Public Information Statement
Issued by NWS Boston, MA

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993 NOUS41 KBOX 021205 PNSBOX CTZ002>004-MAZ002>024-026-RIZ001>008-030015- Public Information Statement National Weather Service Boston/Norton MA 805 AM EDT Wed May 2 2018 ...SEVERE WEATHER PREPAREDNESS WEEK - STAYING SAFE DURING HAIL AND DAMAGING WINDS The National Weather Service (NWS) Boston, MA has declared April 30 through May 4 as Severe Weather Preparedness Week. Each day this week we will highlight a different preparedness topic. While hail and straight-line winds generally do not garner the same attention or respect as tornadoes, they can be just as deadly! Hail can exceed the size of softballs and fall at speeds of over 100 mph, seriously injuring or killing anyone in its path. Straight-line winds can topple trees onto cars, houses, and power lines. Many deaths from straight-line winds are the result of trees falling onto the person, whether they are outside, in their house, or driving in their car. Strong straight-line wind events can even destroy buildings, especially mobile homes and manufactured homes. When damaging straight-line thunderstorm winds or large hail is expected, the National Weather Service will issue a Severe Thunderstorm Warning. When a Severe Thunderstorm Warning is issued for your area, or when threatening thunderstorms approach your area, you should seek shelter immediately! To stay safe during high winds, the same safety rules that are used for tornadoes also apply during straight-line wind events, namely, you should seek shelter in an interior room on the lowest floor of a sturdy building or shelter, get away from windows, and get down low to protect yourself from possible flying debris and falling trees. During large hail situations, you should move indoors and stay away from windows. Wind-blown hail can shatter windows. If you are driving during a large hail episode, pull over into a parking lot or gas station and use blankets or coats to cover yourself in case the windshield shatters and hail enters the vehicle. While not as notorious, or perhaps as spectacular to witness as a tornado, straight-line winds are responsible for most thunderstorm wind damage, especially across southern New England. A downburst is a strong, relatively small, area of rapidly descending air beneath a thunderstorm. It can result from stronger winds aloft being transported downward to the surface, or it can result as air within the downburst is cooled significantly as rain evaporates into initially drier air. This cool, thus dense, air sinks rapidly to the surface. A downburst is differentiated from common thunderstorm winds because the downburst winds have the potential to cause damage near the ground. Surface damage patterns have shown that whether the winds are straight or even a little bit curved, they tend to spread out, or diverge, considerably as they reach the surface. Conversely, damage patterns resulting from a tornado generally converge toward a narrow central track. Intense downbursts can be phenomenal. Speeds have been clocked as high as 175 mph near Morehead City North Carolina and at 158 mph at Andrews Air Force Base in Maryland. Closer to home, 104 mph downburst winds were measured at both Worcester Massachusetts on May 31 1998 and Whitman Massachusetts on May 21 1996. Strong downbursts will definitely cause roaring sounds and people may often refer to a sound like a freight train, terms typically associated with tornadoes. Although downbursts are not tornadoes, they can cause damage equivalent to that of a small to medium tornado. After all, wind is wind. Downbursts are classified as either macrobursts or microbursts, depending on the areal extent of the damaging wind swath. A macroburst`s damage extends horizontally for more than 2.5 miles. A microburst is a small downburst with its damaging winds extending 2.5 miles or less. The small horizontal scale and short time span of a microburst makes it particularly hazardous to aviation. The National Weather Service issues Severe Thunderstorm Warnings for thunderstorms that are expected to produce damaging wind gusts of 58 mph or greater, or hail that is one inch or greater in diameter. Be sure to take some time this week to learn more about severe weather safety. Learning and practicing severe weather safety when the weather is good will allow you to react more quickly when the weather turns bad. $$ For the latest updates, please visit our webpage at www.weather.gov/boston You can follow us on Facebook at www.facebook.com/NWSBoston You can follow us on Twitter at @NWSBoston

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