Climate Summary

Temperature and Precipitation by climate division
Departures from Normal for December 2009 - based on preliminary data.

December 2009 in North Carolina was wet, followed by more wet, with a bit of cold air and more wet. Following the pattern set in October and November, December 2009 ranked as one of the top 5 wettest since 1895 for most climate divisions. Based on preliminary data, December 2009 ranked statewide as the 2nd wettest December on record (behind December 1973, when the NC statewide average 0.10 inches greater).

Unlike November, December 2009 was cold statewide with mean temperatures 2 degrees F below normal. This ranks as the 32nd coldest December on record. With the cold temperatures, a major snowfall event brought 18+ inches to the mountains of western NC, with lesser amounts through the northern and western Piedmont. An ice storm on Christmas followed by high winds caused more widespread damage in the northern mountains, where ice accretion of in excess of 1/2 inch caused damages to trees, power lines, and other infrastructure (including some weather sensors).

Impacts to Agriculture and Water Resources

Continued wet weather caused more delays in the harvest of cotton and soybeans. While many growers have been aggressive in picking cotton to minimize yield loss, fields in eastern NC were still waiting for harvest even after Christmas. Many growers are still waiting for fields to dry and pick soybeans.

After a very wet autumn, no locations in NC are experiencing any lingering drought impacts. The NC Drought Management Advisory Council continues to review observations from across the state, but weekly assessments have been suspended until the threat of drought returns. With a wet winter and spring forecasted in association with El Nino, drought conditions are highly unlikely to return in the near future.

Precipitation for December 2009
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Precipitation for December 2009: Percent of Normal
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Recently Added and Updated SCO Products

New Evapotranspiration Tool
Evapotranspiration (ET) is a combination of evaporation and plant transpiration processes into a total moisture flux from the ground to the atmosphere. It plays an important role in the water and energy balance on earth’s surface and is of particular interest to agricultural and irrigation practices.

ET observations are only available for a limited number of locations across the southeastern United States. Empirical models are usually used to estimate ET at local and regional scales. No estimation technique is universal, but a standard method is the Penman-Monteith equation as specified by the UN Food and Agriculture Organization (FAO) in 1998.

The FAO56 Penman-Monteith method estimates ET rates for a well-watered reference surface based on physical atmospheric observations of solar radiation, temperature, wind speed, and relative humidity. This estimate is commonly referred to as reference crop ET. The reference surface is a theoretical grass reference crop with a height of 0.12m, an albedo of 0.23, and a constant surface resistance of 70s/m. While dependent on time of year and location, the equation is developed for a hypothetical grass reference crop and is thus independent of specific crop characteristics and soil factors. Crop coefficients can be applied to adjust the estimate for a particular crop.

Two products use Google Maps to display reference crop ET values estimated using the FAO56 Penman-Monteith method. One product is a daily ET estimate, which allows the user to select a date from January 1, 2002 to yesterday. The other product is a historical climate tool, which displays average monthly total and daily average ET values, both calculated over the 7-year period from 2002-2008. In addition, users can choose to display an annual time series for a particular station.

For more information or to view this product, please visit http://www.nc-climate.ncsu.edu/et

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Updated Climate Division Data Page
Recent updates to the Climate Division Data page allow users to pull observations for a single month, or calculated statistics over a range of months, in addition to the standard monthly time series. For example, selecting the “Seasonal Time Series” for January through December returns annual statistics, while selecting June through August returns statistics for the summer season. To visit the Climate Division Data page, click here.