Alert archive / Colorado / Severe Thunderstorm Warnings in 2001

Severe Thunderstorm Warning 23, NWS Grand Junction, CO

August 21, 2001Mesa County, Colorado

NWS Grand Junction, CO issued this severe thunderstorm warning at Aug 21, 2001, 7:40 PM MDT for Mesa County, Colorado. It was in force for 35 min. 1 report came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Aug 21, 2001, 7:40 PM MDT (01:40 UTC)
Expired: Aug 21, 2001, 8:15 PM MDT
In force: 35 min
Issued by: NWS Grand Junction, CO
Area: Whole counties; the outline is the Mesonet’s reconstruction

County Mesa County, CO

The radar

The Grand Junction radar (KGJX), 22 km from the middle of the area, began a volume at 01:43 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.

What was reported inside it

Time	Report	Where	Remark
Aug 21, 7:56 PM MDT	Hail 1	Grand Jct, CO

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The nearest sounding before it

Salt Lake City I, UT (KSLC), launched 00:00Z, 1.7 hours before the alert went out and 352 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: 57 J/kg
Mixed-layer CIN: -70 J/kg
Mixed-layer LCL: 1761 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 91 m²/s²
0-3 km storm-relative helicity: 157 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Grand Junction, CO wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 21, 1:14 PM MDT, 6 hours 26 minutes earlier.

Area forecast discussion, Aug 21, 1:14 PM MDT, 6 hours 26 minutes before

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
114 PM MDT TUE AUG 21 2001

THIS EVENING IS LOOKING TO BE AN ACTIVE PERIOD AS AN UPPER LEVEL
TROUGH APPROACHES THE AREA. A GOOD MOIST LAYER IS IN PLACE WITH
AROUND AN INCH OF PRECIPITABLE WATER MEASURED PER THE 12Z GJT
SOUNDING. SPC HAS PUT EASTERN UTAH AND FAR WESTERN COLORADO IN
THE SLIGHT RISK AREA FOR SEVERE WINDS/LARGE HAIL AND FEEL BEST TIMING
WILL BE THIS EVENING...BEGINNING LATE AFTERNOON FOR EASTERN UTAH.
TIMING IS A BIT OFFSET FOR BEST LIFT...AS THE DIURNAL FACTOR
DECREASES AS THE DYNAMIC FACTOR INCREASES. SINCE EASTERN UTAH WILL
FEEL THE EFFECTS OF THE TROUGH EARLIEST...THAT AREA WILL SEE THE BEST
CHANCE OF SEVERE. AN AREA OF UPPER LEVEL DIVERGENCE MAXIMIZES AROUND
06Z OVER WESTERN COLORADO. THEREFORE EXPECT THUNDERSTORMS TO CONTINUE
PAST MIDNIGHT...WITH THE STRONGEST STORMS BETWEEN 23Z AND 06Z.

A SECONDARY WAVE IS SCHEDULED FOR WEDNESDAY...HOWEVER THIS ONE NOT AS
STRONG AND IT MOVES THROUGH BEFORE MAX HEATING.  WILL KEEP
SCATTERED...ESPECIALLY OVER THE MOUNTAIN AREAS. IN THE EVENING...WILL
LEAVE AT LEAST ISOLATED FOR THE EARLY EVENING BEFORE CLEARING. LOW
LEVEL WESTERLY FLOW WILL EFFECTIVELY DRY THE AREA OUT AFTER WEDS
WAVE. LOOK FOR TEMPS TO BE A LITTLE COOLER ON WED.

WITH THE DRIER MORE STABLE AIR MASS IN PLACE ON THU...WILL GO WITH
MOSTLY SUNNY/PARTLY CLOUDY OVER THE AREA. HOWEVER WILL MENTION
ISOLATED OVER THE MOUNTAINS FOR THE AFTERNOON.  ITS JUST TOO EASY FOR
A FEW CELLS TO POP WITH DIURNAL HEATING. HIGH TEMPS WILL REBOUND
AROUND 5 DEGREES DUE TO WARMING ALOFT AND MORE SUN. HEFFERNAN/44

EXTENDED (FRI-TUE)...THE ZONAL WEST-EAST FLOW WILL GRADUALLY BECOME
SOUTHWEST FRI...ALLOWING SUB-TROPICAL MOISTURE TO CREEP NORTH INTO
NEW MEXICO. HOWEVER...IT WILL REMAIN DRY ACROSS WESTERN CO/EASTERN
UT AT LEAST UNTIL SAT...WHEN DEEPER MOISTURE RIDES OVER THE
MOUNTAINS OF CO CREATING THE THREAT OF AFTN CONVECTION. MEANWHILE...
A NEG TILT TROF DEVELOPS FROM CA TO THE DESERT SW BY SUN BUT APPEARS
TO GET SHEARED APART OVER TIME. UPR HIGH RIDGE AXIS STRENGTHENS OVER
GREAT BASIN MON/TUE WITH WARM AND RELATIVELY DRY CONDITIONS. DIURNAL
MTN CONVECTION LOOKS TO BE MAIN STORY WITH WARM TEMPS. DJN.83

.GJT...NONE.

In the hours before

Local storm report, Aug 21, 3:34 PM MDT, 4 hours 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION, CO
334 PM MDT TUE AUG 21 2001

TIME(MDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0325 PM    5 S MANILA                UT   1.25 INCH HAIL
08/21/01   DAGGETT                        REPORTED BY LAW
                                          ENFORCEMENT

DJN

The office that day

Everything else NWS Grand Junction, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 21, 7:09 PM MDT	Severe Thunderstorm Warning	GJT	Delta	51 min

Nearby

Severe Thunderstorm Warnings in Colorado, 2001 Every severe thunderstorm warning in 2001

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.