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February 10, 2009 Tornadoes:
How It Happened

SPC Storm Reports for 02/10/2009

The potential for an outbreak of severe weather on February 10, 2009 was forecast well in advance. The Day 4-8 Convective Outlook issued by the Storm Prediction Center (SPC) on Saturday, February 7th mentioned the risk for severe weather in the Southern Plains on Tuesday:

...IS EXPECTED TO SUPPORT INCREASING CONVECTIVE POTENTIAL...INCLUDING A 
CONSIDERABLE RISK FOR SEVERE STORMS. THIS MAY COMMENCE LATE TUESDAY
AFTERNOON ACROSS PARTS OF THE SOUTHERN PLAINS...

After Saturday, the potential for severe weather was highlighted in subsequent forecasts. By Tuesday, there was a Moderate Risk (issued by the SPC) of severe weather in place across much of Central and Eastern Oklahoma. The NWS Norman Hazardous Weather Outlook (HWO) at 6:50 AM CST mentioned the potential for tornadoes east of the dryline across Central Oklahoma.

Left: Surface observations at 743 AM Feb 10. Right: 1630Z SPC Convective Outlook for Feb 10.

Tuesday, February 10th began unlike most severe weather days in Oklahoma. The morning low in Oklahoma City at Will Rogers Airport dipped down to 40 degrees, and the temperature was in the 40s for most of the morning commute. In fact, temperatures across all of Oklahoma and Western North Texas ranged from 30 degrees northwest to the mid 50s southeast (pictured above, left). The fog being reported in Southeast Oklahoma in that image was evidence of low-level moisture shifting back to the northwest.

The moisture return continued through the morning hours, eventually setting up a broad area of upper 50s and lower 60s surface dewpoints generally along and west of Interstate 44, and along and south of Interstate 40. The low-level moisture return, combined with relatively strong surface heating and cooling air aloft, created a very unstable atmosphere, especially for early February. The moisture and instability can be seen in the maps pictured below, taken from the SPC Mesoanalysis Archive. As a result, the images were generated by the RUC model.

Left: Surface dewpoint contours at 19z Feb 10. Right: CAPE contours at 19z Feb 10.

As would be expected, the area of greatest moisture return featured partly sunny skies with abundant cumulus. This can be seen in the first satellite image shown below, which is a visible satellite image taken at 12:45 PM CST. In that image, you can also see the ragged beginnings of a few thunderstorms, stretching from near Lawton, northeast to near Ponca City. It was around 1 PM that showers and thunderstorms began developing along the leading edge of the moisture return and the surface front.

Left: Visible satellite image at 1845z Feb 10. Right: Visible satellite image at 2233z Feb 10.

Although thunderstorms developed all along the length of the front, the most intense storms in the early afternoon developed near the Wichita Mountains in Comanche County around 1 PM CST. The tornadic supercell, which happened to be the one that first crossed the Oklahoma City metropolitan area (OKC metro), moved northeast through Caddo and Grady Counties over the next 30 to 45 minutes. This supercell reached Southeast Canadian County around 2 PM CST, mainly producing large hail and gusty winds up until that point.

However, as the supercell moved closer to Yukon, it began to show signs of becoming tornadic. By 2:14 PM CST, it was beginning to develop a hook echo, and by 2:18 PM CST, the hook echo was fully developed. The rapid development of this hook echo signature, along with an increasingly strong velocity couplet on SRM, prompted a Tornado Warning at 2:17 PM CST.

Over the next 10 to 15 minutes, a few wall cloud reports were received from the Yukon area and into the western portions of Oklahoma City. At 2:36 PM CST, the first tornado of the day occurred near Northwest Expressway and Rockwell on the northwest side of Oklahoma City.

Products Issued For Oklahoma County Tornadoes
Significant Weather Advisory Oklahoma County
Tornado Warning SE Canadian and NW Oklahoma
Warning Continues for Canadian/Oklahoma Counties
Warning Continues for Canadian/Oklahoma Counties
New Tornado Warning NW Oklahoma County and Srn Logan County
Warning Continues for Oklahoma/Logan Counties
Warning Continues for Oklahoma/Logan Counties
Tornado Reported; Warning Continues for Oklahoma/Logan Counties
Tornado Observed; Warning Continues for Oklahoma/Logan Counties

This tornado was only on the ground briefly and produced EF-1 damage to some buildings near the Northwest Expressway. The supercell progressed northeast across Oklahoma County, continuing to show signs of rotation on radar. At about 2:52 PM CST, the supercell produced its second tornado of the day. This tornado began near 190th and Western, or about 3 miles west of the geographical center of Edmond. The tornado continued north-northeast, moving through neighborhoods and subdivisions on the northwestern side of Edmond. The tornado produced its most severe damage near the Oklahoma and Logan County line, or about 5 miles north of the geographical center of Edmond. The damage in this area was rated EF-2 on the Enhanced Fujita Scale. The tornado dissipated about 3:05 PM CST, just north of the Logan County line and just east of Broadway.

The supercell continued northeast, and later produced three additional tornadoes - all rated EF-0 on the Enhanced Fujita Scale. The first tornado was brief, and occurred about 2 miles northwest of Meridian in Logan County at about 3:26 PM CST. Further northwest, the fourth tornado produced by the supercell developed about 6 miles east-southeast of Langston in far northeast Logan County and moved to a point about 4 miles southwest of Stillwater in Payne County. For all the information on these tornadoes, go to our tornado table. The fifth tornado produced by this supercell in Central Oklahoma occurred in Pawnee County, in the NWS Tulsa CWA.

Around 4:30 PM CST, a thunderstorm began to rapidly develop (pictured in above satellite image) in Young and Stephens Counties in North Texas, or about between Breckenridge, TX and Graham, TX. This area is about 80 miles west of Fort Worth, TX. This storm moved to the northeast and became supercellular over the next hour, moving into Southeast Clay County by 5:30 PM and into Northwest Montague County by 6:00 PM. The supercell thunderstorm was moving into an environment very favorable for tornado development, as evidenced by the two images included below.

Left: 0-1km Storm Relative Helicity at 00z Feb 11. Right: Significant Tornado Parameter at the same time.

As the supercell crossed Northwest Montague County it became tornadic, producing a tornado that was captured on video by a storm chaser. The supercell then produced the most significant tornado of the entire outbreak as it reached the Red River. It's possible there was a small bit of the tornado path in North Texas, but the tornado began in Oklahoma in far southeast Jefferson County at about 6:50 PM CST very near the Red River.

The tornado continued northeast into Love County crossing through rural farmland north of Courtney, Rubottom and Oswalt. The tornado then crossed into Carter County around 7:10 PM CST, where it did its most significant damage. The velocities in the couplet on SRM were on the increase at this time, as can be seen in this image. Over the next 15 minutes, it moved northeast, approaching the town of Lone Grove. Sometime between 7:25 PM CST (Reflectivity and SRM) and 7:30 PM CST (Reflectivity and SRM), the tornado struck Lone Grove. The damage in the city limits was extensive, and was rated as high as EF-4 on the Enhanced Fujita Scale, the second highest rating possible - indicative of maximum wind speeds on the order of 166 to 200 mph.

Products Issued For Lone Grove EF-4 Tornado
Significant Weather Advisory Love and Jefferson Counties
Tornado Warning portions of Carter, Jefferson and Love Counties
Tornado Warning for Southern Carter and Northern Love Counties
Warning Continues for Southern Carter County
Tornado Observed; Tornado Warning continues for Southern Carter County
Large & Violent Tornado On Ground; New Tornado Warning for Eastern Carter and Southern Murray Counties
Tornado Observed; Tornado Warning continues for Carter/Murray Counties
Warning Continues for Carter and Murray Counties

As the tornado was passing through Lone Grove, it moved very close to the Newport Mesonet station. This mesonet site was within 2 miles of the tornado track, and situated to the north of the tornado track. As the tornado passed close to the station, it recorded a northwesterly wind gust to 58 mph in addition to a marked decrease in surface pressure. This is shown in the mesonet site meteogram, courtesy of the Oklahoma Mesonet.

The tornado crossed Interstate-35 about a mile and a half north of the Prairie Valley Road exit. It moved through rural areas of Northeast Carter County to the east of Springer, and eventually crossed into far Southern Murray County, ending about 5 miles southeast of Dougherty. The tornado ended around 8:00 PM CST. This means that it was on the ground for over 30 miles and for over an hour.

The tornado that struck Picher, OK last year was the last EF-4 tornado in the state of Oklahoma. Its damage path was 76 miles in length, although the segment in Oklahoma was much shorter than that. Thus, this tornado segment is the longest in Oklahoma in about 6 years, depending on how the final official tornado statistics shape up. For more facts on the event, visit the Quick Facts page that we have put together.

Image credits: SPC, AWC, UCAR.


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