PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300PM EDT THURSDAY JUL 31 2014 30-DAY OUTLOOK DISCUSSION FOR AUGUST 2014 THE UPDATED 30-DAY OUTLOOK FOR AUGUST 2014 DEPICTS SIGNIFICANT CHANGES FROM THE 0.5-MONTH LEAD OUTLOOK ISSUED JULY 17. THIS IS PARTLY DUE TO SUBSTANTIAL VARIATIONS IN DAY-TO-DAY RUNS OF THE CFS, POTENTIALLY RELATED TO TWO WESTERN PACIFIC TYPHOONS AND THEIR ASSOCIATED INFLUENCE ON THE MID-LATITUDE CIRCULATION UPSTREAM OF THE UNITED STATES. RECENTLY, A WESTERN PACIFIC TYPHOON WAS ABSORBED INTO THE MID-LATITUDE CIRCULATION OFF EAST ASIA, AND MAY HAVE BEEN RELATED TO AN AMPLIFICATION OF THE FLOW PATTERN DOWNSTREAM OVER THE UNITED STATES, FAVORING A WESTERN RIDGE AND EASTERN TROUGH. IT IS CONCEIVABLE THAT THIS SITUATION COULD OCCUR AGAIN AS TWO WESTERN PACIFIC TYPHOONS ARE PREDICTED TO GET CAUGHT UP IN THE WESTERLIES AND USHERED DOWNSTREAM TOWARDS THE UNITED STATES. THE UPDATED 30-DAY OUTLOOK IS BASED PRIMARILY ON FORECASTS OF TEMPERATURE AND PRECIPITATION PATTERNS OUT THROUGH THE EXTENDED-RANGE (THROUGH THE FIRST HALF OF AUGUST), AND RECENT RUNS OF THE CFS. THE ANTICIPATED BACKGROUND 500-HPA CIRCULATION PATTERN THROUGH AT LEAST THE MIDDLE OF AUGUST FAVORS A TROUGH NEAR THE ALEUTIANS, A RIDGE OVER THE FAR WESTERN CONUS, AND ANOTHER TROUGH OVER THE EAST-CENTRAL CONUS. ENSO COMPOSITES PLAYED A VERY SMALL ROLE IN THIS OUTLOOK. IT IS IMPORTANT TO POINT OUT THAT THE LATEST RUNS OF THE GFS (AS OPPOSED TO CFS) MODEL PREDICT A RELAXATION OF THE SOUTHWEST MONSOON DURING WEEK 2, AFTER AN ACTIVE WEEK 1 PERIOD. HOWEVER, THIS RELAXATION APPEARS SHORT-LIVED AND IT WAS DECIDED NOT TO MODIFY THE 30-DAY PRECIPITATION OUTLOOK AS IT NOW STANDS. THE UPDATED MONTHLY TEMPERATURE OUTLOOK FOR AUGUST 2014 FAVORS ABOVE-NORMAL MEAN TEMPERATURES OVER THE FAR WESTERN CONUS, FLORIDA AND ADJACENT PORTIONS OF BOTH GEORGIA AND ALABAMA, AND ALASKA. BELOW-NORMAL MONTHLY MEAN TEMPERATURES ARE FAVORED OVER THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND MIDDLE MISSISSIPPI VALLEY, AND THE WESTERN GREAT LAKES REGION. SINCE THE RELEASE OF THE 0.5-MONTH LEAD TEMPERATURE OUTLOOK ON JULY 17TH, THE CFS HAS TRENDED COLDER OVER MOST OF THE CONUS, ESPECIALLY OVER THE WEST-CENTRAL AND NORTH-CENTRAL STATES. THE LARGE AREAS OF FAVORED ABOVE-NORMAL MONTHLY MEAN TEMPERATURES ON THE PREVIOUS OUTLOOK HAVE BEEN REDUCED IN SIZE TO INCLUDE ONLY THE FAR WEST, FLORIDA. THE CFS PREDICTIONS FOR ALASKA HAVE BEEN FAIRLY STABLE, WITH THE BEST CHANCES FOR RELATIVE WARMTH OVER THE SOUTHERN AND SOUTHWESTERN PORTIONS OF ALASKA, WITH DECREASING PROBABILITIES FARTHER NORTH. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-NORMAL MONTHLY MEAN TEMPERATURES IS INDICATED. THE UPDATED MONTHLY PRECIPITATION OUTLOOK INDICATES ELEVATED ODDS OF ABOVE-MEDIAN PRECIPITATION FROM EASTERN ARIZONA AND COLORADO EASTWARD TO INCLUDE NEW MEXICO AND THE SOUTH-CENTRAL PLAINS. THERE ARE ELEVATED ODDS OF BELOW-MEDIAN PRECIPITATION OVER SOUTHERN TEXAS. THESE TWO SIGNALS ARE REASONABLY CONSISTENT WITH PRECIPITATION DYNAMICAL MODEL GUIDANCE OUT THROUGH 2 WEEKS. IT IS THOUGHT THAT MONSOONAL ACTIVITY WILL BE MORE CONCENTRATED IN THE EASTERN MONSOON REGION (NEW MEXICO, COLORADO, WEST TEXAS), THOUGH AREAS FARTHER WEST ARE ALSO EXPECTED TO RECEIVE MONSOONAL MOISTURE. IN ADDITION, A MEAN FRONTAL BOUNDARY IS PREDICTED TO BE POSITIONED SOMEWHERE IN THE VICINITY OF COLORADO AND WYOMING SOUTHEASTWARD TOWARDS ARKANSAS. RECENT RUNS OF THE CFS CONTINUE TO FAVOR ABOVE-MEDIAN PRECIPITATION ACROSS MOST OF THE INTERIOR WEST, AS WELL AS BELOW-MEDIAN PRECIPITATION IN THE GENERAL VICINITY OF THE GULF COAST. IT IS THOUGHT THAT THE CFS IS OVERDOING BOTH OF THESE SIGNALS, ESPECIALLY THE FAVORED WETNESS IN THE INTERIOR WEST. THE SIGNAL FOR ENHANCED CHANCES OF BELOW-MEDIAN PRECIPITATION IN SOUTHERN TEXAS IS FAIRLY ROBUST. A FINAL CONSIDERATION INVOLVES DROUGHT IN THE SOUTHEAST. WIDESPREAD DETERIORATION OF DROUGHT CONDITIONS APPEARS TO HAVE BEEN PREVENTED BY THE PERSISTENT PRESENCE OF AN AMPLIFIED UPSTREAM TROUGH OVER THE EAST-CENTRAL STATES. THIS IN TURN APPEARS TO BE RELATED TO THE INCORPORATION OF A WESTERN PACIFIC TYPHOON INTO THE WESTERLIES WELL UPSTREAM OF THE U.S. SINCE WE COULD SEE A SIMILAR SITUATION RECUR IN THE NEXT WEEK, IT IS DEEMED TOO RISKY TO FORECAST ANY BELOW-MEDIAN PRECIPITATION NEAR MOST OF THE GULF COAST AND SOUTHEAST. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-MEDIAN PRECIPITATION AMOUNTS IS INDICATED. -------------------------------------------------------------------------- PREVIOUS DISCUSSION FROM 7/17 IS BELOW. -------------------------------------------------------------------------- RECENT OCEANIC CONDITIONS ACROSS THE TROPICAL PACIFIC CONTINUE TO SUPPORT THE FAVORED TRANSITION FROM ENSO-NEUTRAL TO EL NINO LATER THIS SUMMER. HOWEVER, THE ATMOSPHERE REMAINS SOMEWHAT DECOUPLED WITH THE RELATIVELY WARM SEA SURFACE TEMPERATURES (SST) AND THE SUBSURFACE WARMTH OF THE TROPICAL PACIFIC. THESE OBSERVATIONS SUGGESTS THAT THE ENSO PHASE IS STILL NEUTRAL. IT NOW APPEARS THAT THE PREDICTED EL NINO MAY PEAK AT WEAK TO MODERATE STRENGTH BY LATE AUTUMN/EARLY WINTER, COMPARED TO PREVIOUS EXPECTATIONS OF FAVORED MODERATE INTENSITY PEAKING DURING THE SAME PERIOD. DURING THE PAST FEW WEEKS, POSITIVE SST ANOMALIES PERSISTED (THOUGH WEAKENED SLIGHTLY) IN THE EASTERN EQUATORIAL PACIFIC, AND ANOMALIES ARE CLOSE TO ZERO IN THE CENTRAL PACIFIC (180W-150W). THE LATEST WEEKLY SST DEPARTURE IN THE EAST-CENTRAL PACIFIC (NINO 3.4 REGION) IS +0.3C. THE OCEANIC HEAT CONTENT (SUBSURFACE TEMPERATURE ANOMALIES IN THE UPPERMOST 300-METERS OF THE EASTERN AND CENTRAL EQUATORIAL PACIFIC) DECLINED FAIRLY RAPIDLY IN THE LAST FEW MONTHS, AND ANOMALIES ARE NOW CLOSE TO ZERO. DURING THIS SAME PERIOD, THE LARGE RESERVOIR OF SUBSURFACE WARMTH OVER THE CENTRAL AND EASTERN EQUATORIAL PACIFIC HAS DIMINISHED SIGNIFICANTLY IN COVERAGE AND MAGNITUDE, AND IS NOW CONFINED FROM ABOUT 145W-85W, AND EXTENDS DOWN TO A DEPTH OF ABOUT 75 METERS. DURING THE PAST 30-DAYS, TROPICAL RAINFALL WAS SLIGHTLY ABOVE-AVERAGE IN INDONESIA AND THE WESTERN EQUATORIAL PACIFIC, AND LOW-LEVEL (850-HPA) WINDS WERE NEAR LONG-TERM AVERAGES ACROSS MOST OF THE EQUATORIAL PACIFIC. MONTHLY MEAN TEMPERATURES FOR AUGUST 2014 ARE FAVORED TO BE ABOVE-NORMAL ACROSS THE SOUTHERN HALVES OF BOTH THE LOWER GREAT PLAINS AND MISSISSIPPI VALLEY, THE SOUTHEAST, TENNESSEE VALLEY, AND MUCH OF THE MID-ATLANTIC REGION, AS WELL AS IN THE PACIFIC NORTHWEST, MOST OF NEVADA AND CALIFORNIA, AND ALASKA. BELOW-NORMAL MONTHLY MEAN TEMPERATURES ARE MOST LIKELY OVER PORTIONS OF THE NORTHERN GREAT PLAINS, UPPER MISSISSIPPI VALLEY, AND UPPER GREAT LAKES REGION. THIS OUTLOOK IS BASED PRIMARILY ON RECENT RUNS OF THE CFS DYNAMICAL MODEL, NMME, IMME, AND THEIR CONSTITUENT CLIMATE MODELS. IT IS ALSO BASED ON, TO A LESSER DEGREE, THE CAS, SMLR, CCA, AND OCN STATISTICAL TOOLS, AS WELL AS SOIL MOISTURE CONSIDERATIONS. AREAS OF DIMINISHED CONFIDENCE INCLUDE THE FOUR CORNERS MONSOON REGION (WHERE THE CFS IN PARTICULAR PREDICTS ENHANCED ODDS OF BELOW-NORMAL TEMPERATURES, AS OPPOSED TO THE EUROPEAN AND OTHER CLIMATE MODELS WHICH FAVOR NEAR OR EVEN ABOVE-NORMAL TEMPERATURES), AND NORTHERN ALASKA. IN THIS LATTER AREA, RECENT RUNS OF THE CFS APPEAR TO BE TOO COLD, ESPECIALLY GIVEN THE ANOMALOUSLY LOW ICE COVER OBSERVED OVER THE BEAUFORT SEA. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-NORMAL MONTHLY MEAN TEMPERATURES IS INDICATED. PRECIPITATION FOR AUGUST 2014 IS ANTICIPATED TO BE ABOVE-MEDIAN OVER MUCH OF THE INTERIOR WEST. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE SLIGHTLY FAVORED FOR MOST OF THE GULF COAST REGION, AND PORTIONS OF GEORGIA AND SOUTH CAROLINA. THE OUTLOOK IS BASED PRIMARILY ON THE SAME TOOLS NOTED ABOVE FOR TEMPERATURE. FOR THE SOUTHWEST, IT IS CONSISTENT WITH THE EXPECTATION OF BOTH AN ENHANCED MONSOON AND AN ENHANCED EASTERN PACIFIC HURRICANE SEASON. IN THE NORTHERN HIGH PLAINS AND NORTHERN ROCKIES, IT IS MOST LIKELY DUE TO FRONTAL ACTIVITY. PERHAPS THE MOST UNCERTAIN PART OF THIS FORECAST IS THE ANTICIPATED REGION OF FAVORED BELOW-MEDIAN RAINFALL OVER THE GULF COAST STATES AND ADJACENT PORTIONS OF GEORGIA AND SOUTH CAROLINA. THE CFS AND IMME SUPPORT SOME EXTENSION OF THIS AREA OF RELATIVE DRYNESS THROUGH NORTH CAROLINA AND PARTS OF THE MID-ATLANTIC REGION, WHILE THE NMME INCLUDES ONLY TEXAS AND LOUISIANA. THIS IS COMPLICATED BY WHAT APPEARS TO BE THE EARLY STAGES OF A FLASH DROUGHT TRYING TO DEVELOP FROM ALABAMA AND THE FLORIDA PANHANDLE NORTHEASTWARD INTO SOUTHWESTERN VIRGINIA. THE PRECIPITATION FORECAST FOR THE UPCOMING 7-DAYS CALLS FOR SIGNIFICANT RAINFALL (RANGING FROM 0.5 TO 4 INCHES) TO OCCUR ACROSS THE GULF COAST REGION AND SOUTHEAST, WHICH MAY (AT LEAST TEMPORARILY) HELP TO OFFSET THE RAPIDLY DETERIORATING SOIL MOISTURE CONDITIONS NOW SETTING UP IN THE SOUTHEAST. THE OFFICIAL CPC PRECIPITATION OUTLOOK IS THOUGHT TO BE A REASONABLE COMPROMISE BETWEEN VARIOUS COMPETING FACTORS. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-MEDIAN PRECIPITATION AMOUNTS IS INDICATED. THE MAIN FACTORS THAT 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) PERSISTENTLY 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 (CFS) AND FOR THE ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE FORECAST SYSTEM (GEFS). AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE (NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED. FORECASTER: ANTHONY ARTUSA 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 SEP ... WILL BE ISSUED ON THU AUG 21 2014 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$