PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE WASHINGTON DC
3 PM EST MON FEB 18 2002

6 TO 10 DAY OUTLOOK FOR FEB 24 - 28 2002
         .         .         .         .         .         .         .         .
MODEL COMPARISONS: MODELS ARE IN GOOD AGREEMENT FOR ONLY THE FIRST TWO DAYS ON
THEIR PREDICTIONS OF THE 500 HPA CIRCULATION...WITH MORE SIGNIFICANT DIFFER-
ENCES IN A SPLIT FLOW PATTERN ALREADY BEGINNING TO SHOW UP BY DAY 3.  HOWEVER 
BY DAY 5...THE MRF AND UKMET SOLUTIONS INITIALIZED AT 00Z ARE AT LEAST HINTING
AT SOME SIMILARITIES THAT FAVOR A RIDGE ALONG THE WEST COAST OF NORTH AMERICA
...AND A POSITIVELY TILTED TROUGH FROM NORTHEASTERN TO SOUTHWESTERN CANADA...
AND RELATIVELY LOW AMPLITUDE FLOW WITH EMBEDDED SHORT WAVES MIGRATING ACROSS 
THE CONTERMINOUS U.S.  FOR DAYS 6-10...THE MRF AND ECMWF MODEL RUNS PORTRAY A 
PATTERN WHICH MAINTAINS THE WEST COAST RIDGE AND AN EASTERN U.S. TROUGH WITH
CONSIDERABLE AMPLITUDE.  THE DAVA EXTENSION FROM THE DAY 5 ENSEMBLE MEAN PROG
SHOWS A SIMILARLY PHASED PATTERN...THOUGH WITH MUCH LESS AMPLITUDE OVERALL.
IF THE WEST COAST RIDGE AMPLIFIES MORE THAN EXPECTED DURING THIS PERIOD...WE
WOULD LIKELY SEE THE ANOMALOUS COLD OVER THE LOWER 48 TO BE A BIT FURTHER WEST.
         .         .         .         .         .         .         .         . 
CONFIDENCE IN TODAYS FORECAST IS SLIGHTLY BELOW AVERAGE...2 ON A 1-5 SCALE.

THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD IS A BLEND OF
50 PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 8... 25 PERCENT OF TODAYS
HIGH RESOLUTION MRF CENTERED ON DAY 8... AND 25 PERCENT OF TODAYS ECMWF RUN
CENTERED ON DAY 7.  TODAYS ENSEMBLE MEAN D+8 PROG COULD NOT BE INCLUDED IN
THE BLENDED HEIGHT PROG...BUT IT WAS AVAILABLE FOR INCLUSION INTO THE WEEK 2
FORECAST.

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MODEL OF THE DAY:  DAVA

THE TEMPERATURE PROG IS BASED PRIMARILY ON THE MRF ENSEMBLE MEAN 850 HPA BIAS-
CORRECTED TEMPERATURE OUTPUT... AND TO A LESSER DEGREE ON THE USUAL KLEIN AND 
NEURAL NET TEMPERATURE SPECIFICATIONS FROM THE OFFICIAL BLEND.

THE PRECIPITATION PROG IS BASED MOSTLY ON THE MRF ACCUMULATED PRECIPITATION
CORRECTED FOR RECENT BIASES...AND IS ALSO SUBJECTIVELY MODIFIED TO BE CONSIS-
TENT WITH THE OFFICIAL 500 HPA HEIGHT PROG.  TOWARDS THE MIDDLE OF THE 6-10
DAY PERIOD...THE MRF SHOWS A SHORT WAVE DIGGING SOUTHEASTWARD ACROSS THE CEN-
TRAL AND SOUTHERN PLATEAU...WITH GULF MOISTURE BEGINNING TO MOVE UPSLOPE
OVER THE HILL COUNTRY OF CENTRAL TEXAS.
     

8 TO 14 DAY OUTLOOK FOR FEB 26 - MAR 4 2002
                                          
MODEL COMPARISONS:   BY WEEK 2...THE WEST COAST RIDGE IS PREDICTED TO RETRO-
GRADE SOMEWHAT OVER THE EASTERN PACIFIC AND GULF OF ALASKA REGION...ACCORDING
TO THE MRF AND THE ENSEMBLE MEAN NUMERICAL MODELS.  THIS IN TURN WOULD ALLOW
ANOMALOUSLY COLD AIR TO DOMINATE MUCH OF THE EAST...WITH A TENDENCY TO MOVE
WESTWARD AS WELL ONCE THE INITIAL COLD AIRMASS DEPARTS THE LOWER 48.  THE
WARMTH OVER ALASKA ALSO SHIFTS WESTWARD TOWARD THE BERING SEA...WHILE COLDER
TEMPERATURES SPREAD ACROSS EASTERN PORTIONS OF THE 49TH STATE.
  
 
         .         .         .         .         .         .         .         . 
CONFIDENCE IN TODAYS FORECAST IS BELOW AVERAGE...RATED 2 ON A SCALE OF 1-5...
LARGELY BECAUSE OF THE UNCERTAINTIES ASSOCIATED WITH THE PRECEDING 6-10 DAY
PERIOD.

THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD CONSISTS OF
70 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11... AND 30 PERCENT OF TO-
DAYS MRF CENTERED ON DAY 11.

THE TEMPERATURE OUTLOOK IS BASED MAINLY ON THE MRF ENSEMBLE 850 HPA TEMPERATURE
ANOMALIES CORRECTED FOR RECENT MODEL BIASES...AND IS ALSO SUBJECTIVELY MODIFIED
TO BE CONSISTENT WITH AN APPARENT WESTWARD DISPLACEMENT OF THE LONG WAVE PAT-
TERN OVER NORTH AMERICA.

THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE MRF ACCUMULATED PRECIPI-
TATION CORRECTED FOR RECENT ERRORS/BIASES.

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:-----------------------------------------------------

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.

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 - CONTINENTAL 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.

LA NINA - THE COLD 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.

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 SURFACCE 
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.

MRF ENSEMBLE - A SET OF MRF FORECASTS WHICH ARE ALL VALID AT THE SAME TIME
BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS.  THERE ARE CURRENTLY
25 MEMBERS IN THE MRF ENSEMBLE.  THE AVERAGE OF THESE IS THE MRF 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 EAST- 
WARD 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 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 ON THURSDAY MARCH 14.
 
6 to 10 day Outlook Table
 
STATE      TEMP PCPN   STATE     TEMP  PCPN   STATE     TEMP PCPN
WASHINGTON  A    A     OREGON      A    N     NRN CALIF  A    N 
SRN CALIF   A    B     IDAHO       N    N     NEVADA     A    B 
W MONTANA   N    A     E MONTANA   B    N     WYOMING    N    B
UTAH        A    B     ARIZONA     A    B     COLORADO   N    B 
NEW MEXICO  A    B     N DAKOTA    B    N     S DAKOTA   B    B 
NEBRASKA    B    B     KANSAS      N    B     OKLAHOMA   N    B 
N TEXAS     A    A     S TEXAS     A    A     W TEXAS    A    A 
MINNESOTA   B    B     IOWA        B    B     MISSOURI   N    B 
ARKANSAS    N    B     LOUISIANA   N    N     WISCONSIN  B    B 
ILLINOIS    N    N     MISSISSIPPI N    B     MICHIGAN   B    N 
INDIANA     N    N     OHIO        N    N     KENTUCKY   N    N 
TENNESSEE   N    B     ALABAMA     N    B     NEW YORK   N    A 
VERMONT     N    A     NEW HAMP    N    A     MAINE      N    A 
MASS        N    A     CONN        N    A     RHODE ISL  N    A 
PENN        N    A     NEW JERSEY  N    A     W VIRGINIA N    N 
MARYLAND    N    N     DELAWARE    N    N     VIRGINIA   N    N 
N CAROLINA  N    B     S CAROLINA  N    B     GEORGIA    N    B 
FL PNHDL    N    B     FL PENIN    N    B     AK N SLOPE A    B 
AK ALEUTIAN N    A     AK WESTERN  A    N     AK INT BSN A    B 
AK S INT    A    B     AK S COAST  A    B     AK PNHDL   N    B 

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