Rare snowstorm hits Louisiana, Mississippi, and Texas

A rare early December heavy snowstorm hit Louisiana, Texas, and Mississippi yesterday, setting several records. It was the earliest measurable snowfall in recorded history at Beaumont, Port Arthur, and Lake Charles. Also, this snow event set the all time record snowfall amounts for the month of December at Beaumont, Port Arthur, Lake Charles, Lafayette, and New Iberia, and was the first measurable snowfall in recorded history for the month of December at Lafayette. In Mississippi, up to 5 inches of snow fell on areas south of Jackson. The snow knocked out power to 83,000 and caused numerous traffic accidents and road closures across Southeast Louisiana. The snow was caused by an upper-level low pressure system that deepened over the Gulf of Mexico. The snow was unusual because it occurred when the surface temperatures were 32 to 35 degrees.

The one inch of snow reported in New Orleans was that city's earliest snow on record. The previous earliest date for measurable snowfall in New Orleans was Dec. 22, 1989. New Orleans' last snowfall, in 2004, was a dusting. The record snowfall for the city is about 5 inches, recorded Dec. 30, 1963.


Figure 1. Yesterday's snowstorm brought a festive blanket of white to Magee, Mississippi. Image credit: SouthernLady.

A few selected snow amounts from yesterday's storm:

Louisiana
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Amite 8.0 inches
rossroads 6.0 inches
Hammond 6.0 inches
Mount Herman 6.0 inches
Opelousas 6.0 inches
Washington 6.0 inches
Covington 6.0 inches
Baton Rouge 3.0 inches
Plaquemine 2.5 inches
New Orleans 1.0 inches
Lafayette 1.0 inches
New Iberia 0.8 inches
NWS Lake Charles 0.4 inches

Mississippi
---------------
Columbia 5.0 inches
Jayess 5.0 inches
Brookhaven 5.0 inches
Prentiss 4.0 inches

Texas
--------
Lumberton 4.0 inches
West Beaumont 4.0 inches
Woodville 3.0 inches
Beaumont City 2.5 inches
SE TX regional Arpt 1.8 inches
Orange 1.0 inches
Port Neches 1.0 inches
Jasper 0.5 inches

So what happened to global warming?
Record snow events inevitably bring comments like, "so what happened to global warming?" First of all, no single weather event can prove or disprove the existence of climate change or global warming. One needs to look at the entire globe over a period of decades to evaluate whether or not climate change is occurring. It might be instructive to look at what global snow cover is doing this season (it's about 10% below average, Figure 2), but this doesn't mean global warming is occurring. This year's reduced snow cover could be due to natural seasonal variations. Only global average temperatures, when viewed over a time scale of decades, can prove or disprove the existence of global warming. Global average temperatures, when averaged over a decades-long period that removes the "bumps" associated with natural seasonal weather fluctuations, show that global warming is occurring.

Secondly, as both myself and wunderground climate change expert Dr. Ricky Rood have pointed out, global warming won't necessarily lead to a decrease in snowfall in all regions. If it is cold enough to snow, we may actually see increased snow in many locations. Global warming puts more moisture in the atmosphere, due to fact that higher global temperatures evaporate more moisture off of the oceans. I expect that coming decades will bring many record snowfalls, due to the increased moisture available in the atmosphere.


Figure 2. Northern Hemisphere snow cover on December 9, 2008 (blue areas) compared to average (green line). Northern Hemisphere snow cover was about 10% below average the first week of December. Since October, Northern Hemisphere snow cover has been about 5% below average. Bob Hart at Florida State has put together a nice set of regularly updating images showing the current state of global snow cover.

Subtropical Storm Rene possible in the Atlantic next week
The trough of low pressure that brought snow to the deep south will track eastward over the Atlantic over the next few days, reaching the central Atlantic north of the Lesser Antilles Islands by Monday. On Monday or Tuesday, the computer models unanimously agree that the southern portion of the trough will pinch off and form a "cut-off low"--an extratropical storm that is cut off from the jet stream. This low is expected to track slowly westward to a point midway between Bermuda and Puerto Rico by late next week. The low will be over waters marginally warm enough--25°C--to support formation of a subtropical storm, and phase space diagrams from Florida State indicate that this storm will be warm-cored. Wind shear is forecast to be low enough to allow a subtropical or tropical storm to form, and I give a medium (20-50% chance) that we will see Subropical Storm Rene in the Atlantic next week.

Jeff Masters