PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EDT WED APR 30 2003

6 TO 10 DAY OUTLOOK FOR MAY 6 - 10 2003
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THERE IS CONSIDERABLE DISAGREEMENT AMONG THE VARIOUS MODELS ON THE 
6 TO 10 DAY MEAN 500-HPA CIRCULATION PATTERN AFFECTING NORTH AMERICA.
AGREEMENT BETWEEN THE ECMWF AND 00Z GFS DAILY PROGS BEGINS TO BREAK
DOWN NOTICEABLY BY DAY 4...WITH THE GFS BEING FASTER ON EJECTING A
SHORTWAVE TROUGH OUT OF THE DESERT SOUTHWEST AND INTO THE PLAINS...
COMPARED TO THE SLOWER ECMWF.  AMONG THE PRIMARY D+8 MEAN HEIGHT 
PROGS...THE ECMWF HAS THE DEEPEST TROUGH JUST OFF THE WEST COAST OF
THE UNITED STATES.  ALL SOLUTIONS IMPLY AN ACTIVE SOUTHERN STREAM 
OVER THE SOUTHERN TIER OF STATES...AND MODEST RIDGING OVER SOUTH-
CENTRAL CANADA.  A BROAD CONFLUENCE AREA ALOFT IS DEPICTED BY MOST
MODELS OVER THE NORTHEASTERN U.S...WHILE WEAK RIDGING PREVAILS OVER
THE SOUTHEAST.

MODEL OF THE DAY: ECMWF...WHICH RECENTLY HAS BEEN THE BEST PERFORMER.

FORECAST CONFIDENCE FOR THE 6 TO 10 DAY PERIOD IS RATED BELOW AVERAGE 
TODAY... 2 ON A SCALE FROM 1 TO 5...DUE PRIMARILY TO SHORTER WAVE-
LENGTH CIRCULATION FEATURES AND UNCERTAINTIES RELATED TO TIMING OF
THESE WAVES. 

THE OFFICIAL HEIGHT PROG FOR TODAY IS BASED ON 50 PERCENT OF TODAYS
ECMWF CENTERED ON DAY 7... 25 PERCENT OF TODAYS 0Z GFS ENSEMBLE MEAN
CENTERED ON DAY 8... AND 25 PERCENT OF TODAYS OPERATIONAL 0Z GFS 
CENTERED ON DAY 8.

THE TEMPERATURE PROG IS BASED MAINLY ON MOS FORECASTS FROM THE GFS 
ENSEMBLE.  KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-
HPA BLEND FIELD WERE ALSO CONSIDERED.
   
THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM
THE OFFICIAL 500-HPA HEIGHT PROG... THE CALIBRATED AND BIAS-CORRECTED
PRECIPITATION FORECASTS FROM THE OPERATIONAL 00Z GFS RUN... AND 
ANALOGS FROM THE VARIOUS MODELS.  THERE CONTINUES TO BE LITTLE AGREE-
MENT AMONG THE MODELS AND TOOLS TODAY. 

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8 TO 14 DAY OUTLOOK FOR MAY 8 - 14 2003

MODELS SHOW LITTLE CONSISTENCY WITH ONE ANOTHER ON THE CHARACTER OF 
THE 8 TO 14 DAY MEAN CIRCULATION PATTERN.  ABOVE AVERAGE HEIGHTS ARE
EXPECTED OVER SOUTHEASTERN CANADA...WITH ONLY SLIGHTLY ABOVE AVERAGE
HEIGHTS FORECAST OVER THE EASTERN LOWER 48 STATES.  BELOW NORMAL 500-
HPA HEIGHTS ARE GENERALLY FORECAST ANYWHERE FROM BRITISH COLUMBIA TO
THE U.S. PACIFIC NORTHWEST AND WEST COAST...THOUGH SIGNIFICANT DIFF-
ERENCES EXIST AMONG MODELS.

CONFIDENCE IN THE WEEK 2 FORECAST IS BELOW AVERAGE... 2 ON A SCALE 
FROM 1 TO 5... DUE TO A WEAK ANOMALY PATTERN FORECAST BY THE MODELS 
WITH NO CONSENSUS ON SHORT WAVE ACTIVITY WITHIN THE PERIOD.

THE OFFICIAL 500-HPA HEIGHT BLEND FOR THE 8 TO 14 DAY PERIOD CONSISTS
OF 40 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11... 30 PER-
CENT OF THE OPERATIONAL 0Z GFS FOR THE 8 TO 14 DAY PERIOD... AND 30
PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 11.  

THE TEMPERATURE PROG IS BASED ON THE KLEIN AND NEURAL NET SPECIFICA-
TIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG. 

THE PRECIPITATION PROG IS BASED ON NEURAL NET SPECIFICATIONS FROM THE
OFFICIAL 500-HPA HEIGHT PROG... BIAS-CORRECTED AND CALIBRATED RAIN-
FALL FROM THE 00Z OPERATIONAL GFS MODEL... AND ANALOGS FROM THE 
VARIOUS MODELS.

FORECASTER: A. ARTUSA
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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 NARRATIVE DESCRIPTION OF THE FORECAST PATTERNS FOR TEMPERATURE
AND PRECIPITATION FOR BOTH THE 6-10 OR 8-14 DAY PERIODS HAS BEEN
DISCONTINUED.  THE STATE TABLES FOR BOTH THE 6-10 AND 8-14 DAY
PERIODS ARE NOW CONTAINED IN THIS MESSAGE...AVAILABLE AS PMDMRD ON
AWIPS. 

EFFECTIVE THURSDAY MAY 17 2001...THE CLIMATE PREDICTION CENTER
HAS SWITCHED TO 1971-2000 BASE PERIOD MEANS FOR TEMPERATURE...
PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE
OUTLOOKS.  THE 1971-2000 BASE PERIOD MEANS HAVE REPLACED THE
1961-1990 BASE PERIOD MEANS.
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GLOSSARY AND DEFINITIONS:---------------------------------------------

AC - ANOMALY CORRELATION - A MEASURE OF HOW WELL A MODEL FORECASTS
THE HEIGHT OR HEIGHT ANOMALY FIELD OBTAINED BY CORRELATING THE
IMPLIED GRADIENTS OF THE TWO ANOMALY PATTERNS BEING COMPARED.

ANALOG (NATURAL ANALOG) - A WEATHER MAP THAT RESEMBLES ANOTHER
WEATHER MAP - USUALLY FROM DIFFERENT YEARS BUT THE SAME SEASON IN
THE HISTORICAL RECORD.  THE CRITERION FOR SELECTING AN ANALOG IS
OFTEN THE PATTERN CORRELATION BETWEEN THE MAPS.  TWO MAPS WILL JUST
BEGIN TO RESEMBLE EACH OTHER TO THE HUMAN EYE AT A PATTERN
CORRELATION OF ABOUT 40%.  TO BE USEFUL - ANALOGS NEED TO HAVE MUCH
HIGHER CORRELATIONS TO THE ORIGINAL MAP THAN THAT - 80% OR MORE.
ANALOGS ARE INCREASINGLY DIFFICULT TO FIND AS THE GEOGRAPHIC REGION
BEING STUDIED INCREASES IN SIZE.  PERFECT ANALOGS TO THE ENTIRE
NORTHERN HEMISPHERE SIMPLY DO NO EXIST - FOR PRACTICAL PURPOSES.
THIS IS WHY SIMPLE NATURAL ANALOG FORECAST METHODS DO NOT WORK VERY
WELL.

ANOMALY - THE ARITHMETIC DIFFERENCE BETWEEN THE VALUE OF A VARIABLE
AT A GIVEN PLACE AND TIME AND THE LONG-TERM AVERAGE OF THAT VARIABLE
AT THAT PLACE AND TIME OF YEAR.

AO - ARCTIC OSCILLATION - A MEASURE OF THE DIFFERENCE BETWEEN THE
MEAN MID-TROPOSPHERIC HEIGHT OR SEA LEVEL PRESSURE ANOMALY OVER THE
POLAR BASIN AND THE CORRESPONDING AVERAGE ANOMALY IN A RING
SURROUNDING THE POLAR BASIN AT MIDDLE LATITUDES.  THE AO IS
CONSIDERED TO BE THE LEADING MODE OF CLIMATE VARIABILITY OF THE
EXTRATROPICAL NORTHERN HEMISPHERE.  THE AO CAN ALSO BE CONSIDERED TO
INCLUDE THE NAO (NORTH ATLANTIC OSCILLATION) WITH WHICH IT IS
POSITIVELY CORRELATED - BUT NOT IDENTICAL.  THE PHASE OF THE AO IS
CONSIDERED TO BE POSITIVE WHEN HEIGHTS OR PRESSURES ARE BELOW NORMAL
OVER THE ARCTIC BASIN AND ABOVE NORMAL OVER SURROUNDING MID-
LATITUDES - AND IS NEGATIVE FOR THE REVERSE ANOMALY PATTERN.

BLEND - A WEIGHTED AVERAGE OF 500-HPA HEIGHT FORECAST MAPS FROM
SEVERAL MODELS.  WEIGHTS ARE CURRENTLY ASSIGNED SUBJECTIVELY BY THE
FORECASTER.  THE SUM OF THE WEIGHTS MUST BE 1.  WEIGHTS ARE APPLIED
BY MULTIPLYING EACH 500-HPA MAP BY ITS WEIGHT AND ADDING ALL OF THE
WEIGHTED MAPS TOGETHER TO MAKE THE OFFICIAL 500-HPA FORECAST.

CONUS - CONTERMINOUS UNITED STATES.

DAVA - DIVERGENT ANOMALY VORTICITY ADVECTION MODEL.  THIS IS A
BAROTROPIC MODEL WITH DIVERGENCE IN IT TO ALLOW MORE ACCURATE
PREDICTION OF LONG WAVES THAN A STANDARD BAROTROPIC MODEL.
REFERENCE:  QIN J. AND H.M. VAN DEN DOOL - 1996: SIMPLE EXTENSIONS
OF AN NWP MODEL.  MON. WEA. REV. - VOL 124 - PP 277-287.

EL NINO - THE WARM PHASE OF ENSO.

ENSO - EL NINO/SOUTHERN OSCILLATION.

FLOW PATTERN - THE PATTERN OF WIND INFERRED BY THE 500-HPA CONTOURS -
THE WIND TENDS TO BLOW PARALLEL TO THE CONTOURS WITH LOW HEIGHT ON
THE LEFT - IN THE NORTHERN HEMISPHERE - THE OPPOSITE IS TRUE IN THE
SOUTHERN HEMISPHERE.  WIND SPEED IS INVERSELY PROPORTIONAL TO THE
SPACING BETWEEN THE CONTOURS.

GFS - GLOBAL FORECAST SYSTEM.  THIS REFERS TO ANY OF THE GLOBAL
MODELS RUN AT NCEP FOUR TIMES A DAY THAT USED TO BE REFERRED TO AS
THE MRF AND AVN MODELS.  THE MODEL RUN INITIATED AT 00Z (00 GMT) IS
CURRENTLY THE ONLY ONE USED BY CPC IN ITS OFFICIAL BLEND FORECAST -
ALTHOUGH THE OTHERS CAN BE CONSIDERED BY THE FORECASTER IN
FORMULATING THE TEMPERATURE AND PRECIPITATION FORECASTS.

GFS ENSEMBLE - A SET OF GFS FORECASTS WHICH ARE ALL VALID AT THE SAME
TIME BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS.  THERE
ARE CURRENTLY 25 MEMBERS IN THE GFS ENSEMBLE.  THE AVERAGE OF THESE
IS THE GFS ENSEMBLE MEAN.

500-HPA HEIGHT IS THE HEIGHT - IN METERS - ABOVE MEAN SEA LEVEL -
WHICH ABOUT HALF OF THE MASS OF THE ATMOSPHERE LIES ABOVE AND BELOW -
AS MEASURED BY THE PRESSURE.  UPPER AIR STORM SYSTEMS TEND TO BE
STEERED IN THE DIRECTION OF THE WINDS AT 500-HPA.  500-HPA SYSTEMS
CORRELATE STRONGLY WITH SURFACE WEATHER.

HPA - HECTO-PASCALS.  1 HPA = 1 MILLIBAR.

LA NINA - THE COLD PHASE OF ENSO.

MERIDIONAL FLOW PATTERN - OCCURS WHEN 500-HPA CONTOURS EXHIBIT LARGE
NORTHWARD AND SOUTHWARD EXCURSIONS WITH EXTENSIVE AREAS OF SOUTHERLY
AND NORTHERLY FLOW.

MODEL BIAS - THE DIFFERENCE BETWEEN THE MODEL CLIMATOLOGY AND THE
OBSERVED CLIMATOLOGY - EXPRESSED AS BIAS = MODEL CLIMO - OBSERVED
CLIMO.

MODEL OF THE DAY - FOR 6-10 DAYS - IS THE MODEL WHOSE SOLUTION IS
CONSIDERED TO BE MORE RELIABLE THAN USUAL - AND MAY BE GIVEN HIGHER
THAN TYPICAL WEIGHT IN THE BLEND.  NO MODEL OF THE DAY IS CHOSEN FOR
8-14 DAYS.

MOS - MODEL OUTPUT STATISTICS - A STATISITCAL TOOL FOR SPECIFYING THE
SURFACE TEMPERATURE (AND ITS ANOMALY) FROM MODEL FIELDS - CORRECTING
AUTOMATICALLY FOR BOTH BIASES IN THE MODEL FIELDS AND THE
SPECIFICATION METHOD.  IT IS VALID AS LONG AS A GIVEN CONFIGURATION
OF A MODEL IS NOT CHANGED OR MODIFIED. 

MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL
OSCILLATION - A SERIES OF WAVES WITH A PERIOD AVERAGING 50 DAYS THAT
MOVES SLOWLY EASTWARD NEAR THE EQUATOR ALTERNATELY ENHANCING AND
SUPRESSING PRECIPITATION.

NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN.  IT CAN ALSO
BE VIEWED AS THE ATLANTIC HALF OF THE AO (ARCTIC OSCILLATION)
TELECONNECTION PATTERN - STRONGLY INFLUENCES TEMPERATURES OVER EUROPE
AND MUCH OF NORTH AMERICA - ESPECIALLY DURING THE COLD SEASONS - AND
DETERMINES THE MEAN LATITUDE OF THE PREVAILING STORM TRACKS ACROSS
THE NORTH ATLANTIC. THE PHASE OF THE NAO IS CONSIDERED POSITIVE WHEN
PRESSURES AND HEIGHTS ARE BELOW NORMAL OVER GREENLAND AND ICELAND
(STRONG ICELANDIC LOW) AND ABOVE NORMAL AT MIDDLE AND SUBTROPICAL
LATITUDES (STRONG BERMUDA-AZORES HIGH) - AND NEGATIVE FOR THE
REVERSE ANOMALIES.

PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN.

PROG - PROGNOSIS - OR FORECAST.

PROGRESSION OR PROGRESSIVE MOTION - THE NORMAL MOVEMENT OF
ATMOSPHERIC WEATHER SYSTEMS (HIGHS... LOWS... RIDGES... OR TROUGHS)
FROM WEST TO EAST IN THE MIDDLE LATITUDES.

RETROGRESSION OR RETROGRADE MOTION - A TYPE OF MOTION SOMETIMES
OBSERVED IN WEATHER SYSTEMS WHEN THEY END UP IN POSITIONS FURTHER TO
THE WEST THAN THEIR ORIGINAL LOCATIONS - CONTRARY TO THEIR USUAL WEST
TO EAST MOTION.

RIDGE - A REGION OF UNUSUALLY HIGH 500-HPA HEIGHT.

SHORT WAVES - RELATIVELY LOW-AMPLITUDE - FAST-MOVING DISTURBANCES OF
THE 500-HPA FIELD.

SOUTHERN STREAM - A FLOW PATTERN WITH UNUSUALLY STRONG FLOW ACROSS
THE SOUTHERN U.S. - ACCOMPANIED BY UNUSUAL STORMINESS IN THE SOUTH
AND SOUTHEAST.

SPECIFICATIONS - KLEIN AND NEURAL NETWORK SPECIFICATIONS GIVE THE
HISTORICAL RELATIONSHIP BETWEEN 500-HPA HEIGHT ANOMALIES AND SURFACE
TEMPERATURE AND PRECIPITATION.  KLEIN SPECIFICATIONS TEND TO
EMPHASIZE REGIONAL TELECONNECTIONS WHILE THOSE FROM THE NEURAL
NETWORK WORK FROM GLOBAL TELECONNECTIONS.
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TELECONNECTIONS GIVE THE HISTORICAL RELATIONSHIP BETWEEN THE 500-HPA
HEIGHT AT A GIVEN POINT AND ALL OTHER POINTS ON A MAP FOR A GIVEN
TIME OF YEAR. WE AVERAGE THE TOP/BOTTOM 10% OF DAILY MAPS FROM
1950-1999 FOR THE SAME TIME OF YEAR HAVING THE HIGHEST/LOWEST 500-HPA
HEIGHT AT THE SPECIFIED POINT.

TROUGH - A REGION OF UNUSUALLY LOW 500-HPA HEIGHT. 

UTC - UNIVERSAL TIME COORDINATED - SAME AS GREENWICH MEAN TIME (GMT).

WESTERLY WIND - WIND BLOWING FROM WEST TO EAST.

EASTERLY WIND - WIND BLOWING FROM EAST TO WEST.

NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH

SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH.

ZONAL FLOW PATTERN - OCCURS WHEN 500-HPA CONTOURS LIE IN AN EAST-WEST
DIRECTION PARALLEL TO LATITUDE CIRCLES WITH NEARLY PURE WEST-TO-EAST
FLOW.
----------------------------------------------------------------------
THE NEXT MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED THURSDAY
MAY 15 2003.



 
6 to 10 day Outlook Table
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN   
WASHINGTON  N    N     OREGON      N    N     NRN CALIF   A    N     
SRN CALIF   A    N     IDAHO       N    B     NEVADA      A    N     
W MONTANA   N    B     E MONTANA   N    B     WYOMING     N    B     
UTAH        N    N     ARIZONA     N    N     COLORADO    N    N     
NEW MEXICO  N    N     N DAKOTA    N    N     S DAKOTA    N    N     
NEBRASKA    B    N     KANSAS      B    N     OKLAHOMA    B    N     
N TEXAS     B    N     S TEXAS     B    B     W TEXAS     N    N     
MINNESOTA   N    N     IOWA        B    N     MISSOURI    B    N     
ARKANSAS    N    A     LOUISIANA   N    A     WISCONSIN   N    N     
ILLINOIS    N    N     MISSISSIPPI N    A     MICHIGAN    A    N     
INDIANA     N    N     OHIO        A    N     KENTUCKY    A    A     
TENNESSEE   A    A     ALABAMA     A    A     NEW YORK    A    N     
VERMONT     A    N     NEW HAMP    A    N     MAINE       A    B     
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    N     AK N SLOPE  B    B     
AK ALEUTIAN A    N     AK WESTERN  A    B     AK INT BSN  N    B     
AK S INT    A    B     AK SO COAST A    N     AK PNHDL    N    N     
 
8 to 14 day Outlook Table
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN   
WASHINGTON  N    A     OREGON      N    A     NRN CALIF   N    N     
SRN CALIF   N    N     IDAHO       N    A     NEVADA      N    N     
W MONTANA   N    N     E MONTANA   N    B     WYOMING     N    B     
UTAH        N    B     ARIZONA     N    B     COLORADO    N    N     
NEW MEXICO  N    N     N DAKOTA    N    B     S DAKOTA    N    B     
NEBRASKA    N    B     KANSAS      N    N     OKLAHOMA    N    N     
N TEXAS     N    A     S TEXAS     N    A     W TEXAS     N    N     
MINNESOTA   A    N     IOWA        A    N     MISSOURI    N    N     
ARKANSAS    N    A     LOUISIANA   N    A     WISCONSIN   A    N     
ILLINOIS    A    N     MISSISSIPPI N    A     MICHIGAN    A    N     
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A     
TENNESSEE   A    A     ALABAMA     A    A     NEW YORK    A    N     
VERMONT     A    B     NEW HAMP    A    B     MAINE       A    B     
MASS        A    N     CONN        A    N     RHODE IS    A    N     
PENN        A    A     NEW JERSEY  A    N     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    N     AK N SLOPE  B    B     
AK ALEUTIAN A    A     AK WESTERN  A    N     AK INT BSN  N    B     
AK S INT    A    A     AK SO COAST A    A     AK PNHDL    A    A     
 
                           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.
 
$$