MULTI-FACETED STORM: ONE FOR THE TEXTBOOKS

The recent storm is one for the ages and the textbooks! On its southwest end, it brought a rare snowstorm to parts of the Gulf Coast on December 10-11. It brought up to 10 inches of snow in southern Mississippi (Jeff Davis and Lincoln Counties); up to 8 inches of snow in southeast Louisiana (Amite). Beaumont-Port Arthur, TX and Lake Charles, LA had their earliest recorded snowfalls and set new December records from this storm. New Orleans had snow for the first time in nearly four years.

The image below, courtesy of NASA, shows a satellite view of the snow cover remaining on the morning of December 12.

On the storm's northeast end it brought a crippling ice storm that left 1.25 million homes and businesses without power across northeast Pennsylvania, parts of south and east-central New York, south Vermont and south New Hampshire, Massachusetts, and south Maine. The weight of the ice brought down many utility lines, while others were downed by trees and branches falling on them. Scenes like the one below were common throughout the area.

Ice weighed down trees at Salisbury, NH (courtesy of Weather Warrior Kathryn Michener).

The satellite picture below shows the storm system at noon on December 11 (courtesy UCAR). It's a classic comma cloud pattern with the comma head over MS, LA, and AL and the tail winding around from KY to FL. I've superimposed the surface low (L), warm front (red), and cold front (solid blue). In this type of satellite imagery -- called water vapor imagery -- the deep clouds show up as purple, blue, and green colors. Moisture shows up as gray and very dry air shows up as orange and red. It's a textbook example of the satellite image from a developing low pressure system.

The swirl comprising the comma head portion of this cloud pattern is the middle-level and upper-level low pressure area. It's cold aloft and, in this case, cold all the way to the ground. That's where and why the snow was falling. I've also superimposed a dashed blue line, which is a squall line, a line of thunderstorms with strong winds out ahead of the cold front.

The southeast part of the weather system brought at least 23 confirmed tornadoes and additional tornado reports from December 8-11. There were nearly 200 total reports of hail, damaging winds, and tornadoes as the storm system drifted from Texas and Oklahoma across LA, MS, AL, GA, and SC. If the cold pocket aloft had caught up to the surface warm air, it would have been worse. There was an extremely strong source for storm rotation in the low-level winds, but weak instability only allowed a few storms to become strong enough to tap it.

That orange-red corridor in the satellite picture is called the dry slot or dry surge. It charged north-northeast and ended the precipitation over Georgia and South Carolina. Still, some places in these drought-plagued states got more than 4 inches of rain from the storm system before the dry intrusion set in.

I thought I'd end this blog by showing you part of a weather map from 9AM Thursday, three hours before the comma cloud picture (courtesy UCAR). I put an arrow toward New Orleans, LA. That triangular pattern of 3 asterisks indicates moderate snow. How often do you see that in the "Big Easy?"