Published on State Climate Office of North Carolina (http://www.nc-climate.ncsu.edu)
Spring 1999

NCSU Seal North Carolina ClimateSCO Seal

A Newsletter of the State Climate Office of North Carolina

A Public Service Center for
Climate-Environment Interactions
Ryan Boyles, Editor


Volume 3 | Number 2 | Spring 1999

In This Issue...


From the State Climatologist...

Sethu Raman Early spring brought some welcome rain to western North Carolina, ending the drought caused by the La Niña event in the Pacific. With warmer weather approaching, it is time to think about the hurricane season, which officially begins in June. Professor William Gray, a renowned scientist from Colorado State University, has predicted an increase in hurricane activity for the northern Atlantic this year: nine hurricanes with four of them becoming severe. Normal numbers are six with two severe. This in turn increases the chances of a hurricane either making a landfall in North Carolina or passing through our state. The State Climate Office of North Carolina is making every effort to assist the North Carolina Emergency Management Division (NCEM) in their operations. This includes research on past hurricanes that made landfall in North Carolina (such as Hurricane Fran), collaboration with the National Weather Service to improve their forecasts of damaging winds in hurricanes after landfall, and the development of a network of weather stations in eastern North Carolina as part of the NC ECO Net (North Carolina Environmental and Climate Observations Network) that will assist in the operations of NCEM.

The State Climate Office (SCO) hosted a breakfast meeting for North Carolina agricultural leaders to present ideas concerning the development of the NC ECO Net. Twenty-five representatives from key agricultural organizations participated in this meeting, which was organized with the assistance of the Governor's Office and Ms. Jane Patterson, the Governor's Senior Advisor for Science and Technology. The visitors were all very enthusiastic about this network, which will provide vital information necessary for agricultural operations in North Carolina. The SCO has been funded to install five automated weather observing stations for the North Carolina Division of Air Quality. It is the beginning of the statewide NC ECO Net. With these five stations, the SCO will be in charge of operating 22 automated weather stations across North Carolina. This summer we will be busy modernizing the Agricultural Weather Network (AgNet) and in installing these new stations. Devdutta Niyogi will be leading these efforts.

We have three undergraduate students working in the SCO full time this summer. They are Wendy Sellers, Kettyah Chhak, and Aaron Pratt. Wendy and Kettyah have been helping with data dissemination and working part-time during the academic year. This summer they will also work on projects that will enhance our capability for data dissemination and assurance of data quality. Ryan Boyles will lead this effort. In addition we will have Aaron Sims, John Goff, and Robert Gilliam, all recent meteorology graduates from NCSU, working this summer on various projects. I welcome these fine young people to the SCO. They bring a new energy level to our public service.

In closing, I want to acknowledge all the support provided by our Dean, Dr. Jerry Whitten. His vision and sustained support helped us to significantly enhance the public service that we provide for North Carolina citizens. Dean Whitten has announced his intention to return to teaching and research at the end of this year.

Have a nice, safe summer.

At the service of North Carolina,

Sethu Raman's Signature
Sethu Raman
State Climatologist of North Carolina
Professor of Marine and Atmospheric Sciences


Ozone -- A Growing Problem in North Carolina

Many have heard of the importance of the ozone layer in the upper atmosphere, which protects us from harmful ultraviolet light. But there is also ozone near the surface, which is harmful to breathe. This harmful ozone is due to increases in pollution from automobiles and other sources. Ozone causes problems for young children and people with breathing problems, especially if they are doing strenuous activities outdoors.

Ozone is becoming an increasing problem in North Carolina, particularly in urban areas. Over the past few years, the NC Division of Air Quality has been regularly issuing air quality forecasts for the state's major metropolitan regions. Generally, ozone is a problem during the spring and summer months, when the increased sunshine and warm air enhance the development of ozone near the surface.

There are four categories describing air quality conditions:

Code Green Good
Code Yellow Moderate
Code Orange Unhealthy for sensitive groups
Code Red Generally Unhealthy

To better understand and predict air quality issues, the NC Division of Air Quality is working with the State Climate Office by placing monitoring towers throughout the state and using that information to improve forecasts. The air quality of an area is dependent on several factors, including air temperature, wind speed and direction, pollutants released, and precipitation. Understanding the complex weather and climate of North Carolina helps meteorologists in the Division of Air Quality better predict when and where the air we breathe is healthy or unhealthy. The proposed North Carolina Environment and Climate Observing Network will greatly benefit groups like the NC Division of Air Quality, and other agencies in charge of monitoring the quality of the environment in North Carolina, in the monitoring and prediction of ozone.

Contributed by John White, NC Division of Air Quality



The North Carolina "Tornadocane"

Tornadocane [10] On the evening of April 15, 1999, one of the most bizarre and unusual supercell thunderstorms ever observed roared across southeastern North Carolina. It produced several damaging tornadoes, one killer tornado, wind damages, and a gust measured at 165 mph! At one point, the thunderstorm cluster assumed a hurricane-like shape, even forming an eye-like "hole". During this hurricane-shaped stage over Duplin County, a 1/2 to 1 mile wide tornado produced F2 damage, injured at least 11 people near Kenansville and Beulaville, and carved a 30 mile long destruction path.

The storm moved out of northern South Carolina as a heavy-precipitation supercell, moving east-northeast close to the intersection of a warm front and a surface pressure trough. It then moved northeast across southern NC, producing a gust front on its rear flank on which more thunderstorm cells formed. That gust-frontal band, and the forward flank of the original storm, began to curve into spiral bands - eventually assuming the hurricane like shape. The 165 mph gust was recorded just north of Trenton, NC in Jones County, at about 10:20 pm EDT. This gust may have resulted from a tornado strike, or an intense eddy in the downburst.

Meteorologists from the State Climate Office of North Carolina tracked the cell as it crossed North Carolina using their real-time link to the National Weather Service Doppler Radar.

Contributed by Doug Schneider



La Niña Update

The most recent data from the tropical Pacific indicates that moderate La Niña conditions continue to exist. This current event began last summer just as the strongest El Niño recorded this century was ending. Generally speaking, La Niña conditions are opposite those of El Niño, with cooler sea surface temperatures in the tropical Pacific Ocean. Since 1976, only the 1988-89 La Niña event has been stronger than the current. However, examining the record back to 1950 shows that prior to 1975, ten La Niña events were considered stronger than the present episode.

Contributed by Brian Potter



North Carolina Prepares for an Active Hurricane Season

North Carolina is gearing up for an active hurricane season. With the memories of Hurricanes Bertha, Fran, and Bonnie fresh in mind, the prediction from Dr. William Gray, a professor at Colorado State University warrants interest. Colorado State University's hurricane forecaster William Gray is predicting 14 tropical depression, then a tropical storms, nine hurricanes, and four intense hurricanes for the upcoming 1999 hurricane season. Meanwhile, he anticipates the probability of a major storm landfall at about 200 percent of the long-term average for the East Coast (including North Carolina) and Florida Peninsula and 146 percent of the long-term average for the Gulf Coast.

Gray writes that a key factor in the forecast is the call for four major hurricanes with minimum winds of 111 mph. Historically, when such storms make landfall, he said, they cause a vast majority of hurricane-spawned destruction. The predicted 14 tropical storms, nine hurricanes and four intense hurricanes compare to 14, 10 and three that occurred in 1998. Long-term statistical averages yield 9.3 tropical storms, 5.8 hurricanes and 2.2 intense hurricanes annually.

Monthly Tropical Cyclone Distribution The period from 1995-98 was the most active, four consecutive years of hurricane activity on record, yielding 53 named storms, 33 hurricanes and 15 major hurricanes. During this period, three hurricanes made landfall in North Carolina - Bertha, Fran, and Bonnie - the most active period in the state's history since the 1953-55 seasons when six hurricanes made landfall in North Carolina. This and certain other climate signals suggest to Gray and his associates that a period of more major hurricane activity and more intense-storm landfalls along the East Coast and in the Caribbean Basin is now underway.

In a recent press release, Gray states that the periods 1900-25 and 1970-94 were relatively quiescent in terms of major hurricane activity, while seasons from the early 1930s through the late 1960s generally were more active, with more intense storms lashing the Atlantic coast. He attributes this to a phenomenon called the Atlantic conveyor belt, which moves waters north from the vicinity of the Caribbean to an area east of Greenland, where the current sinks to deep levels, moves south and flows into the South Atlantic Ocean and beyond. Gray suggests that this ocean circulation tends to go through decades-long changes, and that the Atlantic conveyor belt became stronger between 1994 and 1995, leading to more major storms since that time. This pattern is reminiscent of that of the 1930s, 1940s and 1950s.

Other factors which are expected to increase hurricane activity in 1999 are:

Through the NC Hazard Mitigation Grant program, the State Climate Office of North Carolina has applied for funds to build 20 new towers in eastern North Carolina as part of the NC ECO Net. These automated weather observing stations will help improve forecasts of landfalling hurricanes in eastern NC. The NC ECO Net will give forecasters detailed information on the winds and rainfall as it occurs during a landfalling hurricane. Such information will save lives and millions of dollars by improving severe weather warnings and flash flood warnings. In addition, it will give researchers a better understanding of the changes in the structure of hurricanes after landfall.

To read Dr. Gray's forecast, go to http://tropical.atmos.colostate.edu/forecasts/ [11]

GRAY RESEARCH TEAM
HURRICANE FORECAST FOR 1999 SEASON
1950-90 Avg. 1999 Forecast
Named Storms 9.3 14
Hurricanes 5.8 9
Intense Hurricanes 2.2 4
Net Tropical Cyclone Activity 100% 160%

Contributed by Doug Schneider



Climatology of Tornadoes in North Carolina

The tornado is nature's most intense storm producing winds as strong as 300 miles per hour. Tornadoes are ranked on the Fujita scale (F0-F5) according to their strength with F0 being the weakest and F5 the strongest. The majority of tornadoes that occur in North Carolina are weak (< F2), however violent tornadoes such as the F4 that struck the Raleigh area on November 28, 1988 are possible. North Carolina exhibits a large spatial variation in the occurrence of tornadoes due to the complex climate of the state. The increased frequency of tornadoes in the southeastern portion of the state suggest mesoscale processes associated with land-sea interaction and physiological differences in soil characteristics may play a role in the formation of tornado producing thunderstorms.

Map of Tornadoes by County [12]
Click on image to view full-size map

Tornadoes are classified by the Fujita scale according to their rotational wind speed. Only 2% of all tornadoes are F5, but account for 70% of all tornado deaths nationwide. Most damage is due to flying debris and violent winds. In some cases tornadoes may contain smaller vortices that rotate within them. Such tornadoes are known as multi-vortex tornadoes. Tornadoes form in areas of strong vertical wind shear (change in wind direction and speed with height) which causes a horizontal spinning effect. Rising air within a thunderstorm (updraft) may act to tilt the rotating air into the vertical direction causing the rotating column to stretch thus increasing rotational speed.

Chart of Tornadoes by Month [13]
Click on image to view full-size chart

The State Climate Office is working with public and private agencies to develop the NC ECO Net, which will be extremely valuable in forecasting severe weather and tornadoes in North Carolina by providing real-time information during emergency situations.


Contributed by Jamie Rhome



Devdutta S. Niyogi Named to National Meteorology Committee

Devdutta S. Niyogi, Assistant State Climatologist and member of the Department of Horticultural Sciences, was recently named to serve a three-year term on the American Meteorological Society's National Committee on Agricultural and Forest Meteorology. He will serve on this committee from 1999-2002. Congratulations to Devdutta Niyog for his achievements!


Precipitation and Temperature

Departure from 30-Year Average
Based on Preliminiary Data

Click on any image to view full size map in a new window

Precipitation
(in inches)

February 1999 Precipitation Departures from Normal [14]
February 1999


March 1999 Precipitation Departures from Normal [15]
March 1999


April 1999 Precipitation Departures from Normal [16]
April 1999
Temperature
(in ° Fahrenheit)

February 1999 Temperature Departures from Normal [17]
February 1999


March 1999 Temperature Departures from Normal [18]
March 1999


April 19998 Temperature Departures from Normal [19]
April 1999


Visitors and Recent Activities

Visitors

Activities

« Back to Newsletters [20]

Source URL: http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring

Links:
[1] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#note
[2] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#ozone
[3] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#tornadocane
[4] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#lanina
[5] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#hurricane
[6] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#tornadoes
[7] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#niyogi
[8] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#maps
[9] http://www.nc-climate.ncsu.edu/office/newsletters/1999Spring#activities
[10] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/tornadocane.gif
[11] http://tropical.atmos.colostate.edu/forecasts/
[12] http://www.nc-climate.ncsu.edu/tornado_by_county.jpg
[13] http://www.nc-climate.ncsu.edu/tornado_by_month.jpg
[14] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/feb99_precip.jpg
[15] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/mar99_precip.jpg
[16] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/apr99_precip.jpg
[17] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/february99_temp.jpg
[18] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/mar99_temp.jpg
[19] http://www.nc-climate.ncsu.edu/images/office/newsletters/1999Spring/apr99_temp.jpg
[20] http://www.nc-climate.ncsu.edu/%3Fq%3Doffice/newsletters