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 and also the birdseye view posts from earlier this hurricane season. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
Search
  • NCHurricane2009

MY 2019 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #138

*******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 SEPTEMBER 25 2019 2:50 PM EDT...


See Karen...and Lorenzo sections below for all active tropical cyclones in the Atlantic basin. Jerry has dissipated into a remnant low pressure cloud swirl...see Jerry section below for details. See areas of interest sections below for all other areas being monitored for tropical cyclone formation. Elsewhere...the new surface low pressure in the open central Atlantic near 37.5N-44W...supported by divergence on the east side of a cut-off upper vortex...is not expected to gain tropical characteristics as it shifts northward and becomes absorbed into the surface frontal low headed towards the north Atlantic from Nova Scotia.


REMNANTS OF JERRY...Curiously...it appears light westerly shear on the north side of a cell of tropical upper ridging has caused Tropical Storm Jerry to dissipate into a remnant cloud swirl low pressure void of thunderstorms in the last 24 hours. When looking at water vapor imagery...an area of dry sinking air is seen overspreading Jerry from the west over the last day...caused by upper convergence on the west side of the upper vortex that Jerry was interacting with yesterday and also by upper convergence on the west side of the upper vortex that has moved from the northeastern US into Nova Scotia. Perhaps then this dry air has been wafted into Jerry by the westerly shear...thus killing off its thunderstorms. The remnant low is heading directly to Bermuda where it might cause some breezy conditions. The remnant low will spend the next few days heading generally east...with a likely southward drift in the open central Atlantic when the surface ridge currently over the eastern US bridges with the Atlantic surface subtropical ridge in the eastern Atlantic. This track will keep Jerry on the north and east periphery of the cell of upper ridging in the area...where Jerry will be under continued light shear. However should Jerry begin re-building any thunderstorms from outflow provided by the upper ridge...will consider re-adding it as an area of interest for tropical development. Otherwise...this will be my final statement on Jerry on this blog.


TROPICAL STORM KAREN...Karen appears to be becoming less organized while pulling northward and away from the Virgin Islands and Puerto Rico...as it gets drawn into the surface ridge weakness caused by the remnant low of Jerry. This is occuring despite the tropical storm being under a favorable cell of tropical upper ridging which features low shear and upper outflow. Perhaps then Karen is struggling to keep its identity seperate from the large low pressure field south of Jerry which was generated earlier by a broad area of upper divergence on the east side of the upper vortex in the western Atlantic. It is also possible the large area of dry air that overspread and killed off Jerry as a tropical cyclone is being ingested by Karen. For now on water vapor imagery it appears Karen is embedded in a band of sheared-off moisture that once belonged to Jerry...and as the forecast track for Karen in the short-term moves the tropical storm northeastward toward Jerry's ridge weakness my best guess is that Karen will remain embedded in the moisture band. My updated forecast intensity is a notable drop from my previous...and shows no change in Karen's intensity for the next 48 hours to give time for the Nova Scotia and western Atlantic upper vortex...whose western upper convergence regions are generating the dry air to the west...to move away from Karen (the western Atlantic upper vortex will drift westward and away under the influence of the large cell of upper ridging in the area while the Nova Scotia vortex moves eastward across the north Atlantic in the mid-latitude westerlies). However my intensity forecast is of low confidence as it would not suprise me if Karen dissipates based on its current satellite apperance. By 96+ hours...it still appears likely that Karen...if it survives...will take an atypical west-southwest track for two reasons. First at the surface...Karen looks like it will be embedded in surface northeasterly flow between a large area of cyclonic flow to the east (from Jerry and Lorenzo) and as the surface ridge currently over the eastern US rebuilds in the western Atlantic as the strong frontal cyclone over central Canada is expected to whirl northward and away while it amplifies its supporting and steering upper trough into a vortex with its strong cold air advection. Second...because at the upper-levels the east pull from Jerry in the middle of the forecast period will help bring Karen toward the east side of the cell of upper ridging...where upper northerly flow would help drag Karen southward should it become a stronger/taller tropical cyclone by that time. Intensity forecasting in the longer range seems uncertain to me as well...but I do show strengthening at 72 hours while Karen remains below the favorable cell of upper ridging. Whether strengthening continues or not at 96+ hours depends on whether or not upper vorticity that Lorenzo's latent heat release will pinch off from the current central Atlantic upper vorticity impenges on the upper ridge from the east...or if the western Atlantic upper vortex opens into a trough in the mid-latitude westerlies that impenges on the upper ridge from the west. With this uncertainty...I only show gradual strengthening continuing during those timeframes.

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

0 Hr Position (1200Z Sep 25)...45 mph maximum sustained wind tropical storm centered north of Puerto Rico at 21.7N-64.9W

IOH 24 Hr Forecast (1200Z Sep 26)...45 mph maximum sustained wind tropical storm centered south of Bermuda at 24.5N-63W

IOH 48 Hr Forecast (1200Z Sep 27)...45 mph maximum sustained wind tropical storm centered southeast of Bermuda at 25N-60W

IOH 72 Hr Forecast (1200Z Sep 28)...60 mph maximum susateind wind tropical storm centered at 23.5N-59W

IOH 96 Hr Forecast (1200Z Sep 29)...75 mph maximum sustained wind hurricane centered at 22.5N-63.5W

IOH 120 Hr Forecast (1200Z Sep 30)...85 mph maximum sustained wind hurricane centered at 22N-69W


HURRICANE LORENZO...Lorenzo in the open eastern tropical Atlantic continues to strengthen and is now a hurricane. Upper-level winds will be favorable for additional strengthening in the next 24 hours under a favorable cell of tropical upper ridging with low shear and upper outflow. No changes to my intensity forecast as Lorenzo so far is on par with my previous. By 48 to 72 hours...Lorenzo is expected to turn increasingly northward as it will be strong/tall enough to be steered by the upper vorticity currently in the central Atlantic...especially as this vorticity gets kicked eastward toward Lorenzo by the upper vortex over Nova Scotia when the vortex later moves across the north Atlantic. By 24 to 48 hours...I expect Lorenzo's western outflow to be blocked by the upper vorticity...thus I do not show major hurricane strength just yet by 24 hours and suggest some weakening at 48 hours. By 72 hours...modeling agrees that Lorenzo's tremendous thunderstorm latent heat release will split the cold core upper vorticity in half into two vortices...which will reduce shear and enhance upper outflow...and this is when I forecast Lorenzo will reach peak intensity as a major hurricane. My forecast track is nudged northward overall from Lorenzo's current position. For the later part of the forecast (after 72 hours)...Lorenzo is expected to continue northward as it encounters a break in surface ridging due to the remnant low of Jerry settling to the northwest of Lorenzo...followed by the break in the surface ridge persisting as energy ejecting from the upper trough (which will later amplify into a vortex) over central Canada will leave behind some upper troughing to the west of Lorenzo...with upper divergence on the east side of this upper troughing keeping the break in the surface ridging. As Lorenzo breaks the initial central Atlantic upper vorticity into two vortices at 72 hours...the northeastern of the two vortices will open into an upper trough over and east of Lorenzo by 96 hours...with Lorenzo tending to get dragged eastward by the resulting upper westerly flow. But with the Atlantic surface subtropical ridging remaining to the east...the result will be a northward track with some eastward lean...with weakening from the upper westerly winds shearing Lorenzo possible by 96 hours. I do not show weakening at 120 hours as the latest GFS model run then shows the upper westerly flow over Lorenzo having some anticyclonic curvature (i.e. less shear) in between the upper troughing to the west and east.

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

0 Hr Position (1200Z Sep 25)...85 mph maximum sustained wind hurricane centered at 14.1N-35.1W

IOH 24 Hr Forecast (1200Z Sep 26)...105 mph maximum sustained wind hurricane centered at 15N-39W

IOH 48 Hr Forecast (1200Z Sep 27)...100 mph maximum sustained wind hurricane centered at 18.5N-40.5W

IOH 72 Hr Forecast (1200Z Sep 28)...120 mph maximum sustained wind major hurricane centered at 22.5N-41W

IOH 96 Hr Forecast (1200Z Sep 29)...100 mph maximum sustained wind hurricane centered at 27N-40W

IOH 120 Hr Forecast (1200Z Sep 30)...100 mph maximum susateind wind hurricane centered at 31N-39W


AREA OF INTEREST #1...The tropical wave west of Hurricane Lorenzo has lost its thunderstorm activity in the last day...perhaps as it encounters less favorable upper convergence on the east side of an inverted upper trough to the west. Although this system will later track west-northwest towards the surface ridge weakness caused by Tropical Storm Karen and remnant low of Jerry and into more favorale upper winds on the southeast side of a cell of tropical upper ridging in the west Atlantic...it is likely that competition with the low pressure fields of Jerry and Karen will prevent this system from developing. Thus I have dropped my odds of tropical cyclone formation to 0%. This is my final statement on this tropical wave as an area of interest on this blog.

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

IOH 24 Hr Outlook (1200Z Sep 26)...0% chance of tropical cyclone formation (tropical Atlantic near 56W)

IOH 48 Hr Outlook (1200Z Sep 27)...0% chance of tropical cyclone formation (northeast of the Lesser Antilles near 20N-61W)


AREA OF INTEREST #2...The surface trough in the south-central Gulf of Mexico has seen a loss of organized thunderstorms...perhaps as the upper vortex in the western Gulf of Mexico has begun to open into a trough captured by the mid-latitude westerlies that is heading eastward over the disturbance and suppressing its upper outflow at the present time. It is curious that this disturbance has not moved at all in the last 24 hours...perhaps as the eastern US surface ridge has weakened from the frontal cyclone over central Canada. However this ridge is expected to rebuild as the frontal cyclone moves northward and away as its strong cold air advection amplifies its steering upper trough into a vortex. Therefore my outlook positions below are based on the surface trough resuming a west-northwest course that increasingly bends northward around the southwest side of the ridge and gets caught in southerly flow out ahead of a lengthy cold front to trail from the frontal cyclone over central Canada. My outlook positions have been shifted east given the loss of westward progress in the last 24 hours. I show a low 10% chance of tropical cyclone formation before this system makes landfall in Mexico as the upper trough in the Gulf will shift eastward and away...later leaving this system under favorable upper winds for development. I will raise odds for development back up should this system survive the short-term unfavorable conditions and later redevelop thunderstorms in the more favorable upper winds. Interests in the Mexican province of Tamualipas and far southern Texas should continue to monitor the progress of this disturbance in case it later redevelops thunderstorm activity capable of flash flooding rain.

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

IOH 24 Hr Outlook (1200Z Sep 26)...0% chance of tropical cyclone formation (central Gulf of Mexico near 23N-92.5W)

IOH 48 Hr Outlook (1200Z Sep 27)...10% chance of tropical cyclone formation (western Gulf of Mexico near 24N-95W)

IOH 72 Hr Outlook (1200Z Sep 28)...10% chance of tropical cyclone formation (just offshore of the east-central Mexico coast near 25.5N-97W)

IOH 96 Hr Outlook (1200Z Sep 29)...0% chance of tropical cyclone formation (inland over the Texas/Mexico border near 27.5N-100W)

1 view

©2019 by Info On Hurricanes.


Questions? Comments? Send to me on IOHurricanes@outlook.com