...CLIMATE DATA CHANGE FOR ROANOKE AND LYNCHBURG...

LONG TERM STATION EXTREMES FOR ROANOKE AND LYNCHBURG HAVE BEEN
UPDATED THROUGH 2007. IN ORDER TO PROVIDE THE LONGEST POSSIBLE
PERIOD OF RECORD FOR EACH STATION...A PROJECT CALLED THREADEX...FOR
THREADED EXTREMES...WAS DEVELOPED. THREADEX PIECES OR THREADS
STATION DATA TOGETHER TO FORM A SINGLE...LONG TERM SET OF DAILY
DATA. THIS DATA SET CAN BE USED TO DETERMINE DAILY EXTREMES OF
TEMPERATURE AND PRECIPITATION. THREADEX IS A COLLABORATIVE EFFORT
BETWEEN NATIONAL CLIMATIC DATA CENTER...THE NATIONAL WEATHER
SERVICE...THE NORTHEAST REGIONAL CLIMATE CENTER...AND STATE
CLIMATOLOGISTS.

THREADEX ADDRESSES THE ISSUE OF FRAGMENTED WEATHER DATA OVER TIME
DUE TO STATION RELOCATIONS...WHICH HAVE HISTORICALLY INCLUDED
INSTRUMENTATION MOVES FROM CITY LOCATIONS TO AIRPORTS...AND MOVES AT
AIRPORTS DUE TO EXPANSIONS...AMONG OTHERS. OBTAINING A LONG TIME
SERIES IS DIFFICULT UNLESS RECORDS FROM THE VARIOUS LOCATIONS ARE
THREADED TOGETHER.

THREADING A STATION RECORD INVOLVES A NUMBER OF STEPS. THE RECORD OF
A CURRENTLY ACTIVE STATION IS USED AS THE STARTING POINT FOR A
STATION THREAD. THIS STATIONS CURRENT RECORD IS USED AS FAR BACK IN
TIME AS POSSIBLE. OTHER LOCAL WEATHER STATIONS NEARBY ARE THEN
IDENTIFIED TO EXTEND THE THREAD FURTHER BACK IN TIME...WITH
PREFERENCE GIVEN TO NATIONAL WEATHER SERVICE AND WEATHER BUREAU
STATIONS. THE THREAD IS EXTENDED BACK IN TIME AS FAR AS POSSIBLE
USING DAILY DATA AVAILABLE IN DIGITAL FORM. PARTNER INPUT WAS THEN
SOLICITED AND THIS LOCAL EXPERTISE WAS USED TO FINE TUNE THE STATION
THREADS.

THREADEX CHANGES THE ROANOKE CLIMATE RECORD TO THE ROANOKE AREA
CLIMATE RECORD...AND THE LYNCHBURG CLIMATE RECORD TO THE LYNCHBURG
AREA CLIMATE RECORD. THREADEX EXTENDS BACKWARD THE ROANOKE PERIOD OF
RECORD FROM 1948...BACK TO 1912. THE PERIOD OF RECORD AT LYNCHBURG
DOES NOT CHANGE AND REMAINS FROM 1893 TO 2008. HOWEVER...SOME
ADDITIONAL DATA CHANGES MAY HAVE BEEN MADE...BOTH AT ROANOKE AND
LYNCHBURG...AND USED TO FILL IN FOR DAYS THAT WERE MISSING.

IF YOU HAVE QUESTIONS OR COMMENTS ABOUT THIS CHANGE...PLEASE CONTACT
THE BLACKSBURG NATIONAL WEATHER SERVICE OFFICE ANYTIME AT
540-552-0084.