Looking Back on the Big Ice Storm of 1997...

Wednesday, January 12, 2011

This is a special post to look back and remember the worst winter storm ever in the history of SW Louisiana.

One of the freakiest and costliest weather events in SW Louisiana History occurred on this date back in 1997. This is a look back at the worst winter storm that has ever affected the region. Do you remember where you were January 12-14, 1997? Many of you remember it as though it happened yesterday beings its so rare around these parts, and I know others don't remember or weren't living in the area at that time, so the purpose of this entry is to take a look back, and give you a little meteorology of the situation as well. It is important to understand how difficult it is to forecast winter weather events, anywhere, but especially here along the Gulf Coast.

Winter weather events are a rare item in SW Louisiana, and forecasting them is no easy task. However, early in January 1997 forecasting skills were pushed to the brim as models insisted on a significant winter storm for the region so close to the Gulf of Mexico. It was uncertain at first as to what type of frozen precipitation would occur, but confidence was increasing in the days leading up to the ice storm. Ice storms are very complex systems to forecast, and a rarity here, as is any type of frozen precipitation event. You never know what to expect when winter weather is involved, and that was certainly the case with this event. Ice storms are more common through the Mid West and Northern U.S., but do occur on occasion along the Gulf Coast. Generally, if we receive frozen precip freezing rain is what we get, and that is almost entirely due to the Gulf itself.

It was a cold start to the new year as a period of cold, overrunning rains fell across the region. The culprit was a strong, shallow Arctic air mass which came through on January 5, displacing a mild regime since New Year's. The overrunning occurred from the 6th-9th with temperatures in the 30s and 40s. Forecast models indicated an even stronger Arctic air mass would move into the area around the 10th-11th, and then indicated a winter storm would occur sometime between the 11th-13th. Some models indicated snow, some freezing rain and/or sleet, but the consistency was there.

By the 11th it was clearly evident that an ice storm of significance was unfolding. The Arctic front had stalled in the Gulf of Mexico, and energy from the Subtropical Jet Stream caused a surface low to form (cyclogenesis) along the front off the Lower Texas Coast. This set up prompted a series of disturbances (short waves) embedded in the Jet Stream to rotate through the area. Very cold air infiltrated the region behind the front on Friday the 10th, and a dry and cold day prevailed with some high clouds moving in ahead of the Gulf low. Moisture increased and overran the cold air in the overnight hours of January 11, and light precip broke out across the area before midnight on the 12th as the first short wave rotated through. The precip was light snow as a layer of cold air still remained in the mid levels of the atmosphere. Temperatures were near freezing at that time. Lake Charles reported light snow for a few hours between 11p.m. on the 11th and 2a.m. on the 12th. Much of the snow didn't accumulate as the air remained very dry early on with the Arctic air firmly entrenched. It would take a while for the atmospheric column to moisten up. The snow ended early on Sunday, the 12th, and overcast skies prevailed with no precipitation across the area until around sunrise. A more potent short wave moved in, and at the time the layer of cold air in the mid levels of the atmosphere had eroded as the warm layer of Gulf air ahead of the surface low moved up over the top of the surface cold air. You have to remember here, that cold air is denser and sinks, while warm air rises.

Widespread precipitation began across the forecast area after sunrise Sunday morning, and continued throughout the day and through the day on Monday the 13th as well as repetitive perturbations moved through ahead of the NE advancing Gulf low. Mostly light to moderate precipitation occurred, and it was all in the form of sleet and freezing rain across the area. A significant snow storm occurred where the colder air was deeper across North Louisiana with up to 6" of snow in some areas up that way. Here, it was a matter of location as to what p-type occurred. From the coastline to the I-10 corridor it was the nastiest of all precip types...freezing rain, while North of I-10 up through Central Louisiana sleet was the dominant precip mode for the duration of the event. The freezing rain and sleet coated nearly every surface with significant ice accumulations. Roads became treacherous and were closed in many locations. Along the I-10 corridor from Beaumont to Lafayette, the freezing rain caused widespread power outages and downed several trees in the area. The most significant damage done by the ice storm was right over Calcasieu Parish. Many portions of the area from Beaumont to Lake Charles were in the dark for up to 6 days in some instances. Schools and businesses closed for the week of the 13th.

Major ice accumulations of 1/2-1" accumulated on nearly everything, and it was the weight of the ice on the trees and power lines that led to all the problems. Roads that weren't icy were nearly impassable anyway because of trees or power lines in the road. The precipitation fell near continuously from the morning of the 12th through the evening of the 13th when the short waves finally exited the region, and as the slow moving surface low moved closer to the area. Temperatures fell below freezing area wide on the morning of the 12th, and remained there until the afternoon of Tuesday the 14th. Problems first arose on Sunday the 12th during the afternoon hours. Power outages began being reported during the NFL Playoffs, and at the height of the storm on Monday nearly half a million people lost power across the area. Another problem arose on the afternoon of the 14th. As temperatures warmed above freezing, the ice began melting, and was falling off of structures. This created another hazard, and made navigating treacherous. The falling chards of ice led to more downed trees and power lines resulting in more power outages. This made conditions life threatening if one was caught under some falling ice. The ice storm was at the time the costliest natural disaster in SW Louisiana history. Damage estimates exceeded several millions of dollars, and we all learned just how severe ice storms can be. Clean up from the ice storm lasted well into the summer of 1997 as tree and limb removal was a lengthy process across the entire area.

Of course I was not a meteorologist at the time, but had a deep interest in the weather at the time, and did my own forecasting for the event. I was confident enough that some ice would occur, but even I was not totally sure what to expect. Also, remember, that back then, I didn't have access to all the same resources that I have now as a degreed meteorologist. Also, forecasting techniques for winter storms have improved greatly in the 14 years since this event. Not only did I learn a lot from the ice storm, it also helped to solidify my dream and passion of pursuing a career in meteorology. In closing, I want to give you a brief lesson in meteorology, and at the same time answer the question why snow is very rare here.

The ice storm was caused by what we refer to in meteorology as isentropic lift or the overrunning effect. This is when there is cold air at the surface, and warm up rides up and over the cold air at the surface. Winds are generally in a North or Northeastward direction at the surface and from the Southwest aloft. This is a very common occurrence down here in the winter months. This produces all those rainy and cold to cool days that are so common in South Louisiana. It's very rare that any ice storm lasts as long as the 1997 storm did ( 2 1/2 days). Most of them last no more than 24 hours.

Why did the precip fall mostly as freezing rain here along the I-10 corridor? Well, it all depended on how much warm air was aloft. In this case, the layer of warm air was thick enough to completely melt the snow as it fell toward the surface, and there was not enough cold air aloft for the precipitation to refreeze before making contact with the ground and other surfaces that were at or below freezing. (Freezing Rain.)The temperatures in the mid levels of the atmosphere say between 850-700 mb. or so were in the 40s to near 50 at the height of the storm with the layer of warm Gulf air.  If the precipitation falls, melts, and then refreezes before reaching the surface, it is called Sleet. If the precipitation is frozen all the way to the ground then it is snow.

So, now you know why snow is rare here. It's because of the Gulf of Mexico and the warm moist air coming up out of the Gulf. Another example of this effect that I can give, can be found right in your own home. Just simply go open your refrigerator, barefooted, you will feel the cold air on your feet, before you feel it at your head. I'm sure we'll experience another ice storm one day, but no one knows when or how severe it will be. Each winter storm is a different animal, and the synoptic features and set up for each one can be vastly different. Next time, we have a winter weather threat I hope you will better understand some of the difficulty involved in forecasting such an event.

-DM-