*******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.**********
...MONDAY MAY 9 2022 10:23 PM EDT...
Although Atlantic Hurricane Season does not officially start till June 1st... continuing daily birdseye view posts as we continue to monitor the deep-layered low pressure 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... Recent satellite imagery of the deep-layered low pressure of interest located offshore of the eastern United States as of this writing. Left true-color taken at 1800Z May 9. Right colorized infrared taken at 0126Z May 10. Red plus marks the observed surface center of the low pressure. Yellow plus marks the upper level vortex center of the low pressure:
An ongoing warm core deep-layer ridge advancing into the northwest Atlantic from eastern Canada has cut-off an amplified upper trough that was exiting the eastern US from the mid-latitude westerlies. The end result is the upper trough is now a western Atlantic upper vortex stacked over the broad frontal surface low pressure that has also been parked offshore of the eastern US. The stacking of these two features has essentially created a deep-layered low pressure. Per the above satellite imagery and as of 1800Z earlier today... the core structure of the deep-layered low consists of a now well-defined surface center near 36N-70W and a well-defined upper vortex center to the southwest of that location. The well-defined surface center has formed with the support of the northeastern upper divergence zone of the upper vortex... and was confirmed with ASCAT-B and ASCAT-C ascending satellite scans of surface winds (https://manati.star.nesdis.noaa.gov/datasets/ASCATBData.php).
Today’s 1800Z position of the surface center was northeast of my previous forecast... however the latest model runs suggest no east-west adjustment is needed for the forecast track. However some of the recent model runs are a little north of previous runs with the long-range end result... for example the 12Z CMC which shows a landfall point as far north as the NC/SC border. Therefore I have nudged my latest forecast track points northward in the updated outlook below. Expect in the next 24 hours for the upper vortex center to drift east and the surface center to thus pivot south on a counter-clockwise arc while steered by the west side of the upper vortex. At 48+ 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 center and upper vortex center 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 10% as the deep-layer low pressure is starting with deficiencies that will limit its ability to quickly gain tropical characteristics... including (1) dry air on its west side caused by the western convergence zone of the upper vortex... (2) a current lack of thunderstorms in the central region of the deep-layered low pressure... (3) the combo of lukewarm low-20 deg C waters and a 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. At 48+ hours and before landfall with the southeast US coast... the thermodynamic picture may be helped as this system swings west into warm Gulf Stream waters... and so I raise subtropical odds of development to 20%. At present I have not elected to raise subtropical development odds above 20% as the models in the longer range still weaken 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. I will note that the longer range 12Z NAVGEM and 18Z GFS runs did a better job of keeping the surface low alive in the long range (i.e. did NOT dissipate the surface low into a trough before landfall)... perhaps these runs picked up on the potential for a weak subtropical cyclone forming?
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 Wednesday.
(2) Coastal sea swells are possible for the southeast US coast by the middle or late part of this 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 10)... 10% chance of subtropical cyclone formation (western Atlantic near 32.5N-71.5W)
IOH 48 Hr Outlook (1800Z May 11)... 20% chance of subtropical cyclone formation (offshore of the Carolinas near 33N-74W)
IOH 72 Hr Outlook (1800Z May 12)... 20% chance of subtropical cyclone formation (offshore of Georgia and northeast Florida near 31N-77.5W)
IOH 96 Hr Outlook (1800Z May 13)... 0% chance of subtropical cyclone formation (just inland over the southeast corner of Georgia near 31N-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...the current well-defined center of the surface low (which was at 36N-70W at 1800Z) whirls southwest to 32.5N-72W by 36 hours... afterwards the center whirls northwest while weakening and dissipates just offshore of the NC/SC border at 84 hours
1200Z ECMWF Model Run...
**For area of interest #1...the current well-defined center of the surface low (which was at 36N-70W at 1800Z) whirls southwest to 33N-72.5W by 24 hours... afterwards the circulation weakens to a dissipating surface trough located just offshore of the Carolinas at 96 hours
1800Z GFS Model Run...
**For area of interest #1...the current well-defined center of the surface low (which was at 36N-70W at 1800Z) whirls southwest to 31.5N-72.5W by 36 hours... subsequently this center gradually weakens and shrinks but keeps its definition as it makes a westward swing and makes landfall at the SC/GA border at 90 hours... the surface low subsequently moves northwest and dissipates inland over the northern part of the border at 102 hours
1200Z NAVGEM Model Run...
**For area of interest #1...the current well-defined center of the surface low (which was at 36N-70W at 1800Z) whirls southwest to 32.5N-72.5W by 36 hours... subsequently this center gradually weakens and shrinks but keeps its definition as it makes a westward swing and makes landfall on the Georgia coast at 90 hours... the surface low dissipates inland not long after (102 hours)