more westward while degeneratnig into a shallow feature only steered by the surface ridge. Although the weather has been quiet so far over the Republic of Cabo Verde Islands...some gusty winds and heavy rains are a possibility over the islands in the next 24 hours if the east half of the circulation remains active and overspreads the islands...especially if the depression strengthens into a tropical storm.

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

0 Hr Position (1800Z Oct 15)...35 mph maximum sustained wind tropical depression centered just east of the southeastern Republic of Cabo Verde Islands at 15.6N-21.6W

IOH 24 Hr Forecast (1800Z Oct 16)...35 mph maximum sustained wind tropical depression under southwesterly shear...centered over northwestern Republic of Cabo Verde Islands at 16.5N-25W

IOH 48 Hr Forecast (1800Z Oct 17)...Remnant surfae trough located west-northwest of the Republic of Cabo Verde Islands in the vicinity of 17.5N-28.5W


AREA OF INTEREST #1...The broad tropical low pressure with showers and thunderstorms over Central America and the western Caribbean has expanded more aggressively into the eastern Pacific in the last 24 hours...but has also expanded into Guatemala...southeastern Mexico...and Bay of Campeche. This large disturbance persists under the favorable low shear and supportive southern upper outflow of the Gulf of Mexico upper ridge...with tropical cyclone formation in the short-term most likely in the eastern Pacific to the south of Guatemala and southeastern Mexico. However we cannot discount this disturbance for the Atlantic side as satellite animation also shows another low pressure spin currently over the northwestern Guatemala/Mexico border region tracking toward the Bay of Campeche waters...albeit this spin currently lacks widespread thunderstorms. My updated outlook positions in the short-term are adjusted westward to account for the current position of this spin...and the fact that this spin will likely be tugged more westward into southeastern Mexico...specifically the Veracruz area...while absorbing the eastern Pacific circulation after it makes landfall and weakens likely in Oaxaca by 48 hours. By 72+ hours...a frontal system over the western US will likely turn this disturbance northward across the western Gulf of Mexico...with some eastward lean in track in the 72 to 96 hour timeframe caused by surface pressure falls to the northeast induced by the divergence zone of a passing cut-off upper trough to be left behind by the current central US upper trough. The eastward lean in track is likely to continue at 120 hours as the western US frontal system nears. I keep the odds of tropical cyclone formation at 0% for the next 48 hours due to the dominance of the current eastern Pacific circulation...and begin to increase odds for 72+ hours due to the low shear/outflow of the Gulf of Mexico upper ridge and the forecast track that takes this system away from land. I begin to slide odds downward by 120 hours though as increasing southwesterly shear from the approaching western US frontal system as well as land interaction with the northern US Gulf coast could make conditions less favorable for development. My peaks odds of development remain only at 30% as the Atlantic (Bay of Campeche/Gulf of Mexico) side circulation may struggle to gain dominance due to the eastern Pacific circulation in the short term and forecast surface pressure falls to the northeast at the 72 to 96 hour timeframe. Regardless of tropical cyclone formation...in the next 72 hours heavy rainfall with possible flash flooding may occur over southeastern Mexico...with possible gusty or damaging winds for the south Pacific coast of Oaxaca should the eastern Pacific circulation strengthen into a tropical storm (see hurricanes.gov for the absolute latest on the eastern Pacific circulation).

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

IOH 24 Hr Outlook (1800Z Oct 16)...0% chance of tropical cyclone formation (southeastern Mexico...Bay of Campeche)

IOH 48 Hr Outlook (1800Z Oct 17)...0% chance of tropical cyclone formation (coastal Veracruz near 20N-96W)

IOH 72 Hr Outlook (1800Z Oct 18)....10% chance of tropical cyclone formation (just offshore of Veracruz near 22N-96W)

IOH 96 Hr Outlook (1800Z Oct 19)...30% chance of tropical cyclone formation (western Gulf of Mexico near 25.5N-95W)

IOH 120 Hr Outlook (1800Z Oct 20)...25% chance of tropical cyclone formation (coastal southeastern Louisiana near 29N-91W)


AREA OF INTEREST #2...The tropical wave with low pressure rotation in the central Atlantic has seen a loss in thunderstorm activity in the last 24 hours...likely due to the loss of the divergence zone out ahead of a central Atlantic upper vortex as that vortex has weakened. As this tropical wave nears the Lesser Antilles in 24 to 72 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 current eastern Canada 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 circulation. In addition a northward turn of this tropical disturbance will be induced in the low-levels the central US frontal system moves into the western Atlantic towards the end of the forecast period and creates a surface ridge weakness. The surface ridge weakness closes at 96 hours...so a westward lean in track is possible by that time...but due to the favorable upper wind outlook I expect this system will have a marginal chance of being a sufficiently strong/tall tropical system by that time to be still be dragged rightward by the broad upper westerly flow to occurr in the wake of the frontal system's upper trough. This broad upper westerly flow will also begin shearing this disturbance...so I begin dropping the odds of development at 96 to 120 hours. I have cut my odds of development down to about half compared to yesterday due to the current loss of thunderstorms and continued lackluster computer model support.

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

IOH 24 Hr Outlook (1800Z Oct 16)...0% chance of tropical cyclone formation (east of the Lesser Antilles near 13N-57W)

IOH 48 Hr Outlook (1800Z Oct 17)...10% chance of tropical cyclone formation (just east of the northern Lesser Antilles near 17N-59W)

IOH 72 Hr Outlook (1800Z Oct 18)...30% chance of tropical cyclone formation (just northeast of the northern Lesser Antilles near 20N-61W)

IOH 96 Hr Outlook (1800Z Oct 19)...25% chance of tropical cyclone formation (north of Puerto Rico near 22N-64W)

IOH 120 Hr Outlook (1800Z Oct 20)...0% chance of tropical cyclone formation (western Atlantic near 24N-67W)

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