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!

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

While hurricane season officially ends November 30th, climatology dictates that by mid-October the threat of big, block-buster hurricanes in the Gulf of Mexico decreases dramatically.

Any tropical activity that may threaten the Gulf of Mexico in October usually has limited opportunity for development and movement (toward the Northern Gulf) as upper level westerly winds and associated increased wind shear become more dominant players in the region.

This doesn’t mean our hurricane season is over in Acadiana quite yet, but recent weather patterns look to continue over the next few weeks making it appear rather promising that we’ll escape without a major hurricane threat this year.

In the past, Acadiana has experienced major hurricane threats in the first week of October such as Lili (2002) and Hilda (1964) and we have dealt with other tropical systems through the end of the month including Hurricane Juan in 1985 which looped in the Gulf during the last few days of October into early November.

There have been other major hurricanes in the Gulf of Mexico in October, most recently Wilma in late October 2005, but most, like Wilma, moved from the Caribbean northeastward toward Florida and the Bahamas.

Typically tropical development in October is confined to the Caribbean and far Eastern Atlantic.

Atlantic systems that do emanate off of the African Coast normally stay Atlantic systems due to more active westerlies that steer systems away from the U.S.

Typically, storms that develop in and near the Caribbean in October usually remain Caribbean and perhaps South Florida threats.

Per the latest long range model data, there may be a window of opportunity for a significant tropical system to develop in the Western Caribbean during the second week of October, but upper level winds, per climatology, should any system smartly to the northeast…we’ll see.

Rob

Although the tropics have quieted down considerably as compared with the last two of weeks, the peak of hurricane season continues into mid-October.

Some of Louisiana’s (and Acadiana’s) bigger storms have come in the last week of September and in the first week of October including hurricanes Hilda in 1964, Lili in 2002 and Rita in 2005. So it is too early to breathe a sigh of relief when regarding the tropics.

Other than a rather disorganized Tropical Storm Maria just north of the Central Caribbean, there are just a few tropical waves worthy of our attention at this time.

Small disorganized disturbances were indicated Tuesday east of the Caribbean and emerging off of the African Coast. Both of these systems have some potential for development but at this time computer models are not suggesting significant organization.

Climatology, longer range models and Madden-JulianOscillation Forecasts all indicate that there will be some development in the Central tropical Atlantic over the next two weeks while the Caribbean will likely become active during the last week of September.

Interestingly enough, although it has been a busy tropical season with 14 named storms so far this season, only two have become hurricanes, Irene and Katia. Both of these storms attained major hurricane status during their lifetimes over water with only Irene striking much of the East Coast as a much lesser storm.

Based on earlier season forecasts of up to 4-5 major hurricanes in the Atlantic Basin it would not be unreasonable to believe that at least one or more major storms could be in the mix over the next three-four weeks with at least the Caribbean, and south of the major Caribbean islands possibly becoming the tropical hot spots later this month into early October.

Any storms that do develop in the Caribbean can be a threat to the Gulf of Mexico but persistent high pressure ridging in the Northwestern Gulf and increased frequency of frontal troughs will likely be players in steering currents over the next several weeks.

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

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.

Like death and taxes it’s nearly always a certainty that tropical activity in the Atlantic Basin ramps up dramatically as mid-August approaches. 

This year should be no different.  Nearly every year the busiest part of the season and the strongest storms develop and threaten the Gulf from the last week of August through the first week of October.

On average you can count on some sort of tropical storm or hurricane watch or warning to be posted along the Louisiana Coastline for portions of at least two of the weeks during the month of September.

The consensus forecasts for the season continue to call for anywhere from 12-18 named tropical storms in the Atlantic Basin, 6-10 becoming hurricanes and 3-6 of those hurricanes will likely become major category 3 storms or stronger at some point in their life-cycles.

The Gulf of Mexico has been rather quiet over the last two years after the twin storms of Gustav and Ike wreaked havoc on Louisiana in 2008.  The statistics alone therefore indicate that we will be busier in the Gulf.  With at least one to two major storms threatening some portion of the Gulf Coast. 

How busy will it be and where will the storms make landfall?  We can’t tell you that at this point, but the time is here to have a hurricane plan in place and have your supplies ready to go before the storms threaten.

Over the last couple of weeks in July, tropical  waves have been coming off of the African Coast with regularity, with some spin and not much African dust.  So at this point the forecast for a busy season are very likely to verify.

Whether it’s a busy hurricane season or not, it only takes one strike close to home to make it a bad season. This has been the mantra of the National Hurricane Center and all emergency preparedness officials.

Still weary from the oil spill last year, recent river flooding and long-term drought issues, Acadiana now embarks upon another anticipated busy hurricane season.

The forecasts from the experts this year predict anywhere from 12-18 named storms, 6-10 hurricanes and up to 3-6 major storms (cat 3 or higher) in the Atlantic Basin this year. The 40 year normal is 11, 6 and 2 respectively.

The last two hurricane seasons, especially last year, were considered busy in the Atlantic Basin. But the U.S. coast did not see a direct hurricane strike in 2009 & 2010.  The Northern Gulf of Mexico was very quiet over the last two years as well.  Odds are that won’t happen again this year.

Interestingly enough, the last two busy years in the Gulf saw back-back Louisiana strikes in the form of Rita & Katrina in 2005 and Gustav & Ike in 2008. In fact, Louisiana has averaged a major storm threatening the coastline once every three years dating back to Lili in 2002.  This year would make it three years since the last major threats.

These statistics don’t necessarily dictate that Acadiana will see a major storm. But the long-term odds do favor at least one tropical storm (near 95%) per season to strike near the area and about a one in three year hurricane threat to Acadiana.

In fact, Drs. Gray and Kltozbach do predict nearly a 47% chance of a major hurricane strike this season along the Gulf Coast from Brownsville to the western Florida Panhandle, which given any storm landfall has an impact, direct or indirectly upon Acadiana.

The question then becomes whether we all prepare for the potential threat or threats to come? 

How will this hurricane season go for Acadiana?

No one can tell us that, the science is no where near able to forecast where landfalls will be. Statistics favor the mostly likely time for major storm threats are generally from the last week of August to the first week of October.

Statistics also favor 1-2 storms possible in the Atlantic Basin in June and again in July, but by September tracking two or more storms on average per week will be likely in the Atlantic Basin given this year’s forecasts.