Climate Summary

Temperature and Precipitation by climate division
Departures from Normal for September 2010 - based on preliminary data.

For the first 3 weeks of September 2010, most folks in North Carolina thought that summer might never end. During this period there was limited rainfall and record-breaking high temperatures. During the period many locations broke records for high temperatures during individual days and for the number of warm days. In particular, both Raleigh and Greensboro broke records for the number of days with 90F temperatures. The hot and dry conditions led to widespread moderate (D1) to severe (D2) drought, with the most severe impacts to agriculture and vegetation.

But during the last week of September 2010, conditions dramatically changed. Heavy rain fell across much of North Carolina over several days. Across most of eastern NC, folks quickly became concerned with flooding and standing water instead of drought. Most of eastern NC experienced the wettest such week on record. Preliminary rainfall records for the last week in September include:

• Wilmington — 22.54 inches
• New Bern 15.47 inches
• Bayboro — 15.31 inches
• Wilson — 11.44 inches
• Greenville — 14.82 inches
• Williamston — 19.10 inches
• Lewiston — 14.79 inches
• Plymouth — 12.11 inches
• Elizabeth City — 10.28 inches

Precipitation for September 2010
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Precipitation for September 2010: Percent of Normal
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Wilmington, NC broke is all-time 5 day precipitation record. The 22.54 inches that fell classifies the storm as a 500-year event, and was more than produced by Hurricane Floyd in 1999.

The rainfall amounts from the last week in September 2010 were enough to have monthly rainfall amounts for eastern NC to rank as the #3 wettest since 1895. Only 1955 and 1999 produced wetter Septembers for the Coastal Plain.

Statewide, September 2010 ranked as the 9th wettest on record and the 18th warmest since 1895.

Impacts to Agriculture and Water Resources

Heat and dry conditions continued to cause problems for crops for most of September, and while the heavy rain in late September will help pastures and prepare soils for winter grains, to also may cause problems for cotton, soybean and peanut harvests.

While streams dropped into drought levels during the first 3 weeks of September, the heavy rainfall in central and eastern NC had ended concerns about water supplies.

The NC Drought Management Advisory Council continues to have weekly technical conferences to review conditions and make recommendations to the US Drought Monitor.

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

New Report and Tool on Rain from Tropical Storms

We know that precipitation from tropical storms can play an important role for agriculture and water resource management during the late summer and autumn. Based on work by Dan McKemy (a recent NCSU graduate), we now understand the contribution of tropical cyclones with more accuracy and precision. A new report suggests that since 1995, rainfall from tropical cyclones contributes nearly 20% to warm season precipitation and more than 10% to annual precipitation totals. The research behind this included a unique effort to more precisely determine whether or not the rainfall observed was associated with a tropical cyclone.

A new tool developed by Dan McKemy and SCO graduate student Corey Davis lets users explore tropical rainfall amounts since 1980 across the state. Learn more by visiting the Tropical Precipitation section of the SCO website.

Winter Climate Outlook

With the return of La Nina, we once again can some confidence in the seasonal climate outlook. Typically, La Nina is associated with warmer, drier conditions in central and eastern NC. The jet stream is more likely to stay west of the southern Appalachian Mountains and bring wet conditions to the Ohio River Valley. With less jet stream influence over the southeastern US, La Nina winters tend to be warmer and drier than normal. This is reflected in the seasonal forecasts provided by National Weather Service’s Climate Prediction Center. CPC guidance suggests that the southern US is more likely to experience below-normal precipitation as compared to above-normal precipitation. The opposite is suggested for the Pacific Northwest and the Ohio River Valley.

The Southeast Climate Consortium (which includes us) has released both its Climate Outlook and Agricultural Outlook for the southeast. Available through http://www.AgroClimate.org, these outlooks provide more detailed guidance on what to expect this fall and winter in the Southeastern US.