Alert archive / Colorado / Tornado Warnings in 2021
Tornado Warning 35, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this tornado warning at Aug 19, 2021, 2:39 PM MDT for Adams County, Broomfield County, Jefferson County, Colorado. It was in force for 36 min. 17 reports came from inside the area while it was in force.
The area
The outline as issued, with what was reported inside it.
The facts
- Issued
- Aug 19, 2021, 2:39 PM MDT (20:39 UTC)
- Expired
- Aug 19, 2021, 3:15 PM MDT
- In force
- 36 min
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Tornado
- Radar indicated
- Hail
- 0.75 in
Counties Adams County, CO, Broomfield County, CO, Jefferson County, CO
The radar
The Denver radar (KFTG), 49 km from the middle of the area, began a volume at 20:39 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 19, 2:40 PM MDT | HAIL 0.75 | 4 Sse Superior, CO | REPORT FROM MPING: DIME (0.75 IN.). |
| Aug 19, 2:40 PM MDT | HAIL 1 | 2 Ne Arvada, CO | |
| Aug 19, 2:45 PM MDT | FUNNEL CLOUD | 1 Nnw Federal Heights, CO | |
| Aug 19, 2:45 PM MDT | HAIL 1 | 1 Nnw Federal Heights, CO | |
| Aug 19, 2:45 PM MDT | HAIL 1.25 | 1 Sse Broomfield, CO | |
| Aug 19, 2:45 PM MDT | HAIL 1.5 | 2 Wsw Westminster, CO | REPORT FROM MPING: PING PONG BALL (1.50 IN.). |
| Aug 19, 2:46 PM MDT | HAIL 1.5 | 1 Wsw Westminster, CO | |
| Aug 19, 2:47 PM MDT | HAIL 1 | 2 W Westminster, CO | 98TH AND SHEIRIDAN. |
| Aug 19, 2:48 PM MDT | HAIL 1 | Westminster, CO | REPORT FROM MPING: QUARTER (1.00 IN.). |
| Aug 19, 2:49 PM MDT | HAIL 1 | 2 Wsw Westminster, CO | REPORT FROM MPING: QUARTER (1.00 IN.). |
| Aug 19, 2:50 PM MDT | HAIL 0.75 | 2 E Broomfield, CO | REPORT FROM MPING: DIME (0.75 IN.). |
| Aug 19, 2:50 PM MDT | HAIL 1 | 1 Ene Westminster, CO | |
| Aug 19, 2:50 PM MDT | HAIL 1 | 2 Ne Westminster, CO | |
| Aug 19, 2:50 PM MDT | HAIL 1.25 | 1 Nnw Westminster, CO | |
| Aug 19, 2:50 PM MDT | HAIL 1.25 | 2 N Federal Heights, CO | |
| Aug 19, 2:53 PM MDT | HAIL 0.75 | 2 Nnw Northglenn, CO | REPORT FROM MPING: DIME (0.75 IN.). |
| Aug 19, 2:53 PM MDT | HAIL 1 | 2 E Broomfield, CO | REPORT FROM MPING: QUARTER (1.00 IN.). |
Local storm reports filed while the alert was in force, from inside its polygon or its counties.
The watch it was issued in
The SPC watch in force over the same counties when this warning went out.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Aug 19, 1:14 PM MDT | Severe Thunderstorm Watch | SPC | 6 hr |
The nearest sounding before it
Denver, CO (KDNR), launched 12:00Z, 8.7 hours before the alert went out and 159 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
- 246 J/kg
- Mixed-layer CIN
- -241 J/kg
- Mixed-layer LCL
- 927 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- -59 m²/s²
- 0-3 km storm-relative helicity
- 35 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
The text
As transmitted.
057
WFUS55 KBOU 192039
TORBOU
COC001-014-059-192115-
/O.NEW.KBOU.TO.W.0035.210819T2039Z-210819T2115Z/
BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Denver CO
239 PM MDT Thu Aug 19 2021
The National Weather Service in Denver Colorado has issued a
* Tornado Warning for...
Broomfield County in northeastern Colorado...
Northeastern Jefferson County in central Colorado...
West central Adams County in northeastern Colorado...
* Until 315 PM MDT.
* At 239 PM MDT, a severe thunderstorm capable of producing a tornado
was located over southwestern Westminster, or 12 miles northwest of
Denver, moving northeast at 15 mph.
HAZARD...Tornado.
SOURCE...Radar indicated rotation.
IMPACT...Flying debris will be dangerous to those caught without
shelter. Mobile homes will be damaged or destroyed.
Damage to roofs, windows, and vehicles will occur. Tree
damage is likely.
* This dangerous storm will be near...
Broomfield around 245 PM MDT.
Federal Heights around 255 PM MDT.
Other locations in the path of this tornadic thunderstorm include
Westminster, Northglenn and Thornton.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.
&&
LAT...LON 4000 10502 3987 10491 3977 10511 3991 10522
3992 10520 3991 10515 3995 10512 3995 10511
3993 10512 3994 10508 3996 10507 3996 10505
3998 10505
TIME...MOT...LOC 2039Z 239DEG 15KT 3987 10510
TORNADO...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
$$
RPK2 follow-up statements
303
WWUS55 KBOU 192054
SVSBOU
Severe Weather Statement
National Weather Service Denver CO
254 PM MDT Thu Aug 19 2021
COC059-192103-
/O.CAN.KBOU.TO.W.0035.000000T0000Z-210819T2115Z/
Jefferson CO-
254 PM MDT Thu Aug 19 2021
...THE TORNADO WARNING FOR NORTHEASTERN JEFFERSON COUNTY IS
CANCELLED...
The tornadic thunderstorm which prompted the warning has moved out
of the warned area. Therefore, the warning has been cancelled.
A Severe Thunderstorm Watch remains in effect until 800 PM MDT for
northeastern Colorado.
LAT...LON 3987 10491 3981 10504 3983 10506 3991 10505
3990 10507 3990 10510 3991 10510 3993 10509
3992 10507 3994 10508 3995 10505 3996 10505
3997 10503 4000 10502
TIME...MOT...LOC 2053Z 239DEG 15KT 3990 10503
$$
COC001-014-192115-
/O.CON.KBOU.TO.W.0035.000000T0000Z-210819T2115Z/
Broomfield CO-Adams CO-
254 PM MDT Thu Aug 19 2021
...A TORNADO WARNING REMAINS IN EFFECT UNTIL 315 PM MDT FOR
SOUTHEASTERN BROOMFIELD AND WEST CENTRAL ADAMS COUNTIES...
At 253 PM MDT, a severe thunderstorm capable of producing a tornado
was located over eastern Westminster, or 12 miles north of Denver,
moving northeast at 15 mph.
HAZARD...Tornado and quarter size hail.
SOURCE...Radar indicated rotation.
IMPACT...Flying debris will be dangerous to those caught without
shelter. Mobile homes will be damaged or destroyed. Damage
to roofs, windows, and vehicles will occur. Tree damage is
likely.
Locations impacted include...
Northglenn and Thornton.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.
&&
LAT...LON 3987 10491 3981 10504 3983 10506 3991 10505
3990 10507 3990 10510 3991 10510 3993 10509
3992 10507 3994 10508 3995 10505 3996 10505
3997 10503 4000 10502
TIME...MOT...LOC 2053Z 239DEG 15KT 3990 10503
TORNADO...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
$$
RPK490
WWUS55 KBOU 192110
SVSBOU
Severe Weather Statement
National Weather Service Denver CO
310 PM MDT Thu Aug 19 2021
COC001-014-192119-
/O.EXP.KBOU.TO.W.0035.000000T0000Z-210819T2115Z/
Broomfield CO-Adams CO-
310 PM MDT Thu Aug 19 2021
...THE TORNADO WARNING FOR SOUTHEASTERN BROOMFIELD AND WEST CENTRAL
ADAMS COUNTIES WILL EXPIRE AT 315 PM MDT...
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.
A Severe Thunderstorm Watch remains in effect until 800 PM MDT for
northeastern Colorado.
LAT...LON 3987 10491 3981 10504 3983 10506 3991 10505
3990 10507 3990 10510 3991 10510 3993 10509
3992 10507 3994 10508 3995 10505 3996 10505
3997 10503 4000 10502
TIME...MOT...LOC 2109Z 239DEG 15KT 3994 10495
$$
RPKThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 19, 1:23 PM MDT | Special Weather Statement | BOU | Logan | 22 min |
| Aug 19, 2:01 PM MDT | Special Weather Statement | BOU | Logan | 29 min |
| Aug 19, 2:13 PM MDT | Special Weather Statement | BOU | Broomfield | 17 min |
| Aug 19, 2:17 PM MDT | Special Weather Statement | BOU | Broomfield | 28 min |
| Aug 19, 2:24 PM MDT | Severe Thunderstorm Warning | BOU | Boulder, Broomfield, Jefferson | 36 min |
| Aug 19, 2:30 PM MDT | Severe Thunderstorm Warning | BOU | Douglas | 30 min |
| Aug 19, 2:46 PM MDT | Severe Thunderstorm Warning | BOU | Adams, Weld | 29 min |
| Aug 19, 2:59 PM MDT | Areal Flood Advisory | BOU | Adams | 61 min |
| Aug 19, 3:05 PM MDT | Tornado Warning | BOU | Adams, Weld | 25 min |
| Aug 19, 3:12 PM MDT | Tornado Warning | BOU | Douglas | 18 min |
| Aug 19, 3:14 PM MDT | Severe Thunderstorm Warning | BOU | Weld | 31 min |
| Aug 19, 3:35 PM MDT | Severe Thunderstorm Warning | BOU | Douglas, Elbert | 25 min |
| Aug 19, 3:42 PM MDT | Severe Thunderstorm Warning | BOU | Weld | 33 min |
| Aug 19, 3:44 PM MDT | Severe Thunderstorm Warning | BOU | Adams, Arapahoe | 31 min |
| Aug 19, 3:46 PM MDT | Tornado Warning | BOU | Douglas, Elbert | 14 min |
| Aug 19, 3:49 PM MDT | Severe Thunderstorm Warning | BOU | Phillips | 41 min |
| Aug 19, 3:51 PM MDT | Severe Thunderstorm Warning | BOU | Sedgwick | 24 min |
| Aug 19, 3:55 PM MDT | Areal Flood Advisory | BOU | Arapahoe, Denver, Douglas | 22 min |
| Aug 19, 3:58 PM MDT | Areal Flood Advisory | BOU | Weld | 30 min |
| Aug 19, 4:04 PM MDT | Severe Thunderstorm Warning | BOU | Arapahoe, Elbert | 41 min |
| Aug 19, 4:06 PM MDT | Areal Flood Advisory | BOU | Logan | 54 min |
| Aug 19, 4:07 PM MDT | Severe Thunderstorm Warning | BOU | Morgan | 32 min |
| Aug 19, 4:10 PM MDT | Areal Flood Advisory | BOU | Phillips | 95 min |
| Aug 19, 4:17 PM MDT | Severe Thunderstorm Warning | BOU | Adams | 43 min |
| Aug 19, 4:18 PM MDT | Severe Thunderstorm Warning | BOU | Elbert | 42 min |
| Aug 19, 4:25 PM MDT | Severe Thunderstorm Warning | BOU | Phillips | 35 min |
| Aug 19, 4:32 PM MDT | Severe Thunderstorm Warning | BOU | Arapahoe | 28 min |
| Aug 19, 4:34 PM MDT | Tornado Warning | BOU | Phillips | 26 min |
| Aug 19, 4:52 PM MDT | Severe Thunderstorm Warning | BOU | Arapahoe, Elbert | 23 min |
| Aug 19, 4:57 PM MDT | Areal Flood Advisory | BOU | Logan | 50 min |
| Aug 19, 4:57 PM MDT | Tornado Warning | BOU | Phillips | 33 min |
| Aug 19, 5:00 PM MDT | Severe Thunderstorm Warning | BOU | Adams, Morgan | 30 min |
| Aug 19, 5:04 PM MDT | Severe Thunderstorm Warning | BOU | Logan | 25 min |
| Aug 19, 5:09 PM MDT | Flash Flood Warning | BOU | Phillips | 3 hr |
| Aug 19, 5:34 PM MDT | Severe Thunderstorm Warning | BOU | Phillips | 26 min |
Nearby
Tornado Warnings in Colorado, 2021Every tornado warning in 2021Tornadoes in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.