April 1, 2006

Storm Chase

Western Oklahoma

Editor:  Putnam E. Reiter

Forecast/Setup -

Risk Area:  Enhanced Moderate
Initial Target Area:  Hobart, Oklahoma

Most of the action this year has been north and east of Oklahoma, so this day certainly looked interesting with the dryline out west.  A cold front moved through the region earlier in the week, pushing deep moisture into Texas.  As the longwave trof over the western U.S. redeveloped a lead shortwave trof was progged to eject into the region on Saturday.  Models agreed that moisture would return into the region and this combined with decent speed and directional shear would provide a favorable environment for severe thunderstorms.

Several concerns presented themselves for this day, cloud cover, moisture quality, and cap strength.  None of these seemed to be a problem Saturday morning.  By early afternoon moisture quality did become a concern as surface moisture mixed out just east of the dryline.  60F dewpoints were located in west central Oklahoma with higher dewpoints along the Red River.  The cap was weak and appeared that it would give way, but some worried that it allow too much development.

Storms developed in the northern Texas panhandle around 3:00pm with the main show in the far northern panhandle.  Storms eventually developed near Lubbock and formed a cluster as they moved northeast towards Oklahoma.  Shortly after this initial development a lone thunderstorm developed ahead of the dryline near Wellington, Texas.

The storms in the northern Texas panhandle ended up being a cluster that moved into Kansas and produced marginal severe weather.  Farther south, the storms moving towards Childress produced large hail and strong winds.  The storm near Wellington is the only one to remain discrete and moved into Oklahoma near Willow.  This storm has classic supercell structure for a while, but eventually lost the battle to the storms near Childress as it had anvil seeding from them.  The storm transitioned into an HP supercell near Sayre.  The storm eventually become linear and developed a squall line with the Texas activity.  This line of storms moved east across Oklahoma producing mainly winds 60-70mph in isolated areas.

SPC Products:  SWO Day 1 Graphics:  Risk Area - Tornado Prob - Damaging Wind Prob - Hail Prob - Storm Plot - LSRs
Surface Maps:  Temperature - Dewpoint - Wind Speed - CAPE - LI - Moisture Convergence
Sounding:  GFS OUN - 00z 04/02
Text Products:  Mesoscale Discussions - Watch Products - Area Weather Updates
Mesoeta 00z Initialization:  Surface Pressure - CIN - 0-3km Helicity - 850mb Temperatures - 850mb Dewpoints - 850mb Windspeed - 850mb Vertical Velocity - 850mb Relative Humidity - 700mb Wind - 700mb Temperatures - 700mb Relative Humidity - 700mb Vertical Velocity - 500mb Vertical Velocity - 500mb Temperature - 500mb Vorticity - 500mb Wind - 500mb Relative Humidity - 250mb Wind - 250mb Relative Humidity

The Chase -

Team 1 - David Underwood, Rob Ferguson, and Putnam Reiter
Team 2 - Wayne and Kathy Robinson
Miles Driven - 411
Departure Time - 13:00 CST
Return Time - 21:30 CST

We left Oklahoma City and headed west on I-40.  We had some annoying equipment problems before getting out of town, but that didn't delay us too much.  We decided that Elk City would be a good stopping point but ended up going on to Sayre.  We stopped and looked at data for a while, noting the storms in the northern Texas panhandle and activity near Lubbock.  Seeing that the dryline probably wasn't the best spot in the world, we decided to stay in Oklahoma and see if storms developed in the convergence zone near us.

Conditions weren't as favorable as we thought they would be, but still figured we could get a storm.  After hanging around Sayre for about 30 minutes we drifted south towards Willow about the time we saw a storm developing.  We drove west of Willow and watched the storm.  The storm was well organized when we reached it about 16:00 CST with a rain free base.  As we got closer we noted a wall cloud with a beavers tail.  Getting just west of Willow, we watched the storm as it moved northeast just to our northwest.  We started back north and went east, playing tag with the storm.  The wall cloud got blown out several times by the rear-flank downdraft and then the storm transitioned to a high-precipitation supercell.  We watched this occur as the updraft enclosed in rain.  The weather service noted that storms in Texas were likely interfering with our storm.  This certainly made sense.  We decided to stay with the storm to see what would happen.  Eventually we got a view of the updraft region again and continued to stay with the storm.  About 18:30 much of our light was gone, even though it was still 45 minutes to sun down.  Also, we noted that the storms had formed a squall line and were racing east.  We jumped on Highway 183 and headed back to Clinton. then on to Oklahoma City.

Lessons Learned -

Not much to say here this time around.  We did a great job forecasting and staying with the storm.  Many people went to the large cluster near Childress, while we stayed on this storm.  It was a near perfect chase for us, the only thing to make it perfect would have been a tornado.

Multimedia -

Just west of Willow, looking west about 5-6 miles.  Picture 1, 2, 3 - Note the white balls on the ground are cotton, not hail.

Encounters -

Engaged Storm:  Willow
Tornado:  No
Funnel:  Not really, some close calls though.
Hail (larger than 0.75 inches):  Not with us, but it did produce baseball hail.
Wall Cloud:  Yes
Wind (above 57.4 mph):  No