Alert archive / California / Mesoscale Discussions in 2004

Mesoscale Discussion 113

February 18, 20045 counties in California

The Storm Prediction Center issued this mesoscale discussion at Feb 18, 2004, 12:57 PM PST for 5 counties in California. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Feb 18, 2004, 12:57 PM PST (20:57 UTC)
Expired
Feb 18, 2004, 3:00 PM PST
In force
2 hr
Issued by
the Storm Prediction Center

Counties Kings County, CA, Merced County, CA, San Benito County, CA, Santa Clara County, CA, Stanislaus County, CA

The radar

The San Francisco radar (KMUX), 90 km from the middle of the area, began a volume at 21:01 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

Oakland, CA (KOAK), launched 12:00Z, 9.0 hours before the alert went out and 152 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, Oakland, CA at 12:00Z on 2004-02-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 47 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, Oakland, CA at 12:00Z on 2004-02-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -4 square meters per square second.1939587897117Sfc1 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
47 J/kg
Mixed-layer CIN
-3 J/kg
Mixed-layer LCL
557 m above ground
0-6 km bulk shear
77 kt
0-1 km storm-relative helicity
-4 m²/s²
0-3 km storm-relative helicity
24 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.

431 
ACUS11 KWNS 182058
SWOMCD
SPC MCD 182057 
CAZ000-182300-

MESOSCALE DISCUSSION 0113
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CST WED FEB 18 2004

AREAS AFFECTED...PORTIONS OF THE INTERIOR VALLEY OF CENTRAL CA

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 182057Z - 182300Z

THUNDERSTORMS EXPECTED TO DEVELOP BY 21Z ACROSS PORTIONS OF THE
INTERIOR VALLEY OF CENTRAL CA...WITH THE STRONGEST STORMS LIKELY
PRODUCING LARGE HAIL.  WILL CONTINUE TO MONITOR FOR POSSIBLE WW.

VIS IMAGERY SHOWS BREAKS IN THE CLOUDS IN THE POST-FRONTAL
ENVIRONMENT ALLOWING FOR SUFFICIENT SURFACE HEATING /SURFACE
TEMPERATURES IN THE UPPER 50S TO AROUND 60/.  THIS IS RESULTING IN
THE AIR MASS BECOMING MORE UNSTABLE AS COLD MID-LEVEL TEMPERATURES
MOVE INLAND WITH THE UPPER TROUGH...WITH CU/MODERATE CU FORMING
ACROSS THIS AREA.  30-40 KT OF DEEP LAYER SHEAR COMBINED WITH
MARGINAL INSTABILITY AS SURFACE HEATING CONTINUES THIS AFTERNOON ARE
EXPECTED TO SUPPORT AN INCREASE IN CONVECTIVE ACTIVITY WITH THE
STRONGER STORMS CAPABLE OF PRODUCING LARGE HAIL.

..PETERS.. 02/18/2004

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

ATTN...WFO...HNX...LOX...STO...MTR...

36972168 37342180 37632097 36221948 35642047 36272125

Nearby

Mesoscale Discussions in California, 2004Every mesoscale discussion in 2004

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.