*******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.*********
...THURSDAY JUNE 13 2024 4:40 PM EDT...
For the Atlantic basin... continuing to monitor two areas of interest for possible tropical cyclone formation as follows:
See area of interest #4 section below for an update on the surface low pressure swirl that was over northern Florida yesterday which has now made its way into the waters offshore of the southeastern United States. The surface trough over the eastern Bay of Campeche is forecast to merge with the current south-central Caribbean tropical wave... resulting in an elongated tropical low pressure area from the Bay of Campeche to Central America that could eventually develop over the next several days... see area of interest #5 section below for more information.
AREA OF INTEREST #4... The surface low pressure spin that was over the northern Florida peninsula yesterday has moved into western Atlantic waters offshore of the southeastern United States... with satellite animation suggesting the center was located near 30.5N-78.5W as of 1800Z. As expected... westerly wind shear over this system has reduced while supportive upper divergence has increased in response to the upper vorticity string over the southeastern US amplifying in response to upstream amplification of warm upper ridging over the western US. As a result this system has become better organized while having a sizeable batch of showers and thunderstorms develop closer to center... albeit the activity only covers the east half of the circulation as some westerly shear remains in the region. Because the original circulation center remains intact... instead of a new one forming off to the east in the sheared-off thunderstorm activity as surmised yesterday... the current position of this system is west of my previous forecast track and my updated one is adjusted accordingly. A northeast acceleration of this system generally parallel to the United States east coast is expected while this system becomes steered in the flow ahead of the surface cold front now approaching from the western Great Lakes region of North America. Regarding odds of tropical cyclone formation... because this system's organization has improved I have raised them but still keep them below 50% as the models are trending with the surface circulation becoming elongated... possibly with multiple centers... instead of staying circular with a well-defined center needed for cyclone status. This is because much of the upper vorticity over the southeastern US is forecast to merge with the high-latitude upper trough that will be associated with the incoming surface cold front... with the merged upper-level energy having an elongated upper divergence zone supporting an elongated surface circulation. Even though the westward-adjusted forecast track is closer to the band of warm Gulf stream waters... the thermodynamic picture at 48+ hours becomes unfavorable for tropical development while this system merges with the incoming cold front and ingests cooler drier air behind the front. This is when I end the outlook by lowering odds of tropical cyclone formation to 0%.
Note the ongoing band of thunderstorms and heavy rainfall across south Florida at this point is associated with the surface trough from which this system originated from rather than this system directly... and the surface trough and band of activity may linger over the next day or so due to upper divergence ahead of the upper vorticity parked over the southeastern US... watch out for ongoing rainfall flood hazards in this region. Once this system merges with the cold front... the remnants may transition into a strengthening non-tropical frontal low that could bring coastal surf across the northeastern US and Atlantic Canada coastlines... with gusty winds possible across Newfoundland by Sunday.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jun 14)... 30% chance of tropical cyclone formation (south-southeast of Cape Hatteras North Carolina near 33N-74.5W)
IOH 48 Hr Outlook (1800Z Jun 15)... 0% chance of tropical cyclone formation (offshore of the northeastern United States near 36N-71W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Formation chance through 48 hours... 20%
Formation chance through 7 days... 20%
AREA OF INTEREST #5... Models remain in agreement that the current south-central Caribbean tropical wave will merge with the current eastern Bay of Campeche surface trough... resulting in a northwest-to-southeast tilted tropical low pressure system spanning the Bay of Campeche and Central America. Due to warm southerly flow ahead of a currently developing surface frontal system over western North America... upper ridging over the western US is currently amplifying which will soon push a portion of the current southeastern US upper vorticity into the western Gulf of Mexico. In turn this will displace the regional tropical upper ridge cell and its maximum region of supporting upper outflow southeastward toward Central America in the short-term... therefore my 5-day outlook below assumes the elongated tropical low pressure system has its best shot at developing a better-defined center in the Caribbean waters toward Central America. Whatever center does develop will tend to take a west-northwest track while pushed by the southwest edge of a surface ridge that will soon build in the convergence zone along the back side of the upper trough that absorbs area of interest #4. I keep my peak odds of tropical cyclone formation at 10% as this area of interest does not currently have a well-defined surface center... and will need time to develop one due to the initial broad nature of the forecast elongated tropical low pressure area. Odds are dropped back to 0% once I forecast the possible better-defined center to make landfall across Belize and the southern Yucatan peninsula. Noting in the long range (5+ days)... the possible better-defined center moves into the Bay of Campeche waters. However by then... upper winds would remain favorable for development as the disrputive western Gulf upper vorticity will be lifted northward and away by an upper trough that moves into the central US (the upper vorticity currently moving into southern California eventually makes its way into the central US as a trough once the current northeast Pacific upper vortex and north Canada polar upper vortex finally merge... which increases the steering westerly flow across the western and central US). Thus I raise odds of development back above 0% once this system enters the Bay of Campeche waters.
Regardless of whether or not this area of interest develops into a tropical cyclone... periods of heavy rainfall with flash flooding potential cannot be ruled out across Central America and southeastern Mexico in the days ahead.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jun 14)... 0% chance of tropical cyclone formation (northeastern Nicaragua near 14N-84W)
IOH 48 Hr Outlook (1800Z Jun 15)... 10% chance of tropical cyclone formation (just inland of the Honduras north coast near 15.5N-86.2W)
IOH 72 Hr Outlook (1800Z Jun 16)... 10% chance of tropical cyclone formation (coastal Belize near 16.5N-88.5W)
IOH 96 Hr Outlook (1800Z Jun 17)... 0% chance of tropical cyclone formation (southwestern Yucatan peninsula near 18.8N-90.5W)
IOH 120 Hr Outlook (1800Z Jun 18)... 10% chance of tropical cyclone formation (central Bay of Campeche near 20.5N-94W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT***************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 40%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Jun 13) CMC Model Run...
**For area of interest #4... becomes an elongated surface low offshore of the southeastern US coastline through 36 hours... subsequently merges with incoming cold front to the west through 66 hours while moving into the waters offshore of the northeastern US... while making landfall over south-central Newfoundland at 84 hours the remnant frontal low loses its identity to stronger frontal low materializing just to the north.
**For area of interest #5... surface trough currently over the eastern Bay of Campeche merges with tropical wave currently in south-central Caribbean sea through 66 hours which results in NW/SE tilted surface trough from the Bay of Campeche to the coast of Nicarauga while at the same time an eastern Pacific compact tropical low develops west-southwest of the Gulf of Tehuantepec with the support of the outflow of the regional tropical upper ridge... through 114 hours the surface trough develops a broad tropical low centered over northern Guatemala which pulls the compact eastern Pacific tropical low/cyclone eastward into a landfall with the Guatemala/Mexico border and then absorbs the eastern Pacific feature... through 132 hours the broad tropical low pressure center moves from northern Guatemala and into the eastern Bay of Campeche with tropical cyclone formation suggested at 20.2N-94W at 150 hours... the strengthening tropical cyclone makes landfall in northern Veracruz through 168 hours
0000Z (Jun 13) ECMWF Model Run...
**For area of interest #4... becomes an elongated surface low offshore of the southeastern US coastline through 42 hours... northeast part of the elongated circulatoin becomes a tropical depression just offshore of Cape Hatteras North Carolina at 48 hours... the tropical depression quickly merges with incoming cold front to the west and becomes a non-tropical frontal cyclone offshore of the northeastern US coast through 66 hours... center of frontal cyclone moves across southeastern Newfoundland at 90 hours and then loses identity to adjacent frontal low to the north shortly thereafter
**For area of interest #5... surface trough currently over the eastern Bay of Campeche merges with tropical wave currently in south-central Caribbean sea through 66 hours which results in NW/SE tilted surface trough from the Bay of Campeche to the Caribbean waters just east of Nicaragua... tropical low develops along surface trough in central Bay of Campeche near 20N-94W at 126 hours... while drifting slowly west-northwest the tropical low becomes a tropical cyclone just offshore of northern Veracruz through 162 hours
0600Z (Jun 13) GFS Model Run...
**For area of interest #4... becomes an elongated surface low offshore of the southeastern US coastline through 36 hours... through 60 hours merges with incoming cold front to the west and loses its identity along the front while located offshore of the northeastern US.
**For area of interest #5... surface trough currently over the eastern Bay of Campeche merges with tropical wave currently in south-central Caribbean sea through 45 hours which results in NW/SE titled surface trough from the Bay of Campeche to south-central Caribbean... through 99 hours the SE end of the surface trough develops into a compact tropical cyclone located just offshore of the Nicaragua/Honduras border... through 126 hours the remainder NW portion of the surface trough develops into a broad Bay of Campeche tropical low that pulls the tropical cyclone northwestward into the northeast coast of the Yucatan peninsula... the remnants of the tropical cyclone move quickly west-northwest across the northern Yucatan and becomes absorbed by the Bay of Campeche tropical low through 138 hours... the Bay of Campeche tropical low remains broad without tropical cyclone formation while drifitng into southeastern Mexico through 168 hours.
**Tropical wave currently at 47.5W longitude crosses the remainder of the Atlantic tropical belt and southern Caribbean waters... through 168 hours rapidly develops into a south-central Caribbean tropical cyclone near 11.2N-80W while enhanced by split flow upper divergence between regional upper vorticity to the northeast and tropical upper ridge associated with AOI #5 to the northwest (upper vorticity is southern cut-off of frontal upper trough that absorbs AOI #4)
**South part of the western Atlantic frontal upper trough that absorbs AOI #4 begins to become cut-off from the rest of the upper trough at 102 hours due to the force of the warm upper ridge over eastern North America tied to the warm sector of a developing large-scale western North America frontal system and also due to the force of the tropical upper ridge cell over AOI #5... the eastern divergence zone of the cut-off upper vorticity produces a surface low just southeast of Bermuda by 102 hours... surface low proceeds to move northwest under influence of northeast quadrant of the upper vorticity with the surface center passing just northeast of Bermuda just after 132 hours as it becomes a tropical cyclone... tropical cyclone continues northwest in general direction of northeastern US coastline through 168 hours while reaching 36.2N-70W (tropical cyclone formation was suggested despite system initially being over waters below 26 deg C while upper air temps forecast to be warm and stabilizing with 200 mb heights well above 1200 dekameters... not until 168 hours does this system reach narrow ribbon of 26 deg C associated with Gulf Stream).
0600Z (Jun 13) NAVGEM Model Run...
**For area of interest #4... becomes an elongated surface low offshore of the southeastern US coastline through 36 hours... merges with incoming cold front to the west and becomes a strenghtening elongated non-tropical frontal low offshore of the northeastern US coast through 60 hours... remnant frontal low's center crosses southeastern Newfoundland at 84 hours and then loses identity to adjacent frontal low to the north shortly thereafter
**For area of interest #5... surface trough currently over the eastern Bay of Campeche merges with tropical wave currently in south-central Caribbean sea through 72 hours which results in NW/SE tilted surface trough from the Bay of Campeche to the Caribbean waters just east of Nicaragua... NW part of trough evolves into Bay of Campeche tropical low at 120 hours located near 20.5N-94W... tropical low proceeds to accelerate northwest toward ridge weakness associated with large frontal system approaching from western North America and makes landfall at the Texas/Mexico border at 162 hours where it weakens to a surface trough.
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