Information AboutThundersnow |
| CATEGORIES ABOUT THUNDERSNOW | |
| snow or ice weather phenomena | |
| storms | |
|
FORMATION There are usually three forms of thundersnow:
One unique aspect of thundersnow is that the snowfall acts as an Acoustic Suppressor of the thunder. The thunder from a typical thunderstorm can be heard many miles away, while the thunder from thundersnow can usually only be heard within a two to three kilometer radius from the lightning. In the United States , March is their peak month of formation, and on average, only three events are reported per year.Patrick S. Market, Chris E. Halcomb, and Rebecca L. Ebert. A Climatology of Thundersnow Events over the Contiguous United States. Retrieved on 01-11-2006. Thundersnow, while rare anywhere, is more common with Lake Effect Snow in the Great Lakes area of the United States and Canada , the Midwest ern U.S., the Great Salt Lake , and has also been reported around Kanazawa and the Sea Of Japan and even around Mount Everest during expeditions. When such storms happen at Ski Area s, these Mountain s are often Evacuate d for Safety . Thundersnow was reported in observed thundersnow. Areas of Wisconsin including Eau Claire, La Crosse, and Madison observed this during a large winter blizzard mixed with ice and sleet on February 23 and 24, 2007, the same storm causing thundersnow to be observed in the area of Dubuque, Iowa. Thundersnow was also recorded in parts of Western Kansas and around Wichita, Kansas on April 13, 2007. A thundersnow event occurred on January 28, 2004 across central and southern Britain as a result of a squall line embedded in air of Arctic origin. The squall resulted in a sudden drop in temperature and pressure along with brief but heavy snowfall and blue lightning, and even a tornado near the town of Bath. This event is particularly notable because of the local temperate maritime climate, which usually prevents such extremes of weather. Report of thundersnow and tornado. Retrieved on 07-06-2007. From lake effect precipitation This type of thundersnow occurs after a cold front or shortwave aloft passes by, which steepens the Lapse Rate s between the lake temperature and the temperatures aloft. A difference in temperature of 25 degrees Celsius or more between the lake temperature and the temperature around 5000 feet/1500 meters (the 850 hPa level) usually marks the onset of thundersnow if surface temperatures are expected to be below freezing. However there are several factors affecting its development. The primary factor is convective depth; this is the vertical depth in the troposphere that a parcel of air will rise from the ground before it reaches the equilibrium (EQL) level and stops rising. A minimum depth of 2.5 km is necessary and an average depth of 3 km or more is generally accepted as sufficient. Wind Shear is also a significant factor, linear snow squall bands produce more thundersnow than clustered bands, thus a directional wind shear with a change of less than 30 degrees between the ground and 2km in height must be in place, any change in direction greater than 30 degrees through that layer will tear the snow squall apart. A bare minimum Fetch of 50 km is required in order for air passing over the lake or ocean water to sufficiently saturate with moisture and acquire thermal energy from the water. The last component is the echo top or storm top temperature, which must be at least -30C. It is generally accepted that there is no longer any super cooled water vapour present in a cloud at this temperature but rather ice crystals suspended in the air. This allows for the interaction of the ice cloud and Graupel pellets within the storm to generate a charge and have lightning or thunder result.USA Today. Jack Williams. Warm water helps create Great Lakes snowstorms. Retrieved on 01-11-2006. From synoptic forcing Synoptic snow storms tend to be large and complex with many possible locations and factors effecting the development of Thundersnow. The best location in a storm to typically find thundersnow on the northwest side, within what is known as the comma head of a mature and White Juan were such cases. From upslope flow Similar to the lake effect regime, thundersnow is usually witnessed in terrain in the cold sector of an Extratropical Cyclone when a shortwave aloft moves into the region. The shortwave will steepen the local lapse rates, allowing for a greater possibility of both heavy snow at elevations where it is near or below freezing, and occasionally thundersnow. National Weather Service Office, Sacramento, California. Alexander Tardy. Western Region Technical Attachment No. 02-13: Thundersnow in the Sierra Nevada. Retrieved on 01-11-2006. SEE ALSO REFERENCES EXTERNAL LINKS Links to individual events
|
|
|