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FXUS06 KWBC 081903
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT TUE AUGUST 08 2023
6-10 DAY OUTLOOK FOR AUG 14 - 18 2023
LIKE YESTERDAY, THE GFS, ECMWF, AND CANADIAN ENSEMBLE MEANS AND THE 0Z
DETERMINISTIC ECMWF MODELS ARE IN GOOD AGREEMENT ON THE PREDICTED LONGWAVE
PATTERN DURING THE 6-10 DAY PERIOD. HOWEVER, MOST TOOLS ARE SHOWING LESSER
ANOMALIES FOR MOST 500-HPA FEATURES, HINTING AT THE POTENTIAL FOR A PATTERN
CHANGE BEGINNING AT THE END OF THE PERIOD. BUT AT THIS TIME, THE MEAN HEIGHT
BLEND FEATURES REFLECT YESTERDAY’S GUIDANCE, WITH AN ANOMALOUS TROUGH CENTERED
OVER THE ALEUTIANS, AN AMPLIFIED RIDGE OVER WESTERN NORTH AMERICA, A BROAD AREA
OF ANOMALOUSLY HIGH 500-HPA HEIGHTS ALONG THE SOUTHERN CONUS, AND A MODERATE
MID-LEVEL TROUGH CENTERED NEAR THE GREAT LAKES.
DESPITE THIS BROAD PATTERN AGREEMENT, THERE IS CONSIDERABLY LESS CONSISTENCY IN
THE VARIOUS TEMPERATURE AND PRECIPITATION TOOLS, SUCH AS THE CALIBRATED,
RE-FORECAST, AND CONSOLIDATED TOOLS. THE FORECAST LEANS TOWARD THE CONSOLIDATED
TOOLS AND THE OTHER GUIDANCE THAT HAS BEEN MOST CONSISTENT OF LATE, AND MOST
ACCURATE OVER THE PAST FEW WEEKS. IN SOME CASES, OBSERVATIONS OVER THE PAST FEW
WEEKS WITH SIMILAR PATTERNS WERE CONSIDERED, WHICH DIDN’T AGREE PARTICULARLY
WELL WITH ANY OF THE FORECAST TOOLS AT THE TIME.
ANOMALOUS RIDGING SUPPORTS INCREASED ABOVE-NORMAL TEMPERATURE PROBABILITIES
THROUGHOUT THE WESTERN AND SOUTHERN CONUS. TODAY’S GUIDANCE BRINGS SLIGHTLY
ABOVE-NORMAL 500-HPA HEIGHTS FARTHER NORTH TOWARD THE CENTRAL TIER OF THE
CONUS, BUT TEMPERATURE GUIDANCE REMAINS INCONSISTENT IN THE REGION. WARMTH IS
FAVORED BY MOST GUIDANCE ALONG THE SOUTHERN AND WESTERN PORTIONS OF THE CONUS
IN CONJUNCTION WITH THE ANOMALOUSLY HIGH 500-HPA HEIGHTS, AS HAS BEEN THE CASE
FOR A FEW WEEKS, BUT THERE ARE VARIABLE RESULTS ACROSS THE PLAINS, MIDDLE AND
UPPER MISSISSIPPI VALLEY, AND LOWER OHIO VALLEY. GEFS-BASED TOOLS BRING WARM
AIR STRONGLY NORTHWARD INTO THE CENTRAL AND NORTHERN CONUS, REACHING THE
CANADIAN BORDER. MEANWHILE, TOOLS BASED ON THE CANADIAN ENSEMBLE KEEP SUBNORMAL
TEMPERATURES MUCH FARTHER SOUTH AND EAST INTO THE LOWER OHIO VALLEY, AND THE
ECMWF BIAS-CORRECTED AND RE-FORECAST TOOLS SPLIT THE DIFFERENCE. GEFS GUIDANCE
HAS SHOWN A STRONG WARM BIAS FROM THE CENTRAL PLAINS INTO THE OHIO RIVER VALLEY
RECENTLY, SO ITS MUCH WARMER SOLUTION IS NOT FAVORED AT THIS TIME. BASED ON
OTHER GUIDANCE, SLIGHTLY ABOVE-NORMAL ODDS FOR WARMER THAN NORMAL WEATHER
STRETCH FROM SOUTHERN PORTIONS OF THE CENTRAL PLAINS THROUGH THE LOWER OHIO
VALLEY, WITH ODDS BEING NEAR NORMAL OR FAVORING SUBNORMAL TEMPERATURES IN THE
NORTHERN PLAINS AND UPPER MIDWEST. SOUTHERLY FLOW EAST OF THE MODERATE
MID-LEVEL TROUGH CENTERED NEAR THE GREAT LAKES IS EXPECTED TO BRING WARMER THAN
NORMAL CONDITIONS TO THE ATLANTIC SEABOARD. MEANWHILE, THE TROUGH SOUTH OF THE
ALEUTIANS FAVORS SUBNORMAL TEMPERATURES IN SOUTHWESTERN PARTS OF ALASKA CLOSER
TO THE ANOMALOUSLY NEGATIVE 500-HPA HEIGHTS, WHILE INCREASING 500-HPA HEIGHTS
WILL MAKES THE TEMPERATURE FORECAST IN SOUTHEASTERN ALASKA UNCERTAIN. AS A
RESULT, NO TILT OF THE ODDS TOWARD EITHER EXTREME IS IDENTIFIED THERE. FARTHER
NORTH, SOUTHWESTERLY SURFACE FLOW INCREASES THE ODDS FOR ABOVE-NORMAL
TEMPERATURES ACROSS THE NORTHWESTERN QUARTER OF THE MAINLAND.
THE MID-LEVEL TROUGH OVER EASTERN NORTH AMERICA FAVORS ENHANCED ABOVE-NORMAL
PRECIPITATION PROBABILITIES ACROSS ALONG THE EASTERN SEABOARD AND OVER THE
GREAT LAKES AND OHIO VALLEY. SEVERAL TOOLS FAVOR ABOVE-NORMAL PRECIPITATION
FARTHER SOUTH AS WELL, FROM CENTRAL TEXAS EASTWARD ACROSS THE GULF COAST
STATES. HOWEVER, OBSERVED RAINFALL AMOUNTS IN THIS REGION HAVE BEEN
CONSIDERABLY LOWER THAN INDICATED BY GUIDANCE RECENTLY, AND THE CURRENT
FORECAST IS CONSISTENT WITH OBSERVED PRECIPITATION AMOUNTS DURING THE PAST FEW
WEEKS UNDER A SIMILAR 500-HPA HEIGHT PATTERN. FARTHER WEST, THE ANOMALOUS
500-HPA RIDGE FAVORS BELOW-NORMAL PRECIPITATION ACROSS THE SOUTHWEST,
CONSISTENT WITH A PATTERN THAT WOULD INHIBIT THE MONSOON CIRCULATION. THE DRIER
TOOLS WERE ALSO PREFERRED FOR THE PACIFIC NORTHWEST AND INTERMOUNTAIN WEST
GIVEN THE STRENGTH OF THE RIDGE ALOFT. THE ONE EXCEPTION IS OVER NORTHERN
CALIFORNIA, WHERE A SOUTH-SOUTHWESTERLY FLOW ALOFT, SOUTH OF THE POSITIVE
500-HPA ANOMALY CENTER, COULD BRING ABOVE-NORMAL PRECIPITATION INTO NORTHERN
CALIFORNIA. CLIMATOLOGICALLY, PRECIPITATION NORMALS ARE LOW THIS TIME OF YEAR
IN THAT REGION, SO LITTLE PRECIPITATION IS NECESSARY FOR AMOUNTS TO VERIFY
ABOVE NORMAL.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 15% OF TODAY'S GFS
SUPERENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S OPERATIONAL 6Z GFS
CENTERED ON DAY 8, 15% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8,
25% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND 35% OF TODAY'S 0Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO
EXCELLENT AGREEMENT ON THE LONGWAVE PATTERN, REDUCED BY INCONSISTENCY IN
TEMPERATURE AND PRECIPITATION GUIDANCE ALONG WITH OBSERVATIONS OVER THE PAST
FEW WEEKS.
8-14 DAY OUTLOOK FOR AUG 16 - 22 2023
ENSEMBLE MEANS ARE IN GOOD AGREEMENT THAT SOME PARTS OF THE LONGWAVE PATTERN
OVER THE NORTH PACIFIC AND NORTH AMERICA WILL RETROGRADE OR WEAKEN DURING
WEEK-2 AS A POTENTIAL PATTERN ADJUSTMENT GETS UNDERWAY. AN ANOMALOUS TROUGH OF
MODERATE STRENGTH OVER THE BERING SEA AND ALEUTIANS FLOWS INTO AN AMPLIFIED
RIDGE ACROSS THE NORTHEAST PACIFIC AND WESTERN CONUS, WITH HIGHER MID-LEVEL
HEIGHTS REACHING NORTHWARD TOWARD SOUTHEASTERN ALASKA WITH TIME. ABOVE-NORMAL
500-HPA HEIGHTS PERSIST ALONG THE SOUTHERN TIER OF THE CONUS, EXPANDING
SLIGHTLY NORTHWARD AS THE PERIOD PROGRESSES, WHILE THE MID-LEVEL TROUGH
CENTERED NEAR THE GREAT LAKES IS EXPECTED TO WEAKEN SLIGHTLY WHILE DRIFTING
SLOWLY TO THE NORTHWEST.
THIS PATTERN CONTINUES TO SUPPORT INCREASED ABOVE NORMAL TEMPERATURE
PROBABILITIES THROUGHOUT THE WESTERN AND SOUTHERN CONUS, DESPITE SIMILAR
GUIDANCE INCONSISTENCIES AS NOTED DURING THE 6-10 DAY PERIOD. BUT WITH SOME
500-HPA FEATURES WEAKENING OR RETROGRADING SLIGHTLY, ODDS FOR WARMTH ARE NOT AS
HIGH AS THEY HAVE BEEN RECENTLY. PROBABILITIES STILL EXCEED 70 PERCENT IN FAR
SOUTHERN FLORIDA, WHERE MOST GUIDANCE KEEPS THE BEST CHANCES FOR ABOVE-NORMAL
TEMPERATURES, BUT PEAK CLOSER TO 60 PERCENT IN OTHER PARTS OF THE SOUTHERN AND
WESTERN CONUS, WITH THE HIGHEST CHANCES SUPPRESSED RELATIVELY FAR TO THE SOUTH
COMPARED TO EARLIER OUTLOOKS. MEANWHILE, THE NORTHWESTWARD DRIFT OF THE
MID-LEVEL TROUGH INITIALLY CENTERED NEAR THE GREAT LAKES REGION INCREASES ODDS
FOR SUBNORMAL TEMPERATURES FARTHER WEST INTO THE INTERMOUNTAIN WEST, BUT STILL
WELL TO THE EAST OF THE PACIFIC NORTHWEST. SOUTHERLY FLOW TO THE EAST OF THE
MID-LEVEL RIDGE SHOULD KEEP ENHANCED CHANCES FOR WARMER THAN NORMAL WEATHER
ACROSS THE EASTERN SEABOARD. ENHANCED CHANCES FOR ABOVE-NORMAL TEMPERATURES
ALSO BEGIN TO PUSH INTO EASTERN ALASKA AS THE MID-LEVEL TROUGH OVER THE
ALEUTIANS WEAKENS, AND ABOVE-NORMAL HEIGHTS OVER THE WESTERN CONUS AND NORTH
PACIFIC EXPAND NORTHWARD. BIAS-CORRECTED TOOLS FOR THE ENSEMBLES ARE MUCH
COLDER IN SOUTHEASTERN ALASKA THAN THE RAW ENSEMBLE MEAN OUTPUTS AND THE
REFORECAST TOOLS, BUT THE WARMER SOLUTIONS BETTER FIT THE EXPECTED MID-LEVEL
PATTERN.
GUIDANCE IS NOT IN GOOD AGREEMENT REGARDING PRECIPITATION TOTALS FOR WEEK-2.
THE TROUGH CENTERED NORTHEAST OF THE GREAT LAKES CONTINUES TO FAVOR ABOVE
NORMAL PRECIPITATION IN THE NORTHEASTERN CONUS. TO THE WEST, WITH TROUGHING IN
SOUTH-CENTRAL CANADA AND RISING 500-HPA HEIGHTS OVER THE CENTRAL ROCKIES AND
PLAINS, AN UPTICK IN PRECIPITATION IS EXPECTED OVER A LARGE PART OF THE CENTRAL
AND WESTERN CONUS, INCLUDING INCREASING RAINFALL ASSOCIATED WITH THE SOUTHWEST
MONSOON. NO TOOLS ARE PARTICULARLY ROBUST, HOWEVER, AND SOME GUIDANCE, SUCH AS
THE ECMWF ENSEMBLE REFORECAST TOOLS, PLACE ABNORMALLY LOW PRECIPITATION ACROSS
THE INTERIOR WEST. BUT A PREPONDERANCE OF THE GUIDANCE SLIGHTLY FAVORS
ABOVE-NORMAL PRECIPITATION THROUGHOUT THE INTERIOR WEST, AND THIS IS THE
FAVORED SOLUTION AT THIS TIME. FARTHER NORTHWEST, SLOWLY-BUILDING MID-LEVEL
HEIGHTS OVER AND NEAR EASTERN ALASKA, COMBINED WITH THE WEAKENING TROUGH CLOSER
TO THE ALEUTIANS, ENHANCES THE ODDS FOR WETTER THAN NORMAL WEATHER ACROSS MOST
OF THE STATE. BUT AS IS THE CASE ACROSS THE CONUS, GUIDANCE IS NEITHER ROBUST
NOR IN PARTICULARLY GOOD AGREEMENT.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 15% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 15% OF TODAY'S GFS SUPERENSEMBLE MEAN
CENTERED ON DAY 11, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY
11, AND 40% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO
FAIR MODEL AGREEMENT AND CONTINUITY ON THE LONGWAVE PATTERN, BUT WITH
UNCERTAINTIES INTRODUCED BY EXPECTED CHANGES IN THE 500-HPA PATTERN LATER
WEEK-2, ALONG WITH CONTINUED INCONSISTENCY AMONG THE TOOLS FORECASTING SENSIBLE
WEATHER.
FORECASTER: RICH TINKER
NOTES:
AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OCCASIONALLY MANUAL
INTERVENTION IS NECESSARY TO ADDRESS QUALITY CONTROL AND CONSISTENCY ISSUES. IN
THESE CASES, FORECASTS ARE MANUALLY DRAWN BUT A FULL DISCUSSION IS NOT ISSUED.
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
THE TEMPERATURE MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WARMER (ORANGE,
"A"), COLDER (BLUE, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL AVERAGE
VALUES FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "F"). LABELS ON THE
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).
PROBABILITY OF N IS ALWAYS < 40%.
THE PRECIPITATION MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WETTER (GREEN,
"A"), DRIER (TAN, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL MEDIAN VALUES
FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "INCHES"). LABELS ON THE
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).
PROBABILITY OF N IS ALWAYS < 40%.
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 1991-2020 BASE PERIOD MEANS AS REFERENCE IN
THE CLIMATE OUTLOOKS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON
AUGUST 17.
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:
20090719 - 19540808 - 19960722 - 19980804 - 20030722
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:
20090718 - 19540807 - 19540802 - 19960721 - 19960726
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR AUG 14 - 18 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A A
SRN CALIF A N IDAHO A B NEVADA A N
W MONTANA N N E MONTANA B N WYOMING B N
UTAH A B ARIZONA A N COLORADO A N
NEW MEXICO A B N DAKOTA B N S DAKOTA B N
NEBRASKA B N KANSAS N N OKLAHOMA A N
N TEXAS A B S TEXAS A B W TEXAS A B
MINNESOTA B A IOWA B A MISSOURI N A
ARKANSAS A N LOUISIANA A B WISCONSIN B A
ILLINOIS B A MISSISSIPPI A N MICHIGAN A A
INDIANA N A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA A N NEW YORK A A
VERMONT A A NEW HAMP A A MAINE A A
MASS A A CONN A A RHODE IS A A
PENN A A NEW JERSEY A A W VIRGINIA A A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN N N AK WESTERN N N AK INT BSN N A
AK S INT N A AK SO COAST N A AK PNHDL N N
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR AUG 16 - 22 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A N NRN CALIF A A
SRN CALIF A A IDAHO A N NEVADA A A
W MONTANA B N E MONTANA B A WYOMING B A
UTAH A A ARIZONA A A COLORADO A N
NEW MEXICO A N N DAKOTA B A S DAKOTA B N
NEBRASKA A N KANSAS A N OKLAHOMA A N
N TEXAS A N S TEXAS A N W TEXAS A N
MINNESOTA B N IOWA A N MISSOURI A N
ARKANSAS A N LOUISIANA A N WISCONSIN N N
ILLINOIS A N MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A N RHODE IS A N
PENN A N NEW JERSEY A N W VIRGINIA A N
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A N S CAROLINA A N GEORGIA A N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN N N AK WESTERN N N AK INT BSN N A
AK S INT N N AK SO COAST N N AK PNHDL A B
LEGEND
TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN
A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN
B - BELOW B - BELOW
THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE.
FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS
PMDMRD.
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