Respect the Severe Thunderstorm Warning

| April 28, 2016

Damage from the La Plata MD F4 tornado of 4/28/2002

Many people do not take severe thunderstorm warnings seriously. This can be a deadly mistake. It is important that you monitor severe thunderstorm warnings on your MyWARN app. A rare violent tornado in Maryland is a case study illustrating this point.

The first indications of trouble came early on Sunday morning, April 28, 2002 as the Storm Prediction Center in Norman, OK issued a moderate risk severe weather outlook across a large portion of the Mid Atlantic and Northeast United States as a strong low pressure system moved eastward from the Great Lakes. Accompanied by strong upper level winds, the low pressure system was forecast to cause widespread wind damage.

Later outlooks on that Sunday continued to emphasize the threat and began to mention the possibility of tornadoes. However, persistent cloudiness during the late morning led forecasters to downgrade the threat to slight by noon.

But by early afternoon, the severe weather outbreak was underway and a PDS (Particularly Dangerous Situation) Tornado Watch was issued for portions of Kentucky, Virginia, West Virginia and western Maryland.

At mid-afterooon, the severe weather threat was upgraded back to moderate for Maryland and the Mid Atlantic with the threat of tornadoes prominently mentioned. The SPC discussed the possibility of severe weather in Maryland shortly before 3 pm and a new tornado watch was issued for most of Maryland at 3:05.

The National Weather Service service assessment from the disaster found that advance notice of the severe weather outbreak had been excellent, with several releases during the day highlighting the threat and tornado watches that were issued well in advance of the storms.

The situation became serious by 4:30 p.m. as tornadoes were reported on the ground in Southeast Virginia, heading toward southern Maryland.

There was one breakdown occurred at a critical time, as the biggest tornado of the day was touching down. At 6:45 p.m. the warning team at the NWS Baltimore/Washington office issued a severe thunderstorm warning for Charles and Calvert Counties in Maryland. The forecasters chose not to issue a tornado warning, because the storm had appeared to weaken on radar. Also, a piece of critical information had not been relayed to them: that the same storm had produced tornadoes around 5 p.m. while it was still in Virginia.

As the supercell crossed the Potomac River, it rapidly intensified. At 6:56, the tornado touched down west of La Plata. At 7:00 p.m., forecasters decided to upgrade the warning and were attempting to call the EOC in La Plata, but lines were already jammed with reports of the tornado. When the forecasters finally made reached the 911 center, they were told that the tornado was already doing damage. The tornado caused its first fatalities in at 7:10 p.m.

The most important lesson for you is this: thunderstorms often display cycles of weakening and intensification. The severe thunderstorm warning issued at 6:45 that included LaPlata carried the familiar line “Severe thunderstorms can produce tornadoes with little or no advance warning.” Severe thunderstorm warnings deserve your attention!

The LaPlata tornado would remain on the ground for thirty miles, all the way into Calvert County. The F4 damage was reported along the path near La Plata. Four people died and over 100 were injured by the devastating storm.

Originally classified as an F5, later damage surveys downgraded the damage to that equivalent to an F4 tornado, one of only three F4 tornadoes ever in Maryland. Interestingly, two of the three F4’s struck La Plata.

FEMA reported that 85 homes were totally destroyed and another 167 heavily damaged by the twister.

The amazing thing is, that despite the excellent advance outlooks, watches and warnings, many people in the disaster area reported that they had no warning. If people in LaPlata had had the MyWARN app, they would have had hours of advance notice and precious minutes to take action.

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