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FXUS06 KWBC 101916
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD
300 PM EDT FRI SEPTEMBER 10 2010
6-10 DAY OUTLOOK FOR SEP 16 - 20 2010
RECENT ENSEMBLE MEAN SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT ON THE EXPECTED
MEAN 500-HPA CIRCULATION PATTERN OVER NORTH AMERICA FOR THE 6-10 DAY PERIOD. A
MOSTLY ZONAL FLOW PATTERN IS ANTICIPATED ACROSS THE NORTHERN PART OF THE
COUNTRY WHILE A SUBTROPICAL RIDGE IS FORECAST OVER THE SOUTHWESTERN AND
SOUTH-CENTRAL CONUS. TROUGHS ARE FORECAST NORTH OF HUDSON BAY EXTENDING
SOUTHEASTWARD TO THE NORTHEAST CONUS, AND OVER THE SOUTHERN GULF OF ALASKA. THE
SUBTROPICAL RIDGE EXPECTED OVER THE SOUTHWEST IS FORECAST TO EXTEND
NORTHWESTWARD TO THE ROCKIES, GREAT BASIN, SOUTHWESTERN CANADA, AND ALASKA. THE
TROUGH ANTICIPATED OVER THE SOUTHERN GULF OF ALASKA IS FORECAST TO UNDERCUT THE
RIDGE EXPECTED OVER ALASKA. THE LATEST OPERATIONAL RUNS OF THE ECMWF AND GFS
ARE IN BASICALLY GOOD AGREEMENT WITH THEIR RESPECTIVE ENSEMBLE MEANS ALTHOUGH
AS USUAL THE OPERATIONAL RUNS ARE GENERALLY MORE AMPLIFIED WITH THE MAIN
CIRCULATION FEATURES AND THE OPERATIONAL RUNS DEPICT SLIGHTLY HIGHER HEIGHTS
OVER THE SOUTHEAST.
THE ENSEMBLE SPAGHETTI DIAGRAMS GENERALLY INDICATE MODERATE SPREAD OVER MUCH OF
THE CONUS, AND MODERATE TO LARGE SPREAD OVER THE NORTHEAST PACIFIC. THE SPREAD
OVER THE CONUS SEEMS TO BE MAINLY RELATED TO TIMING DIFFERENCES IN THE ZONAL
FLOW. LARGE SPREAD IS ALSO INDICATED OVER THE CENTRAL ATLANTIC DUE TO
UNCERTAINTIES IN REGARD TO THE EVOLUTION OF TROPICAL SYSTEMS. THE PNA INDEX
WHICH RECENTLY HAS BEEN POSITIVE IS FORECAST TO REMAIN POSITIVE THROUGH DAY 14.
THE AO INDEX WHICH RECENTLY HAS BEEN NEGATIVE IS FORECAST TO REMAIN NEGATIVE
THROUGH DAY 14.
TODAYS BLEND CHART INDICATES A VERY LOW AMPLITUDE HEIGHT ANOMALY PATTERN OVER
THE CONUS. NEAR TO BELOW NORMAL HEIGHTS ARE EXPECTED OVER THE GREAT LAKES,
EASTERN, AND NORTHWESTERN CONUS, AND NEAR TO ABOVE NORMAL HEIGHTS ARE FORECAST
OVER THE REMAINDER OF THE CONUS AND ALASKA. THE AREA OF BELOW NORMAL HEIGHTS
EXPECTED OVER THE NORTHEAST AND GREAT LAKES FAVORS BELOW NORMAL TEMPERATURES
FOR PARTS OF THOSE REGIONS. COOLER THAN NORMAL SEA SURFACE TEMPERATURES FAVORS
BELOW NORMAL TEMPERATURES FOR COASTAL SECTIONS OF CALIFORNIA. THE EXPECTATION
OF NEAR TO ABOVE NORMAL HEIGHTS FAVORS ABOVE NORMAL TEMPERATURES FOR ALASKA AND
THE INTERIOR WESTERN CONUS.
THE TROUGH EXPECTED TO APPROACH THE PACIFIC NORTHWEST LEADS TO A FORECAST OF
ENHANCED CHANCES FOR ABOVE MEDIAN PRECIPITATION FOR COASTAL SECTIONS OF THAT
REGION. SURFACE LOW PRESSURE EXPECTED OVER THE CENTRAL PLAINS AND MIDDLE
MISSISSIPPI VALLEY FAVORS ABOVE MEDIAN PRECIPITATION FOR PARTS OF THOSE
REGIONS. MUCH OF THE REST OF THE CONUS AND ALASKA IS FAVORED TO HAVE NEAR TO
BELOW MEDIAN PRECIPITATION. THE PRECIPITATION FORECAST ALONG THE GULF COAST AND
SOUTHEAST IS HIGHLY UNCERTAIN BECAUSE OF THE POSSIBILITY OF TROPICAL ACTIVITY
DURING THE PERIOD.
TODAY`S OFFICIAL 500-HPA BLEND CONSISTS OF 15 PERCENT OF TODAY`S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8...15 PERCENT OF TODAY`S 6Z GFS ENSEMBLE MEAN
CENTERED ON DAY 8...5 PERCENT OF TODAY`S OPERATIONAL 0Z ECMWF CENTERED ON DAY
8...25 PERCENT OF TODAY`S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8...5
PERCENT OF YESTERDAY`S OPERATIONAL 12Z ECMWF CENTERED ON DAY 7...30 PERCENT OF
YESTERDAY`S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 7...AND 5 PERCENT OF
YESTERDAY`S 12Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 7.
MODEL OF THE DAY: YESTERDAY`S 12Z ECMWF ENSEMBLE
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 ON A SCALE OF 1
TO 5, DUE TO GOOD MODEL AGREEMENT DEPICTING THE OVERALL PATTERN OFFSET BY THE
EXPECTATION OF ZONAL FLOW AND RELATIVELY WEAK HEIGHT ANOMALIES.
8-14 DAY OUTLOOK FOR SEP 18 - 24 2010
FOR WEEK 2, THE ENSEMBLE MEANS INDICATE THE OVERALL CIRCULATION PATTERN WILL BE
SLOWLY PROGRESSIVE COMPARED TO THE FORECAST FOR THE 6-10 DAY PERIOD. A ZONAL
FLOW PATTERN IS EXPECTED ACROSS THE NORTHERN CONUS WHILE A SUBTROPICAL RIDGE IS
EXPECTED OVER THE SOUTHERN PLAINS AND SOUTHWEST. RECENT OPERATIONAL GFS RUNS
ARE IN FAIRLY GOOD AGREEMENT WITH THE VARIOUS ENSEMBLE MEANS. THE ENSEMBLE
SPAGHETTI CHARTS INDICATE MODERATE SPREAD OVER THE CONUS, LARGE SPREAD OVER THE
NORTHEAST PACIFIC, AND LARGE SPREAD OVER THE CENTRAL ATLANTIC AND GULF OF
MEXICO WHICH IS A REFLECTION OF THE UNCERTAINTY ASSOCIATED WITH THE FUTURE
EVOLUTION OF TROPICAL SYSTEMS.
TODAYS WEEK 2 BLEND CHART INDICATES NEAR TO BELOW NORMAL HEIGHTS OVER THE
ALASKAN PANHANDLE, THE NORTHWEST AND SOUTHEAST CONUS, AND ALONG THE GULF COAST,
AND NEAR TO ABOVE NORMAL HEIGHTS OVER THE REMAINDER OF THE CONUS AND ALASKA.
AS AN UPPER-LEVEL RIDGE MOVES SLOWLY EASTWARD, A WARMER AND DRIER PATTERN IS
EXPECTED OVER PARTS OF THE CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY DURING
WEEK 2 COMPARED TO THE 6-10 DAY PERIOD. OTHERWISE THE FORECAST ANOMALY PATTERNS
FOR WEEK 2 ARE NOT SUBSTANTIALLY DIFFERENT FROM THOSE FORECAST DURING THE 6-10
DAY PERIOD.
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 5 PERCENT OF TODAY`S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11...5 PERCENT OF TODAY`S 6Z GFS ENSEMBLE MEAN
CENTERED ON DAY 11...10 PERCENT OF TODAY`S GFS SUPERENSEMBLE MEAN CENTERED ON
DAY 11...30 PERCENT OF TODAY`S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY
11...10 PERCENT OF TODAY`S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11...35
PERCENT OF YESTERDAY`S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10...AND 5
PERCENT OF YESTERDAY`S 12Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 10.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 ON A SCALE OF
1 TO 5, DUE TO FAIR MODEL AGREEMENT OFFSET BY THE UNCERTAINTY OF A FORECAST IN
ZONAL FLOW AND A FLAT HEIGHT ANOMALY PATTERN, AND UNCERTAINTIES ASSOCIATED WITH
THE EVOLUTION OF SYSTEMS IN THE TROPICS.
FORECASTER: RANDY SCHECHTER
NOTES:
AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OTHERWISE -
FORECASTS INCORPORATE FORECASTER INPUT.
THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS
THE SAME AS THAT IN THE TABLES: A-ABOVE N-NEAR NORMAL B-BELOW
IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL
BE A GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY
EVEN A NORMAL (I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY
SEASONS. IN SUCH CASES A FORECAST OF NEAR NORMAL IS EFFECTIVELY A
FORECAST OF LITTLE OR NO PRECIPITATION.
THE CLIMATE PREDICTION CENTER USES 1971-2000 BASE PERIOD MEANS FOR
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN
THE CLIMATE OUTLOOKS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON
SEPTEMBER 16
ANALOGS TO THE 5 DAY MEAN OBSERVED PATTERN CENTERED 3 DAYS AGO (D-3)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 5 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19770924 - 19640901 - 19530825 - 19540914 - 19550920
ANALOGS TO THE 7 DAY MEAN OBSERVED PATTERN CENTERED 4 DAYS AGO (D-4)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 7 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19770923 - 19530823 - 19540914 - 19640902 - 19850914
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