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PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300PM EST THURSDAY JAN 31 2013 30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2013 THE MONTHLY OUTLOOK FOR FEBRUARY 2012 IS UPDATED USING THE LATEST GUIDANCE FROM NUMERICAL MODELS, INCLUDING THE NCEP CLIMATE FORECAST SYSTEM VERSION 2 (CFSV2) FEBRUARY FORECAST AND THE NORTH AMERICAN ENSEMBLE FORECAST SYSTEM (NAEFS) FORECAST FOR THE NEXT 2 WEEKS. NAEFS IS A MULTI-MODEL ENSEMBLE (MME) CONSOLIDATION OF BIAS-CORRECTED FORECASTS FROM THE NCEP GLOBAL ENSEMBLE FORECAST SYSTEM (GEFS) AND THE ENSEMBLE PREDICTION SYSTEM FROM ENVIRONMENT CANADA. NUMERICAL WEATHER PREDICTION FOR THE SHORTER RANGE IS USED WHEN ANOMALIES ARE LARGE ENOUGH TO IMPACT THE MONTHLY AVERAGES OF TEMPERATURE OR PRECIPITATION. ACROSS THE EQUATORIAL PACIFIC, SST ANOMALIES REMAIN RELATIVELY UNCHANGED THROUGH JANUARY, WHILE THE LATEST WEEKLY NINO 3.4 ANOMALY HAS WARMED DURING THE SECOND HALF OF JANUARY TO -0.2C. THE MJO CONTINUES TO BE ACTIVE DURING THE SECOND HALF OF THE MONTH AND IS PREDICTED TO CONTINUE INTO THE FIRST HALF OF FEBRUARY. CURRENT MODEL FORECASTS FOR THE FIRST 2 WEEKS OF THE MONTH, HOWEVER, ARE NOT CONSISTENT WITH EXPECTED IMPACTS OF THE CURRENT MJO. THE FEBRUARY MONTHLY UPDATED FORECAST RELIES PRIMARILY ON THE MODEL GUIDANCE AND IN PARTICULAR THE MODEL FORECASTS FOR THE FIRST TWO WEEKS OF THE MONTH. EARLY IN THE MONTH MODELS INDICATE A MID-LEVEL RIDGE OVER THE CENTER OF THE U.S. AND A TROUGH OVER THE SOUTHWEST. THE UPDATED TEMPERATURE OUTLOOK FOR FEBRUARY INDICATES ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR THE SOUTH-CENTRAL U.S., LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE ENHANCED FOR NORTHERN CALIFORNIA, OREGON, AND NORTHWEST NEVADA. PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED FOR SOUTHEASTERN ALASKA AND THE ALASKAN PANHANDLE. THE UPDATED PRECIPITATION OUTLOOK FOR FEBRUARY INDICATES ENHANCED PROBABILITIES OF ABOVE MEDIAN PRECIPITATION FOR THE NORTHERN PLAINS AND WESTERN GREAT LAKES REGION AND FOR THE SOUTHWEST NEAR THE FOUR CORNERS REGION, AS WELL AS FOR WESTERN AND NORTHERN ALASKA. PROBABILITIES OF BELOW MEDIAN PRECIPITATION ARE ENHANCED FOR THE PACIFIC COAST OF OREGON AND NORTHERN CALIFORNIA AND ALONG THE GULF COAST. THE MESSAGE FOR THE HALF-MONTH LEAD MONTHLY OUTLOOK MADE EARLIER IN JANUARY FOLLOWS: ENSO-NEUTRAL CONDITIONS CONTINUED DURING DECEMBER 2012. THE MOST RECENT WEEKLY SST ANOMALY FOR THE NINO 3.4 REGION IS -0.6 C HAVING COOLED DURING THE LAST MONTH. SUBSURFACE EQUATORIAL HEAT CONTENT TO 300 METERS DEPTH CONTINUED TO DECREASE IN DECEMBER 2012. OUTGOING LONGWAVE RADIATION ANOMALIES ARE NEGATIVE OVER THE MARITIME CONTINENT INDICATING ENHANCED CONVECTION AND POSITIVE OVER THE CENTRAL PACIFIC WHERE CONVECTION IS SUPPRESSED. ENSO-NEUTRAL CONDITIONS ARE EXPECTED TO PERSIST THROUGH FEBRUARY. THERE IS CURRENTLY AN ACTIVE MJO, WHICH HAS CONTRIBUTED TO THE PATTERNS OF ANOMALOUS CONVECTION DESCRIBED ABOVE. EVOLUTION OF MJO-RELATED CONVECTION MAY IMPACT THE FEBRUARY TEMPERATURE AND PRECIPITATION OVER NORTH AMERICA. A SUDDEN STRATOSPHERIC WARMING (SSW) BEGAN JANUARY 6 AND IS EXPECTED TO CONTINUE INTO FEBRUARY. SSW HAS BEEN ASSOCIATED WITH SUBSEQUENT TROPOSPHERIC ANOMALIES AND CHANGES TO THE TEMPERATURE PATTERN OVER NORTH AMERICA, INCLUDING BELOW NORMAL TEMPERATURES IN THE EASTERN U.S. THE TEMPERATURE OUTLOOK FOR FEBRUARY 2013 INDICATES ELEVATED PROBABILITIES OF BELOW NORMAL TEMPERATURES FROM THE NORTHERN ROCKIES ACROSS THE NORTHERN PLAINS INTO THE WESTERN GREAT LAKES REGION AND UPPER MISSISSIPPI VALLEY. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ELEVATED FROM CALIFORNIA INTO THE SOUTHWEST, AS WELL AS FOR NORTHERN ALASKA. THE FORECAST TEMPERATURE PATTERN FOR FEBRUARY IS SUPPORTED BY DYNAMICAL MODEL FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFSV2) AND THE MODELS OF THE NATIONAL MULTI-MODEL ENSEMBLE (NMME) AND THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME), INCLUDING THE FRACTION OF ENSEMBLE MEMBERS FROM THE NMME AND CFSV2 FORECASTING ABOVE AND BELOW NORMAL TEMPERATURES. THE PRECIPITATION OUTLOOK FOR FEBRUARY 2013 INDICATES ELEVATED PROBABILITIES FOR BELOW MEDIAN PRECIPITATION FOR THE SOUTHWEST QUARTER OF THE U.S. AND ALONG THE GULF COAST. PROBABILITIES OF ABOVE MEDIAN PRECIPITATION FOR FEBRUARY EXTEND ACROSS THE NORTHERN PLAINS TO THE MISSISSIPPI RIVER. ELEVATED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION ARE ALSO INDICATED FOR NORTHWEST ALASKA. THE FORECAST PRECIPITATION PATTERN FOR FEBRUARY IS SUPPORTED BY DYNAMICAL MODEL FORECASTS FROM THE CFSV2 AND THE MODELS OF THE NMME AND IMME. AREAS WHERE THE LIKELIHOODS OF MONTHLY MEAN TEMPERATURE AND MONTHLY ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES OF BELOW, NEAR AND ABOVE NORMAL TEMPERATURE OR PRECIPITATION ARE SHOWN AS EQUAL CHANCES (EC). THE MAIN FACTORS WHICH USUALLY INFLUENCE THE MONTHLY CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH COMPRISE ENSO. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM THREE OR MORE DECADES INTO EL NINO, NEUTRAL AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "COMPOSITES" AND USED AT TIMES TO SUBJECTIVELY MODIFY THE FORECAST. 2) TRENDS - APPROXIMATED BY THE OCN TOOL AS THE DIFFERENCE BETWEEN THE MOST RECENT 10-YEAR MEAN OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN LOCATION AND TIME OF YEAR AND THE 30-YEAR CLIMATOLOGY PERIOD (CURRENTLY 1981-2010). 3) THE TROPICAL 30-60 DAY OSCILLATION - CALLED THE MADDEN JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE ARCTIC OSCILLATION (AO), THE SIMILAR NORTH ATLANTIC OSCILLATION (NAO), AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING BOREAL WINTER AND ARE GENERALLY CONSIDERED TO HAVE LOW PREDICTABILITY. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 6) PERSISTANTLY DRY OR WET SOILS IN THE SPRING AND SUMMER AND SNOW AND ICE COVER ANOMALIES IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS AND ACT AS A KIND OF MEMORY IN THE CLIMATE SYSTEM. 7) STATISTICAL FORECAST MODELS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOG (CA), AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM VERSION 2 (CFSV2) AND FOR ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE FORECAST SYSTEM (GEFS). THE EARLIER VERSION OF THE CFS MODEL WAS DISCONTINUED AS OF OCTOBER, 2012. AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE (NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED. FORECASTER: DAN COLLINS THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD. THE PROBABILITY ANOMALIES FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS. THE NEXT MONTHLY OUTLOOK...FOR MAR ... WILL BE ISSUED ON THU FEB 21 2013 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$
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