Jack Beven
EF0
Hello, everyone!
I wasn't able to chase the tornadic cell in Palm Beach County. However, another supercell or supercell-wannabe occurred over northern Miami-Dade County to the north of the National Hurricane Center between about 4-5:30 PM EDT.
This cell had a good tilted updraft and showed evidence of mid-level rotation both visually and in WSR-88D doppler winds. What was lacking was low-level organization - only on one occasion did an RFD appear to wrap around the updraft, and the low-level rotation was broad and slow. While there were many instances of rapidly rising scud under the updraft base, these never really congealed into a persistent wall cloud. After several attempts to wrap up, the storm eventually died when the updraft was undercut by a combination of sea breeze fronts and the FFD.
The CAPE was about 2800 J/kg in the Miami area this afternoon, which is very good by South Florida standards. The 12Z Miami hodograph showed a straight-line profile more favorable for splitting cells than right-moving supercells. However, there was backed low-level flow near the east coast associated with the sea breeze front during the afternoon, and there may have been boundary collisions to aid deviant cell motions and enhance the helicity. The Miami-Dade county cell started out moving east-northeastward, then turned east-southeastward and slowed its forward motion. Before it died, it turned southward and southwestward.
The Palm Beach County cell may have had the advantage of interacting with an old frontal boundary. If so, that may have given it the extra push needed for it to produce a tornado.
All in all, an interesting afternoon of weather - an event with marginal dynamics on the synoptic scale enhanced by the local mesoscale effects of South Florida.
Chase time - about 90 minutes. Chase distance - about 200 feet.
Jack Beven
I wasn't able to chase the tornadic cell in Palm Beach County. However, another supercell or supercell-wannabe occurred over northern Miami-Dade County to the north of the National Hurricane Center between about 4-5:30 PM EDT.
This cell had a good tilted updraft and showed evidence of mid-level rotation both visually and in WSR-88D doppler winds. What was lacking was low-level organization - only on one occasion did an RFD appear to wrap around the updraft, and the low-level rotation was broad and slow. While there were many instances of rapidly rising scud under the updraft base, these never really congealed into a persistent wall cloud. After several attempts to wrap up, the storm eventually died when the updraft was undercut by a combination of sea breeze fronts and the FFD.
The CAPE was about 2800 J/kg in the Miami area this afternoon, which is very good by South Florida standards. The 12Z Miami hodograph showed a straight-line profile more favorable for splitting cells than right-moving supercells. However, there was backed low-level flow near the east coast associated with the sea breeze front during the afternoon, and there may have been boundary collisions to aid deviant cell motions and enhance the helicity. The Miami-Dade county cell started out moving east-northeastward, then turned east-southeastward and slowed its forward motion. Before it died, it turned southward and southwestward.
The Palm Beach County cell may have had the advantage of interacting with an old frontal boundary. If so, that may have given it the extra push needed for it to produce a tornado.
All in all, an interesting afternoon of weather - an event with marginal dynamics on the synoptic scale enhanced by the local mesoscale effects of South Florida.
Chase time - about 90 minutes. Chase distance - about 200 feet.
Jack Beven
