*******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.**********
...THURSDAY SEPTEMBER 26 2019 1:03 PM EDT...
See Karen and Lorenzo sections below for all active tropical cyclones in the Atlantic basin. See areas of interest sections below for all other areas being monitored for tropical cyclone formation.
TROPICAL STORM KAREN...While located in the open western Atlantic between Bermuda and Puerto Rico...Karen has developed a circular thunderstorm mass over and south of its center that has allowed it to re-strengthen to 45 mph maximum sustained winds after briefly dipping to 40 mph overnight. This is occuring with supportive upper outflow from the cell of tropical upper ridging the tropical storm is currently under. In addition...the dry sinking air mass to the west that killed off Jerry...generated in the western convergence zones of an upper vortex over Atlantic Canada and western Atlantic...is dispersing as the upper vortices move away from Karen's environment. Therefore my shorter-term intensity forecast shown below is raised...but only cautiously for the time being as Karen has had a history of not intensifying despite favorable conditions. Forecast track is adjusted more northward and slighlty westward as the circulation of Jerry's remnant low appears to be pulling Karen faster to the north and less to the east than I previously thought. But by 72+ hours...it still appears likely that Karen 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 the short-term northeast track of Karen will move the tropical storm into 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. It appears from the latest 0600Z GFS model run that the western Atlantic upper vortex will open into a trough that tries to link with the mid-latitude westerlies...and impenge on the west side of the upper ridge cell such that it begins shearing Karen by 96 and 120 hours...thus my intensity forecast is lowered for those timeframes. My forecast track is nudged northeastward for those times as well as my current intensity forecast suggests Karen will initially be strong/tall enough to be influenced by the upper southwesterly flow ahead of the upper trough. However after 120 hours...if the shear weakens Karen as I currently forecast...a more west track would ensue as it becomes a shallow feature steered by the surface ridging. One a final note...I do wonder if indeed Karen strengthens as I forecast if its thunderstorm latent heat release will split the upper trough into two upper vortices to reduce the shear and allow Karen to instead continue more northwest by 120 hours.
******Infohurricane.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Sep 26)...45 mph maximum sustained wind tropical storm centered south of Bermuda at 26.6N-63.3W
IOH 24 Hr Forecast (1200Z Sep 27)...50 mph maximum sustained wind tropical storm centered southeast of Bermuda at 28.5N-61W
IOH 48 Hr Forecast (1200Z Sep 28)...65 mph maximum sustained wind tropical storm centered at 27N-60W
IOH 72 Hr Forecast (1200Z Sep 29)...85 mph maximum sustained wind hurricane centered at 25N-64W
IOH 96 Hr Forecast (1200Z Sep 30)...75 mph maximum sustained wind hurricane centered at 25N-68W
IOH 120 Hr Forecast (1200Z Oct 1)...50 mph maximum sustained wind tropical storm centered northeast of the Bahamas at 26N-72W
MAJOR HURRICANE LORENZO...It could be argued that Lorezno is the most impressive hurricane of the season thus far...at least from a satellite view perspective...while acheiving a much larger size than Hurricane Dorian while reaching category 4 strength. My overall intensity forecast is raised due to these recent developments...and also as the 0600Z GFS model run shows less shear in the long range as this powerful hurricane begins to interact with the upper vorticity currently in the central Atlantic. My track forecast is shifted westward due to Lorenzo's current positiion and heading...but is still expected to begin to turn more northward while it is clearly strong/tall enough to be steered by the upper vorticity. In the next 24 hours...I expect Lorenzo's western outflow to be blocked by the upper vorticity...thus I show some slight weakening during that time. By 48 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. The 0600Z GFS model run from this morning appears to have intepreted the large size of Lorenzo's thunderstorm field...with it showing the thunderstorm latent heat release pushing the northeastern of the two forecast vortices further away from Lorenzo such that shear will be less than previously thought...so I show weakening from light shear by 72 hours but not as much as before. A piece of energy ejecting from the developing upper vortex over central Canada should settle west of Lorenzo by 96+ hours...with divergence on the east side of this energy continuing to promote low surface pressures and hence a surface ridge weakness for Lorenzo to continue north. A slight east angle in track is shown at this time from upper southwesterly flow ahead of this energy...with the surface subtropical ridge in the eastern Atlantic preventing a sharp eastward turn. It appears the shear from this upper-level energy will be less than previously anticipated as well due to Lorenzo's thunderstorm latent heat release keeping the energy jammed away further to the west...thus the slow weakening I show by that point has more to do with increasingly cooler waters along the forecast track. By 120+ hours...another stronger piece of energy from the central Canada upper vortex and a surface frontal cyclone it will support will swing across the north Atlantic...and with Lorenzo by that point north of the Atlantic subtropical ridge...a northeast turn toward the direction Azores appears likely. The cooler waters and a tremendous area of supportive divergence on the east side of this upper-level energy should help Lorenzo transition into a strong non-tropical frontal cyclone...likely still packing hurricane force winds. Therefore interests in the Azores should monitor the progress of this hurricane.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Sep 26)...130 mph maximum sustained wind major hurricane centered at 15.4N-40.2W
IOH 24 Hr Forecast (1200Z Sep 27)...125 mph maximum sustained wind major hurricane centered at 18.5N-41.5W
IOH 48 Hr Forecast (1200Z Sep 28)...135 mph maximum sustained wind major hurricane centered at 22.5N-41.5W
IOH 72 Hr Forecast (1200Z Sep 29)...125 mph maximum sustained wind major hurricane centered at 27N-41W
IOH 96 Hr Forecast (1200Z Sep 30)...120 mph maximum sustained wind major hurricane centered at 31N-40W
IOH 120 Hr Forecast (1200Z Oct 1)...100 mph maximum sustained wind hurricane transitioning to non-tropical centered southwest of the Azores at 35N-36W
AREA OF INTEREST #1...The surface trough in the southwestern Gulf of Mexico continues to lack thunderstorms...but does have a field of clouds that suggests some spin. Currently this disturbance is suppressed by upper convergence on the back side of an upper trough heading eastward and exiting the Gulf of Mexico...but by 24+ hours the disturbance will encounter much more favorable upper winds for re-generating thunderstorms and possibly for development in the wake of the departing upper trough. My outlook positions are nudged southward based on the current position of this disturbance...and shows a west-northwest track that bends increasingly northward around the southwest side of the eastern US surface ridge and while getting caught in southerly flow out ahead of a lengthy cold front to trail from the frontal cyclone over central Canada. I show a low 10% chance of tropical cyclone formation...waiting to see if in fact that more favorable upper winds allow this system to rebuild thunderstorms before either cancelling this disturbance as an area of interest (if it doesn't redevelop thunderstorms) or to raise odds of development (if thunderstorms redevelop and organize). 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 27)...0% chance of tropical cyclone formation (western Gulf of Mexico near 23N-95W)
IOH 48 Hr Outlook (1200Z Sep 28)...10% chance of tropical cyclone formation (just offshore of the east-central Mexico coast near 24.5N-97W)
IOH 72 Hr Outlook (1200Z Sep 29)...0% chance of tropical cyclone formation (inland over the Texas/Mexico border near 26.5N-100W)
AREA OF INTEREST #2...A tropical wave currently east-southeast of Hurricane Lorenzo that recently emerged from western Africa is producing increasing thunderstorm activity. Upper-level winds in the next 72 hours will be favorable for this tropical wave to develop due to low shear and upper outflow provided by a cell of tropical upper ridging forecast to persist in the eastern Atlantic. However after that time...upper trough energy settling west of Hurricane Lorenzo appears it will become amplified southward into the Atlantic tropics due to the strong upper anticyclone of Lorenzo...which will begin to increase unfavorable westerly shear over this tropical wave. My outlook positions below suggest a northward angle in track by 96+ hours from the surface ridge weakness created by Hurricane Lorenzo. My peak 120-hour odds of development are only 20% at this time due to lack of computer model support showing this tropical wave developing.
******Infohurricanes.com Outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Sep 27)...0% chance of tropical cyclone formation (tropical Atlantic near 27.5W)
IOH 48 Hr Outlook (1200Z Sep 28)...10% chance of tropical cyclone formation (tropical Atlantic near 32.5W)
IOH 72 Hr Outlook (1200Z Sep 29)...20% chance of tropical cyclone formation (tropical Atlantic near 37.5W)
IOH 96 Hr Outlook (1200Z Sep 30)...20% chance of tropical cyclone formation (tropical Atlantic near 16N-41W)
IOH 120 Hr Outlook (1200Z Oct 1)...5% chance of tropical cyclone formation (tropical Atlantic near 17.5N-45W)