Alert archive / Florida / Mesoscale Discussions in 2018

Mesoscale Discussion 1716

December 20, 201817 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Dec 20, 2018, 7:38 AM EST for 17 counties in Florida. It was in force for 97 min.

The area

The outline as issued.

The facts

Issued: Dec 20, 2018, 7:38 AM EST (12:38 UTC)
Expired: Dec 20, 2018, 9:15 AM EST
In force: 97 min
Issued by: the Storm Prediction Center
Chance of a watch: 80%

Counties Brevard County, FL, Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Highlands County, FL, Indian River County, FL, Lee County, FL, Okeechobee County, FL, Orange County, FL, Osceola County, FL, Polk County, FL, Sarasota County, FL, Seminole County, FL, Volusia County, FL

The radar

The Melbourne radar (KMLB), 84 km from the middle of the area, began a volume at 12:37 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 439Dec 20, 7:55 AM EST

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 12:00Z, 0.6 hours before the alert went out and 101 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 620 J/kg
Mixed-layer CIN: -264 J/kg
Mixed-layer LCL: 569 m above ground
0-6 km bulk shear: 57 kt
0-1 km storm-relative helicity: 318 m²/s²
0-3 km storm-relative helicity: 316 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.9

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 20, 6:28 AM EST	Mesoscale Discussion	SPC	Manatee, Sarasota	62 min
Dec 20, 7:55 AM EST	Tornado Watch	SPC	Brevard, Charlotte, Collier, DeSoto, Glades, Hardee and 15 more	7 hr
Dec 20, 10:49 AM EST	Mesoscale Discussion	SPC	Brevard, Charlotte, DeSoto, Glades, Hardee, Hendry and 11 more	116 min
Dec 20, 1:41 PM EST	Mesoscale Discussion	SPC	Brevard, Collier, Glades, Hendry, Highlands, Indian River and 7 more	2 hr
Dec 20, 2:15 PM EST	Severe Thunderstorm Watch	SPC	Brevard, Broward, Collier, Glades, Hendry, Indian River and 6 more	6 hr
Dec 20, 5:55 PM EST	Mesoscale Discussion	SPC	Broward, Miami-Dade	2 hr

Nearby

Mesoscale Discussions in Florida, 2018 Every mesoscale discussion in 2018

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.