KATC StormTeam 3 Weather BLOG

Addendum to this blog entry…surprise shower activity on December 31st brought 0.09″ of rain officially to Lafayette, making 2011 the 2nd driest of all time with year end totals unofficially at 35.88″.

 While the Japanese earthquake and tsunami was the natural disaster story of the year in 2011, in the U.S. droughts, floods, fires, very deadly tornado outbreaks, an East Coast earthquake and Hurricane Irene composed most of the weather/disaster headlines nationally.

Locally in Acadiana, there were some major headlines as well with a couple of weather stories related to climate rather than individual events.

The National Weather Service in Lake Charles summarizes many of the specific weather events in Acadiana with some of the top stories this year involving an ice storm, tornadoes, a river flood “that wasn’t”, a “beneficial” tropical storm and all-time records for the hottest summer and the driest year. 

The first of two deadly events of the year involved an ice storm on February 3 and 4th laying down a glaze of ice 1/4″ or more across portions of Acadiana along and north of the I-10 corridor that left more than 26,000 without power and numerous traffic accidents causing one fatality. 

About a month later a severe weather outbreak produced at least 4 tornadoes in Jeff Davis and Acadia Parishes including an EF2 tornado that struck Rayne. The Rayne tornado produced 111-135mph winds damaging or destroying more than 600 homes and responsible for 12 injuries and one death. The tornadic damage cost were estimated in the tens of millions.

This was the beginning of a very deadly, record breaking tornado season in the U.S. with the Mississippi and Missouri devastating EF4/5 tornadoes responsible for taking hundreds of lives and producing hundreds of millions of dollars in damage-swaths.

While a drought continued in Acadiana from the previous year, this spring we found ourselves dealing with a potential “flood of our generation” as water rose to dangerous levels in the Mississippi and Atchafalaya River Basins.

Spring floods across the Central and Northern U.S. manifested in some of the highest levels recorded in the Lower Mississippi River in April and May. This resulted in the opening of the Morganza Spillway for the first time since 1973 to relieve Mississippi River pressure from Baton Rouge to New Orleans dumping excess water into the Atchafalaya Swamp.

Fortunately the river levees held and predicted flooding inundations by the Army Corps of Engineers never materialized across both river basins.  Thanks to the ongoing drought, the Atchafalaya Basin absorbed and held delivery of more than 50 Superdomes worth of water per day for several weeks as water levels met or exceeded 1973 levels.

Outside of large tracts of farmland and crops being lost fortunately there were very few homes and camps inundated by the flood water, but preparing for the flood was quite costly for many.

The Atchafalaya Flood had some positive effects helping recharge portions of the swamp and build new wetland areas along the immediate Acadiana Coast at the Atchafalaya River outlet, but the effects of additional pollutants in the Basin, if any, from the Mississippi River has yet to be determined.

The threat of flooding from the river basins eased by mid-June as heat increased and drought worsened across Acadiana.

The summer of 2011 went into the record books as the hottest on record in 118 years with June, July and August temperatures collectively averaging roughly 3 degrees above normal. Daytime highs this summer were generally 1-2 degrees above normal with afternoon heat much more expansive with the lack of frequency of typical scattered showers and storms that the area normally enjoys during the hot summer months.

Interestingly enough Acadiana’s overnight lows were even warmer averaging 4-5 degrees above normal which was likely related to less night-time evaporative cooling from less rainfall.

Heat waves and droughts work hand and hand and feed off each other, and this year that was especially true for Louisiana into Texas.

As 2011 comes to an end, the drought across Acadiana continues to worsen as rainfall totals for the year are roughly 55% of normal area-wide.  The news is worse if after examining 2010′s rainfall for Lafayette of 42.52″, which was the 8th driest on record…and this year is on pace to be the driest…period.

Rainfall records have been kept in Lafayette since 1893 and the driest year in this 118 year period was 35.80″ in 1924.  Unless more than 1.40″ of rain falls between now and New Year’s Eve, 2011 will beat that record with 34.40″ to date through mid-December.  Normal yearly rainfall in Lafayette is near 62 inches.

In fact, the rain totals of 2010 and 2011 combined of roughly 77-78 inches will go down in the record books as the driest back to back years on record.  Similar dry spells/multi-year droughts have occurred in the area in 1901-1902, 1924-1925 and 1962-1963 where 82-85″ of rain fell in these two-year periods.

Even during the Dust Bowl Era of the 1930s Lafayette averaged better than 48″ of rain per year between 1935 and 1939.  This period was preceded by more than 70″ of rain in 1934 and came to a wet and flooded halt during the infamous year of the hurricane flood in 1940, when 98.72″ fell in Lafayette.

So based on records that span more than 100 years, and given we are in the midst of the driest back to back years within this period, it can be definitely determined that Lafayette and many of the surrounding areas are in the midst of a 100 year drought situation.

Due to the nature of how most of our rainfall is delivered in Acadiana, through scattered and generally random shower and thunderstorm activity, there are likely many spots in Acadiana that are doing worse drought-wise, while other areas conversely are likely doing marginally better.

Interestingly enough, if it weren’t for Tropical Storm Lee this year which delivered a 5-10″ rain area-wide in early September, much of Acadiana would be where Texas is this year…in the midst of a 300 to 500 year drought.

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

With impending tropical weather threatening Acadiana this weekend I wanted remind everyone to stay apprised of the weather conditions very closely as there will likely be big changes ahead.  Part of that obviously (or hopefully) is watching KATC TV and following us on katc.com.

In addition our weather page, you can find pertinent links to very important web-sites on our Hurricane Center Page.  Our hurricane Center includes a tracking map and links to the local National Weather Service, the National Hurricane Center and Emergency Preparedness information.  These links are all essential to have on hand during a storm.

During the last two plus years I have found Facebook and Twitter as excellent tools for not only disseminating information but gathering it.  They both have strong and weak points, but Facebook in particular I think is important to have on hand, and on your smart-phone, for a hurricane or any emergency situation where traditional lines of communication may be compromised.

Facebook is easy to use and it’s a great way to stay in contact with loved ones and friends…and say what you will about social media, I believe at the very least, it is a great tool in an emergency situation.

During any emergency KATC will be broadcasting live and streaming on the web on katc.com, but you can also follow us on twitter too.  The “tweets” from the Weather Lab meteorologists can be followed right on our weather page so you don’t even have to mess with setting that up if you don’t want to.

On Facebook, I would highly recommend following KATC’s page for the latest news, Dave Baker, Natalie Noah and me (Rob) for the latest weather updates.  If you click on the aforementioned links make sure you “like” the page to get our information streaming to your home page.

Good luck with the storm this weekend and for the rest of hurricane season.  Rob

April 2011 was the second warmest on record going back to 1893 in Lafayette missing being the warmest all time by 1/10 of a degree.

Mean temperatures (which are the averages of daily highs and lows) near 73.9 degrees this April was nearly 7 degrees above normal.  

This year was also 3-4 degrees warmer than last year so our utility bills will likely be higher for all of us this month.

Although some benefical rains did fall in the last week of the month and recent early May rains have also helped to stall the drought, rainfall deficits area-wide are still near 60% of normal for the year.  Most of the area will likely stay in, or close to severe drought status.

The outlook for May calls for a continuation of above normal temperatures for Acadiana with below normal rainfall.

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.

Although 2010 finished on the wet side, rainfall deficits for the entire year made 2010 the 7th driest on records.  Were it not for a very wet weather system that produced more than 3 inches of rain on December 29th and 30th, 2010 would have finished in the top five driest on record.  Accurate rainfall records have been kept in Lafayette since 1893, 117 years.

Acadiana-wide rainfall totals ranged anywhere from 15-25 inches below normal.  Average yearly rainfall in Lafayette is near 62 inches while the numbers shade a few inches higher southeastward toward Morgan City and a few inches lower to the northwest.

Drought conditions continue for a good part of Acadiana while the status of the drought worsens farther west toward the Texas border.  Per the last blog entry, not much help is expected over the next few months while a La Nina pattern continues into at least early summer.

I’m not a big fan of saying whether it will be a “mild” or “cold” winter…we have had plenty of milder than normal winters in the past where temperatures have averaged well above normal but we have had one shot of 15 degree weather.  Most folks will remember that as a cold winter. 

Other previously mild winters we have seen accumulating snow…perception cold winter.   I can recall playing golf on a past Christmas Eve in shorts in a colder than normal winter…what did I remember from that winter…playing golf!  Far too many times as we say in the weather and TV business, “perception is reality”.

The bottom line is that each winter we have on average 20-30 days of 70 degree plus temperatures (December through February) and this year will be no different.  Some years we barely get below freezing but for a handful of days or less…other years we’ll see more than 5 or 6 mornings where we plunge into the mid-20s…like last year. 

Incidentally last December through February was a “colder” than normal winter with temperatures in Acadiana ranging more than 5 degrees below normal…and it started with the earliest snow on record on December 4th!  That winter was followed by the warmest summer on record in Acadiana!

Everybody is asking me this year is whether we will see snow?  If your forecast is based just on long-term trend forecasts many think the odds below or above normal can be determined…but as we all know, Mother Nature’s randomness decides whether we’ll see a snow or a hurricane for that matter. 

Long-term trend forecasts are not that good.  So I say with above normal forecast confidence, that anything can happen!  A ringing endorsement by the non-committal!

The Climate Prediction Center did forecast slightly cooler than normal and wetter than normal conditions last winter but they are going with the opposite for the balance of this winter through March. 

The predictions are calling for in general, above normal temperatures accompanied by below normal precipitation patterns.

This year the temperature forecast calls for a fairly good signal for above normal temperatures as the developing La Nina should induce more ridging across the south. 

The pattern of the last few weeks of November through the first two weeks of December may favor this pattern with regular cold fronts but with milder than normal return periods. 

Forecast confidence is below normal for the temperature pattern however, as just a slight shift of the mean winter longitudinal cold front axis could translate to much warmer or much colder than normal.  We’ll see.

Precipitation forecasts are calling for below normal rains which does not bode well for Acadiana and the state for that matter, as most of the region is in a moderate to severe drought with many spots across the west central and northern part of the state mired in an extreme drought.

Finishing off 2010, rainfall in Lafayette is more than 20 inches below normal.  If drier than normal conditions continue through the winter, they may likely perpetuate through the spring.  This could set the stage for a serious drought situation for much of the state until tropical season arrives.   It is never good when you are wishing for a tropical storm or hurricane to end a drought. 

Based on current trends, forecast “confidence” is above normal for the precipitation pattern.

Droughts have had a history of becoming multi-year events in Acadiana and this may be the start of one such period…again, we’ll see.

Widespread rain and thunderstorms in the first couple of days in November brought impressive rain totals to Acadiana mainly across the I-10 Parishes southward.  Coastal parishes experienced the heaviest rains with totals generally in the 4-6 inch range. 

Hot spots in Vermilion Parish exceeded 8 inches across from Abbeville southwestward where flooding occured including water in some homes. 

Rain totals in Lafayette were in the 2.5-3.5 inch range while most areas north of I-10 indicated 1-2 inches of the wet stuff.

These rains have certainly eased the severity of the on-going drought, but the area will likely stay in “moderate to severe” drought status as many areas remain more than 10-15 inches below year to date normals.

In addition, due to the recent rains, the burn ban has been lifted.  Dry conditions will stay in Acadiana through the second week of November with the next significant chances of rain arriving about mid-month.

Our very dry weather pattern over the last several months has manifested into a severe to extreme drought for western portions of Acadiana and for much of the southwestern and western part of the state.  Fortunately rains earlier this week have eased the drought over portions of Acadia, Lafayette and St Martin Parishes.

Assuming Acadiana experiences normal precipitation patterns through the rest of the year, 2010 will likely fall within the top 10 driest years over a 117 year time span. 

Currently Lafayette has officially received 32.53″ of rain when normally we should be near 49.79″.  If Acadiana receives normal precipitation for the rest of the year (roughly 10″) then 2010 go into the record books in the top 10 driest years.

With La Nina developing the long term pattern this winter should bring continued below normal rains.  So it will be interesting to see how things play out for the balance of the year. 

Normally Acadiana receives approximately 60″ of rain per year with the driest being 35.80″ in 1924 and the most 98.72″ in 1940 (where a slow moving August hurricane produced more than 24″ in 48 hours in Lafayette).

Below are the top 10 driest years on record in Acadiana.

1.  1924-35.80″                             

2.  1902-37.25″

3.  1917-37.70″

4.  1936-41.15″

5.  1954-41.65″

6.  1962-42.33″

7.  1938-42.92″

8.  1960-42.98″

9.  2005-43.38″

10. 1999-44.86″