Alert archive / Florida / Mesoscale Discussions in 2009

Mesoscale Discussion 2255

December 18, 200916 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Dec 18, 2009, 6:39 AM EST for 16 counties in Florida. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Dec 18, 2009, 6:39 AM EST (11:39 UTC)
Expired: Dec 18, 2009, 8:45 AM EST
In force: 2 hr
Issued by: the Storm Prediction Center

Counties Brevard County, FL, Broward County, FL, Charlotte County, FL, Collier County, FL, Hernando County, FL, Indian River County, FL, Lee County, FL, Manatee County, FL, Martin County, FL, Miami-Dade County, FL, Monroe County, FL, Palm Beach County, FL, Pasco County, FL, Pinellas County, FL, Saint Lucie County, FL, Sarasota County, FL

The radar

The Miami radar (KAMX), 131 km from the middle of the area, began a volume at 11:42 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 804Dec 18, 7:45 AM EST

The nearest sounding before it

Miami, FL (KMFL), launched 00:00Z, 11.7 hours before the alert went out and 129 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: 653 J/kg
Mixed-layer CIN: -16 J/kg
Mixed-layer LCL: 662 m above ground
0-6 km bulk shear: 8 kt
0-1 km storm-relative helicity: 40 m²/s²
0-3 km storm-relative helicity: 66 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 18, 4:14 AM EST	Mesoscale Discussion	SPC	Miami-Dade	2 hr
Dec 18, 7:19 AM EST	Tornado Watch	SPC	Broward, Charlotte, Collier, Glades, Hendry, Lee and 6 more	7 hr
Dec 18, 11:16 AM EST	Mesoscale Discussion	SPC	Broward, Collier, Glades, Hendry, Martin, Miami-Dade and 2 more	59 min

Nearby

Mesoscale Discussions in Florida, 2009 Every mesoscale discussion in 2009

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.