...Fall Severe Weather Season...
...Review Severe Weather Safety Rules...

As the first cool fronts of the fall season arrive, the threat of a significant tropical weather event is decreasing for southeast Louisiana and coastal Mississippi. However the likelihood of severe weather and associated hazards of tornadoes and damaging winds is increasing. Often the severe weather develops as warm and unstable air moving northward from the Gulf of Mexico interacts with cold fronts or upper level disturbances moving eastward through the area. Severe thunderstorms and tornadoes can develop in this unstable environment.

***As part of our severe weather preparedness activities...the National Weather Service office will issue a test tornado warning on the NOAA Weather Radio system at 915 AM on Wednesday October 30th, 2013.  The test warning will be issued under the Routine Weekly Test header and will not impact the emergency alert system.  The test message will activate the display of most NOAA Weather Radios with a test message.  This would be a good time to make sure your NOAA Weather Radio is in good working order and review your severe weather plans.***

FALL AND WINTER SEVERE WEATHER CLIMATOLOGY

Historical records show that the fall season, particularly November, has produced a large share of severe weather in Gulf Coast region. The fall season is only secondary to the primary severe weather season that occurs during the spring months. In addition, the severe weather often occurs at night. The severe weather may take the form of damaging straight-line winds, tornadoes, and large hail. Below is a graphic that shows the number of tornadoes that have touched down in our warning area between 1950 and 2009.  You can see that while the springs months are our busiest time climatologically, there is a secondary increase in tornado activity in November.

While not as pronounced as the month of November, the threat of severe weather and tornado extends through-out the cool season months of December through February. Several of the stronger tornado events in south Mississippi and Southeast Louisiana have occurred during the winter months, such as a strong tornado that struck Pearl River County, on Christmas Day of 2012.

 

 

Examples of several recent damaging severe weather events in southeast Louisiana and south Mississippi include:

  • One of the strongest tornadoes ever recorded in southeast Louisiana occurred during the early morning hours of Dec 6, 1983 when a violent (F4) tornado touched down near LaPlace. The tornado tracked 7 miles and destroyed 30 houses, damaged another 125 homes and injured 25 people, 5 with serious injuries.

      

  • November 21, 1997 - a strong tornado moved across St Tammany Parish, Louisiana, and continued into Pearl River County, Mississippi. Covington, Louisiana, and surrounding areas were particularly hard hit with nearly 70 homes damaged and 4 downtown buildings damaged. 47 people suffered mainly minor injuries.

      

  • October 29, 2002 - a weak tornado moved across the southeast portion of the Baton Rouge area during the early morning hours, knocking down trees and damaging house roofs. Straight-line wind damage occurred in several other areas from Baton Rouge area eastward to Pearl Rive County, Mississippi.

      

  • November 24, 2004 - damaging straight-line winds and several tornadoes were reported during the early morning hours in an area from near Baton Rouge eastward into coastal Mississippi. A strong tornado touched near the Slidell airport damaging 152 homes in a nearby subdivision. The same storm system produced another strong tornado that touched down around sunrise just north of Gulfport. The tornado damaged homes and businesses. Fortunately only a few relatively minor injuries were reported. Straight-line wind damage occurred in other areas of southeast Louisiana and south Mississippi.

      

  • November 15, 2006 - Severe thunderstorms produced tornadoes as they tracked across areas north of Lake Pontchartrain into southwest Mississippi during the early morning hours. Several strong tornadoes touched down from east of Greensburg, Louisiana, across northern Washington Parish to east of Tylertown, Mississippi. Unfortunately, one fatality occurred near Montpelier in St Helena Parish when a strong tornado struck a house and adjacent trailer.

      

EVENING AND OVERNIGHT TORNADOES

Listed below are a couple of interesting facts with regard to tornadoes that occur during the November through February period in Southeast Louisiana and South Mississippi:

  • 39 percent of tornadoes occur during the evening and overnight hours from November through February, compared to 33 percent during the remainder of the year.

      

  • For tornadoes that occur during the evening and overnight, there is a higher percentage of strong or violent tornadoes (32 percent) in the November to February time frame compared to the remainder of the year (24 percent).

      

  • Most of the fatality producing tornado events (20 events) in our area have occurred at night (13 events).

      

Because of the threat of tornadoes that can occur at night, especially strong tornadoes, it is important to have a means to monitor severe weather in the overnight hours when you may not be following the weather. NOAA Weather Radio is a valuable warning device, since it can be kept in the “silent” mode, and automatically alert if a Warning is issued for your county or parish.

SEVERE WEATHER DEFINITIONS, WATCHES, AND WARNINGS

Severe thunderstorms, by definition, can produce wind gusts of 58 mph or higher, and hail greater than one inch in diameter. Wind gusts associated with severe thunderstorms can down trees, power lines, blow out plate glass windows, and heavily damage house roofs.

Tornadoes can also develop from severe thunderstorms. Tornadoes can inflict damage ranging from minor damage to roofs and trees to total destruction of well constructed buildings.

The National Weather Service issues Watches and Warnings to help inform you of the approaching hazards of severe weather.

A Severe Thunderstorm or Tornado Watch is issued when atmospheric conditions are conducive for severe thunderstorms and tornado. Typically watches cover large portions of a state or states and are in effect for around 6 hours. If a watch is in effect, be alert and monitor weather conditions and listen to television or radio for the latest watches and warnings.

A Tornado Warning or Severe Thunderstorm Warning is issued when reliable ground truth reports have been received or when doppler radar indicates there is a high threat of tornadoes, damaging winds, or large hail.

SEVERE WEATHER SAFETY RULES

If a watch is issued for your area...closely follow local media and NOAA Weather Radio for potential warnings. Be prepared to move to a safe location.

If a warning is issued for your area...take action immediately. Seek shelter in an interior room on the lowest floor of a well constructed building away from doors or windows. An interior small room such as a bathroom or closet, or even a hallway away from doors and windows are typically the best location

If you are living in a travel trailer or mobile homes make sure it is anchored securely as these structures are more vulnerable to severe thunderstorm winds and tornadoes. If possible, move to stronger and well constructed building if severe weather develops.

RELIABLE SOURCE OF WEATHER INFORMATION

One of the most important features of your severe weather safety plans is to have a reliable means to receive severe weather warnings. If severe weather is forecast, monitor commercial television, radio or cable television for the latest weather information,including watches and warnings.

A battery operated NOAA Weather Radio is an excellent means to receive severe thunderstorm and tornado warnings. Weather radios can be programmed to automatically alert if warnings are issued for your parish or county. Weather Radios are especially helpful at night when people may not be monitoring the weather or television. The Weather Radios can be programmed to automatically alarm if a warning is issued.

Many newer cell phones take advantage of the Wireless Emergency Alerts (WEA) feature implemented during the past couple of years. This system allows government agencies to send urgent messages directly to cell phones in an impacted area. NWS Tornado and Flash Flood Warnings are currently sent through the WEA system to cell phones in the warned area. Apps or additional software are not needed and messages will look very similar to text messages when received. The WEA website and your cell phone service provider for supply additional information.

For additional information on severe weather visit the National Weather Service web site or contact the National Weather Service forecast office in Slidell at telephone number 985-649-0357 or 504-522-7330 and use ext. 4 to speak to a forecaster.


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