Event Summary
     National Weather Service, Raleigh NC

April 16, 2007 High Wind Event
Updated 2007/04/20

Event Headlines

...Wind gusts in excess of 45 MPH were reported across most of the state with gusts in excess of 55 MPH reported across a large portion of the Mountains and Northern Piedmont...
...During the height of the storm on Monday afternoon, there were more than 200,000 customers without power across North Carolina...
...According to media reports, over 300 reports of downed trees and power lines were made in Wake County with nearly a 100 made in the city of Durham...

Event Overview

An unseasonably strong nor’easter rapidly developed off the North Carolina coast late on Sunday, April 15, 2007. The surface low had already strengthened to 990 MB over northwest North Carolina by 18Z/15 (200 PM EDT Sunday). Due to the unusual southerly track and strength of the 500 MB low across the Tennessee Valley and North Carolina, the surface low continued to deepen as it moved east across northern North Carolina late Sunday and Sunday night, reaching 983 MB near the Chesapeake Bay region by 00Z/16 (800 PM EDT Sunday).

The low pressure system rapidly intensified into a strong damaging nor’easter as it moved up the eastern seaboard and became nearly stationary around New York City on Monday. At 12Z/16 (800 AM EDT Monday) the storm was centered over New York City with a pressure of 969 MB. The storm slowly weakened and drifted eastward Monday night and Tuesday.

Several factors led to the damaging wind event including a very tight surface pressure gradient and 70 to 80 KT wind maximum at 850 MB. In addition, a strong 500 MB rise/fall couplet was observed (310 meter falls over Upton NY (OKZ) / 190 meter rise over Atlanta, GA (FFC) at 12Z/16). The strongest winds across central North Carolina peaked during the mid morning to mid afternoon hours with surface heating and convective mixing allowing stronger winds aloft to reach the surface. The winds continued to produce damage well into the night over the elevated terrain of western North Carolina.

The storm system had a variety of impacts on North Carolina as it produced several days of very active weather. There were numerous severe thunderstorms on Sunday as the surface and upper level low pressure systems moved across the state. Heavy rain also affected portions of the Piedmont where some areas totaled between 2 and 4 inches producing minor flooding of streams and some main stem rivers.

However, the most widespread impact across the state came on the back side of the rapidly intensifying nor’easter on Monday. Strong gradient winds buffeted North Carolina with northwest winds gusting between 45 and 62 mph over the Piedmont to the coast. The winds were stronger over the Mountains and Foothills where wind gusts to between 60 and 80 mph were common.

These winds were strong enough to prompt High Wind Warnings from the Mountains eastward across the Piedmont into the Coastal Plain. There were countless trees downed by the winds with the Mountains, Foothills, and Piedmont especially hard hit. During the height of the storm on Monday afternoon, there were more than 200,000 customers without power across North Carolina.

Trees fell on houses, vehicles, and in some cases across highways. One large tree even fell into the southbound lanes of I-85 near Oxford blocking both lanes of the busy interstate for several hours. The cities of Chapel Hill, Durham, Raleigh, Greensboro, Winston-Salem, and Burlington reported many trees downed, with numerous reports that they had fallen onto houses and vehicles. Several people narrowly escaped injury from the falling trees.

Maximum Wind Gust Map

Maximum wind gust map

Wind Gust Data from RAWS Sites

Remote Automated Weather Stations (RAWS) are instrumentation platforms that monitor the weather and provide weather data that assists land management agencies with a variety of projects such as monitoring fire danger, monitoring air quality, and providing information for research applications. There are more than two dozen RAWS sites in North Carolina. The instrumentation array is rather simple, a photograph of the RAWS site at the Duke Forest is available here.

Most of the stations owned by the wildland fire agencies are placed in locations where they can monitor fire danger. RAWS units collect, store, and forward data to a computer system at the National Interagency Fire Center (NIFC) in Boise, Idaho, via the Geostationary Operational Environmental Satellite (GOES). The GOES is operated by the National Oceanic and Atmospheric Administration (NOAA).

One advantage of the RAWS dataset is the availability of the data both internally to the NWS and on the internet with various web pages providing access to the data in various formats. The three images below display the wind gusts observed at three RAWS locations across central North Carolina on Monday, April 16.

The RAWS locations shown below are at Lexington (Davidson County), Duke Forest (Orange County), and in Rocky-Mount (Nash County). The maximum wind gust for each hour is shown on the graph which uses LST (Local Standard Time) which is one hour behind EDT (Eastern Daylight Time). The wind gusts dramatically pick up between 6 and 9 AM with the maximum wind gust generally observed between 10 AM and 12 PM. The wind gusts gradually relax a bit during the afternoon before dramatically diminishing between 6 and 8 PM.

Selected Photographs of the Winter Weather Event

Photos courtesy of Melanie Ray and Jonathan Blaes.
(Click the image to enlarge.)

A downed tree blocks a road in Cary - Click to enlarge           A downed tree pulled utility lines and part of the pole off this utility pole in Cary - Click to enlarge           Part of a utility pole were dragged 
to the road in Cary by a fallen tree - Click to enlarge

A large hardwood tree fell near this home in Cary - Click to enlarge           A large hardwood tree fell in the yard of this home in Cary - Click to enlarge           Another large hardwood tree fell near this home in Cary by a fallen tree - Click to enlarge

A large hardwood tree fell across Bridgeport Drive in North Raleigh - Click to enlarge           A pine tree fell on the roof of this home in North Raleigh in the yard of this home in Cary - Click to enlarge           A small tree was blown apart by the wind in North Raleigh - Click to enlarge

Case Study Team

Phillip Badgett
Jonathan Blaes

For questions regarding the web site, please contact Jonathan Blaes.

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