*******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.**********
...WEDNESDAY MAY 11 2022 11:50 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 Carolinas for acquisition of tropical characteristics. See area of interest #1 section below for more details.
AREA OF INTEREST #1…The deep-layered low pressure system that has been offshore of the eastern US coast continues to consist of an upper vortex parked over a decaying surface frontal low. Since early this morning (before sunrise)… the northern of the two surface centers of this low pressure system clearly became the dominant while establishing a tight cloud swirl on satellite pictures. As of 1800Z earlier this evening… the swirl center passed 34N-72.5W. Although most of the nearby deep-layered ridge has shifted into the northwest Atlantic… warm southerly flow on the east side of the current western US frontal low will promote an ongoing lobe of deep-layered ridging over the northeast US and eastern Canada…expected to be strong enough to buckle the west track of the deep-layered low pressure into a southward angle. This track should keep the surface swirl center of the deep-layered low just offshore of North Carolina in the next 24 hours… and result in a landfall on the South Carolina coast around 36 hours. Given the consolidated surface swirl center has formed more north… my updated forecast track in the outlook below is adjusted accordingly.
A recent update to the National Hurricane Center (NHC) sea-surface temperature data shows a slight drop in the temperature of the warm Guif stream waters (https://www.nhc.noaa.gov/sst/). And combined with the northward-adjusted forecast track… in the next 24 hours the cloud swirl surface center will be passing over 24 deg C waters which is just below the 26 deg C threshold needed for tropical development. However the coolish upper vortex (1200 dekameters in height at 200 mb) may be enough to help produce thunderstorms at that water temperature. The formation of a defined surface swirl center… currently featuring some small pockets of showers and thunderstorms….is also a positive compared to the multiple centers seen yesterday. Therefore I have raised odds of subtropical cyclone formation to 15%. This is only a small increase in development odds as the NHC has not introduced this system into a tropical weather outlook… and it is possible that any thunderstorm increase that occurs in the next 24 hours might be too short-lived to classify a subtropical cyclone.
Regarding impacts to land areas:
(1) The surface circulation of the deep-layered low has been weakening under the core of the overhead upper vortex where there is a lack of upper divergence… sea swells that have been affecting the US mid-Atlantic coast should continue to weaken through tonight.
(2) For the Carolina coast… locally heavy rain may develop tomorrow or Friday should this system see an increase in thunderstorms or develop into a weak subtropical cyclone (subtropical depression for example)
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z May 12)…15% chance of subtropical cyclone formation (offshore of Cape Fear North Carolina near 33N-77.5W)
IOH 48 Hr Outlook (1800Z May 13)…0% chance of subtropical cyclone formation (Georgia/South Carolina border near 32.5N-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… surface low wobbles west-southwest while slowly weakening and shrinking… dissipates over the southern tip of South Carolina at 42 hours
1200Z ECMWF Model Run...
**For area of interest #1…surface low wobbles west-southwest while slowly weakening and shrinking… dissipates offshore of South Carolina between 24 and 48 hours
1200Z GFS Model Run...
**For area of interest #1… surface low wobbles west-southwest while slowly weakening and shrinking… dissipates offshore of South Carolina at 33 hours
1200Z NAVGEM Model Run...
**For area of interest #1… surface low dissipates offshore of North Carolina Outer Banks at 24 hours