Colorado, 2001

Damaging Winds in Colorado, August 20, 2001

August 20, 2001 · NWS BOU · 5 events in 4 counties and zones

5 thunderstorm wind, as filed by the National Weather Service.

Where it happened

Every event with a place to put it. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

Open the live radar over this ground

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
5

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Denver/Boulder, CO wrote its last area forecast discussion before the first event at Aug 20, 12:00 AM MST, 13 hours 33 minutes earlier.

Area forecast discussion, Aug 20, 12:00 AM MST, 13 hours 33 minutes before
NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER COLORADO
100 AM MDT MON AUG 20 2001

...THE MONSOON RETURNS...

MDLS CONSISTENT IN SPRDG TROPICAL MONSOONAL MSTR NWD FM MEX INTO
CNTRL RCKYS THRU PRD.  MRNG STLT LOOP SHWS ABUNDANT CLDNS OVR AREA
WITH WDSPRD CONVECTION STILL ON GOING INTO ERLY MRNG HRS.  MDLS
ALSO SHW GUD SHT WV MOVG ACRS AREA DURING MAX HEATING TIME THIS
AFTN.  FOR THIS REASON WILL UP POPS MST PLACES TO SCT WITH LIKELY
MTNS THIS AFTN AND NGT.  NGM HAS HIR PRECIPITIBLE WATERS AND MORE
SATURATION IN FCST UPR AIR SOUNDINGS THAN MESOETA.  NGM CAPES ARE
ALSO HIR AND FVRD ATTM.  GO ALG WITH SPC THINKING ON PSBL SVR TSTMS
OVR NERN CRNR BUT LIC TO CYS LINE MAY BE TOO FAR W.  A DRYLINE TYPE
BOUNDARY WILL FORM OUT THERE TDA.  ON TUE THE MONSOON FLO IS STILL
IN PLACE BUT FCST SOUNDINGS ARE NOT AS SATURATED AS TDA BUT NGM
CAPES ARE STILL QUITE HI...BUT THE ABSENCE OF A GUD SHT WV MAY WELL
REDUCE THE THRT OF PCPN...SO WILL LWR POPS SUM TUE.  WITH ALL THE
INCRSD MSTR AND CLDNS TDAS MAX TEMPS WILL NOT WRM TO YSTRDYS LVLS
AND OVRNGT MIN TEMPS WILL BE WRMR.

IN XTNDD PRD...WILL MAKE NO CHNGS ATTM.

GARD...WFO BOULDER

.DEN...NONE.

In the hours before

Special weather statement, Aug 20, 9:00 AM MST, 4 hours 33 minutes before
COZ030>051-202000-

SIGNIFICANT WEATHER OUTLOOK FOR NORTHEAST AND NORTH CENTRAL COLORADO
NATIONAL WEATHER SERVICE DENVER COLORADO
1000 AM MDT MON AUG 20 2001

THIS OUTLOOK PERTAINS TO THE FOLLOWING COLORADO COUNTIES

ADAMS     ARAPAHOE     BOULDER   CLEAR CREEK   DENVER       DOUGLAS
ELBERT    GILPIN       GRAND     JACKSON       JEFFERSON    LARIMER
LINCOLN   LOGAN        MORGAN    PARK          PHILLIPS     SEDGWICK
SUMMIT    WASHINGTON   WELD

SYNOPSIS: MONSOONAL MOISTURE WILL ENCROACH UPON THE AREA TODAY AS
A DEEP SOUTHWESTERLY FLOW ALOFT BECOMES ESTABLISHED OVER THE
SOUTHWESTERN U.S.  SCATTERED SHOWERS AND THUNDERSTORMS WILL SPREAD
FROM WEST TO EAST ACROSS THE MOUNTAINS AND FOOTHILLS THIS AFTERNOON
AS A POTENT SHORT-WAVE MOVES ACROSS THE STATE.  THE THUNDERSTORMS
MAY BRING BRIEF HEAVY RAINS, BUT FLOODING IS NOT EXPECTED SINCE THE
STORMS WILL MOVE BRISKLY TO THE NORTHEAST AT 20 MPH.

A SURFACE LOW PRESSURE AREA WILL FORM THIS AFTERNOON OVER SOUTHWEST
NEBRASKA, CAUSING LOW-LEVEL WINDS TO TURN SOUTHEAST THIS AFTERNOON
ACROSS THE COLORADO PLAINS.  THE SOUTHEASTERLY FLOW WILL SERVE TO
ADVECT HIGHER SURFACE DEWPOINTS INTO THE EASTERN PLAINS.  THE
SURFACE MOISTURE WILL MAKE IT AS FAR WEST AS FORT MORGAN AND
SCATTERED AFTERNOON THUNDERSTORMS CAN BE EXPECTED ROUGHLY EAST OF A
CHEYENNE WYOMING TO LIMON LINE.  ABUNDANT INSTABILITY THROUGHOUT THE
ATMOSPHERE WILL CAUSE A FEW STORMS TO PRODUCE HAIL IN EXCESS OF AN
INCH.  THE FAR NORTHEAST CORNER OF THE STATE IN PARTICULAR WILL HAVE
TO BE MONITORED AFTER 4 PM FOR POSSIBLE SEVERE THUNDERSTORMS.
HOWEVER, A WIDESPREAD SEVERE OUTBREAK IS NOT EXPECTED TODAY.

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY.

The radar

The Denver radar (KFTG), 37 km away, was scanning. The volume nearest the first event began at 20:29 UTC.

Open the radar archive at this moment

Event by event

5 thunderstorm wind. Local standard time, as filed.

Thunderstorm Wind, Douglas

When
August 20, 1:33 PM MST
Where
Douglas County, 14 mi NW of Parker
Measured
52 kt (60 mph)
Reported by
TRAINED SPOTTER
Coordinates
39.667, -104.950

Thunderstorm Wind, Adams

When
August 20, 1:35 PM MST
Where
Adams County, 4 mi S of Thornton
Measured
50 kt (58 mph)
Reported by
NEWSPAPER
Coordinates
39.833, -104.950

Strong thunderstorm winds blew the roof off of a building.

Thunderstorm Wind, Denver

When
August 20, 1:40 PM MST
Where
Denver County, Denver
Measured
50 kt (58 mph)
Reported by
NEWSPAPER
Coordinates
39.733, -104.933

Strong thunderstorm winds knocked over several trees. One tree landed on a mail truck.

Thunderstorm Wind, Jefferson

When
August 20, 1:41 PM MST
Where
Jefferson County, Broomfield
Measured
54 kt (62 mph)
Reported by
TRAINED SPOTTER
Coordinates
39.900, -105.067

Thunderstorm Wind, Denver

When
August 20, 1:57 PM MST
Where
Denver County, Denver Intl Arpt
Measured
53 kt (61 mph)
Reported by
AWOS,ASOS,MESONET,ETC
Coordinates
39.767, -104.883

What these are

Thunderstorm Wind
Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Colorado in 2001Every state in 2001This day in weather historyWarnings in Colorado, August 2001

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5265104, 5265100, 5265101, 5265102, 5265103.