PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE WASHINGTON DC
3 PM EDT FRI AUG 9 2002
6 TO 10 DAY OUTLOOK FOR AUG 15 - 19 2002
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MODEL COMPARISONS: TODAYS MODEL RUNS ARE IN GOOD AGREEMENT OVER THE NORTH AMER-
ICAN CONTINENT AND SURROUNDING OCEANIC AREAS REGARDING THE 500 HPA MEAN CIRCU-
LATION PATTERN...WITH TODAYS OPERATIONAL AVN PERHAPS A BIT TOO FAST ON THE MEAN
TROUGH PREDICTED TO BE CENTERED OVER THE NORTHCENTRAL STATES.  OTHER THAN THAT
...THE MODELS ARE CLOSELY PHASED WITH EACH OTHER REGARDING THE NORTH AMERICAN
LONGWAVE TRAIN AND DEMONSTRATE GOOD TELECONNECTIVITY ACROSS MOST OF THE NORTH-
ERN HEMISPHERE.  THE ECMWF HAS HIGHLY AMPLIFIED RIDGES ALONG THE WEST AND EAST
COASTS OF THE UNITED STATES...AND SEEMS TO BE CONSIDERABLY OVERDONE ON THE AMP-
LITUDE OF THESE FEATURES.
THE OFFICIAL 500 HPA BLEND IS GOING WITH A MODERATELY INTENSE RIDGE WITH AN
ASSOCIATED POSITIVE HEIGHT ANOMALY CENTER NEAR KODIAK ISLAND ALASKA AND THE AD-
JACENT EASTERN ALEUTIANS - A BROAD TROUGH OVER CENTRAL SECTIONS OF NORTH AMER-
ICA - RESIDUAL RIDGING OVER THE EASTERN U.S...AND ABOVE NORMAL HEIGHTS OVER
PRACTICALLY THE ENTIRE ARCTIC BASIN.  THIS LAST FEATURE WOULD SUGGEST ... AT
LEAST IN A GENERAL SENSE...THAT THE MIDDLE LATITUDES WOULD EXPERIENCE AN IN-
CREASE IN CYCLONIC ACTIVITY AND PRECIPITATION...WITH A SUPPRESSION OF NEAR
RECORD HEAT OVER MANY AREAS.
CONFIDENCE IN TODAYS FORECAST IS RATED AS ABOVE AVERAGE... 4 ON A SCALE OF
1 TO 5.  THIS IS ATTRIBUTED TO GOOD MODEL AGREEMENT...EXCEPTIONAL CONTINUITY
WITH THE OFFICIAL HEIGHT FORECASTS ISSUED OVER THE PAST FEW DAYS...AND IMPRES-
SIVE HEMISPHERIC TELECONNECTIVITY FOR THE SUMMER SEASON.
THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 40 PERCENT
OF TODAYS AVN ENSEMBLE MEAN CENTERED ON DAY 8... 35 PERCENT OF TODAYS DAVA CEN-
TERED ON DAY 8... 20 PERCENT OF THE HIGH RESOLUTION OPERATIONAL AVN MODEL CEN-
TERED ON DAY 8...AND 5 PERCENT OF TODAYS ECMWF CENTERED ON DAY 7.
MODEL OF THE DAY: AVN ENSEMBLE MEAN
THE TEMPERATURE PROG IS A CONSENSUS OF THE KLEIN AND NEURAL NET SPECIFICATIONS
FROM THE OFFICIAL HEIGHT PROG...MOS OUTPUT FROM THE AVN ENSEMBLE MEMBERS...
HISTORICAL ANALOGS FROM THE VARIOUS MODELS...AND 850 HPA BIAS CORRECTED AVN
TEMPERATURES FROM THE PAST 7- AND 30- DAYS...AS WELL AS RECENT OBSERVATIONS.
THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATION FROM
THE OFFICIAL HEIGHT PROG... THE AVN FORECAST RAINFALL CORRECTED FOR MEAN  7-
AND 30-DAY BIASES... THE CALIBRATED AVN PRECIPITATION PATTERNS... HISTORICAL
ANALOGS FROM THE VARIOUS MODEL HEIGHT PATTERNS... AND RECENT OBSERVATIONS.
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8 TO 14 DAY OUTLOOK FOR AUG 17 - 23 2002
THE ENSEMBLE MEAN AND DAVA PROGS AT THE WEEK 2 RANGE ARE IN REASONABLY GOOD
AGREEMENT ON PERSISTING THE NORTH AMERICAN WAVETRAIN WHICH IS PREDICTED FOR
DAYS 6-10.  HOWEVER...THE OPERATIONAL D+11 AVN CONTINUES TO ADVANCE THE CENTRAL
NORTH AMERICAN TROUGH EASTWARD...AND CONNECTS IT WITH ANOTHER TROUGH OVER THE
FAR EASTERN ATLANTIC TO PRODUCE ONE VERY BROAD AREA OF CYCLONIC CURVATURE ACROSS
THE NORTH ATLANTIC.  OVER THE HIGHER LATITUDES OF BOTH CANADA AND THE NORTH AT-
LANTIC...THE AVN COMBINES RIDGING OVER THE GULF OF ALASKA WITH BLOCKING OVER THE
DAVIS STRAIT REGION...THEREBY FAVORING A NEGATIVELY PHASED NAO PATTERN DURING
THE WEEK 2 FORECAST PERIOD.  TODAYS AVN IS MORE OF AN OUTLIER COMPARED TO THE
OTHER TWO PRINCIPAL MODELS WHICH HAVE GENERALLY BEEN MORE SKILLFUL OVER THE PAST
SEVERAL MONTHS...AND THEREFORE WAS NOT GIVEN MUCH WEIGHT IN THE BLENDED MIX.
CONFIDENCE IS JUDGED TO BE NEAR AVERAGE FOR WEEK 2 TODAY... RATED 3 ON A SCALE
OF 1-5.
THE BLENDED 500-MB HEIGHT PATTERN USES 40 PERCENT OF TODAYS AVN ENSEMBLE MEAN
CENTERED ON DAY 11... 15 PERCENT OF TODAYS HIGH RESOLUTION 00Z AVN CENTERED ON
DAY 11...AND 45 PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 11.
THE TEMPERATURE PROG IS A CONSENSUS OF THE KLEIN AND NEURAL NETWORK SPECIFICA-
TIONS FROM THE OFFICIAL HEIGHT PROG...HISTORICAL TEMPERATURE ANALOGS BASED ON
THE ENSEMBLE MEAN AND OPERATIONAL AVN PROGS...AND 850 HPA BIAS CORRECTED AVN
TEMPERATURES FROM THE PAST 7 AND 30 DAYS.
THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATIONS FROM
THE OFFICIAL HEIGHT PROG... THE AVN MODEL ACCUMULATED PRECIPITATION CORRECTED
FOR MEAN 7- AND 30-DAY BIASES... THE CALIBRATED AVN PRECIPITATION...AND ANALOGS.
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 PRECIPI-
TATION.
THE NARRATIVE DESCRIPTION OF THE FORECAST PATTERNS FOR TEMPERATURE AND PRECIP-
ITATION 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.
AVN - THE RUN OF THE MRF MODEL INITIATED AT 12 UTC (AS OF 07/2002 THE NAME
FOR ALL RUNS OF THE NCEP GLOBAL SPECTRAL MODEL).
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.
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.
MRF - MEDIUM RANGE FORECAST MODEL (AS OF 07/2002 RENAMED THE AVN)
MRF ENSEMBLE - A SET OF MRF (AVN) FORECASTS WHICH ARE ALL VALID AT THE SAME
TIME BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS.  THERE ARE CUR-
RENTLY 25 MEMBERS IN THE MRF (AVN) ENSEMBLE.  THE AVERAGE OF THESE IS THE
MRF (AVN) ENSEMBLE MEAN.
MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLA-
TION - 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.
PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN.
PROG - PROGNOSIS - OR FORECAST.
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 SOUTH-
ERN 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 TELECONNEC-
TIONS 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.
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THE NEXT MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON THURSDAY AUGUST 15
2002.
6 to 10 day Outlook Table
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  N    B     OREGON      A    B     NRN CALIF   A    B
SRN CALIF   N    B     IDAHO       N    B     NEVADA      A    B
W MONTANA   B    B     E MONTANA   B    N     WYOMING     B    B
UTAH        N    B     ARIZONA     A    B     COLORADO    N    B
NEW MEXICO  A    B     N DAKOTA    B    B     S DAKOTA    B    B
NEBRASKA    B    N     KANSAS      N    N     OKLAHOMA    N    N
N TEXAS     A    N     S TEXAS     A    B     W TEXAS     A    B
MINNESOTA   B    N     IOWA        B    N     MISSOURI    B    A
ARKANSAS    N    A     LOUISIANA   A    N     WISCONSIN   B    N
ILLINOIS    B    A     MISSISSIPPI A    N     MICHIGAN    N    N
INDIANA     N    A     OHIO        N    A     KENTUCKY    N    A
TENNESSEE   N    A     ALABAMA     A    N     NEW YORK    A    A
VERMONT     A    N     NEW HAMP    A    N     MAINE       A    N
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    N     GEORGIA     A    N
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  A    A
AK ALEUTIAN A    A     AK WESTERN  A    N     AK INT BSN  N    N
AK S INT    N    N     AK SO COAST N    N     AK PNHDL    B    B
8 to 14 day Outlook Table
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  B    N     OREGON      B    N     NRN CALIF   N    B
SRN CALIF   N    B     IDAHO       B    N     NEVADA      B    B
W MONTANA   B    A     E MONTANA   B    A     WYOMING     B    A
UTAH        B    B     ARIZONA     N    B     COLORADO    B    N
NEW MEXICO  N    B     N DAKOTA    B    N     S DAKOTA    B    N
NEBRASKA    B    N     KANSAS      N    A     OKLAHOMA    N    N
N TEXAS     A    B     S TEXAS     A    B     W TEXAS     A    B
MINNESOTA   B    N     IOWA        N    A     MISSOURI    N    A
ARKANSAS    N    N     LOUISIANA   A    N     WISCONSIN   N    N
ILLINOIS    N    A     MISSISSIPPI N    N     MICHIGAN    N    B
INDIANA     N    N     OHIO        N    N     KENTUCKY    N    A
TENNESSEE   N    A     ALABAMA     N    A     NEW YORK    A    B
VERMONT     A    B     NEW HAMP    A    B     MAINE       A    B
MASS        A    B     CONN        A    B     RHODE IS    A    B
PENN        A    B     NEW JERSEY  A    B     W VIRGINIA  N    N
MARYLAND    A    N     DELAWARE    A    N     VIRGINIA    A    N
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     N    A
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  B    B
AK ALEUTIAN A    A     AK WESTERN  N    A     AK INT BSN  B    N
AK S INT    N    N     AK SO COAST N    A     AK PNHDL    B    N
                           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 - ON AFOS AS
NFDPMDMRD.
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