October 2012 Climate Update

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North Carolina Climate, the monthly newsletter of the State Climate Office of NC, highlights the SERCC's Climate Perspectives tool, a climate outlook for the fall and early winter season, as well as a climate summary for September with impacts across the state.


Climate Perspectives — A Tool to Put Recent Climate in a Longer-Term Perspective

The State Climate Office of NC has been working with partners at the NOAA-supported Southeast Regional Climate Center (SERCC) to develop new tools focused on the broader southeastern United States. A flagship product from this effort is Climate Perspectives (http://www.sercc.com/perspectives). This tool has been available through the SERCC website over the past couple of years, and we regularly include figures from it in our monthly climate summaries.

So what does Climate Perspectives do? First and foremost, the tool lets users quickly look at recent conditions (temperatures, precipitation) over the past few days, weeks, months, and years, and see how they compare and rank over the entire history of a location. Below is the tabular option for Raleigh-Durham Airport showing in a compact form how temperatures and precipitation rank for various periods ending September 30, 2012.

A regional map is also available so users can view how all locations might rank and compare for each variable. This product often is used in our regular climate summaries to show statewide conditions for the past month, season, and year.

Climate Perspectives is a popular product for our climatologists, and we hope others will find it useful as well. A new web-tutorial that introduces the tool and its features can be accessed through the main Climate Perspectives page listed above, or directly at:


Climate Outlook for Fall and Early Winter
Contributed by Bradley McLamb

The outlook for fall and early winter is a complicated one due in part to the below-normal confidence in the evolution of the El Niño-Southern Oscillation (ENSO) during this time. Computer models have indicated for several months that an El Niño event — which features warmer-than-normal sea surface temperatures (SSTs) across the central and eastern equatorial Pacific — would develop heading into fall, and would have direct impacts on temperature and precipitation patterns across the southeastern US. However, after a period of warming during late summer in the ENSO region of the Pacific, sea surface temperatures have actually begun to cool.

Sea surface temperature anomalies for August 6, 2012 (left) and October 1, 2012 (right)
Imagery courtesy of NOAA/NESDIS

Despite the cooling of SSTs over the past two months, a weak El Niño still appears to be developing and could remain through early winter based on the general consensus of the ENSO forecast models, which would increase the likelihood of below-normal temperatures and above-normal precipitation across the Southeast throughout the period.

If El Niño conditions develop, what would it mean for North Carolina in terms of wintry precipitation? Comparing all ENSO winters since 1959 to the predictions for winter 2012-13, three winters stand out as close matches: 1969-70, 1976-77, and 2004-05. Each featured a weak El Niño with SST anomalies of approximately 0.7 to 0.8°C, quite similar to those predicted for the upcoming winter.

Sea surface temperature anomalies for October through March 1969-70 (top left), 1976-77 (top right) and 2004-05 (bottom)
Imagery courtesy of NCEP/NCAR

After analyzing the mean SST anomalies for these three winters, it appears the 1969-70 El Niño event is the closest match to what is forecast for the upcoming winter. The winter of 1969-70 brought below-normal precipitation and snowfall to North Carolina; however there were also several cold air outbreaks with temperatures well below-normal.

Any forecast for the upcoming season will have below-normal confidence due to the uncertainty in the equatorial Pacific. However, current information does suggest that a weak El Niño will likely remain in place through early to mid-winter, which could result in increased precipitation and below-normal temperatures for the next few months. In addition, an early season snowfall cannot be ruled out for the Southeast, and is more likely statistically-speaking when looking at the three winter cases previously mentioned, which all featured December snow.


Climate Summary for September 2012: Wet in the west, Dry in the east

Temperature and Precipitation by climate division
Departures from Normal for September 2012
Based on Preliminary Data
Temperature and Precipitation Departures from Normal

September 2012 in North Carolina was dominated by the precipitation patterns — storms brought substantial rainfall to western and parts of central NC, while most of the coastal plain was dry for the month. Statewide rainfall ranked as the 36th wettest September since 1895. Associated with these storms was urban and flash flooding that is typical in central and western NC. These rains continued to ensure plenty of water for our streams and reservoirs.

Temperatures were generally above normal in the mountains and a bit cooler than normal in central and eastern NC. Statewide average temperatures ranked as the 46th coolest for Septembers since 1895.

Precipitation for September 2012
Based on estimates from NWS Radar; Data courtesy NWS/NCEP
MPE Precipitation

Precipitation for September 2012: Percent of Normal
Based on estimates from NWS Radar; Data courtesy NWS/NCEP
MPE Precipitation Percent of Normal

Local Storm Reports for September 2012
Preliminary Count of LSRs courtesy National Weather Service
LSR Summary


Impacts to Agriculture and Water Resources

Drought continues not to be of much concern, although parts of the state, including much of the southern coastal plain, is being carefully watched for any drought impacts. Drier conditions in the fall are often seen as useful for many growers as they look to harvest crops such as soybeans and cotton.

US Drought Monitor for North Carolina
Courtesy NC DENR Division of Water Resources

Drought Monitor

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