Alert archive / Oregon / Mesoscale Discussions in 2012
Mesoscale Discussion 2121
The Storm Prediction Center issued this mesoscale discussion at Nov 20, 2012, 10:51 AM PST for Clatsop County, Lincoln County, Tillamook County, Oregon; Pacific County, Washington. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Nov 20, 2012, 10:51 AM PST (18:51 UTC)
- Expired
- Nov 20, 2012, 12:45 PM PST
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 5%
Counties Clatsop County, OR, Lincoln County, OR, Tillamook County, OR, Pacific County, WA
The radar
The Portland,OR radar (KRTX), 73 km from the middle of the area, began a volume at 18:53 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
Salem/Mcnary, OR (KSLE), launched 12:00Z, 6.9 hours before the alert went out and 102 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.
- Mixed-layer CAPE
- 6 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 512 m above ground
- 0-6 km bulk shear
- 92 kt
- 0-1 km storm-relative helicity
- 201 m²/s²
- 0-3 km storm-relative helicity
- 199 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
229
ACUS11 KWNS 201852
SWOMCD
SPC MCD 201851
ORZ000-WAZ000-202045-
MESOSCALE DISCUSSION 2121
NWS STORM PREDICTION CENTER NORMAN OK
1251 PM CST TUE NOV 20 2012
AREAS AFFECTED...COASTAL SWRN WA AND COASTAL NWRN ORE
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 201851Z - 202045Z
PROBABILITY OF WATCH ISSUANCE...5 PERCENT
SUMMARY...A STRONG CONVECTIVE BAND AROUND 30 NM OFFSHORE IS FORECAST
TO REACH THE COAST AROUND 1930Z AND POSE A THREAT FOR STRONG
WINDS...PERHAPS LOCALLY REACHING SVR THRESHOLDS. A WW IS NOT NEEDED
OWING TO ONLY SPORADIC SVR COVERAGE...AT MOST.
DISCUSSION...AS A FRONT CONTINUES APPROACHING THE COAST...COMING
INTO CLOSER RANGE OF THE LANGLEY HILL WA RDA...RADAR DATA REVEAL A
NEARLY CONTINUOUS ARC OF LOW-TOPPED FRONTAL CONVECTION OFF THE COAST
FROM GRAYS HARBOR COUNTY TO TILLAMOOK COUNTY. MORE
DISCRETE/SEMI-DISCRETE CONVECTION LIES JUST NORTH OF THE LINE AND
AHEAD OF THE LINE. CURRENT EXTRAPOLATION TAKES THE PRIMARY
CONVECTIVE ARC TO THE COAST AROUND 1930Z...AS IT POSSESSES A
SHOREWARD COMPONENT OF MOTION AROUND 30 KNOTS. VISIBLE SATELLITE
IMAGERY INDICATES A NARROW AXIS OF MODEST INSOLATION AHEAD OF THE
CONVECTIVE ARC TO SUPPORT MARGINAL DESTABILIZATION. MODIFIED NAM
SOUNDINGS WHERE INSOLATION-DRIVEN BOUNDARY-LAYER HEATING HAS
OCCURRED SUGGEST THAT MLCAPE VALUES OF 400-800 J/KG WILL IMPACT
INLAND LOCATIONS. AND...WITH LANGLEY HILLS VWP DATA INDICATING
STRONG LOW-LEVEL AND DEEP SHEAR /E.G. 0-1-KM BULK SHEAR MAGNITUDE OF
44 KT/...CONVECTIVE ORGANIZATION WILL LIKELY BE MAINTAINED TO THE
COAST. WHILE SOME VEERING OF THE NEAR-SFC FLOW WILL OCCUR AS THE
FRONT APPROACHES...DOWNWARD MOMENTUM TRANSFER IN CONVECTION MAY
SUPPORT AN ISOLATED SVR WIND GUST OR TWO.
..COHEN/BUNTING.. 11/20/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...SEW...PQR...
LAT...LON 44732400 45432402 46272408 47372424 47032376 46152353
45252351 44502374 44392402 44732400Nearby
Mesoscale Discussions in Oregon, 2012Mesoscale Discussions in Washington, 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.