Calendar Says February, But Record Temps Feel Like August
By Bob Henson
The strong, recurrent Pacific jet stream that's been delivering massive amounts of rain to California has also been pushing mild Pacific air downslope off the Rockies and eastward, keeping the southern two-thirds of the U.S. absurdly warm for early February. From New Mexico to Virginia southward to the Gulf Coast, trees and shrubs are budding out en masse up to three weeks ahead of schedule (see Figure 1).
In Texas, Dallas-Fort Worth recorded its last freezing temperature on Jan. 8. With no freezes expected into at least the last week of the month, there's a chance that the Jan. 8 reading of 20 degrees F will be Dallas-Fort Worth's last freeze of the winter. That would eclipse the earliest final freeze of the season (Feb. 5, 2000), in records extending back to 1899. The February warmth comes after a three-month span that was milder in Texas than any Nov/Dec/Jan period since the 1930s Dust Bowl, according to state climatologist John Nielsen-Gammon.
The warm, moist air prevailing along the South has been teaming up with occasional jet-stream intrusions to produce severe thunderstorms, including an unusually large number of tornadoes for the year thus far. This includes six confirmed tornadoes across southeast Louisiana on Feb. 7, with an EF3 twister causing more than 30 injuries and damaging or destroying more than 600 homes in and near East New Orleans (see the detailed National Weather Service survey report on all six tornadoes).
As of Feb. 13, theNational Oceanic and Atmospheric Administration's (NOAA) Storm Prediction Center (SPC) had tallied 163 U.S. tornadoes for the year thus far, not quite a record but far above average. On Tuesday morning, NOAA/SPC placed parts of the western and central Gulf Coast under a slight risk of severe weather, with a small enhanced-risk area along the central Texas coast near a large thunderstorm complex that had already produced several tornado reports west of Houston.
Figure 1. An index of the seasonal progress of leafy plants shows conditions 20 days or more ahead of schedule over large parts of the South and Southwest as of Sunday, Feb. 12.USA National Phenology Network / @TheresaCrimmins.
Close to the Century Mark in Oklahoma
While there's been quite a few ups and downs to the national temperature picture in recent days, with frequent frontal passages, the low temperatures haven't been all that low and the highs have been unusually high, as noted by Weather Underground blogger Steve Gregory. For the month to date through Feb. 12, NOAA had compiled a preliminary total of 1,207 daily record highs and 10 daily record lows, for a staggering ratio of more than 100 to 1. It's a picture in line with recent months: November 2016 had the largest ratio of record highs to lows of any month in modern records. It's also consistent with the inexorable effect of human-produced greenhouse gases in boosting temperatures to make record warmth more widespread and extreme than record cold.
One especially strong pulse of warm air jet pushed across the Southern Rockies and into the South from Friday into Sunday. As the already-mild air descended the Rockies, it warmed further due to downslope compression, leading to some eye-popping readings. Several stations in southwest Oklahoma soared into the upper 90s on Saturday. The town of Magnum hit an astounding-for-February 99°F, which tied the state record for any winter month (Dec/Jan/Feb) that was set at Arapaho on Feb. 24, 1918.
Here's a sampling of the all-time February heat records set over the past several days. In many cases, you have to go to mid-March to find comparable warmth!
Wichita Falls, Texas: 94°F (next-earliest reading at least this warm was 98°F on 3/1/2006; records began in 1923)
Liberal, Kansas: 90°F (next-earliest 90° was 3/11/1989; records began in 1893)
Amarillo, Texas: 89°F (next-earliest 89° was 3/10/1989; records began in 1892)
Goodland, Kansas: 87°F (next-earliest 87 was 3/10/1989; records began in 1895)
Denver, Colorado: 80°F (next-earliest reading at least this warm was 81°F on 3/16/2015; records began in 1872). A cooperative observing station at the site of Denver's former Stapleton Airport, where official readings were taken until the mid-1990s, reported 83°F.
Lubbock, Texas: 91°F (next-earliest reading at least this warm was 95°F on 3/11/1989; records began in 1911)
Norfolk, Virginia : 82°F (ties all-time monthly high set on 2/4/1890 and other dates; records began in 1874)
High temperatures across Oklahoma on Saturday, February 11, were similar to readings one might expect in early July.Oklahoma Mesonet / @okmesonet
Temperature departures from average for the period February 1-12, 2017. The warm anomalies will likely persist, as models are calling for continued milder-than-average weather over most of the nation through late February.NOAA / CPC Climate Prediction Center