Alert archive / North Carolina / Mesoscale Discussions in 2009

Mesoscale Discussion 542

April 20, 2009Chatham County, Georgia; 18 counties in North Carolina; 10 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Apr 20, 2009, 7:36 PM EDT for Chatham County, Georgia; 18 counties in North Carolina; 10 counties in South Carolina. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued
Apr 20, 2009, 7:36 PM EDT (23:36 UTC)
Expired
Apr 20, 2009, 9:00 PM EDT
In force
84 min
Issued by
the Storm Prediction Center
All 29 counties

Chatham County, GA, Beaufort County, NC, Bladen County, NC, Columbus County, NC, Craven County, NC, Duplin County, NC, Greene County, NC, Hyde County, NC, Jones County, NC, Lenoir County, NC, Martin County, NC, Onslow County, NC, Pamlico County, NC, Pender County, NC, Pitt County, NC, Sampson County, NC, Tyrrell County, NC, Washington County, NC, Wayne County, NC, Beaufort County, SC, Berkeley County, SC, Charleston County, SC, Colleton County, SC, Dorchester County, SC, Georgetown County, SC, Horry County, SC, Jasper County, SC, Marion County, SC, Williamsburg County, SC

The radar

The Wilmington radar (KLTX), 33 km from the middle of the area, began a volume at 23:35 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

Newport, NC (KMHX), launched 12:00Z, 11.6 hours before the alert went out and 139 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-pSkew-T log-p diagram, Newport, NC at 12:00Z on 2009-04-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 286 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Newport, NC at 12:00Z on 2009-04-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 118 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
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
286 J/kg
Mixed-layer CIN
-16 J/kg
Mixed-layer LCL
759 m above ground
0-6 km bulk shear
52 kt
0-1 km storm-relative helicity
118 m²/s²
0-3 km storm-relative helicity
154 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.7

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.

IssuedProductOfficeCountiesLasted
Apr 19, 8:51 PM EDTTornado WatchSPCBarrow, Bartow, Butts, Carroll, Catoosa, Chattooga and 42 more6 hr
Apr 19, 11:21 PM EDTMesoscale DiscussionSPCBarrow, Bartow, Butts, Carroll, Chattooga, Cherokee and 35 more84 min
Apr 20, 12:20 AM EDTMesoscale DiscussionSPCElbert, Franklin, Greene, Hart, Lincoln, McDuffie and 4 more55 min
Apr 20, 12:42 AM EDTTornado WatchSPCBaldwin, Banks, Clarke, Columbia, Elbert, Franklin and 19 more5 hr
Apr 20, 1:22 AM EDTMesoscale DiscussionSPCBarrow, Bibb, Butts, Chattahoochee, Clayton, Coweta and 26 more53 min
Apr 20, 2:52 PM EDTMesoscale DiscussionSPCChatham83 min
Apr 20, 3:16 PM EDTSevere Thunderstorm WatchSPCBryan, Chatham, Effingham, Liberty, Long, McIntosh6 hr
Apr 20, 4:55 PM EDTMesoscale DiscussionSPCBryan, Bulloch, Chatham, Effingham, Evans, Liberty and 1 more95 min
Apr 20, 12:22 PM EDTMesoscale DiscussionSPCBeaufort, Bertie, Camden, Chowan, Craven, Edgecombe and 19 more83 min
Apr 20, 2:09 PM EDTMesoscale DiscussionSPCAlamance, Caswell, Durham, Edgecombe, Franklin, Granville and 11 more2 hr
Apr 20, 2:50 PM EDTTornado WatchSPCAlamance, Bertie, Camden, Caswell, Chatham, Chowan and 18 more7 hr
Apr 20, 4:57 PM EDTMesoscale DiscussionSPCAlamance, Camden, Caswell, Chatham, Chowan, Durham and 13 more93 min
Apr 20, 7:15 PM EDTMesoscale DiscussionSPCGates, Halifax, Hertford, Northampton, Warren90 min

Nearby

Mesoscale Discussions in North Carolina, 2009Mesoscale Discussions in South Carolina, 2009Mesoscale Discussions in Georgia, 2009Every 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.