DROUGHT INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BLACKSBURG VA
1210 PM EDT THU SEP 4 2008
...RAINFALL FROM FAY BRINGS DROUGHT IMPROVEMENT...
SYNOPSIS...
MOST OF THE BLACKSBURG HYDROLOGIC SERVICE AREA (HSA) RECEIVED
VERY BENEFICIAL RAINS FROM THE REMAINS OF FAY...RANGING ANYWHERE
FROM ABOUT AN INCH IN SOUTHERN WEST VIRGINIA TO 8 INCHES OVER
PARTS OF THE NORTH CAROLINA MOUNTAINS. THE RESULT WAS A GENERAL
1-CATEGORY IMPROVEMENT IN THE U.S. DROUGHT MONITOR IN MOST OF THE
REGION.
EXTREME DROUGHT IN THE NORTHWEST NORTH CAROLINA MOUNTAINS AND
FOOTHILLS WAS REPLACED BY SEVERE DROUGHT...THE LARGE AREA OF
SEVERE IN VIRGINIA WAS REPLACED BY MODERATE DROUGHT.
THE BLACKSBURG HSA COVERS 27 COUNTIES IN SOUTHWEST VIRGINIA...4 IN
EXTREME SOUTHEAST WEST VIRGINIA AND 9 IN NORTHWEST NORTH CAROLINA
AND INCLUDES PORTIONS OF THE FOLLOWING RIVER BASINS:
JAMES...ROANOKE...NEW...GREENBRIER...DAN...YADKIN...CLINCH AND
HOLSTON.
SUMMARY OF IMPACTS...
THE U.S. DROUGHT MONITOR (USDM)...RELEASED SEPTEMBER 4TH AND
REFLECTING CONDITIONS THROUGH 8 AM ON SEPTEMBER 2ND SHOWED D2...OR
SEVERE DROUGHT...IN ONLY THREE NORTH CAROLINA
COUNTIES...ASHE...WATAUGA AND WILKES. MODERATE DROUGHT (D1)
COVERS THE REST OF THE NORTH CAROLINA COUNTIES AND MOST OF
THE REMAINDER OF THE HSA IN VIRGINIA. ABNORMALLY DRY (D0) PERSISTS
IN THE FAR NORTHWEST HSA...ALLEGHANY AND BATH COUNTIES AND INTO
SOUTHEASTERN WEST VIRGINIA. IT SHOULD BE POINTED OUT THAT THE
CATEGORIES ON THE U.S. DROUGHT MONITOR ARE GENERALIZED AND THE
LOCAL IMPACTS OF DROUGHT MAY BE MORE OR LESS THAN WHAT IS DEPICTED
ON THE MAP.
THE CATEGORIES OF DROUGHT ARE EXPLAINED BELOW:
D0 IS THE LEAST INTENSE INDICATOR OF DROUGHT ON A SCALE THAT RANGES
FROM D0 THROUGH D4. IT IS BASICALLY A DROUGHT WATCH THAT INDICATES A
REGION GOING INTO OR COMING OUT OF DROUGHT.
D1 IS MODERATE DROUGHT...CONDITIONS THAT MAY BE ASSOCIATED WITH D1
INCLUDE SOME CROP DAMAGE...INCREASED FIRE RISK...FALLING RIVER...
STREAM...AND RESERVOIR LEVELS AND SOME WATER SHORTAGES.
D2 IS SEVERE DROUGHT...CROP OR PASTURE DAMAGE IS LIKELY. FIRE RISK IS
POTENTIALLY HIGH...ALONG WITH WATER SHORTAGES AND POSSIBLE WATER
RESTRICTIONS.
D3 IS EXTREME DROUGHT...MAJOR CROP AND PASTURE LOSSES AND WIDESPREAD
WATER SHORTAGES AND RESTRICTIONS.
D4 IS EXCEPTIONAL DROUGHT...WIDESPREAD CROP AND PASTURE LOSSES...
WATER SHORTAGES AND WATER EMERGENCIES. MAY BE THOUGHT OF AS THE
50-YEAR DROUGHT OR THE 2 PERCENT ANNUAL CHANCE OF OCCURRENCE.
THE CATEGORIES ARE BASED ON A NUMBER OF KEY INDICATORS: 1) PALMER
DROUGHT INDEX (PDSI) 2) CPC SOIL MOISTURE MODEL 3) USGS WEEKLY
STREAMFLOW PERCENTILES 4) THE STANDARDIZED PRECIPITATION INDEX AND
5) THE SATELLITE VEGETATION INDEX.
PALMER DROUGHT SEVERITY INDEX (PDSI)...
THE TABLE BELOW SHOWS THE AUGUST 30 AND AUGUST 16 2008 PDSI FOR
THE SIX CLIMATE ZONES WHICH COVER THE BLACKSBURG HSA.
THE BENEFICIAL EFFECTS OF FAY ARE CLEARLY EVIDENT IN THE NUMBERS
BELOW. ACCORDING TO THIS INDEX ONLY THE NORTH CAROLINA MOUNTAINS
REMAIN IN ANY CATEGORY OF DROUGHT...MODERATE. IT SHOULD BE POINTED
OUT THAT THE PDSI IS ONLY ONE OF MANY DROUGHT MEASURES AND DOES TEND
TO RESPOND VERY QUICKLY TO SHORT-TERM RAINFALL.
STATE CLIMATE ZONE PDSI PRECIP TO PDSI
8/30 END DROUGHT 8/16
NC N. MOUNTAINS -2.48 7.99 -4.81
NC N. PIEDMONT -0.11 -3.02
VA W. PIEDMONT -0.72 -3.08
VA CENT. MTNS. -0.67 -1.40
VA SW MOUNTAINS -0.93 1.06 -2.91
WV SOUTHERN +0.07 +0.30
THE PALMER INDEX IS CALCULATED WEEKLY AND INDICATES THE RELATIVE
DRYNESS OR WETNESS AFFECTING AN AREA. THERE ARE SEVEN PDSI
CATEGORIES DEFINING WET AND DRY CONDITIONS AS SHOWN IN THE TABLE
BELOW:
-4.0 OR LESS - EXTREME DROUGHT
-3.0 TO -3.9 - SEVERE DROUGHT
-2.0 TO -2.9 - MODERATE DROUGHT
-1.9 TO +1.9 - NEAR NORMAL
+2.0 TO +2.9 - UNUSUAL MOIST SPELL
+3.0 TO +3.9 - VERY MOIST SPELL
+4.0 OR ABOVE - EXTREMELY MOIST
CROP MOISTURE...
THE NWS CLIMATE PREDICTION CENTER CROP MOISTURE INDICES IMPROVED
SIGNIFICANTLY DURING THE PERIOD
RIVERS AND STREAMFLOW...
7-DAY AVERAGE STREAMFLOW PERCENTILE CLASSES AS OF SEPTEMBER 3
FROM RIVER BASINS IN THE UNITED STATES GEOLOGICAL SURVEY
(USGS) NETWORK HAVE ALSO RESPONDED DRAMATICALLY TO THE RECENT
RAINS. FLOWS ARE AT THE 25TH PERCENTILE OR GREATER IN ALL MAJOR
RIVER BASINS IN THE HSA AND THUS ARE NOT SHOWN IN TABLE FORM.
RESERVOIR LEVELS...
POOL ELEVATIONS ON SEVERAL RESERVOIR ROSE SHARPLY AFTER THE THE HEAVY
RAINS...MOST NOTABLY AT W. KERR SCOTT ON THE YADKIN RIVER WHICH
CLIMBED OVER 8 FEET. IT HAS SINCE DROPPED BACK 4 FEET BUT IS
STILL AT NORMAL POOL. OTHER RESERVOIRS HAVE HAD SMALLER RISES OR
AT LEAST REMAINED STEADY. THE MAJOR EXCEPTION IS AT LAKE MOOMAW
WHICH FELL AN ADDITIONAL 3 FEET THE PAST TWO WEEKS AND IS NOW
ABOUT 16 FEET BELOW NORMAL POOL.
RESERVOIR CURRENT POOL NORMAL POOL
SMITH MOUNTAIN LAKE VA 790.82 795
CLAYTOR LAKE VA 1843.04 1846
LAKE MOOMAW VA 1566.25 1582
PHILPOTT RESERVOIR 963.62 974
BLUESTONE LAKE WV 1410.02 1410
W. KERR SCOTT NC 1030.08 1030
CARVINS COVE RESERVOIR...A MAJOR SOURCE FOR ROANOKE DRINKING
WATER...IS NOW 6.6 FEET BELOW THE SPILLWAY...UP NEARLY 1 FOOT IN
THE PAST TWO WEEKS. SPRING HOLLOW RESERVOIR...WHICH SERVES ROANOKE
COUNTY...HAS FALLEN ANOTHER 2 FEET IN THE PAST TWO WEEKS AND IS NOW
28 FEET BELOW ITS SPILLWAY.
CLIMATE SUMMARY...
AUGUST RAINFALL CAME IN ABOVE AVERAGE...THANKS ALMOST ENTIRELY
TO THE RAINFALL FROM FAY. WITH 57 STATIONS REPORTING AVERAGE AUGUST
RAINFALL ACROSS THE HSA WAS 4.71 INCHES VERSUS THE MONTHLY NORMAL OF
3.63 INCHES. CONSIDERABLE VARIATION WAS FOUND HOWEVER...WITH AMOUNTS
RANGING FROM 1.85 INCHES AT EARLEHURST IN ALLEGHANY COUNTY VA TO 8.03
INCHES AT BLOWING ROCK IN WATAUGA COUNTY NC. THE NORTHWEST HSA
GENERALLY RECEIVED THE LEAST RAIN DURING THE MONTH WHILE THE HIGHEST
AMOUNTS FELL OVER NORTHWEST NORTH CAROLINA. FORTUNATELY...THIS WAS A
RARE CASE OF THE POOR GETTING RICHER AS THE CAROLINA MOUNTAINS HAVE
BEEN THE FOCUS OF THE MOST INTENSE AND PROLONGED DROUGHT CONDITIONS.
FOR THE SUMMER SEASON AVERAGE HSA RAINFALL WAS 11.35 INCHES VERSUS
A NORMAL OF 11.79 OR ESSENTIALLY NORMAL. THE TABLE BELOW SHOWS
RAINFALL AMOUNTS AND PERCENTAGES OF NORMAL OVER VARIOUS DURATIONS
IN THE PAST YEAR.
MONTH OR SEASON PRECIPITATION NORMAL % OF NORMAL
JULY 3.87 3.92 99
JUNE 2.77 3.92 71
SUMMER 2008 (JUN-AUG) 11.35 11.79 96
SPRING 2008 (MAR-MAY) 11.55 12.28 94
WINTER 07-08 (DEC-FEB) 7.19 9.99 72
FALL 2007 (SEP-NOV) 8.49 10.51 81
PRECIPITATION/TEMPERATURE OUTLOOKS...
THE FIVE-DAY PRECIPITATION FORECAST FROM THE HYDROMETEOROLOGICAL
PREDICTION CENTER (HPC) THROUGH SEPTEMBER 9 IS DOMINATED BY THE
FORECAST TRACK OF NOW TROPICAL STORM HANNA. CURRENT
INDICATIONS ARE THAT THE BULK OF HANNAS RAINS WILL STAY EAST
OF THE REGION AND BRING ONLY 0.50 INCHES TO THE WESTERN HSA
AND POSSIBLY UP TO 1.50 INCHES TO THE FAR EASTERN SECTIONS.
ANY SHIFT IN THE TRACK COULD DRASTICALLY CHANGE THIS FORECAST.
IN THE LONGER RANGE OUTLOOKS THROUGH SEPTEMBER 17 ABOVE
NORMAL RAINFALL IS FORECAST ALONG THE ENTIRE U.S. EAST COAST.
THIS IS DUE PRIMARILY TO THE VERY ACTIVE TROPICS BUT FORECAST
UNCERTAINTY REMAINS VERY HIGH WITH SPECIFIC STORM TRACKS
BECOMING CRITICAL IN RAINFALL PATTERNS.
NEXT ISSUANCE DATE...
THE NEXT DROUGHT STATEMENT WILL BE ISSUED ON OR ABOUT SEPTEMBER 18
UNLESS CHANGED CONDITIONS WARRANT AN EARLIER UPDATE.
RELATED WEBSITES...
ADDITIONAL INFORMATION ON CURRENT AND FORECAST DROUGHT CONDITIONS
MAY BE FOUND AT THE FOLLOWING WEB ADDRESSES:
U.S. DROUGHT MONITOR...
http://www.drought.unl.edu/dm/
NATIONAL INTEGRATED DROUGHT INFORMATION SYSTEM...
http://www.drought.gov
NWS CLIMATE PREDICTION CENTER...
http://www.cpc.ncep.noaa.gov/
UNITED STATES GEOLOGICAL SURVEY...
http://water.usgs.gov/waterwatch/
NORTH CAROLINA DROUGHT MANAGEMENT ADVISORY COUNCIL...
http://www.ncdrought.org/
VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY...
http://www.deq.virginia.gov/
ACKNOWLEDGMENTS...
THE DROUGHT MONITOR IS A MULTI-AGENCY EFFORT INVOLVING THE NATIONAL
WEATHER SERVICE...NATIONAL CLIMATIC DATA CENTER...USDA...STATE AND REGIONAL
CLIMATOLOGISTS AND DROUGHT MITIGATION CENTER. INFORMATION FOR THIS
STATEMENT HAS BEEN GATHERED FROM NWS...STATE COOPERATIVE EXTENSION SERVICES
...THE USDA...USACE AND USGS.
QUESTIONS OR COMMENTS...
PLEASE CONTACT...
NATIONAL WEATHER SERVICE
1750 FORECAST DR.
BLACKSBURG VA 24060
PHONE: 540-552-1341
PC