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Dark clouds and gusty winds

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Posted: Jun 10, 2014 1:28 PM by Meteorologist Josh Eachus
Updated: Jun 10, 2014 1:28 PM
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Topics: weather, forecast, severe, wind, storms

Dark, ominous clouds enveloped Southeastern Louisiana and Southern Mississippi on Tuesday Morning.

A line of heavy thunderstorms that developed ahead of a cold front in Western Louisiana blew into the region just after dawn. WBRZ viewers snapped numerous photos of the stormy sky featuring bubbling cloud bases and dark wall-like features.

The two phenomena captured were mammatus clouds and a gust front.

Mammatus clouds are rounded, smooth, sack-like protrusions hanging from the underside of a cloud. Such clouds often accompany severe thunderstorms, but do not produce severe weather; they may accompany non-severe storms as well. Though there are a variety of theories as to how they occur, typically mammatus develop on account of cooler liquid or ice particles sinking to the cloud base and condensing into the bubble-like structures visible from the ground.

A gust front is the leading edge of gusty surface winds produced by strong downdrafts in a thunderstorm. Cold air from high up in storm clouds is much denser than relatively warmer surface air and thus it comes crashing to the surface. Once it hits the ground, the air spreads outward, much in the same fashion as pancake batter when poured onto a griddle. Often the winds blow in the same direction the storm is travelling. Because associated clouds are so low and thick, blocking the sun's light, they often appear very dark.

Straight-line winds along or immediately behind Tuesday's gust front are the likely culprit for several area wind damage reports. The National Weather Service has received reports of downed trees and powerlines in Amite County, Mississippi near Liberty. Snapped trees have also been reported in Pointe Coupee Parish near Batchelor.

While some have speculated that the damage was created by a tornado, strong thunderstorm wind gusts can create very similar damage. An EF0 tornado has winds of 65-85mph. A severe storm wind gust must exceed 57mph. Either wind speed is physically capable of snapping trees and power poles.

The National Weather Service has denoted both the Liberty and Batchelor incidents as highwind reports.

You can get additional forecasts and updates from Meteorologist Josh Eachus at wbrz.com/weather, by liking Josh on Facebook and following him on Twitter.

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