HAZARD:

TORNADO PROFILE:

A tornado is defined by Strahler in his Physical Geography Text as a violently rotating column of air extending from a to the ground. Normally and associated tornadoes develop in warm, moist air in advance of strong eastward moving cold fronts in late and early spring. Tornadoes can also occur along a “dryline” which separates very warm, moist air to the east from hot, dry air to the west. Both of these scenarios are common in the Central Plains. Another way that tornadoes can be created occurs when warm moist air flows upslope. Under the right temperature and moisture conditions, intense thunderstorms can produce tornadoes in higher terrain.

As shown on Figure 29, tornadoes can occur in every state, although the mid-west states have by far the greatest potential for this type of event. According to the Maryland Hazard Analysis, the state had 210 tornado touchdowns reported between 1950 and 1998. The most recent tornado outbreak occurred in the LaPlata vicinity in 2002 as shown on Figure 30.

Tornadoes can be ranked by intensity by using the Fujita Scale devised by Dr. Theodore Fujita at the University of in 1971. This scale is shown on Figure 28, and is broken into 6 categories from F-0 to F-5. F-0 relates to a tornado having a wind speed up to 72 miles per hour, while an F-5 tornado would have winds up to 318 mph.

COUNTY PERSPECTIVE AND HISTORY:

As shown in the Maryland Hazard Analysis, Garrett County has a composite tornado risk of 4 on a scale of 1-5. The local planning committee agrees with this risk assessment. Even though Garrett County is located in mountainous terrain it still has been subjected to violent including tornadoes. Between 1950 and 1998 there were 8 reported touchdowns of tornadoes in Garrett County as shown on Figure 31. Two of these events were rated Class F-3 and the remainder were F-1 or F-2. In 1980 Garrett County suffered a string of tornadoes which caused damage to a number of homes in Crellin. In 1998, two outbreaks of tornado activity occurred at the border of Garrett County and Somerset County just to the north. Both of these events were related to thunderstorms developing from passing cold fronts. The combination of warm moist air flowing up slope from the southwest and the cold front passing from the north and west created ideal conditions for tornado activity. One of these tornadoes was rated F-4 after it crossed the county line and hit Frostburg in Allegany County as shown on Figure 30.

MUNICIPAL PERSPECTIVE:

As is the case with most other related events, municipalities in Garrett County share the same concerns as the county. Two municipalities, Grantsville and Accident, are located on high, relatively flat land, and are probably more susceptible to wind events than municipalities like Friendsville and Kitzmiller, which are located in a valley setting affording some protection by surrounding mountains.

PREVIOUS MITIGATION MEASURES:

While mitigating tornado damage is nearly impossible, Garrett County does have a state mandated Building Code which includes wind loading requirements and tie-down requirements for mobile homes as shown on Figure 24. Additionally, the county’s hazard warning system can be activated following notification of impending by NOAA.