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

One of the more important tools I have found in recent years on forecasting tropical activity beyond the normal 1-10 day computer model forecasts is the use of the Madden-Julian Oscillation (MJO) analysis.

Without getting too technical, the MJO describes large-scale waves of weather, or atmospheric perturbations that travel across the entire planet from west to east across the tropical latitudes.  These very large waves of weather, that move roughly at 10-15mph, are characterized by large regions of either enhanced or suppressed tropical rainfall patterns.

The frequency of the large scale planetary waves, can influence an area from anywhere between 30-60 days, but also help us to determine shorter scale weather phenomenon, including areas of enhance tropical storm/hurricane activity, monsoonal rainfall patterns and short-term droughts.

The MJO can also dictate on whether an El Nino or La Nina will develop and will influence each pattern’s severity.

But the true benefit to understanding the MJO and its affect on us in Louisiana is during tropical season. 

The Climate Prediction Center provides weekly analysis of the MJO and while very technical, and challenging my meteorological background, the forecast products including the Global Tropical Hazards Assessment Discussion (GTHAD) yield very important information to us as forecasters.

The GTHAD is is a two week global forecast that depicts areas of concern including above or below normal rainfall and areas of tropical development.  I found this forecast product over the last few years to give me extra ammunition when forecasting longer range tropical predictions.

Now mind you we cannot tell you specifically how strong tropical storms or hurricanes will be, nor where will they strike this far out, but we can say with this product we can forecast where activity is expected to develop with greater certainty over a two week time frame.

Today’s note: If you examine the the most recent GTHAD, the Atlantic Basin looks quite busy, as it usually gets this time of year.

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.

A strengthening low pressure system in the western Gulf of Mexico this evening will advance northeastward Saturday and head toward the Florida Panhandle Saturday afternoon.  Breezy conditions with period of rain will be likely through Saturday afternoon with activity likely to taper off Saturday night.  Rough conditions offshore have been reported this afternoon with sustained winds as high as 35-40kts with gusts to near 60kts.  Additional strong storms that develop this evening and tomorrow will insure that very rough conditions will continue through Saturday.  Meanwhile inland most of the precipitation will stay as rain with general accumulations through Saturday evening in the 1-2″ range but isolated amounts to 3″ will be possible for St Mary Parish.  Heavier rains and the slight risk of severe weather with this system may clip extreme Southeastern Louisiana and head toward the Florida Panhandle.  Most of the rain generated in Acadiana through Saturday will be driven by the upper level low that is guiding this system.  The upper low won’t clear the area until Sunday morning.  So after the rains end there will likely be lingering drizzle/mist and perhaps some fog into Saturday night.  Lingering cloud cover Sunday morning should yield to partial clearing and some sun Sunday afternoon.  Temperatures will stay in the upper 40s to lower 50s through Saturday evening dropping into the low-mid 40s for Sunday morning.  Milder conditions are possible for Sunday afternoon with highs in the upper 50s to near 60.  Spring-like conditions with mostly sunny skies are anticipated for Monday and Tuesday of next week with highs pushing into the mid-upper 60s.  The next weather-maker will arrive for next Wednesday likely producing a round of thunderstorms.  Even warmer temperatures should follow late next week into the weekend with highs pushing into the low-mid 70s!  Another round of even healthier (possibly severe)  storms may follow for next Sunday.  As we start to see the warmer temperatures ahead of frontal troughs over the next few weeks the risk of severe weather will increase with each system.  Normally our spring severe weather season begins in the latter part of February, but given this El Nino winter pattern it is not unusual to have more frequent severe weather events starting as early as late January.  At least for this weekend it will just be a rain event.  Have a great weekend and Geaux Saints!  Rob

Rain and embedded rumbles of thunder will be likely for our Wednesday as low pressure develops in the Gulf of Mexico this Tuesday evening.  The surface low this time around won’t be a deep one but this system has plenty of upper support which will likely generate rain and elevated embedded thunderstorms, especially for our Wednesday afternoon.  Since this system is more elevated in nature we are not expecting any organized severe weather.  Estimating rainfall totals has become quite problematic with almost all of the models coming in with rain totals of an inch or less today.  But as we have been saying all along in this El Nino enhanced winter…”go with a wetter forecast”.  With that being said, rain accumulations should be generally between .10-.25″ overnight with 1-2″ the best forecast at this point for Wednesday.  The rains should stay below flooding thresholds, but if the embedded storms can get cranking and train over a particular area then isolated amounts up to 3″ could be possible.  The rain and storms should end sometime tomorrow evening with lingering clouds and fog possible for Wednesday night into Thursday morning.  Thursday should bring mostly cloudy skies with a few intervals of sun and mild temperatures, but a fairly strong cold front should push across the area for New Year’s Eve possibly engendering a few light showers.  Friday and Saturday will be blustery with highs ranging in the upper 40s to lower 50s while lows drop into the low-mid 30s.  Next week continues to look rather interesting with the coldest air of the season edging into our area.  Combine that with an hyper-active sub-tropical jet stream and then wintry weather could become an issue.  Right now the models have been tilting toward a drier but cold solution for early-mid next week…but we’ll see what Mr. El Nino and friends may have in store.  The bottom line though is that we may indeed see lows dropping into the mid-upper 20s by next Wednesday morning with highs struggling to make the 40s…stay tuned!

The parade of El Nino enhanced Gulf of Mexico low pressure systems will continue this week with another system developing Tuesday/Wednesday.  An upper level low/trough off the coast of Baja/California will make a bee-line for the area developing a low pressure system off the Texas Coast Tuesday.  This will bring clouds back into the area Tuesday with soaking rains likely developing Tuesday night into Wednesday.  Current computer models are indicating efficient delivery of the rain process which will likely lead to 2-3″ of rain to the area with the possibility of more based that nearly every storm system over the last month has come in more dynamic than advertised by the models.  There shouldn’t be any severe weather with this system but embedded storms are certainly possible especially over the coastal parishes and Southeastern Louisiana, where 2-4″ or more will be possible.  Like nearly every system this year it will be another rough one offshore mid-week.  So it looks like we’ll be finishing off a record wet December with more wetness unfortunately.  Thursday should be dry and mild but quick-moving showers will probably redevelop for New Year’s Eve with a strong cold front.  It will be nice and cold with sunny skies for the first few days of the new year with light freezes possible come Saturday and Sunday mornings.  Rob

The “El Nino-enhanced” active sub-tropical jetstream will likely keep the clouds with us through mid-week with rain likely to return for Thursday.  We certainly don’t need any more rain with our grounds at complete saturation but at least the next weather system should keep the heavier rains offshore with mostly light to moderate rain expected with the next system.  Area-wide rain totals from yesterday and last night were generally in the 1-3″ range with coastal hot-spots of 4-6″ found in Vermilion, Iberia, St Mary and St Martin (Upper and Lower) Parishes.  Fortunately there were no major reports of flooding in homes in Acadiana but that wasn’t the case apparently over eastern Louisiana.  breezy and quite cool weather will stay with us for Wednesday with a few breaks in the clouds possible but not likely…in fact we probably won’t see much sun until the weekend.  As I mentioned earlier, rain will return Thursday as yet another low pressure system gets cranked up in the western Gulf of Mexico.  This system should stay a little farther offshore bring mostly light to moderate over-running rains to the area…but once again the coastal parishes will have the best opportunity for more soaking rain…no break for the weary.  Lingering clouds, drier and decidely colder weather should move in for Friday into the weekend with plenty of sun expected for both Saturday and Sunday.  Colder, slightly modified arctic air should move in Saturday keeping our highs near 50 with overnight lows possibly near freezing or slightly below by Sunday morning.  It looks dry at least through early-mid next week but if I were making a forecast off of the long-range models today I would be guessing cloudy, cool and occasionally wet for Christmas Eve/Day time-frame…but that will likely change…so stay tuned!

The front end of our weekend will be marred by another low pressure system in the Gulf that will bring another round of widespread rain into the region.  Cloudy and quite cool conditions will persist through Friday afternoon with patchy light rain/sprinkles developing along the coast by midday advancing inland during the afternoon.  Widespread rain will be likely Friday night through at least Saturday morning with rain totals expected to be in th 1-2 inch range.  Isolated spots may get more, especially along the coastal parishes where some embedded elevated heavier showers and storms may develop.  This low pressure system will be slow to move out of the Gulf and will likely weaken as it moves right over Acadiana Saturday.  This means lingering showers and overcast skies will continue through much of Saturday with fog and drizzle becoming quite likely for Saturday evening and night.  We are cautiously optimistic that drier and milder air will move in for Sunday allowing for some intervals of sun and pushing temperatures into the upper 60s to lower 70s.  Incidentally for our offshore friends this Friday/Friday night system looks to be close to another “gale” storm so batten down the hatches and expect 30kt winds or better with heavy rains and embedded strong storms.  Yet another weather system will likely bring rough offshore conditions with showers and storms to Acadiana late Monday into Monday night with another couple of inches of rain possible…will it ever end?  Hopefully drier and cooler weather will move in and stay for the mid-latter part of next week.  It still looks interesting as we go into Christmas week with cold air lurking and another active storm system in the mix…the latest model run has backed off somewhat, but our odds for a white Christmas in Acadiana are generally 1000-1…this year it may be closer to100-1 or less!  Something possibly to look forward to while we remain mired in this dreary El Nino pattern!

Heavy rainfall led to widespread flooding during the early morning hours across portions of Iberia and St Mary Parishes.  Storm total rainfall accumulations ranged up to 6-9″.  Rain totals were in the 6-7″ range in and near New Iberia and Jeanerette into portions of St Mary Parish with over 8.5″ reported in the Centerville area in St Mary Parish.  Fortunately the showers and storms did not reorganize Tuesday afternoon/evening with just on and off showers anticipated through this evening.  Rain chances should end by midnight but fog should follow.  The National Weather Servicehas issued a Dense Fog Advisory for the area as the winds are expected to relax in a nearly saturated lower atmosphere.  The fog should lift quickly around daybreak or shortly thereafter as drier west -northwest winds will freshen and increase from the north-northwest.  Temperatures will stay rather mild this evening in the upper 60s but should drop into the mid-upper 50s tomorrow morning.  In fact, it may chill down several degrees during the day in spite of mostly sunny skies.  So it will likely feel cooler by lunch time so make sure you send the kids and yourself off with a jacket or sweater.  Breezy and cold conditions will move in for our Wednesday night with lows by Thursday morning likely to be in the mid-upper 30s.  While Wednesday and Thursday will be partly to mostly sunny and cool clouds will return Thursday night with rain not far behind on Friday.  Friday’s weather system may produce and inch or two of rain, especially along the coastal parishes, but I am not expected a repeat of what ocurred over the last 24 hours.  A wetter and stormier weather system however is on the docket for early next week.  In between, we’ll characterize this weekend as partly cloudy and seasonably mild.  Slight rain chances on the 8 Day Forecast this weekend are a hedge on the leftover Friday system and for the following system early next week.  It remains rather obvious that an active, hard to time El Nino storm pattern will stay with us through Christmas…no rest for the meteorologists nor our saturated grounds.