Possible storm track scenario for parts of the U.S. and impact on the Lower RGV
Red "L" depict low level surface cyclone; dashed line shows mean movement. "???" indicates possible outcomes of cyclone location on Atlantic coast, possibly driven by Arctic and North Atlantic Oscillation outcomes.

RGV Winter Outlook? Variable!
Unknowns Make December-February Forecast Difficult

And the forecast is...? As the NOAA 2008 U.S. Winter Outlook explains, the "absence of La Niña and El Niño makes predicting weather patterns on seasonal timescales increasingly challenging". Instead, other [short term] climate patterns over the Arctic and North Atlantic regions may play a significant role in influencing U.S. winter weather.

One of the methods that has shown some success, lacking a strongly detected signal in the El Niño Southern Oscillation or other atmospheric teleconnections is to follow recent trends, generally for the most recent decade. Thus, the trend for warmer weather in most of the central, a good portion of the southern, and part of the eastern U.S. over the past several winters, and drier weather across the southern and southeastern tier of the U.S., continues with the December 2008 through February 2009 forecast.

What Does it Mean for the Valley?
As the chart above shows, the forecast of somewhat drier, and warmer, weather across Deep South Texas, combined with a pocket of above normal precipitation from North Texas through Kansas, would imply an active storm track moving generally from southwest to northeast from the four corners region through the central Plains, then continuing northeast into the mid Atlantic and eastern Great Lakes region. Such a track would favor a breezy to windy southeast flow across the Lower Rio Grande Valley, along with temperatures a little above average. Cool or cold fronts trailing each low pressure system would return cooler air to the region for a day or two, before conditions quickly reverted to mild temperatures, and more humid conditions, especially toward the coast.

Does this mean that late winter into early spring 2009 will repeat 2008, when uncomfortable winds and minimal rainfall quickly built a drought, which helped aid an active wild fire season? Not necessarily. First, the copious rainfall from July through September, 2008, as well as replenishing downpours for a good portion of the area in mid November, should help keep soil moisture levels at reasonable levels into early February, barring frequent marginal freezes or a hard freeze or two. Second, the pattern leading us through autumn has been anything but stable across the U.S.; thus, while the "typical" condition associated with the forecast may well come to pass, there could be persistent periods of cool and wet, cold and dry, or mild and dry, with changeable winds. Variable, indeed!

Stay tuned.

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