PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST TUE DEC 25 2001 6 TO 10 DAY OUTLOOK FOR DEC 31 2001 - JAN 04 2002 MODEL COMPARISONS: THE VARIOUS MODEL SOLUTIONS TODAY CONTINUE TO BE GENERALLY CONSISTENT WITH EACH OTHER AND WITH THE OVERALL TREND SHOWN IN MODEL SOLUTIONS FOR THE PAST SEVERAL DAYS. THE NEGATIVE ANOMALY ASSOCIATED WITH THE EAST COAST TROUGH IS NOW JUST OFF THE NEW ENGLAND COAST SOUTH OF THE CANADIAN MARITIMES... WHICH IS THE WAY THE MRF AND ENSEMBLE MEAN WERE TRENDING YESTERDAY. AT HIGH LATITUDES THE PATTERN IS ALREADY TRENDING IN THE DIRECTION THAT DID NOT APPEAR UNTIL THE WEEK TWO MEANS YESTERDAY... WITH THREE BLOCKING CENTERS... ONE EACH OVER THE GREENALND SEA... THE NORTHWEST TERRITORIES... AND THE CHUKCHI SEA. ALL MODELS SHOWE THE CANADIAN CENTER AS THE DOMINANT ONE. . . . . . . . . THESE FACTORS... PLUS THE FACT THAT MODEL SKILL IS GENRALLY HIGH WHEN A POSITIVE PHASE OF THE PNA PATTERN IN IN PLACE... RESULT IN A CONSIDERABLY ABOVE AVERAGE CONFIDENCE IN THE EXPECTED ACCURACY OF TODAYS FORECAST. THE MODELS ARE TRENDING TOWARDS A PATTERN THAT HAS GOOD TELECONNECTIVITY... WITH A POSITIVE PHASE OF THE PNA PATTERN AND A VERY STRONG NEGATIVE PHASE OF THE NAO PATTERN... BUT THE SOMEWHAT WEAK ANOMALY FIELD SHOWN IN THE ENSEMBLE MEAN PROG COMPARED WITH THE STRONG PATTERNS SHOWN BY THE MRF... ECMWF AND DAVA MODELS... SUGGESTS SOME UNDERLYING UNCERTAINTIES... AT LEAST IN DETAILS AMONG THE MEMBERS. CONFIDENCE IN TODAYS FORECAST IS WELL ABOVE AVERAGE - RATED 5 ON A 1-5 SCALE. THE OFFICIAL 500 MB HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 30 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8... 20 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7... 20 PERCENT OF TODAYS MRF CENTERED ON DAY 8... 20 PERCENT OF TODAYS PRC (ACTUALLY NOW THE DAVA MODEL IS IN THIS SLOT) MEAN 500MB HEIGHT FORECAST CENTERED ON DAY 8 AND 10 PERCENT OF YESTERDAYS PRC (DAVA) CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: THE MRF ENSEMBLE THE TEMPERATURE PROG IS BASED PRIMARILY ON A COMPROMISE BETWEEN THE KLEIN AND NEURAL NET OBJECTIVE SPECIFICATIONS FROM THE BLEND WHICH WERE IN FAIR AGREEMENT... WITH THE KLEIN SOMEWHAT COLDER OVERALL AS IS OFTEN THE CASE. THE PRECIPITATION PROG IS BASED MOSTLY ON THE NEURAL NET GUIDANCE TOOLS FROM THE OFFICIAL FORECAST PATTERN AND A CONSENSUS OF THE NEURAL NET CATEGORICAL PROBABILITY DISTRIBUTION FROM THE ENSEMBLE MEMBERS. 8 TO 14 DAY OUTLOOK FOR JAN 02 - 08 2002 THE MEAN HEIGHT FORECASTS FROM THE MODELS APPEAR TO BE REASONABLE EXTENSIONS FROM THE 6-10 DAY PERIOD. THEY SHOW THE INITIAL BLOCK IN CANADA WEAKENING AND SPLITTING IKNTO TWO PARTS... WITH ONE PART SINKING SOUTHWARD TOWARDS BRITISH COLUMBIA AND THE OTHER PART RETROGRADING TOWARDS THE CHUKCHI SEA AREA. BOTH ARE PLAUSIBLE DEVELOPMENTS FROM THE 6-10 DAY PERIOD... BUT BOTH DO NOT USUALLY OCCUR SIMULTANEOUSLY. THE MRF SHOWS MOST OF THE ENERGY OF THE BLOCK RETROGRADING TO THE NORTHWEST COAST OF ALASKA AND A RENEWAL OF THE RESERVOIR OF ARCTIC AIR OVER THE INTERIOR OF ALASKA AND NORTHWEST CANADA... WITH HINTS THAT SOME OF IT MIGHT MOVE SOUTHEASTWARD INTO THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY BYT THE END OF THE WEEK TWO PERIOD. THEREFORE THIS PART OF THE FORECAST MUST BE RATED AS ONLY SOMEWHAT ABOVE NORMAL IN CONFIDENCE OVERALL AND PROBABLY NO BETTER THAN AVERAGE CONFIDENCE OVER ALASKA AND THE NORTHERN BORDER STATES OF THE LOWER 48. MOST ENSEMBLE MEMBERS SEEM TO FAVOR A SOMEWHAT MILDER SCENARIO WITH MOST OF THE BLOCK SUBSIDING TO SOUTHWESTERN CANADA LEADING TO MODERATING TEMPERATURES OVER THE NORTHERN GREAT PLAINS AND NO RENEWED BUILDUP OF ARCTIC AIR IN CANADA AND NORTHWESTERN CANADA. IN ANY CASE BELOW NORMAL HEIGHTS WITH A BROAD TROUGH OVER THE EASTERN AND SOUTHERN PART OF THE U.S. IS FAVORED BY BOTH THE MRF AND THE ENSEMBLE MEAN... RESULTING IN PERSISTENTLY COLD AND MOSTLY DRY WEATHER IN THESE AREAS... EXCEPT FOR CONTINUINMG LAKE EFFECT SNOWS. . . . . . . . . WEIGHTS ON THE VARIOUS MODELS IN THE BLEND FOR THE OFFICIAL 500 MB HEIGHT PROG FOR THE 8 TO 14 DAY PERIOD WERE ASSIGNED CONSIDERING THEIR RECENT CONSISTENCY AND THEIR RELATIVE ANOMALY CORRELATION SKILLS OBSERVED FOR THE PAST TWO MONTHS... AND CONSIST OF 35 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... 15 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 11... 25 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 7... 10 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 7... 5 PERCENT OF YESTERDAYS MRF CENTERED ON DAY 10... AND 10 PERCENT OF TODAYS ECMWF PROG CENTERED ON DAY 7. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON A CONSENSUS OF THE NEURAL NET AND KLEIN SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG WHICH WERE IN GOOD AGREEMENT. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE NEURAL NET GUIDANCE FROM THE OFFICIAL HEIGHT PROG AND THE ENSEMBLE MEMBERS... AND CONSIDERATION OF PAST OBSERVED PATTERNS WITH THE PRINCIPAL ANOMALY CENTERS MENTIONED ABOVE... AND GIVES A MOSTLY DRY PATTERN EXCEPT FOR THE PACIFIC NORTHWEST AND THE SOUTHERN TIER OF STATES... WHERE NEAR MEDIAN AND SMALL AREAS OF ABOVE MEDIAN TOTALS ARE MORE LIKELY. THE GENERAL ABSENCE OF PRECIPITATION FROM THE LOWER 48 IS CONSISTENT WITH THE DAILY MRF PROGS. FORECASTER: A. J. WAGNER NOTES: A WEB PAGE WITH FORECAST TOOLS ON IT IS AVAILABLE EACH DAY AT 3 PM AT: WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/SHORT_RANGE AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OTHERWISE - FORECASTS INCORPORATE FORECASTER INPUT. 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. 500 MB HEIGHT IS THE HEIGHT - IN METERS - ABOVE MEAN SEA LEVEL - AT 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. 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. . . . . . . . . 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. 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. DAVA MEANS DIVERGENT ANOMALY VORTICITY ADVECTION MODEL. THIS IS A BAROTROPIC MODEL WITH DIVERGENCE IN IT TO ALLOW MORE ACCURATE PREDICTION OF LONG WAVES THAN A NON-DIVERGENT 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. 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. THE NEXT MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON THURSDAY JANUARY 17. . . . . . . . . 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A A SRN CALIF A N IDAHO N B NEVADA A B W MONTANA N B E MONTANA N N WYOMING N A UTAH A B ARIZONA A B COLORADO N A NEW MEXICO N A N DAKOTA N B S DAKOTA N B NEBRASKA N N KANSAS B A OKLAHOMA B A N TEXAS N A S TEXAS B N W TEXAS B A MINNESOTA B B IOWA B B MISSOURI B B ARKANSAS B B LOUISIANA B N WISCONSIN B B ILLINOIS B B MISSISSIPPI B B MICHIGAN B N INDIANA B B OHIO B N KENTUCKY B B TENNESSEE B B ALABAMA B B NEW YORK B N VERMONT B N NEW HAMP B B MAINE B N MASS B B CONN B B RHODE ISL B B PENN B B NEW JERSEY B B W VIRGINIA B B MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA B B S CAROLINA B N GEORGIA B N FL PNHDL B N FL PENIN B A AK N SLOPE A N AK ALEUTIAN N A AK WESTERN A B AK INT BSN A B AK S INT A N AK S COAST A A AK PNHDL A N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A B NRN CALIF A N SRN CALIF A B IDAHO N B NEVADA A B W MONTANA A N E MONTANA N N WYOMING N N UTAH N B ARIZONA A B COLORADO N B NEW MEXICO N B N DAKOTA N A S DAKOTA N N NEBRASKA N N KANSAS N B OKLAHOMA B B N TEXAS B B S TEXAS B N W TEXAS N N MINNESOTA N N IOWA N N MISSOURI B B ARKANSAS B B LOUISIANA B N WISCONSIN B N ILLINOIS B B MISSISSIPPI B B MICHIGAN B N INDIANA B B OHIO B N KENTUCKY B B TENNESSEE B B ALABAMA B B NEW YORK B B VERMONT B B NEW HAMP B B MAINE B B MASS B B CONN B B RHODE ISL B B PENN B B NEW JERSEY B B W VIRGINIA B B MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA B B S CAROLINA B B GEORGIA B N FL PNHDL B N FL PENIN B A AK N SLOPE N B AK ALEUTIAN N A AK WESTERN A B AK INT BSN A B AK S INT A B AK S COAST A N 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 N - NEAR NORMAL 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. NNNN NNNN