Alert archive / Florida / Mesoscale Discussions in 2021
Mesoscale Discussion 398
The Storm Prediction Center issued this mesoscale discussion at Apr 19, 2021, 4:36 AM EDT for 11 counties in Florida. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 19, 2021, 4:36 AM EDT (08:36 UTC)
- Expired
- Apr 19, 2021, 7:00 AM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Brevard County, FL, DeSoto County, FL, Hardee County, FL, Highlands County, FL, Hillsborough County, FL, Indian River County, FL, Manatee County, FL, Okeechobee County, FL, Osceola County, FL, Polk County, FL, Sarasota County, FL
The radar
The Tampa radar (KTBW), 81 km from the middle of the area, began a volume at 08:35 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 00:00Z, 8.6 hours before the alert went out and 81 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
- 1430 J/kg
- Mixed-layer CIN
- -14 J/kg
- Mixed-layer LCL
- 988 m above ground
- 0-6 km bulk shear
- 42 kt
- 0-1 km storm-relative helicity
- 51 m²/s²
- 0-3 km storm-relative helicity
- 66 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 2.0
The text
As transmitted.
095
ACUS11 KWNS 190836
SWOMCD
SPC MCD 190836
FLZ000-191100-
Mesoscale Discussion 0398
NWS Storm Prediction Center Norman OK
0336 AM CDT Mon Apr 19 2021
Areas affected...Central Florida Peninsula
Concerning...Severe potential...Watch unlikely
Valid 190836Z - 191100Z
Probability of Watch Issuance...20 percent
SUMMARY...An isolated large hail threat will continue from near the
Tampa area eastward across the central Florida Peninsula. The threat
should remain too marginal for weather watch issuance.
DISCUSSION...The latest water vapor imagery shows a shortwave trough
across the eastern Gulf of Mexico. A plume of mid-level moisture
extends from near the shortwave trough east-northeastward across
central Florida. Thunderstorm development is taking place within
this plume in a moist airmass situated across the southern and
central Florida Peninsula. Surface dewpoints across central Florida
are generally near 70 F which is contributing to moderate
instability (MLCAPE 1000-1500 J/kg). Thunderstorms are expected to
continue to develop early this morning from near Tampa Bay eastward
across central Florida, along an east-to-west corridor of enhanced
low-level convergence. According to the Melbourne, Florida WSR-88D
VWP, 0-6 km shear is near 40 kt and there is some veering of the
winds with height in the boundary layer. This will support a couple
supercells. The stronger rotating storms could produce isolated
large hail and perhaps a few strong wind gusts.
..Broyles/Grams.. 04/19/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MLB...TBW...
LAT...LON 27618035 27278098 27028204 27058246 27458266 27858263
28108210 28418072 27618035SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 18, 9:35 PM EDT | Mesoscale Discussion | SPC | Brevard, Hardee, Hernando, Hillsborough, Lake, Manatee and 7 more | 85 min |
Nearby
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.