MY 2022 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #5
*******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.**********
...SUNDAY MAY 8 2022 10:05 PM EDT...
Although Atlantic Hurricane Season does not officially start till June 1st... continuing daily birdseye view posts as we continue to monitor the broad surface low offshore of the eastern United States for acquisition for tropical characteristics. Regardless of whether or not the surface low pressure acquires tropical characteristics... it is already bringing impact to the mid-Atlantic and northeastern United States coast. See area of interest #1 section below for more details.
AREA OF INTEREST #1... A broad frontal surface low pressure has made its way into the western Atlantic from the southeastern United States... and remains supported by an amplified upper trough trailing not far behind and also heading into the western Atlantic. A deep-layer ridge over eastern Canada will cut-off the upper trough from the mid-latitude westerlies... resulting in the trough becoming an upper vortex... will be monitoring the surface low pressure for acquisition of tropical characteristics as the surface low pressure meanders under the upper vortex over the next few days.
The updated forecast track in the outlook below is based on today’s latest model data which shows in the next 24 hours the center of the upper vortex taking shape just southwest of current position of the broad surface low pressure. The models today are better at showing a well-defined surface center developing near the broad surface low’s current position (35N-72.5W)... which is where the supportive northeastern upper divergence zone of the new upper vortex would be located. Then by 48 hours the upper vortex center is shown to drift east which makes the well-defined surface center pivot south on a counter-clockwise arc while steered by the west side of the upper vortex. At 72+ hours... the blocking southwest flank of the deep-layer ridge is forecast to weaken from a piece of energy to eject from the current western Canada upper trough regime... allowing the surface low and upper vortex to drift west-southwest toward the southeast US coast under the influence of what remains of the deep-layer ridge.
I have dropped the 24-hour odds of subtropical cyclone formation to 0% as the broad surface low is starting with deficiencies that will limit its ability to quickly gain tropical characteristics... including the lack of a well-defined center at present... dry air on its west side caused by the western convergence zone of the nearby upper trough... and the lack of thunderstorms near the broad central region of the surface low. The 48-hour odds are raised to 20% (over the 15% in the prior blog post) as the models today are better at showing a well-defined surface center forming (as discussed in the prior paragraph). However this is only a small rise in the odds due to a trifecta of negative thermodynamic factors as follows... (1) the 0 to 48 hour forecast track which keeps the surface low east of the warm Gulf Stream waters which are currently in a lukewarm low-20 deg C range... (2) not very cold upper vortex currently measuring 1200 dekameters in height at 200 mb... would like to see colder upper air temps for more confidence in thunderstorm generation for these water temps... (3) the above-mentioned dry air. Despite the west swing of this system into warmer Gulf Stream waters at 72+ hours... at present I have not elected to raise subtropical development odds above 20%. This is due to the models in the longer range weakening the surface low beneath the core of the upper vortex (where upper divergence is lacking)... so in the end the surface low may be too weak to take advantage of warm waters by the time it reaches them.
Regarding impacts to land areas:
(1) A tight surface pressure gradient remains set up between the north side of the surface low and south side of the Canadian deep-layer ridge. This is driving a strong toward-shore wind and ocean flow for the northeastern and mid-Atlantic US east coast. Sea swells... rip currents... and gusty winds will continue here through the early work week.
(2) Coastal sea swells are possible for the southeast US coast by the middle of this work week should the surface low maintain strength through acquisition of tropical characteristics. However the odds of this occurring appear low at present based on the above-mentioned latest model data
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z May 9)...0% chance of subtropical cyclone formation (western Atlantic near 35N-72.5W)
IOH 48 Hr Outlook (1800Z May 10)... 20% chance of subtropical cyclone formation (western Atlantic near 32N-71.5W)
IOH 72 Hr Outlook (1800Z May 11)...20% chance of subtropical cyclone formation (offshore of the Carolinas near 32.5N-74W)
IOH 96 Hr Outlook (1800Z May 12)...20% chance of subtropical cyclone formation (offshore of Georgia and northeast Florida near 30.5N-77.5W)
IOH 120 Hr Outlook (1800Z May 13)...0% chance of subtropical cyclone formation (just inland over the Florida/Georgia border near 30.5N-81.5W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...
**For area of interest #1...broad surface low develops better defined center near 32.5N-72.5W at 42 hours... through 78 hours the defined center makes a counter-clockwise loop and weakens while reaching 35.5N-71.5W (simultaneously the outer circulation becomes elongated north-south)... through 120 hours the entire low pressure system weakens to a surface trough drifting west toward the SE US coast
1200Z ECMWF Model Run...
**For area of interest #1...broad surface low develops better defined center near 32.5N-73W at 48 hours... subsequently the surface low weakens to a trough that drifts west-southwest toward the SE US coast thru 120 hours
1200Z GFS Model Run...
**For area of interest #1...broad surface low develops better defined center near 32.5N-72.5W at 39 hours... through 78 hours the defined center makes a counter-clockwise loop and weakens while reaching 32.5N-71.5W... subsequently the surface low weakens to a trough that drifts west-southwest toward the NE Florida coast thru 120 hours
1200Z NAVGEM Model Run...
**For area of interest #1...through next 36 hours the broad surface low develops a well-defined center that makes a counter-clockwise loop just offshore of the US mid-Atlantic coast and NC Outer Banks... through 66 hours and while weakening this center swings southwest and reaches 30N-74W... through 120 hours weakens to a westward-accelerating surface trough that crosses the Florida peninsula and enters the eastern Gulf of Mexico