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 #145

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


...WEDNESDAY OCTOBER 2 2019 1:15 PM EDT...

Hurricane Lorenzo transitions into a non-tropical remnant gale after swiping the Azores...see Lorenzo section below for details. See area of interest sections below for areas being monitored for tropical cyclone formation.


REMNANTS OF LORENZO...After packing a punch in the Azores...Hurricane Lorenzo has transitioned into a remnant non-tropical frontal cyclone still packing hurricane-force winds (80 mph maximum sustained as of 11 AM EDT) while supported by tremendous divergence on the east side of an upper trough in the north Atlantic. The latest modeling agrees that Lorenzo's surface cold air advection on its west side will split off a portion of the upper trough into a smaller trough that shifts eastward toward the British Isles...thus it appears Lorenzo will move into the British Isles in about 48 hours (2 days). However as it makes landfall here...the small upper trough will merge with the upper trough currently over western Europe...leaving Lorenzo to quickly weaken under convergence on the west side of the European upper trough. Thus Lorenzo's non-tropical remnant could bring gusty winds to the British Isles...but not as severe as what was seen in the Azores. This is my final statement on Lorenzo on this blog as it no longer is a tropical feature.


AREA OF INTEREST #1...The surface low pressure in the northwestern Caribbean Sea persists thanks to supportive divergence on the east side of a western Atlantic upper trough. The heaviest thunderstorm activity remains sheared eastward from the lowest surface pressure by the upper trough and is currently located between the Cayman Islands and central Cuba. In the next 24 hours...conditions look unfavorable for tropical development due to the shear...but by 48+ hours I begin to climb the odds of tropical cyclone formation as the western Atlantic upper trough is forecast to weaken and split in half...leaving this disturbance in favorable low shear and high upper outflow between the split halves. The initial motion of this disturbance should be slow as the steering eastern US surface ridge becomes eroded by the frontal system stretched from the central US to Atlantic Canada...and will be positioned where the upper-level winds are most favorable for thunderstorm activity which I have nudged southward to be over western Cuba and the northeastern Yucatan peninsula based on the current positon of the lowest surface pressure and the latest GFS model upper wind forecast. After 36 hours...a surface ridge building behind the central US frontal system should steer this disturbance...likely sending the disturbance northwestward across the Gulf of Mexico around its southwest side through 96 hours. By 120 hours...it appears this disturbance will slow down and drift southwestward as a sharp upper trough and surface frontal cyclone currently offshore of western North America moves across the US/Canada border region...kicks the central US surface ridge into the western Atlantic...and with its western upper convergence builds another surface ridge emerging from the western US that will provide the southwest drift. I drop the odds of development at 96+ hours as this disturbance moves into unfavorable southwesterly shear from the western split of the current western Atlantic upper trough which will be in the western Gulf of Mexico by that time. Regardless of tropical development or not...over the next couple of days heavy rains with flash flooding are possible over western Cuba and possibly the northeastern Yucatan peninsula of Mexico. My forecast positions below are not of high confidence at this time as the surface low pressure remains broad and could consolidate in a different location...which would change the track forecast.

******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 (southeastern Gulf of Mexico...northwestern Caribbean Sea...western Cuba...northeastern Yucatan peninsula of Mexico)

IOH 48 Hr Outlook (1200Z Oct 4)...15% chance of tropical cyclone formation (southern Gulf of Mexico near 22N-87W)

IOH 72 Hr Outlook (1200Z Oct 5)...25% chance of tropical cyclone formation (Gulf of Mexico near 24.5N-91W)

IOH 96 Hr Outlook (1200Z Oct 6)...10% chance of tropical cyclone formation (Gulf of Mexico near 26.5N-94W)

IOH 120 Hr Outlook (1200Z Oct 7)...10% chance of tropical cyclone formation (Gulf of Mexico near 24.5N-95W)


AREA OF INTEREST #2...The western Atlantic broad surface low pressure located north of the Caribbean islands continues to be supported by divergence on the east side of the western Atalntic upper trough. Warm air advection ahead of a pair of frontal lows emerging from the central US to Atlantic Canada frontal system is expected to amplify upper ridging over the western Atlantic and over this disturbance...which will reduce the shear imparted by the current western Atlantic upper trough and potentially allow for this disturbance to develop over the next 48 hours. This disturbance will generally track northeast in the ridge weakness between the Atlantic subtropical ridge and eastern US surface ridge induced by the eastern of the pair of frontal lows...and I have peak odds of development only at 10% as this system will need time to consolidate to develop at all...and just after 48 hours will already be overspread by increasing southwesterly shear from the upper trough of the western of the two frontal lows. Development will no longer be possible by 72 hours while the disturbance becomes absorbed by the cold front of the western frontal low.

******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 (just southeast of Bermuda near 30N-64W)

IOH 48 Hr Outlook (1200Z Oct 4)...10% chance of tropical cyclone formation (western Atlantic near 31N-61W)

IOH 72 Hr Outlook (1200Z Oct 5)...0% chance of tropical cyclone formation (absorbed by cold front in central Atlantic near 33N-55W)


AREA OF INTEREST #3...A tropical wave over western Africa has seen an increase in thunderstorm activity while nearing the west coast of Africa and Atlantic tropical waters as the Euro (ECMWF) and NAVGEM models continue to suggest the tropical wave evolving into a surface low in the coming days...therefore I have introduced this feature as an area of interest for tropical development. Upper-level winds will be favorable for tropical development as the upper vortex in the eastern Atlantic drifts northward and away in upper southwesterly flow in the wake of upper troughing supporing Lorenzo's non-tropical remnant gale...which will allow the upper ridge cell (with low shear and upper outflow) over Africa to join the upper ridge cell currently in the central tropical Atlantic. The pair of frontal lows to emerge from central US and Atlantic Canada will have no effect on this system while passing too far north...but a rather amplifed upper trough associated the western of the two frontal lows will strengthen the Atlantic surface subtropical ridge by 120 hours such that a westward acceleration in track of this tropical disturbance will be possible. My peak 120-hour odds of develpoment are only 30% at the present time due to a current surge of dry saharan air just to the northwest of the tropical wave and also as the NAVGEM model which is usually a low reliability model for tropical activity is the only model most gung-ho about developing this system.

******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 (west coast of Africa)

IOH 48 Hr Outlook (1200Z Oct 4)...10% chance of tropical cyclone formation (tropical Atlantic southeast of the Republic of Cabo Verde Islands near 11N-20W)

IOH 72 Hr Outlook (1200Z Oct 5)...20% chance of tropical cyclone formation (tropical Atlantic southwest of the Republic of Cabo Verde Islands near 12N-25W)

IOH 96 Hr Outlook (1200Z Oct 6)...25% chance of tropical cyclone formation (tropical Atlantic near 13N-30W)

IOH 120 Hr Outlook (1200Z Oct 7)...30% chance of tropical cyclone formation (tropical Atlantic near 13.5N-36W)

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