Alert archive / California / Mesoscale Discussions in 2012

Mesoscale Discussion 2128

November 29, 2012Del Norte County, Humboldt County, California

The Storm Prediction Center issued this mesoscale discussion at Nov 29, 2012, 5:08 PM PST for Del Norte County, Humboldt County, California. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued
Nov 29, 2012, 5:08 PM PST (01:08 UTC)
Expired
Nov 29, 2012, 7:45 PM PST
In force
3 hr
Issued by
the Storm Prediction Center
Chance of a watch
5%

Counties Del Norte County, CA, Humboldt County, CA

The radar

The Eureka (Bunker Hill) radar (KBHX), 50 km from the middle of the area, began a volume at 01:12 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

Medford/Jackson, OR (KMFR), launched 00:00Z, 1.1 hours before the alert went out and 192 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, Medford/Jackson, OR at 00:00Z on 2012-11-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Medford/Jackson, OR at 00:00Z on 2012-11-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 331 square meters per square second.1939587897117136Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
658 m above ground
0-6 km bulk shear
79 kt
0-1 km storm-relative helicity
331 m²/s²
0-3 km storm-relative helicity
525 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.

804 
ACUS11 KWNS 300109
SWOMCD
SPC MCD 300108
CAZ000-ORZ000-300345-

MESOSCALE DISCUSSION 2128
NWS STORM PREDICTION CENTER NORMAN OK
0708 PM CST THU NOV 29 2012

AREAS AFFECTED...FAR NRN COASTAL CA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 300108Z - 300345Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...GUSTY WIND POTENTIAL WILL INCREASE LATER THIS EVENING AS A
LINE OF SHOWERS AND WEAK STORMS APPROACHES THE COAST.

DISCUSSION...A LINE OF LOW TOPPED BUT STRONGLY FORCED CONVECTION IS
CURRENTLY SITUATED JUST OFF THE NRN CA COAST...WITHIN A LOW LEVEL
WARM ADVECTION REGIME AND SUPPORTED BY THE LEFT EXIT REGION OF THE
UPPER JET.

RADAR TRENDS HAVE AT TIMES SHOWN WEAK CIRCULATIONS WITH SMALL BOWING
SEGMENTS WITHIN THE LINE. IF THEY HOLD TOGETHER...THE NRN BOW MAY
AFFECT DEL NORTE COUNTY BY AROUND 02-03Z...AND THEN FARTHER SWD
ACROSS COASTAL HUMBOLDT COUNTY LATER THIS EVENING.

INSTABILITY IS EXTREMELY WEAK...AND ONLY GETS WEAKER NEAR THE COAST
WITH A SLIGHT OFFSHORE SURFACE COMPONENT. HOWEVER...SHEAR IS VERY
STRONG. LOCALLY STRONG WIND GUSTS ARE LIKELY AS THESE STORMS IMPACT
THE COAST...AND PERHAPS ACROSS HIGHER ELEVATIONS AS AMBIENT FLOW IS
VERY STRONG AND MAY BE AUGMENTED BY THE FORCED LINE.

..JEWELL/THOMPSON.. 11/30/2012

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

ATTN...WFO...MFR...EKA...

LAT...LON   40632343 39852384 39872404 40192445 40532453 40912424
            41372413 41812433 42012422 42012339 40632343

Nearby

Mesoscale Discussions in California, 2012Every 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.