Alert archive / Maryland / Mesoscale Discussions in 2012

Mesoscale Discussion 1640

July 28, 2012Kent County, New Castle County, Sussex County, Delaware; 12 counties in Maryland; Berks County, Chester County, Lehigh County, Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2012, 8:00 PM EDT for Kent County, New Castle County, Sussex County, Delaware; 12 counties in Maryland; Berks County, Chester County, Lehigh County, Pennsylvania. It was in force for 30 min.

The area

The outline as issued.

The facts

Issued: Jul 28, 2012, 8:00 PM EDT (00:00 UTC)
Expired: Jul 28, 2012, 8:30 PM EDT
In force: 30 min
Issued by: the Storm Prediction Center

Counties Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, City of Baltimore, MD, Dorchester County, MD, Harford County, MD, Kent County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Wicomico County, MD, Berks County, PA, Chester County, PA, Lehigh County, PA

The radar

The Dover AFB radar (KDOX), 65 km from the middle of the area, began a volume at 00:03 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 0.0 hours before the alert went out and 142 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: 537 J/kg
Mixed-layer CIN: -16 J/kg
Mixed-layer LCL: 1917 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: -55 m²/s²
0-3 km storm-relative helicity: 29 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.

789 
ACUS11 KWNS 290000
SWOMCD
SPC MCD 290000 
PAZ000-DEZ000-MDZ000-NJZ000-290030-

MESOSCALE DISCUSSION 1640
NWS STORM PREDICTION CENTER NORMAN OK
0700 PM CDT SAT JUL 28 2012

AREAS AFFECTED...CHESAPEAKE BAY VICINITY / SERN PA

CONCERNING...SEVERE THUNDERSTORM WATCH 535...

VALID 290000Z - 290030Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 535
CONTINUES.

SUMMARY...AN ISOLD SEVERE WIND GUST RISK WILL REMAIN IN THE SHORT
TERM /NEXT HR OR SO/ NEAR THE CHESAPEAKE BAY VICINITY AND A PERHAPS
ENDING SOONER IN SERN PA.

DISCUSSION...SURFACE MESOANALYSIS PLACES SEVERAL SEA
BREEZE/CONVECTIVE OUTFLOW BOUNDARIES SLOWLY MOVING S ACROSS THE ERN
SHORE AND FARTHER N MOVING WWD INTO THE GREATER PHI METRO.  TEMPS
BEHIND THE BOUNDARIES HAVE FALLEN INTO THE 70S AND LOWER 80S DEG F. 
AS THE STORMS CONTINUE TO MOVE E WITHIN A NARROWING RELATIVELY HIGH
THETA-E CORRIDOR...THE STORMS MAY CONTINUE TO POSE AN ISOLD DMGG
WIND RISK.  THIS WILL OCCUR BEFORE THE RICHER THETA-E BECOMES
PINCHED OFF AND THE AFOREMENTIONED SEA BREEZE/OUTFLOW BOUNDARIES
EFFECTIVELY UNDERCUT THE EXISTING STORMS AND LESSEN THE REMAINING
SEVERE POTENTIAL.  THIS IS EXPECTED FIRST IN SERN PA BY 0030Z AND
FARTHER S AROUND 01Z.

..SMITH/MEAD.. 07/29/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...CTP...LWX...

LAT...LON   38387527 38277617 38747696 39887625 40737587 40627535
            39627549 38387527

Nearby

Mesoscale Discussions in Maryland, 2012 Mesoscale Discussions in Delaware, 2012 Mesoscale Discussions in Pennsylvania, 2012 Every mesoscale discussion in 2012

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.