*******Note that forecast 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.*********
...SUNDAY OCTOBER 13 2024 11:59 PM EDT...
Tropical cyclones Leslie lost tropical characteristics over the weekend while zooming into the Azores… see remnants of Leslie section below for more information. Elsewhere monitoring the following areas of interest:
(1) An eastern Atlantic tropical wave of low pressure which continues to have development potential while moving toward the northeastern Caribbean Islands over the next five days… see area of interest #40 section below for details.
(2) A broad area of low pressure in the central and western Caribbean which may gradually develop in the days ahead as it drifts into Central America... see area of interest #42 section below for details.
REMNANTS OF LESLIE... Tropical Storm Leslie accelerated rapidly east-northeast into the Azores over the weekend in deep-layer westerly flow ahead of an overspreading cold front and associated upper trough that recently entered the northwest Atlantic from eastern Canada. Although the tropical storm regained thunderstorms early on Saturday it was downgraded to a surface trough but still packing 50 mph maximum sustained winds as the east-northeast acceleration contributed to the surface spin losing wind speed in the northwest quadrant… thus losing its closed surface circulation status. Since then the remnant low of Leslie merged with the incoming front and lost thunderstorms while ingesting cooler drier air behind the front… but the gale force status of this system as it moved into and across the Azores on Sunday remained while encountering supportive split flow upper divergence between westerlies on the north side of the mid-ocean upper anticyclone and the southwesterly flow ahead of the approaching NW Atlantic upper trough. Over the next 48 hours ex-Leslie takes and east-southeast then east dive into the northern Canary Islands in the flow on the northeast corner of the upper anticyclone. Models agree during this time the approaching upper trough digs toward ex-Leslie... allowing it to maintain gale force strength with ongoing split flow upper divergence between the northeast side of the upper anticyclone and digging-in upper trough to the northwest. After 48 hours the upper divergence maximum of the upper trough will be north of ex-Leslie where it will continue to generate one or more frontal lows... thus ex-Leslie is likely to lose its identity to the northern frontal low(s) as it moves toward northwestern Africa or southern Portugal in this timeframe.
Regarding impact to land areas... the Azores are seeing gusty winds and coastal surf… with these conditions to reach the northern Canary Islands within the next 48 hours. This is my final statement on Leslie on this blog as it is no longer tropical… however statements regarding impacts to land areas will remain on the home page bulletins of this site until ex-Leslie loses its identity.
AREA OF INTEREST #40... The surface tropical wave of low pressure that was pulling away from the Republic of Cabo Verde Islands early this weekend has since developed a well-defined low pressure swirl toward its northern apex… which recently crossed 18N-35W this weekend. This northern location has hampered development as the swirl has ingested dry Saharan air. There is also a suppressing wave of upper vorticity that was over coastal Africa that is now surging west toward the surface tropical wave while pushed by the current mid-Ocean upper anticyclone/ridge. However with time the chasing upper vorticity fades from its prolonged isolation from high-latitude cold air... allowing the mid-ocean upper anticyclone featuring low shear and upper outflow to increasingly take over. And with the tropical wave also tracking west toward lower concentrations of dry Saharan air with time… will still be monitoring the tropical wave for signs of development in the days ahead. A north-central Atlantic surface ridge building under the convergence zone of the upper trough now entering the northwest Atlantic should steer the tropical wave west along 17.5N to 18N latitude through 72 hours… potentially bending more north toward 19N latitude by 96 hours when reaching the SW edge of the surface ridge. The track then continues west into the waters just north of the northeastern Caribbean Islands by day 5 as the strong eastern North America surface ridge that builds behind the currently developing eastern North America frontal low slides offshore into the western Atlantic. Given the now well-defined swirl in satellite pictures and increasingly favorable conditions that lie ahead as outlined above… I have nudged my odds of tropical cyclone formation upward to 50%. Interests across the northeastern Caribbean Island (northern Lesser Antilles… Virgin Islands… and Puerto Rico) should be monitoring the progress of this tropical wave in the days ahead.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 5 days… 50% (just northeast of the northern Lesser Antilles near 19N-61W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Formation chance through 48 hours... 10%
Formation chance through 7 days... 40%
AREA OF INTEREST #42... For the Caribbean Sea... a surface trough that was over the NW Caribbean is merging with a south-central Caribbean broad low pressure area that developed on Friday… in recent NHC TAFB surface analyses the south-central Caribbean low pressure area was added as a tropical wave crossing 80W longitude. In the upper-levels suppressing upper vorticity that was over the southern Caribbean has been rolling in from east and disrupting the organization of the thunderstorm activity… with the activity constantly rolling west into Central America. The most recent round of thunderstorms rolled into Central America by 1400Z Sunday after which time it fizzled… with a new round now developing in the south-central Caribbean afterwards. Upper-level winds become increasingly favorable for development going forward as the overhead upper vorticity is now collapsing from prolonged isolation from high-latitude cold air... and likewise the next wave of upper vorticity that is rolling into the Caribbean from the central Atlantic never makes it overtop this disturbance while also fading… allowing the southwestern lobe of the mid-ocean upper anticyclone (featuring outflow and low shear) to increasingly take over. Noting after day 2 a deep-layer ridge is likely to build over the eastern US after the currently developing eastern North America frontal low departs… therefore forecasting possible tropical cyclone formation offshore of Central America through day 4 after which time the deep-layer ridge will have most likely pushed this system into Central America by day 5. As such interests in Central America should be remain aware of the possible Caribbean tropical development in the days ahead. Continuing to assign a 30% chance of tropical cyclone formation as not all models are in agreement on developing this area of interest.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
Formation chance through 4 days... 30% (over or near coastal Nicaragua)
Formation chance days 4 to 5... 0% (over inland Nicaragua)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Not in the official outlook
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
1200Z (Oct 13) CMC Model Run...
**For area of interest #40... moves into the eastern Bahamas through 168 hours without further development shown
**For area of interest #42... no development shown
1200Z (Oct 13) ECMWF Model Run...
**For area of interest #40... moves into the waters northeast of the eastern Bahamas through 168 hours without further development shown
**For area of interest #42... no development shown
1800Z (Oct 13) GFS Model Run...
**For area of interest #40... compact tropical cyclone formation suggested ENE of the northern Lesser Antilles at 99 hours… as a compact hurricane passes just north of the Virgin Islands and Puerto Rico and makes landfall on the north coast of the Dominican Republic through 168 hours
**For area of interest #42... tropical storm formation suggested just offshore of Nicaragua at 114 hours… tropical storm slides west into Nicaragua through 120 hours… proceeds to weaken to a remnant low that then entered the eastern Pacific through 168 hours
1800Z (Oct 13) NAVGEM Model Run...
**Not available at above-mentioned source
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