MY 2024 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #5

*******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 MAY 30 2024 11:25 AM EDT...

Even though the 2024 Atlantic Hurricane Season does not officially start until June 1... continuing daily birdseye view posts on the Atlantic tropics while tracking an ongoing disturbance in the southern Caribbean Sea... see area of interest #3 section below for more information.

For the mid-latitudes of the Atlantic... as forecast by models over the last several days a cut-off deep-layer low pressure has materialized west-northwest of the Azores due to upstream warm core deep-layer ridging. Although the upper-layers of this circulation are colder than previously forecasted (200 mb heights of 1189 dekameters instead of 1196 dekameters)... this system is parked over waters just below 20 deg C resulting in an instability profile not sufficient for tropical development so far. In addition the surface layer of this system has a broad center instead of well-defined center needed for tropical development. Also noting the models are in agreement that the current upper trough/surface frontal system over eastern North America will evolve into a second cut-off deep-layer low pressure in the northwest Atlantic in the days ahead as warm core deep-layer ridging prevails across the far north Atlantic in the warm sector of frontal systems to slide across Canada. Because the forecast northwest Atlantic cut-off low will be further west toward warmer Gulf Stream waters... it has more potential to have instability needed for transition into a tropical system (for example referencing the recent 1800Z GFS model run from last evening). However not declaring a new tropical area of interest for the northwest Atlantic at this time as the majority of recent model runs suggest the upper-layers of the northwest Atlantic system and current system west-northwest of the Azores merge... resulting in a lack of focused upper divergence needed to trigger a well-defined northwest Atlantic surface center that would be required for tropical development.

For the eastern and central tropical Atlantic... the unusually robust for May tropical wave that was at 27.5W longitude in the previous update is now located at 37.5W longitude and has lost its concentrated thunderstorm activity due to increasing westerly shear and dry Saharan air. A similar tropical wave recently emerged from the west coast of Africa and is now at 20W longitude... however it too has lost its concentrated thunderstorm activity despite not yet reaching the high shear region due to dry Saharan air.

AREA OF INTEREST #3... The following is a sequence of colorized infrared satellite imagery showing progression of ongoing southern Caribbean disturbance from May 28 through today. Dashed line shows the position of the associated passing surface tropical wave of low pressure... and an "L" indicates the position of mid-level rotation based on satellite animation and/or curvature of thunderstorm activity:

Since my previous update on May 28 evening... the ongoing tropical disturbance in the southern Caribbean Sea has undergone the following changes which can be followed using the above satellite chart. The initial mid-level low pressure spin that occurred west of the surface tropical wave around 0000Z May 29 dissipated along with much of the initial thunderstorm activity... and by 0830Z May 29 the tropical wave was pronounced midway between Jamaica and northern Nicaragua with a short-lived mid-level spin of its own. The tropical wave has since proceeded to make landfall across Central America... however since 0300Z this morning the cyclonic curvature of renewed thunderstorm activity suggested the tropical wave has left behind a mid-level low pressure spin located just offshore of the Nicaragua/Costa Rica border... and the CIMSS 850 mb vorticity product appears to agree with this observation (https://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=vor&zoom=&time=). Because the thunderstorm activity has since flourished with this mid-level rotation with the support of outflow induced by an ongoing regional upper anticyclone... this is an ongoing area of interest.

This disturbance has been slow to move due to the surface ridge weakness associated with the frontal lows now departing eastern North America... however as the surface ridge currently over the Great Lakes region of North America encroaches into the region a westward drift into Central America is expected. Although the GFS model has dropped showing short-term development in this region... I have maintained a peak 20% odds of tropical cyclone formation due to the recent flourishing of this system's thunderstorm activity. Regardless of further development or not... increased rainfall with flash flooding potential is possible for Costa Rica and Nicaragua over the next couple of days.

In the longer-term... the remnants of this disturbance may accelerate northeast and re-emerge over Caribbean waters... then move across the northern Caribbean Islands and into the western Atlantic while transitioning into a system supported by the eastern divergence zone of an upper trough that arrives from the southeastern US in 96+ hours (this upper trough will be the southern fracture of the current trough over western North America). At this time the traditionally reliable model guidance suggests the upper trough will be too low in amplitude (apply excess westerly wind shear) such that long-range tropical development would be unlikely in this scenario.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (0600Z May 31)... 20% chance of tropical cyclone formation (southeast coast of Nicaragua near 11.5N-84W)

IOH 48 Hr Outlook (0600Z Jun 1)... 0% chance of tropical cyclone formation (southeastern Nicaragua near 11.5N-84.5w)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 AM 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 (May 29) CMC Model Run...

**For area of interest #3... no development shown

0000Z (May 30) CMC Model Run...

**For area of interest #3... no development shown

1200Z (May 29) ECMWF Model Run...

**For area of interest #3... no development shown

0000Z (May 30) ECMWF Model Run...

**For area of interest #3... no develpoment shown

1800Z (May 29) GFS Model Run...

**For area of interest #3... remnants over Central America interact with divergence zone of upper trough that ejects from southeastern US such that it transitions into a surface trough extending northeast across Jamaica... eastern Cuba... and southeastern Bahamas through 141 hours (northeastern part of surface trough later intensifies into western Atlantic surface low near 26.5N-62.5W by 168 hours... however westerly shear imparted by upper trough likely excessive for tropical development here)

**Upper trough currently over eastern Canada evolves into cut-off upper vortex whose eastern divergence zone triggers a surface frontal cyclone near 37.5N-60W by 81 hours... from 81 to 126 hours the surface frontal cyclone whirls beneath the upper vortex taking it to 41N-60W and then back to 37.5N-60W... from 126 to 168 hours the upper vortex and frontal cyclone drift northeast to 40N-57.5W (from 81 to 168 hours the model run suggests tropical characteristics to frontal cyclone which are possible from combo of 20 to 24 deg C waters along forecast track and cold temps of upper vortex)

0600Z (May 30) GFS Model Run...

**For area of interest #3... remnants over Central America interact with divergence zone of upper trough that ejects from southeastern US such that it transitions into a surface trough extending northeast across Jamaica...Haiti... and southeastern Bahamas through 132 hours (northeastern part of surface trough later intensifies into western Atlantic surface low near 27N-57.5W by 168 hours... however westerly shear imparted by upper trough likely excessive for tropical development here)

1800Z (May 29) NAVGEM Model Run...

**For area of interest #3... broad tropical low develops just west-southwest of Jamaica through 114 hours... broad tropical low subsequently moves northeast across Cuba and central Bahamas through 150 hours after which time it becomes absorbed by possible tropical low offshore of South Carolina.

**Divergence zone of upper trough that emerges from southeastern US by day 5 triggers a possible tropical low offshore of South Carolina through 168 hours

0600Z (May 30) NAVGEM Model Run...

**For area of interest #3... broad tropical low develops southwest of Jamaica through 108 hours... broad tropical low subsequently moves northeast across Cuba and central Bahamas through 132 hours... while accelerating east-northeast the broad tropical low tranisitions into elongated non-tropical frontal low supported by upper trough ejecting from southeastern US and reaches 27.5N-64.5W by 168 hours.