Alert archive / California / Mesoscale Discussions in 2008

Mesoscale Discussion 9

January 5, 20085 counties in California

The Storm Prediction Center issued this mesoscale discussion at Jan 5, 2008, 10:46 AM PST for 5 counties in California. It was in force for 119 min.

The area

The outline as issued.

The facts

Issued: Jan 5, 2008, 10:46 AM PST (18:46 UTC)
Expired: Jan 5, 2008, 12:45 PM PST
In force: 119 min
Issued by: the Storm Prediction Center

Counties Alameda County, CA, Contra Costa County, CA, Marin County, CA, San Mateo County, CA, Santa Cruz County, CA

The radar

The San Francisco radar (KMUX), 70 km from the middle of the area, began a volume at 18:45 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, 6.8 hours before the alert went out and 16 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: 49 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 906 m above ground
0-6 km bulk shear: 77 kt
0-1 km storm-relative helicity: 63 m²/s²
0-3 km storm-relative helicity: 156 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.

000 
ACUS11 KWNS 051846
SWOMCD
SPC MCD 051846 
CAZ000-052045-

MESOSCALE DISCUSSION 0009
NWS STORM PREDICTION CENTER NORMAN OK
1246 PM CST SAT JAN 05 2008

AREAS AFFECTED...PORTIONS NRN CA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 051846Z - 052045Z

BAND OF CONVECTION FROM NEAR POINT REYES SWWD OVER OPEN PACIFIC IS
EXPECTED TO MOVE EWD AND INLAND...FROM THERE SEWD ACROSS SFO BAY
AREA DURING NEXT 2-3 HOURS.  INDIVIDUAL TSTMS WITHIN THIS LINE...AS
WELL AS ANY PRECURSORY/DISCRETE TSTMS...MAY PRODUCE HAIL...STG
GUSTS...AND A BRIEF TORNADO OR TWO.

PERSISTENT...DISCRETE AND SOMEWHAT RIGHT-MOVING CELL AHEAD OF THE
LINE...WAS APCHG BUOY 46012 AS OF 1820Z.  THIS PROBABLY IS A
MINI-SUPERCELL GIVEN ITS VIS AND REFLECTIVITY CHARACTERISTICS. 
ROTATION IS AND SHOULD BE DIFFICULT TO ASCERTAIN ON RADAR THIS FAR
OUT BECAUSE OF BEAM OVERSHOOTING OF LOW-LEVEL MESOCIRCULATION...AKIN
TO SAMPLING PROBLEMS WITH SMALL/SHALLOW/DISTANT SUPERCELLS IN
TROPICAL CYCLONES.  THIS STORM....IF IT IS NOT ABSORBED BY THE LINE
FIRST...MAY AFFECT SFO BETWEEN 1930-20Z...AND OTHER DISCRETE
DEVELOPMENT ALSO IS POSSIBLE TO ITS S AND AHEAD OF MAIN CONVECTIVE
BAND.

THERMODYNAMIC ENVIRONMENT SHOULD BECOME AT LEAST MRGLLY FAVORABLE
OVER COASTAL REGION AND BAY AREA DURING NEXT 1-2 HOURS. 
ADDITIONAL/WEAK SFC HEATING AND 40S SFC DEW POINTS...BENEATH 8-8.5
DEG C/KM LOW-MIDLEVEL LAPSE RATES...YIELD MLCAPES UP TO 250 J/KG IN
MODIFIED MODEL SOUNDINGS...WITH VERY WEAK CINH AND MAX TOPS AROUND
20 KFT.  SFC MESOANALYSIS SHOWS PRESSURE FALLS ACROSS MOST OF SFO
BAY AREA AND SURROUNDING COUNTIES...AHEAD OF CONVECTIVE/CONFLUENCE
LINE.  ACCORDINGLY...SOMEWHAT ACCELERATED/BACKED FLOW IS PRESENT
OVER THIS REGION...UNLIKE RUC/NAM/NAM-KF SOUNDINGS THAT SHOW NO ELY
COMPONENT OF SFC WIND IN  AREA.  SUCH FLOW WILL CONTINUE TO ENHANCE
BOTH LOW LEVEL HODOGRAPHS AND STORM-RELATIVE INFLOW IN PRE-STORM
ENVIRONMENT.  BACKED FLOW ALSO IS PRESENT EWD INTO CENTRAL
VALLEY...WHERE STRONGER SFC HEATING AND SIMILAR VERTICAL SHEAR
PROFILES MAY SUPPORT SOME SVR POTENTIAL THIS AFTERNOON.

..EDWARDS.. 01/05/2008

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

ATTN...WFO...STO...MTR...

37972301 38112283 38132262 38222242 38202216 38082188
37862161 37522158 37212176 36932194 36952209 37092229
37172240 37332241 37412245 37482245 37502252 37772251
37822254 37902270 38022289

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 4, 4:39 PM PST	Mesoscale Discussion	SPC	Alpine, Tuolumne	5 hr
Jan 5, 11:37 AM PST	Mesoscale Discussion	SPC	El Dorado, Nevada, Placer, Sierra, Tuolumne	5 hr

Nearby

Mesoscale Discussions in California, 2008 Every mesoscale discussion in 2008

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.