*******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.**********
...MONDAY OCTOBER 14 2019 3:06 PM EDT...
Tropical Storm Melissa loses thunderstorms and tropical characteristics in the northwestern Atlantic...see Melissa 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 will become disrupted by upper vorticity from the current central North America upper vortex to get cut off by amplifying Gulf of Mexico upper ridging. Because upper-level winds will be much more favorable to area of interest #3 approaching from the southeast...I suspect this disturbance will not develop while getting absorbed by the area of interest in about 72 to 96 hours.
REMNANTS OF MELISSA...Tropical Storm Melissa has lost all nearby thunderstorm activity as westerly shear takes over the circulation due to the loss of the definition of the overhead upper trough to the much colder upper vortex over central North America and upper trough diving southeast from Greenland. The upper trough from Greenland is producing a rapidly developing surface frontal cyclone to the northeast...with Melissa's remnant low pressure expected to continue moving eastward toward this frontal cylcone while it loses its definition along the surface cold front of the cyclone. This is my final statement on Melissa on this blog as it is no longer a tropical feature.
AREA OF INTEREST #1...The broad tropical low pressure with showers and thunderstorms in the southern Caribbean region has now shifted westward over Central America and the western Caribbean. This disturbance persists while its local warm core upper ridge and outflow...bolstered by the thunderstorm latent heat release...merges with the much larger scale upper ridge in the Gulf of Mexico...therefore upper winds are expected to remain favorable for possible tropical cyclone development during the 120-hour forecast period. For the next 72 hours surface ridging is expected to persist over the southern US and 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 24 to 48 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 72 hours). My odds of development in the short-term remain low...currently at 10% or less...due to the high probability of land interaction and also due to continued lackluster support in today's model runs. The odds are briefly dipped to a minimum of 0% at 48 hours due to land interaction with the Yucatan peninsula that will keep the entire disturbance over land. By 96+ 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 Mexico and south Texas. Odds are not raised between 72 and 96 hours as the other frontal system passing by to the north in 24 to 48 hours will leave behind a cut-off upper trough that could increase wind shear during this time. However by 120 hours I begin to climb odds of development to 30% as the passing cut-off upper trough moves away and the forecast track of this disturbance takes this system more offshore...especially if an eastward lean in the north track occurs between 96 and 120 hours as today's model suggest...due to the tug of surface pressure drops to the northeast induced by the divergence zone of the passing cut-off upper trough. Regardless of tropical cyclone formation...in the coming days heavy rainfall with possible flash flooding may occur over land areas from Nicaragua all the way to Veracruz in southeastern Mexico...including all the areas mentioned in between in the outlook below.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 15)...10% chance of tropical cyclone formation (northwestern Caribbean...western Honduras...and just east of Belize)
IOH 48 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 72 Hr Outlook (1800Z Oct 17)...10% chance of tropical cyclone formation (southeastern Mexico...Bay of Campeche)
IOH 96 Hr Outlook (1800Z Oct 18)....10% chance of tropical cyclone formation (just offshore of Veracruz near 22N-96.5W)
IOH 120 Hr Outlook (1800Z Oct 19)...30% chance of tropical cyclone formation (western Gulf of Mexico offshore of south Texas and Tamaulipas near 25.5N-95W)
AREA OF INTEREST #2...The active tropical wave currently emerging from western Africa into the Atlantic tropics has a well-organized low pressure spin...and upper winds are favorable for tropical development due to persistent eastern tropical Atlantic upper ridging with low shear and upper outflow. Therefore I have begun a tropical cyclone formation forecast as outlined below...and I recommend interests in the Republic of Cabo Verde Islands should begin preparing for some damaging gusty winds as the chances are increasing that this system will become a strengthening tropical storm moving through the islands...with impacts being felt as early as tomorrow. The westward track is bent increasingly northward in the first part of the forecast as this system evolves into a strong/tall enough tropical cyclone to be dragged by the cut-off upper trough scheduled to be left behind by the large northeast Atlantic upper trough. Weakening is shown at 48+ hours as this system nears shearing upper westerly winds induced by the cut-off upper trough...with a westward turn shown in the track by 96 hours as this system weakens to a shallow low pressure no longer steered by the cut-off upper trough.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
0 Hr Position (1800Z Oct 14)...Tropical low pressure centered just southeast of the Republic of Cabo Verde Islands at 14N-19.5W
IOH 24 Hr Forecast (1800Z Oct 15)...45 mph maximum sustained wind tropical storm centered over the southeastern Republic of Cabo Verde Islands at 15.5N-22W
IOH 48 Hr Forecast (1800Z Oct 16)...50 mph maximum sustained wind tropical storm under southwesterly shear...centered over northwestern Republic of Cabo Verde Islands at 16.5N-25W
IOH 72 Hr Forecast (1800Z Oct 17)...35 mph maximum susateind wind tropical depression under southweserly shear...centered west-northwest of the Republic of Cabo Verde Islands at 17.5N-28.5W
IOH 96 Hr Forecast (1800Z Oct 18)...Remnant surface trough located in the vicinity of 17.5N-32W
AREA OF INTEREST #3...The active tropical wave the central Atlantic continues to have a low pressure spin when animating satellite imagery...and its thunderstorm activity has increased due to a divergence zone on the southeast side of large-scale central Atlantic upper vorticity that has been persistent. Although this upper vorticity is currently unfavorably shearing this disturbance...the upper vorticity is forecast to diminish while staying isolated from mid-latitude upper troughs. As this tropical wave nears the Lesser Antilles in 48 to 96 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 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 24 to 48 hours moves into the western Atlantic toward the end of the forecast period and creates a surface ridge weakness. The surface ridge weakness closes at 120 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 decent 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 by that timeframe. I am torn between the continued favorable upper wind outlook and simulatenous lackluster computer model support...so I have bumped my peak odds of tropical cyclone formation up to 60% and do not plan to increase the odds beyond this unless comptuer models begin showing development and/or this system becomes better organized.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 15)...5% chance of tropical cyclone formation (tropical Atlantic near 11N-53W)
IOH 48 Hr Outlook (1800Z Oct 16)...30% chance of tropical cyclone formation (east of the Lesser Antilles near 13N-57W)
IOH 72 Hr Outlook (1800Z Oct 17)...45% chance of tropical cyclone formation (just east of the northern Lesser Antilles near 17N-59W)
IOH 96 Hr Outlook (1800Z Oct 18)...60% chance of tropical cyclone formation (just northeast of the northern Lesser Antilles near 20N-61W)
IOH 120 Hr Outlook (1800Z Oct 19)...40% chance of tropical cyclone formation (north of Puerto Rico near 22N-64W)