Climate Summary: A Cool, Dry Start to Autumn

Temperature and Precipitation by climate division
Departures from Normal for October 2011
Based on Preliminary Data

October 2011 was cool and a bit dry for North Carolina. Temperatures were generally 1F or greater below normal across the southern tier of the state. Indeed, October was the first month since January 2011 with below-normal temperatures. Statewide average temperatures ranked as the 25^th coldest October since 1895. Rainfall (and even some snow) was more mixed. Some areas, including parts of central and northeastern NC, experience near normal precipitation. Much of western and southeastern regions of the state were dry. October is typically one of the drier months of the year, especially those years without tropical storms. Statewide average rainfall for October 2011 ranked as the 61st driest since 1895.

Mount Mitchell and Beech Mountain both reported snow during the first weekend in October, marking a new preliminary record for the earliest snowfall in NC. Below is the Public Information Statement from the NWS Office in Greenville-Spartanburg, which covers much of western NC:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
207 PM EDT THU OCT 6 2011
...PUBLIC INFORMATION STATEMENT...
...EARLIEST SEASONAL MEASURABLE SNOW IN NORTH CAROLINA...
THE NWS COOPERATIVE OBSERVER ON BEECH MOUNTAIN, NORTH CAROLINA RECORDED ONE HALF (0.5) INCH OF SNOW THAT OCCURRED BETWEEN 10 AM AND NOON ON SATURDAY MORNING, OCTOBER 1ST, 2011. THAT IS THE EARLIEST MEASURABLE AUTUMN SNOW ON RECORD AT A NATIONAL WEATHER SERVICE OBSERVATION SITE IN NORTH CAROLINA. THIS SNOWFALL REPORT WAS ENTERED ON THE OBSERVERS OBSERVATION RECORD FOR OCTOBER 2ND BECAUSE THE SNOWFALL OCCURRED AFTER HIS DAILY REPORTING TIME OF 7AM ON OCTOBER 1ST. COOPERATIVE OBSERVER REPORTS INCLUDE DATA FOR THE LAST 24 HOURS...TYPICALLY FROM 7 AM THE PREVIOUS DAY TO 7 AM THE DAY OF THE REPORT. THE PREVIOUS EARLIEST FALL AND WINTER SEASON MEASURABLE SNOW IN NORTH CAROLINA WAS FOUR (4.0) INCHES AT MT. MITCHELL ON THE 5TH OF OCTOBER 1980.

Thanks to the fine folks at NWS-GSP, Dr. Baker Perry at Appalachian State University, and William Schmitz at the SE Regional Climate Center for helping to confirm the new record.

Storm-wise, it was a quiet month. A line of storms in eastern NC on October 13 produced some hail, and another set of storms produced a funnel cloud near Fayetteville on October 19.

Local Storms Reports for October 2011
Preliminary Count of LSRs courtesy National Weather Service
http://www.nc-climate.ncsu.edu/lsrdb/index.php

Precipitation for October 2011
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Precipitation for October 2011: Percent of Normal
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

Impacts to Agriculture and Water Resources

Agriculture production is winding down, and most growers are active with harvests for cotton, soybeans, and peanuts. Recent drier conditions have generally been helpful for fieldwork. Rainfall in October was below normal, but impacts to water resources haven’t changed much. Some streams in central NC continue to be below normal, and reservoirs in the upper Cape Fear and upper Neuse river basins are also below normal for this time of year.

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

Winter Outlook – La Niña Returns, Decides to Stay for a While

For several months, the seasonal climate forecast models have been in disagreement as to whether or not La Niña would return to the tropical Pacific Ocean. But both surface and sub-surface ocean temperatures across that region have been cool over the past month, signifying the official return of La Niña. La Niña is when the eastern tropical Pacific Ocean is much cooler than normal, and is the opposite phase from El Niño (or the warm phase). Both phases in ocean temperatures in the Pacific, and their atmospheric response, are collectively called the El Niño / Southern Oscillation.

Based on the historical climate patterns over NC during La Niña events, we’re more likely to be drier than normal over the next 3-5 months. Typically, La Niña forces the jet stream and storm tracks to be less amplified over the eastern US. This means fewer storms that draw substantial moisture from the Gulf of Mexico, fewer coastal storms, and fewer storms that track on the eastern side of the southern Appalachian Mountains. The result is usually a drier winter for NC. The most recent La Niña event occurred this past winter, and indeed NC was drier than normal. However, the relationship between La Niña and NC winter temperatures is not as strong – we're almost as likely in North Carolina to have a cold winter as a warm winter during La Niña.

ENSO events tend to hang around for at least a few months. Oceans are much more dense than the atmosphere, and so temperature changes occur more slowly. Based on the current conditions in the tropical Pacific Ocean, there's higher confidence that La Niña will continue for a while (although the models still don't agree much beyond the next few months). The persistence for La Niña, and the historical relationship between La Niña and precipitation patterns, is the driving guidance behind the NWS Climate Prediction Center's winter outlook.

An Overview of Peanut Leaf Spot Advisories and the 2011 Growing Season


By Dr. Barbara Shew
Research Assistant Professor and Extension Specialist
Department of Plant Pathology, North Carolina State University
______________________________________________________

Peanuts are an important crop in North Carolina. The value of the peanut crop fluctuates, but prices currently are high due to shortages caused by droughts in production areas across the country. Cost of production is also high and growers work hard to protect their investment.

Like many plants, peanuts are susceptible to several different diseases. In North Carolina, the most important peanut diseases are leaf spots, which infect the leaves and cause them to defoliate (see picture at right). Defoliated plants produce poor yields – losses of 50% or more are common if leaf spots are not controlled. Because of these potential losses, growers use fungicides to protect their crop. A fungicide spray is effective for about two weeks, so five or six sprays are needed to give continuous protection from early July through mid-September.

Three elements need to come together before a plant disease can occur – a susceptible host, a pathogen, and favorable environment. In the case of leaf spots in North Carolina, all peanut varieties are susceptible and the leaf spot fungi are always present. This means that the severity of leaf spot depends on the environment.

North Carolina usually has warm, humid summer nights that provide perfect conditions for leaf spots. However, we also have periods when weather is too hot or dry for disease, so that fungicide sprays are not necessary. Delaying sprays during dry weather saves money and reduces the amount of fungicide in the environment. Not spraying during droughts also reduces the risk of spider mite outbreaks that are associated with dry weather and fungicide overuse.

Weather-based leaf spot advisories can tell peanut growers when they need to spray – or don’t need to spray – for leaf spots based on recent weather conditions. The State Climate Office of North Carolina calculates leaf spot advisories from data collected at weather stations located in the Coastal Plain, where the state’s 80,000 acres of peanuts are grown. At the start of the season, I work with the Office to make any adjustments to the advisories. During the season, I check the advisory output, add any relevant messages, and then send the advisory by email to County Agents, growers, consultants, and farmers (see picture at left). Users receive advisories every day from July 1 to the end of September. Advisories also can be found at http://ncsupeanut.blogspot.com.

The 2011 growing season provided an excellent example of how peanut leaf spot advisories can help growers make control decisions. By the end of June, severe drought covered most of the production area. Heat and drought persisted until late July or early August and conditions were very unfavorable for disease (Table 1). Spider mites were a constant concern. Scattered showers and thunderstorms picked up as July moved into August. Spray advisories became more frequent, but varied across locations. Drought persisted in some southeastern counties, which did not get real relief until hurricane Irene arrived. Following Irene, temperatures moderated and moisture was plentiful, if not excessive, and conditions became very favorable for leaf spots and other diseases (Table 1).

Table 1. Number of days on which advisories were issued or lethal conditions occurred for all locations during the summer of 2011.

¹ Days on which a spray advisory was issued, which indicates the overall favorability for disease development during an interval
² Days in which extreme heat or very low humidity would have killed leaf spot fungi during an interval

Advisories also helped with leaf spot control decisions in September. In most years, the final spray is applied in early September in anticipation of harvest later in the month. In 2011, many growers wanted to delay harvest so that plants could make up for yield lost to drought earlier in the summer. Also, many growers sprayed just before Irene hit because they worried that fields would be too wet to spray for days or weeks after the storm. As a result, spray schedules were a bit out of whack – and growers needed to when or if another spray would be needed to protect the crop until harvest.

Across the production region in 2011, no location had more than 4 sprays advised, whereas a grower spraying every two weeks would have sprayed five or six times through mid-September (Table 2). The average number of sprays advised across locations was 3.4 sprays. At an average cost of $17 per spray, this represents a savings of $27 to $44 per acre out of a projected fungicide budget of $85 per acre for five sprays or $102 for six sprays.

We also provide advisories for another important peanut disease, Sclerotinia blight. Both advisories have wide acceptance among North Carolina’s peanut growers. Growers use advisories in many ways, with some following them closely at all times and others using them to supplement their experience or advice from consultants. Advisories also help Extension Specialists and County Agents give general disease control advice since they provide a daily overview of weather conditions that affect peanut diseases across the state.

Peanut disease advisories are possible because of the outstanding resources provided by the State Climate Office of North Carolina and represent excellent collaboration between the SCO, the Department of Plant Pathology, and County Extension Agents. We continue our work together to improve advisories so that North Carolina’s growers can produce a healthy peanut crop.

Table 2. Summary of leaf spot sprays advised from data collected at twelve locations in peanut production areas in 2011.

¹ The total number of days in 2011 on which a spray advisory was issued, which indicates the overall favorability for disease development at that location
² The number of days in 2011 which extreme heat or very low humidity would have killed leaf spot fungi