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Blue Northers

By: Christopher C. Burt, 9:22 PM GMT on November 20, 2013

Blue Northers

A powerful cold front is expected to plow through Texas on Thursday dropping temperatures in Amarillo from the 70°s to 30°s in just a few hours. A little snow may follow. This front will be what they call in Texas a ‘blue norther’. They occur several times every year (and sometimes several times in a single month) from November through April. Here are some extreme examples of the phenomenon.

Origin of the term ‘Blue Norther’

Although the meteorological dynamics behind the sudden drop in temperature caused by the passage of a sharp cold front are common to many places in the world, the term ‘Blue Norther’ appears to have its origins and common usage as uniquely Texan. The Texas State Historical Society has this to say on the subject:

BLUE NORTHER. The term blue norther denotes a weather phenomenon common to large areas of the world's temperate zones—a rapidly moving autumnal cold front that causes temperatures to drop quickly and that often brings with it precipitation followed by a period of blue skies and cold weather. What is peculiar to Texas is the term itself. The derivation of blue norther is unclear; at least three folk attributions exist. The term refers, some say, to a norther that sweeps "out of the Panhandle under a blue-black sky"—that is, to a cold front named for the appearance of its leading edge. Another account states that the term refers to the appearance of the sky after the front has blown through, as the mid-nineteenth-century variant blew-tailed norther illustrates. Yet another derives the term from the fact that one supposedly turns blue from the cold brought by the front. Variants include blue whistler, used by J. Frank Dobie, and, in Oklahoma, blue darter and blue blizzard. Though the latter two phrases are found out-of-state, blue norther itself is a pure Texasism. The dramatic effects of the blue norther have been noted and exaggerated since Spanish times in Texas. But that the blue norther is unique to Texas is folklore.

The only error I can find in this description is that a blue norther is not solely an autumnal occurrence. In fact, they are just as common, if not more frequent, during the spring months and occur during the winter as well.

During the Dust Bowl of the 1930s, blue northers were mostly responsible for the dust storms that plagued northern Texas and other locations in the Plains. Above, is a blue norther-caused dust storm bearing down on Amarillo, Texas on April 14, 1935, a day known in history as ‘Black Sunday’. Photo from Library of Congress.

Extreme Blue Northers

One of the most extreme blue northers on record occurred just last April (2013) when a cold front plowed south into northern Texas and dropped the temperature at Amarillo from a high of 89°F on the afternoon of April 22nd to a coldest-ever-so-late-in-the-season temperature of 20°F by the morning of April 24th. This, however, does not entirely explain just how extreme and fast the drop in temperature was. After reaching a record high of 89°F at 4 p.m. on April 22nd in Amarillo the thermometer had fallen to 86°F at 7 p.m. just prior to the frontal passage. The wind was blowing from the SW at 14 mph. By 9 p.m. it was 58°F with the wind from the north at 37 mph with gusts to 55 mph. By midnight it was 38°F and by 2 a.m. on April 23rd it was 33°F and snowing. The temperature continued to drop to a low of 29°F by 6 a.m. So, all in all, a 60°F (33.3°C) drop in temperature over just about 12 hours.

But wait, there’s more! There were FOUR blue northers to hit Texas in just that single month of April 2013! The first one hit on April 8-9 with a similar drop in temperature at Amarillo from 89°F on April 8th to 29°F on April 9th with winds gusting to almost 50 mph. Another struck on April 14-15 dropping the temperature from 88°F to 39°F and then yet another struck on April 17-18th. Below is the surface analysis for 00UTC on April 18th:

Note the extreme range of temperature at this hour over northern Texas: 37°F and snowing in the NW tip of the Texas Panhandle (at Dalhart) while it was 94°F at a site just 200 miles to the south.

Here is the April 2013 monthly climate summary for Amarillo:

Perhaps the single most extreme blue norther in Texas history was that associated with the famous arctic outbreak of February 1899, the greatest such in the annals of U.S. weather history. In his classic weather book Texas Weather author George W. Bomar states that temperatures on the afternoon of February 3, 1899 had almost reached 100° at sites along the Rio Grande (specifically 99° at Fort Ringgold and 97° at Fort McIntosh—now known as Laredo). The cold front swept through Texas on February 8-9 and by February 12th the dome of high pressure was centered over the state with Abilene measuring a barometric pressure reading of 31.06”. Temperatures had fallen below zero F° across the northern two-thirds of the state with a minimum of -23°F at Tulia on February 12th. Fort Ringgold registered 7°F and McIntosh (Laredo) 5°F also on the 12th, all-time record low temperatures for the sites.

As is often the case with blue northers little precipitation accompanied the passage of the front.

Another infamous blue norther was that of November 11, 1911 although it was more notable in Oklahoma, Missouri, and points north than in Texas. More about this can be found here< on the NWS-Norman, Oklahoma web site as well as here on the NWS-Kansas City web site.

The blue norther expected to race across Texas on Thursday is not expected to be of historical significance with temperature drops of only about 40°F at most locations.

Christopher C. Burt
Weather Historian

Extreme Weather Temperature

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.