Special Story: Below Average...Since October!

For Oklahoma City and Tulsa (and their respective metro areas), the past several months have been two things: cool and dry.  For both cities, February marked the fifth consecutive month with an average observed monthly temperature finishing below normal and, for Oklahoma City, the sixth consecutive month with total monthly precipitation finishing below normal, while for Tulsa the seventh consecutive month with total monthly precipitation finishing below normal.  It may be hard to believe that we're talking about such a rainfall deficit since 2013 marked the second wettest year on record for Oklahoma City, with 52.78 inches of rainfall recorded.  Unfortunately, most of that precipitation was picked up in the first half of the year.  However, Tulsa on the other hand finished 7.88 inches below the normal precipitation last year, with only 33.09 inches being recorded, and is therefore desperate for rain.

Let us now look at the temperature and precipitation anomalies by examining the following graphics.  October, in general, actually finished relatively near average, with only two-tenths of a departure from normal in Oklahoma City and sixth-tenths of a departure from normal in Tulsa.  The rainfall deficit from that month would also not be as drastic as in the latter months.  But then came November.  Remember the mini ice/snow storm that came the weekend before Thanksgiving?  Despite a few instances here and there, temperatures were relatively at or above normal until that point.  Then came six consecutive days with well-below average temperatures for Oklahoma City and nine consecutive days with below-average temperatures for Tulsa.  And unfortunately, the ice storm was one of the dominant precipitation-makers during the month, with only a few days towards the beginning of the month providing some additional precipitation.  As you can see from the graphics, all this precipitation was not enough, with November's total monthly precipitation finishing close to or just over an inch below normal for the cities.

When the ice storm came in November, perhaps you were wondering at the time what this winter would bring.  As we look back, that November storm only seemed to be a teaser to what was ahead in the coming months.  December finished even more below average than November, at close to or just over 4 degrees.  Very chilly low temperatures contributed to this, looking at the single-digit temperature being the lowest recorded temperature for the month.  And, of course, let's not forget the snow storm in early December and major ice storm right before Christmas.  For generally the first two weeks of December, temperatures were well-below average as a result of the first winter storm, which is also when the 5 and 7 degrees for Oklahoma City and Tulsa, respectively, was recorded.  Remember snow being on the ground for about a week because temperatures refused to rise above freezing?  Then, of course, the ice storm crippled the Oklahoma City metro area, also bringing frigid temperatures.  But, even a snow storm and a major ice storm could not bring enough precipitation to these metro areas to finish close to normal for the month.

January was a complex month for Oklahoma City.  If it's drilled into your head that January should have finished warmer than average, that's acceptable.  After all, the average high temperature actually finished nearly 2 degrees above average!  And that 75 degrees you see as the highest temperature recorded for the month even set a record high on the day it was recorded.  But these warm maximum temperatures were no match for the chilly lows.  With the average low temperature finishing nearly 4 degrees below average for the month, the cool side won the battle and caused the average monthly temperature to finish 1 degree below normal.  Should I skip over talking about precipitation?  All I will mention is that January was the sixth driest January on record for Oklahoma City.

January for Tulsa did not have maximum temperatures that were quite as warm, but as with Oklahoma City, the battle between warm maximums and cold minimums finished with the cold temperatures winning, as the average low for the month was over 4 degrees below normal!  And take a look at that -2 degrees being the coldest recorded temperature!  A precipitation deficit was also a problem in the Tulsa metro area during the month of January.

February is typically the month that delivers the most wintry weather to Oklahoma, and this February proved to do just that.  We were only a couple of days into the month when a snow storm delivered a few inches of snow to central and southern Oklahoma.  Then a few more winter storms occurred in that same week!  And even with the winter weather exiting, the cold weather did not want to leave.  In fact, the first 12 days of February finished below normal for Oklahoma City and Tulsa.  Then a major pattern shift happened, and those below average temperatures became above-average temperatures for ten days straight.  But the sign of spring would not last, with colder temperatures returning to finish out the month.  Precipitation-wise, February also proved to be a gloomy display for the cities, with the only precipitation-makers being the couple of winter storms at the beginning of the month!

We're now about a week into March, and winter has not wanted to let go.  Except for yesterday, March has recorded average temperatures well below normal.  The winter storm at the beginning of this month gave us a sign that winter may not leave, and today is doing the exact same.  Therefore, it should come as no surprise as to how far below normal the average temperature is for the month currently.  With warmer days ahead, though, this will change.

So why in the world has it been so cold and dry lately?  The graphic to the left shows the general pattern setup during the meteorological winter (December through February).  That, however, pretty much explains the story in the preceding months and for this month so far.  A strong region of low pressure aloft has been situated over southern Canada and the Upper Midwest and Great Lakes regions of the United States and sandwiched in between two regions of strong high pressure aloft.  The result has been cooler-than-average temperatures for the central and eastern United States this winter, while on the contrary, Florida and the western United States have been above average.  The second graphic to the right shows the surface air temperature anomaly during the meteorological winter.  Again, the central and eastern United States have generally been well-below average, while southern Florida and most of the west have been above average.

The drier-than-average conditions lately have been a result of the jet stream position.  Most of the active weather has been in the eastern United States because surface low pressure systems have strengthened east of Oklahoma and the central and southern Plains.  When the patterns have changed briefly, we have gotten the winter storms.  But for the most part, it has been unusually dry across not only Oklahoma, but also for a great deal of the southern Plains this winter.

So what lies ahead?  Will we see a pattern change anytime soon?  The Climate Prediction Center outlooks for this month and the next three months show "Equal Chances" for both temperature and precipitation for Oklahoma, so we unfortunately cannot narrow anything down at this point.  The 6 to 10 and 8 to 14 day outlooks, however, show temperatures that should be near normal to slightly above normal for the state.  Still, precipitation is expected to remain below normal during these time periods.  You can see the latest up-to-date outlooks provided by the Climate Prediction Center here.

Something Climate Prediction Center currently has its eyes on is the return for an El Niño setup in the Pacific Ocean.  Right now, we are in an El Niño Southern Oscillation (ENSO) neutral setup, but the Climate Prediction Center has issued an El Niño Watch for a 50 percent chance of the return of El Niño conditions starting this summer or fall.  The presence of El Niño results in warmer-than-average waters over the eastern Pacific and a persistent Pacific Jet Stream over the southern United States, still resulting in cooler weather but wetter weather for our region.  Again, this is something the Climate Prediction Center will be watching out for in the coming months.  It would certainly be good news for drought-stricken areas in Oklahoma and in California.  More information on this can be found here.

AC

Sources: NWS Norman, NWS Tulsa, NWS Miami-South Florida, Climate Prediction Center