Alert archive / Florida / Mesoscale Discussions in 2021
Mesoscale Discussion 809
The Storm Prediction Center issued this mesoscale discussion at May 30, 2021, 12:35 PM EDT for 24 counties in Florida. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 30, 2021, 12:35 PM EDT (16:35 UTC)
- Expired
- May 30, 2021, 3:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 24 counties
Broward County, FL, Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Highlands County, FL, Hillsborough County, FL, Indian River County, FL, Lake County, FL, Lee County, FL, Manatee County, FL, Martin County, FL, Miami-Dade County, FL, Monroe County, FL, Okeechobee County, FL, Orange County, FL, Osceola County, FL, Palm Beach County, FL, Polk County, FL, Saint Lucie County, FL, Seminole County, FL, Sumter County, FL
The radar
The Tampa radar (KTBW), 130 km from the middle of the area, began a volume at 16:33 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Tampa Bay, FL (KTBW), launched 12:00Z, 4.6 hours before the alert went out and 130 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1117 J/kg
- Mixed-layer CIN
- -11 J/kg
- Mixed-layer LCL
- 737 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 15 m²/s²
- 0-3 km storm-relative helicity
- 24 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted.
178
ACUS11 KWNS 301636
SWOMCD
SPC MCD 301635
FLZ000-301900-
Mesoscale Discussion 0809
NWS Storm Prediction Center Norman OK
1135 AM CDT Sun May 30 2021
Areas affected...portions of the Florida Peninsula
Concerning...Severe potential...Watch unlikely
Valid 301635Z - 301900Z
Probability of Watch Issuance...20 percent
SUMMARY...Thunderstorms will continue to develop this afternoon
along the Atlantic and Gulf of Mexico sea breezes. Gusty
thunderstorm winds will be the primary threat, although small hail
will be possible with the strongest thunderstorms. A watch is
currently not expected.
DISCUSSION...Strong diurnal heating across the Florida Peninsula,
along with weak low-level flow, should allow for both the Atlantic
and Gulf of Mexico coastal sea-breezes to advance inland this
afternoon. Localized convergence along the sea-breezes and weak
large-scale ascent associated with a weak upper trough will support
thunderstorm development through the afternoon. The background
environment for these thunderstorms will be moist and unstable, with
most-unstable CAPE values in the 2000-3000 J/kg range and
little-to-no convective inhibition. Weak effective-layer shear
should preclude more robust thunderstorm organization, leading to
predominantly cellular and multi-cellular cluster modes, with
storm-scale outflows interacting with the sea-breezes driving the
development of new updrafts. Gusty thunderstorm outflows will be the
predominant threat through the afternoon, although localized
small-to-marginally severe hail will also be possible with the most
intense updrafts.
A watch is currently not anticipated given the transient and highly
localized nature of any organized severe threat. However, convective
trends will be monitored.
..Marsh/Goss.. 05/30/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MFL...MLB...TBW...
LAT...LON 26628205 27528249 28538249 28838208 29018109 27958058
26808012 25878015 25318038 25288088 26018163 26628205Nearby
Mesoscale Discussions in Florida, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.