KATC StormTeam 3 Weather BLOG

So far the winter of 2011/2012 has been warmer than normal by 3-4 degrees in Acadiana with temperatures in December 2011 about 1 degree above normal, while January 2012 was 6 degrees above normal. 

Lafayette’s average high was 68 degrees this January, while last year it was 60.  This makes a big difference in our heating bills, but unfortunately it will likely translate to a mosquito/bug boon this spring and summer.

That is unless we see colder conditions in February; as of this writing, the first two weeks of February should be at or slightly below normal temperature-wise per the Climate Prediction Center while our above normal precipitation pattern may continue for a couple more weeks.

The long-range models offer a chance of a few light freezes mid-February, but not much more.  The second half of February is offering a back to above normal temperature pattern.

There are two major factors that dictate our winter weather pattern: La Nina (or El Nino) and the Arctic Oscillation…La Nina years, which has dominated over the last three winters, usually allows for milder than normal conditions over the lower 48 and Acadiana.

But last winter and the winter before the Arctic Oscillation was positive delivering much colder weather to the US…this year the Arctic Oscillation has been negative over North America but positive over Europe (and that’s where the winter has been more severe so far).

Although it has been a mild winter this year, it’s not a record breaker, but it certainly highlights that each year can be quite variable.  Last year we experienced roughly 25 freezes through this time…this year about 8-10.

The Climate Prediction Center is also forecasting above normal temperatures for the Gulf South through the spring/summer…however, it will likely not be as hot as the record-breaker last summer…we hope!

Winter Temperature Forecast (December through February)

While I’m not a big fan of making long-term seasonal outlooks (reasons to be explained below), based on the data from the Climate Prediction Center (CPC) and the National Oceanic and Atmospheric Administration (NOAA) it does appear that Acadiana will see a drier than normal winter with temperatures expected to be at or above normal.

While there is high confidence in the precipitation forecast, there is below normal confidence by this author on the temperature forecast.

Cooler than normal equatorial Pacific water temperatures have been developing over the last several months indicating that a “La Nina” pattern has re-developed. 

This pattern is similar to the last two winters for Louisiana/Acadiana which was characterized by below normal rains and well below normal temperatures.

The winter of 2009/2010 (December through February) averaged more than 4 degrees below normal with 17 days of freezing temperatures in Lafayette while the winter of 2010/2011 averaged 2.5 degrees below normal with 27 days of freezing of temperatures.

Last winter would have been considered just as cold as the winter before if it were not for a dramatic swing in the second half of February where temperatures soared consistently into the 70s and 80s.

Interestingly enough there is enormous variability in the number of freezes Acadiana will see in any given winter with some years experiencing just a handful of freezes and other winters more than two dozen.  Last year may have been close to a record for the number of freezes, but these statistics are not readily available. 

Winter Precipitation Forecast (December through February)

In addition, when forecasting winter temperatures we must understand that even in an above normal winter, Acadiana can experience an arctic outbreak that could bring temperatures into the teens or lower.  So perception versus reality also becomes an issue with these type of forecasts.

The real wildcard for winter forecasting, especially for temperatures, is the Arctic Oscillation, which per the last two winters trumped our La Nina influenced weather pattern ushering strong cold fronts to the area.

Per NOAA, “The Arctic Oscillation is always present and fluctuates between positive and negative phases.  The negative phase of the Arctic Oscillation pushes cold air into the U.S. from Canada. The Arctic Oscillation went strongly negative at times the last two winters, causing outbreaks of cold and snowy conditions in the U.S. such as the “Snowmaggedon” storm of 2009.  Strong Arctic Oscillation episodes typically last a few weeks and are difficult to predict more than one to two weeks in advance.”

With all of the above being said, it is with much consternation that we make the long-term outlooks. 

Based on the current information supplied by NOAA and the CPC and given La Nina has kicked back in across the Pacific, Acadiana will likely see drought conditions perpetuating and/or worsening through the spring.

We will buy into above normal temperatures for now, but I would expected several very strong cold fronts nonetheless thanks to a more unpredictable Arctic Oscillation.  

Another key to nailing the temperature forecast is where will the upper level trough axis be most prevalent this winter. 

If the upper “troughing” is similar to the last two years, we will adjust our temperature forecast downward, but just a subtle shift of average trough a few hundred miles to the east will translate to much above normal temperatures.

So there here it is: a low confidence forecast for above normal temperatures and a high confidence forecast of below normal precipitation this winter for Acadiana. 

Based on our late October pattern it would also be a fair prediction that November through early January could actually be below normal in Acadiana with the latter part of January into February possibly more dramatically warmer than normal skewing the numbers for the entire winter. 

And based on the last two winters I would also expect a dozen or more freezes and the possibility of one or two events that may bring temperatures down into the mid-20s or slightly lower.

As for predicting any snow or ice events, your guess will be as good as mine.  If the aforementioned forecast pans out, I wouldn’t be too excited for a winter storm…but if the pattern plays out closer to the last two winters we may indeed get one or two shots at the frozen stuff.

And per usual chances for a White Christmas in Acadiana will remain an abysmal 1 in 1000 year chance…here’s to “wish-casting”!

Rob Perillo

After a substantially colder than normal December and January, and a very cold first week of February, Acadiana experienced above normal temperatures over the last several weeks of the month.  This pushed February 2011 to  slightly above normal conditions.  Daytime highs for the entire month averaged 1.5 degrees above normal (near 66 degrees) while overnight lows were right on mark (at 44.9 degrees).

Continuing from the 2010 theme, precipitation for February was 43% of normal in Lafayette, with significant drought conditions possibly developing over the next few months.

The long range outlook from the Climate Prediction Center into March calls for above normal temperatures to continue while precipitation should be below normal. 

I would certainly expect more of the same for April and May as this would be consistent with continuing La Nina or Nuetral conditions with the Southern Oscillilation.

The question I’m getting most right now, is if we can start planting our gardens?  In Acadiana, on average, we see our last substantial freeze usually in the last week of February through the first week of March.  However, freezes have been recorded as late as the first couple of weeks in April.

Climatologically speaking, there is a 50% chance of a freeze after March 1st.  Factor in current trends it appears we are looking freeze free through the first 10-11 days of March but there will be arctic air lurking in the high U.S. Plains around the second week of the month, but currently I do not see a storm system that will bring that air to Acadiana.

But if you can wait a few more weeks for planting, you’ll all but guarantee not having to repeat the process later in March or April.  I would however recommend to fertilize our lawns as they’re coming out of winter stasis.

After running some of the actual temperatures for Acadiana of December of 2010 through the present our averages have been running significantly below normal.  Average “mean” temperatures for December 2010 (high/low divided by 2) were about 4 degrees below normal.  The mean for January through the third week of the month has been 2.5 degrees below normal.

The forecasts from the Climate Prediction Center this winter was for above normal temperatures…as I blogged about last month, just a subtle shift of the average trajectories of cold Canadian air can make a big difference…and it has across Louisiana. 

Part of the colder than normal temperatures experienced across the Gulf South can also be attributed to an extra stormy pattern along the East Coast with healthy snow storms ushering snow-chilled arctic air farther to the south.

Although the 30 day pattern from the Climate Prediction Center is still insisting on above normal temperatures for the area, I would take that with less than a grain fo salt.  The shorter term “long-range” models through the next two weeks is decidedly colder than normal for Acadiana with a possible major Eastern U.S. arctic outbreak centered around February 1st…we’ll see!

Bottom line for now, expect higher tha normal heating bills this winter.  Rob

Your thinking is right!  The winter of 2009-10 had a number of events.  From the earliest measurable snowfall on record in December, to the deep freeze in early January, and the 6th coldest February on record with another measurable snow.  The El Nino pattern was in full swing this winter as system after system rolled up the Texas coast with plenty of rain, clouds, and too many dreary gray days to count.  Even though it is now March, we still can’t seem to shake the cold, or the rain.  I, like many others are anxious for Spring to get here!

Let’s start with temperatures.  Overall the winter was colder than average.  When you take the 90 days of climatological winter (December, January, February), the average temperature is about 53.8 degrees.  This number comes from averaging all of the normal highs and lows for those months.  This winter we finished at 49.0 degrees.  Almost 4 degrees below normal, which is pretty significant for a three month average.  In south Louisiana we don’t have any average highs that are below 60 degrees, but this year we failed to reach a 60 degree high  52 times!  In fact only 26 of the 90 days did we have an above average temperature day!  We dropped below the freezing mark 17 times this winter, compared to only 7 times last winter.  We had almost as many days below freezing this winter as we’ve had for the past three!  There weren’t any breaks this year either.  We’ll go warm, then cold, then warm again in a normal winter.  When I’m talking about breaks, I mean a day where it hits 70 or higher.  Over the past 10 years, we’ve hit 70 degrees about 33 times on average.  This year, only 17.  80 degrees?  Forget about it…last winter we hit 80 once, this year..0!  By the way, February 2010 was tied for the 6th coldest February on record.  Only 2 days were at or above average.  The average temperature was 47.4 degrees, normal is 54.3.  We had 6 days in January where we dropped into the 20s.  The lowest temp of the winter…20 degrees on January 10th, sandwiched in between a pair of 21s on the 9th and the 11th.  And you wonder why everything is brown outside!

Snow…Twice this winter.  December 4th and February 12th.  We’ve had two snows in one winter before, but never three.  I was really hoping to break that record last week, but the snow never came.  December 4th we picked up 0.5″ of snow, and on February 12th we picked up 0.4″.

Rain…Above normal for the winter.  A total of 18.62″, or a little over 3″ above.  We had over 10″ of rain in December, almost 6″ in February.  We caught a break in January with only 2.02″.  Probably because the first 10 days of January were so cold that the air couldn’t hold any moisture!

March is coming in like a lion with the rain, and eventually this afternoon the wind.  It should be cloudy tomorrow, with sunshine returning Wednesday and holding for the rest of the week.  Temperatures aren’t expected to climb to normal until late this weekend when we might hit 70 on Sunday.

StormTeam3 Meteorologist Dave Baker

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