Alert archive / Iowa / Severe Thunderstorm Warnings in 2001

Severe Thunderstorm Warning 71, NWS Omaha, NE

April 11, 2001Fremont County, Iowa

NWS Omaha, NE issued this severe thunderstorm warning at Apr 11, 2001, 3:21 AM CDT for Fremont County, Iowa. It was in force for 39 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline the Iowa Environmental Mesonet reconstructed for it; the warning itself named whole counties.

The facts

Issued: Apr 11, 2001, 3:21 AM CDT (08:21 UTC)
Expired: Apr 11, 2001, 4:00 AM CDT
In force: 39 min
Issued by: NWS Omaha, NE
Area: Whole counties; the outline is the Mesonet’s reconstruction

County Fremont County, IA

The radar

The Omaha radar (KOAX), 87 km from the middle of the area, began a volume at 08:22 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Apr 11, 2:00 AM CDT	Tornado Watch	SPC	5 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 8.4 hours before the alert went out and 87 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: 18 J/kg
Mixed-layer CIN: -145 J/kg
Mixed-layer LCL: 493 m above ground
0-6 km bulk shear: 55 kt
0-1 km storm-relative helicity: 84 m²/s²
0-3 km storm-relative helicity: 131 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.6

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WUUS53 KOAX 110823
SVROMA
IAC071-110900-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE OMAHA NE
321 AM CDT WED APR 11 2001

THE NATIONAL WEATHER SERVICE IN OMAHA HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  FREMONT COUNTY IN SOUTHWEST IOWA

* UNTIL 400 AM CDT

* AT 317 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  SEVERE THUNDERSTORMS WITH DAMAGING WIND FROM 21 MILES WEST OF
  THURMAN TO 13 MILES SOUTHWEST OF HAMBURG...OR FROM 28 MILES EAST OF
  LINCOLN TO 29 MILES NORTHWEST OF FALLS CITY...MOVING NORTHEAST AT
  55 MPH.

* SOME LOCATIONS AFFECTED...
  SIDNEY...HAMBURG...FARRAGUT...IMOGENE...

THIS IS A VERY DANGEROUS STORM WITH WINDS OF UP TO 80 MPH AND 
WIDESPREAD DAMAGE ARE POSSIBLE TAKE SHELTER ON THE LOWEST FLOOR OF 
YOUR HOME OR BUSINESS. KEEP AWAY FROM WINDOWS AND GLASS DOORS.

MOTORISTS ALONG INTERSTATE 29 SHOULD BE PREPARED FOR EXTREME CROSS 
WINDS
 
A TORNADO WATCH REMAINS IN EFFECT UNTIL 700 AM CDT WEDNESDAY MORNING
FOR SOUTHWESTERN IOWA AND EASTERN NEBRASKA.

LAT...LON 4089 9584 4069 9581 4058 9576 4060 9539
          4078 9540 4092 9545

MEAD

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 Omaha, NE wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 10, 3:06 PM CDT, 12 hours 15 minutes earlier.

Area forecast discussion, Apr 10, 3:06 PM CDT, 12 hours 15 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA NE
306 PM CDT TUE APR 10 2001

PRIMARY CONCERNS ARE SEVERE WEATHER POTENTIAL THROUGH
WED...RAINFALL...TEMPS...AND WINDS AS A MAJOR CYCLONE MOVES
NORTHEAST ACROSS THE AREA.

IN THE SHORT TERM...VERY MOIST AND UNSTABLE AIR FROM AMA N.E. TO TOP
AT 850 MB WAS UNDERESTIMATED BY MODELS.  ETA AGAIN SEEMS TO LOSE
SOME OF THE MOISTURE WHILE AVN REMAINS MOIST.  THIS AIR ADVECTING
NWD UNDER A SERIES OF RIPPLES IN THE UPPER JET HAS RESULTED IN
REPEAT TSTM DEVELOPMENT AND SLOWED TIEH NWD ADVANCE OF THE WARM
FRONT.  AS THIS PROCESS IS LIKELY TO CONTINUE WITH UPPER DIFL LIKELY
INCREASING AHEAD OF MAIN LOW OVERNIGHT...THE PROSPECTS FOR SVR WX
WILL CONTINUE.  ALSO THINK THE MODELS WILL REMAIN TOO FAST WITH THE
WARM FRONT.  FLOODING IS POSSIBLE...BUT STORMS SHOW FAST
MOVEMENT...SO WILL NOT HEADLINE FOR NOW.

ETA AND AVN ARE IN EXCELLENT AGREEMENT ON POSITIONS OF LOW AT SFC
AND ALOFT THRU 36 HRS...WITH ETA FASTER AFTER THAT.  DESPITE THESE
SIMILARITIES...THE AVN IS FASTER IN LIFTING THE DRY SLOT INTO OUR
AREA WEDNESDAY.  WILL TAKE A COMPROMISE SOLUTION.

WIND WILL ALSO BE A PROBLEM WED AND WED NIGHT AS THE STRONG LOW
MOVES THROUGH ERN NEB THEN MN.  GRADIENT DOES NOT LOOK QUITE AS
TIGHT AS LAST SYSTEM...SO FAR.  WINDS SHOULD DIE OUT GRADUALLY ON
THU AS WINDS ARE COUNTERACTED BY A DYING GRADIENT.

THU. NIGHT LOOKS COOL AND DRY PER GUIDANCE...WITH NO BIG CHANGES TO
EXTENDED.

.OMA...NONE.
POLLACK

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 11, 12:20 AM CDT	Severe Thunderstorm Warning	OAX	Monona	40 min
Apr 11, 3:34 AM CDT	Severe Thunderstorm Warning	OAX	Mills	41 min
Apr 11, 3:45 AM CDT	Severe Thunderstorm Warning	OAX	Montgomery, Page	45 min
Apr 11, 3:57 AM CDT	Severe Thunderstorm Warning	OAX	Pottawattamie	48 min
Apr 11, 12:38 PM CDT	Tornado Warning	OAX	Mills	37 min
Apr 11, 12:45 PM CDT	Tornado Warning	OAX	Pottawattamie	30 min
Apr 11, 1:04 PM CDT	Tornado Warning	OAX	Harrison	26 min
Apr 11, 1:12 PM CDT	Tornado Warning	OAX	Pottawattamie	18 min
Apr 11, 1:29 PM CDT	Tornado Warning	OAX	Shelby	31 min
Apr 11, 1:30 PM CDT	Tornado Warning	OAX	Harrison	30 min
Apr 11, 1:40 PM CDT	Tornado Warning	OAX	Monona	35 min

Nearby

Severe Thunderstorm Warnings in Iowa, 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.