Thursday, November 21, 2013

The Winter 2013-14 Outlook

The Climate Prediction Center (CPC) released its latest outlook for the coming winter this morning.  This year’s forecast is challenging as there are few climate signals that are strong enough to give clues as to what to expect.  Thus the outlook is based more on trends.

Climate outlooks are probabilistic forecasts meaning that they give you information about the chances of seeing departures from the average.  It cannot tell you when or where snowstorms will occur.  The outlook is designed to tell you what the average conditions will be.

This year warmer than normal conditions are expected for the Southwest, the South-Central U.S., parts of the Southeast, New England and western Alaska.  The Northern Plains and the Alaskan Panhandle are expected to see colder than normal conditions.  South Carolina has an equal chance of seeing warmer, near normal, or colder conditions as there are no clues to guide the forecast.

The temperature outlook for the 2013-14 winter.  Click on the image for a larger view.  Image Credit: NOAA.

The bigger story this winter may be a developing drought for South Carolina as drier than normal conditions are more likely.  This follows on the heels of a warm, dry fall and a cool, wet summer.  Incipient drought conditions are already developing in some parts of South Carolina and a dry winter will only make it worse.  This could lead to low soil moisture for spring planting and an increase wildfire danger by late winter.

The precipitation outlook for the 2013-14 winter.  Click on the image for a larger view.  Image Credit: NOAA.

Drought conditions are expected to worsen over the Southwest and parts of the southern Plains.  This is an area that has been battling drought for the last three years and that is not expected to change in the near future.

Climate outlooks often key off of climate influences like El Nino – La Nina.  Mike Halpert, acting director of NOAA’s Climate Prediction Center, had this to say to say about the lack of these signals:

“It’s a challenge to produce a long-term winter forecast without the climate pattern of an El Niño or a La Niña in place out in the Pacific because those climate patterns often strongly influence winter temperature and precipitation here in the United States.  Without this strong seasonal influence, winter weather is often affected by short-term climate patterns, such as the Arctic Oscillation, that are not predictable beyond a week or two. So it’s important to pay attention to your local daily weather forecast throughout the winter.”

The Arctic Oscillation has two phases, positive or negative.  A negative phase allows cold arctic air to slide south into the U.S. and can put the country in a deep freeze depending on the strength of the phase.  A positive phase has the opposite effect and can result in warmer than normal conditions.  The record warm March of 2012 was an example of the positive phase for an extended period.

South Carolina has experienced wild swings in temperatures over the past week related to the Arctic Oscillation and this is likely to continue for the rest of November into December.  This means that cold waves will periodically invade followed by warmer periods.  It will be a roller coaster temperature ride into early winter.

Warmer than normal conditions are expected for South Carolina next spring with equal chances of wet or dry conditions.  This could favor an early spring and an active pollen season.  Research indicates that pollen counts have been increasing recently due to warmer springs.  The spring of 2012 saw record pollen counts over much of the Southeast.  However, the weather may be quite variable which may not be conducive to early planting.

Here is a video from on the winter outlook for this year: