*******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.**********
...FRIDAY OCTOBER 4 2019 2:48 PM EDT...
See area of interest sections below for areas being monitored for tropical and subtropical cyclone formation.
AREA OF INTEREST #1...The broad surface low pressure in the northwestern Caribbean Sea has moved slowly northwestward into the southern Gulf of Mexico while leaving behind its heavier thunderstorm activity to the east...that activity is now associated with area of interest #4 discussed below. At the present time this disturbance is producing some bands of clouds and thunderstorms in the southern Gulf that are beginning to be sheared northward from the lowest surface pressure due to upper southwesterly flow from an upper vortex in the Gulf of Mexico. Between now through 48 hours...a surface ridge building over the central United States will steer steer this disturbance west-northwestward around its southwest side. By 72+ hours...it appears this disturbance will slow down and drift southwestward into Veracruz Mexico as a sharp upper trough currently making landfall in western North America moves across the US/Canada border region...and with its western upper convergence builds another surface ridge emerging from the western US that will provide the southwest drift. There has been a change in the long-rane GFS model upper-level wind forecast between 1200Z yesterday and 1200Z today which now shows the sharp upper trough absorbing the upper vortex in the western Gulf of Mexico...with this upper trough having a stronger presence in the Gulf of Mexico overall such that the unfavorable southwesterly shear appears it will now persist through the duration of the 120-hour forecast period. As a result I have dropped my odds of development to 0%...and will plan this to be my final statement on this disturbance as an area of interest on this blog should the National Hurricane Center remove it from its tropical weather outlook by my next update.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Oct 5)...0% chance of tropical cyclone formation (southern Gulf of Mexico near 22.5N-91W)
IOH 48 Hr Outlook (1200Z Oct 6)...0% chance of tropical cyclone formation (southwestern Gulf of Mexico near 23.5N-93.5W)
IOH 72 Hr Outlook (1200Z Oct 7)...0% chance of tropical cyclone formation (southwestern Gulf of Mexico near 22.5N-95W)
IOH 96 Hr Outlook (1200Z Oct 8)...0% chance of tropical cyclone formation (southwestern Gulf of Mexico just offshore of Veracruz near 21N-96.5W)
IOH 120 Hr Outlook (1200Z Oct 9)...0% chance of tropical cyclone formation (inland over southeastern Mexico near 21N-97.5W)
AREA OF INTEREST #2...A tropical wave that recently emerged from western Africa is now passing south of the Republic of Cabo Verde Islands where it continues to produce showers and thunderstorms. Because its associated activity has not become better organized...I have slightly lowered odds of tropical cyclone development. In the short term upper-level winds are favorable for tropical development as an expansive upper ridge cell (with low shear and upper outflow) from Africa is expanding into the eastern tropical Atlantic. The pair of frontal lows to emerging across the north Atlantic and from the northeastern US will have no effect on this system while passing too far north...but a rather amplifedupper trough associated the western of the two frontal lows will strengthen the Atlantic surface subtropical ridge with its western convergence by 72 to 96 hours such that a westward acceleration in track of this disturbance will be possible. I do not raise odds of development above 10% between 72 to 96 hours and drop the odds back to 0% by 120 hours as lingering central Atlantic upper vorticity is expected to begin negatively shearing this disturbance...especially by 120 hours as it merges with a cut-off upper vortex associated with the disturbance in area of interest #3.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Oct 5)...0% chance of tropical cyclone formation (tropical Atlantic southwest of the Republic of Cabo Verde Islands near 25W)
IOH 48 Hr Outlook (1200Z Oct 6)...5% chance of tropical cyclone formation (tropical Atlantic near 30W)
IOH 72 Hr Outlook (1200Z Oct 7)...10% chance of tropical cyclone formation (tropical Atlantic near 36W)
IOH 96 Hr Outlook (1200Z Oct 8)...10% chance of tropical cyclone formation (tropical Atlantic near 42W)
IOH 120 Hr Outlook (1200Z Oct 9)...0% chance of tropical cyclone formation (tropical Atlantic near 47W)
AREA OF INTEREST #3...In their 5-day tropical weather outlook...the National Hurricane Center has introduced a surface cold front and upper trough emerging from eastern Canada the northeastern US as various computer model runs have suggested over the last couple of days that these features could evolve into a cut-off deep-layered low pressure by 5 days capable of acquiring tropical characteristics in the open central Atlantic. At the surface...the cut-off is expected to be induced by a strong surface ridge to build in the central Atlantic in 72 to 96 hours due to increasing western convergence of the sharpening upper trough...and the upper trough is expected to sharpen with a portion of the trough becoming a cut-off upper vortex due to broad upper ridging amplifying to the west in warm surface southerly flow ahead of a strong central Canada frontal cyclone to form from the sharp upper trough currently making landfall over western North America. The surface and upper-level ridging is expected to drive the resulting cut-off deep-layered low pressure southwestward by days 4 and 5. Although this feature is expected to form over waters typically too cool for tropical development...the cold temperatures of the cut-off upper vortex could still de-stabilize the atmosphere for thunderstorm activity to develop. My 120-hour peak odds of development are 30% as the NAVGEM...CMC...and Euro models generally agree on subtropical development...the GFS is the only major computer model that does not show this (curiously despite also predicting a vigorous cut-off upper vortex that would promote a surface low pressure counterpart with its eastern divergence). Should the GFS join the rest of the models...and/or if the other models continue to strongly agree...I will be raising my odds of development in my next update.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Oct 5)...0% chance of subtropical cyclone formation (western Atlantic near 35N-60W)
IOH 48 Hr Outlook (1200Z Oct 6)...0% chance of subtropical cyclone formation (central Atlantic near 35N-45W)
IOH 72 Hr Outlook (1200Z Oct 7)...0% chance of subtropical cyclone formation (southwest of the Azores near 35N-32W)
IOH 96 Hr Outlook (1200Z Oct 8)...5% chance of subtropical cyclone formation (central Atlantic near 33N-36W)
IOH 120 Hr Outlook (1200Z Oct 9)...30% chance of subtropical cyclone formation (central Atlantic near 31N-41W)
AREA OF INTEREST #4...Showers and thunderstorms extending from the northwestern Caribbean Sea...in the vicinity of Jamaica and eastern Cuba...to the eastern Bahamas and adjacent western Atlantic waters...is being supported by upper divergence between the eastern fracture of an upper trough in the region which has recently evolved into a cut-off upper vortex and a Caribbean upper ridge cell. The souhwestern part of this expansive area of activity also appears boosted by outflow of the upper ridge cell. This disturbance appears it will initially slowly drift northward or orthwestward under the influence of the central US surface ridge as that ridge later moves into the western Atlantic...and as the cut-off upper vortex gravitates northwestward toward and eventually merges with the sharp upper trough currently making landfall over western North America. The merger should be completed by 72 hours...upon which time a tremendous area of upper divergence on the east side of the merged upper trough as well as outflow of upper ridging to the east could cause subtropical cyclone development by that time. However by 96+ hours...whatever surface low pressure forms from this disturbance will have merged with the cold front of the merged upper trough...making this disturbance lose tropical characteristics. What happens after 120 hours could get quiet interesting at a location northwest of Bermuda and offshore of the eastern US coast...as the CMC...NAVGEM...and Euro models suggest by next week a round of amplifying warm upper ridging to the west and north could cut-off the tremendous merged upper trough into a rather impressive upper vortex...with this disturbance perhaps evloving into a large and strong subtropical cyclone whose thunderstorms would be supported by the cold temepratures of the upper vortex depsite being over waters below 26 deg C. The only major model that does not show such a solution is the GFS. It is too early to know exactly how this disturbance could evolve that far out in time as computer model accuracy is typically low by that time...so for now will just keep an eye out to see if the models continue suggesting this solution over the next few days.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Oct 5)...0% chance of subtropical cyclone formation (northeast of the eastern Bahamas near 25N-69W)
IOH 48 Hr Outlook (1200Z Oct 6)...0% chance of subtropical cyclone formation (northeast of the eastern Bahamas near 26N-69W)
IOH 72 Hr Outlook (1200Z Oct 7)...10% chance of subtropical cyclone formation (western Atlantic near 29N-69.5W)
IOH 96 Hr Outlook (1200Z Oct 8)...0% chance of subtropical cyclone formation (western Atlantic near 35N-70W)
IOH 120 Hr Outlook (1200Z Oct 9)...0% chance of subtropical cyclone formation (western Atlantic near 39N-61W)