PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU JUN 21 2007 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS WHICH USUALLY INFLUENCE SEASONAL CLIMATE INCLUDE: 1) EL NINO AND LA NINA - WHICH COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO 2) TRENDS - APPROXIMATED BY 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 1971-2000). THE OCN TOOL REPRESENTS THE TREND. 3) TROPICAL 30-60-DAY OSCILLATION - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE COLD SEASONS. THESE PHENOMENA ARE CURRENTLY KNOWN TO BE PREDICTABLE ONLY OVER A WEEK OR SO. 5) PERSISTENTLY DRY OR WET SOILS IN THE 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. 6) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA)... AND SCREENING MULTIPLE LINEAR REGRESSION (SMLR). 7) DYNAMICAL FORECAST MODELS... INCLUDING NCEPS CLIMATE FORECAST SYSTEM (CFS). 8) AN OBJECTIVE CONSOLIDATION (CALLED CON IN THE TEXT) OF THE OCN... CCA... SMLR AND CFS FORECASTS IS USED AS A FIRST-GUESS IN PREPARING THE FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF OUR FORECAST TOOLS. SEA SURFACE TEMPERATURES (SSTS) ALONG THE EQUATOR ARE CURRENTLY SLIGHTLY ABOVE NORMAL IN THE CENTRAL AND WESTERN PACIFIC OCEAN... AND BELOW NORMAL IN THE EASTERN PACIFIC. SSTS IN THE NINO 3.4 REGION OF THE EAST CENTRAL PACIFIC OCEAN (THE MEAN TEMPERATURE FROM 5N TO 5S AND 170W TO 120W) GIVE A GOOD INDICATION OF THE STRENGTH OF EL NINO (WARM SSTS) OR LA NINA (COLD SSTS). SSTS IN THE NINO 3.4 REGION ARE CURRENTLY CLOSE TO THEIR LONG TERM AVERAGE SUGGESTING ENSO IS NEUTRAL. EARLY IN THE YEAR A RAPID DECREASE IN NINO 3.4 SST ANOMALIES... THE DEVELOPMENT OF BELOW NORMAL SSTS NEAR THE EQUATOR ALONG THE SOUTH AMERICAN COAST... AND DYNAMICAL MODEL PREDICTIONS OF PACIFIC SSTS RAISED CONCERNS ABOUT A TRANSITION TO LA NINA CONDITIONS BY MID 2007. HOWEVER... BELOW NORMAL SSTS HAVE NOT DEVELOPED IN THE CENTRAL PACIFIC... AND SUB-SURFACE OCEAN TEMPERATURES IN THE CENTRAL PACIFIC HAVE RECENTLY BECOME SLIGHTLY ABOVE NORMAL. THESE INDICATORS MAKE A TRANSITION TO LA NINA CONDITIONS MUCH LESS LIKELY IN THE NEXT FEW MONTH THAN HAD APPEARED EARLIER IN THE YEAR. MOST DYNAMIC MODELS CONTINUE TO PREDICT A TRANSITION TO LA NINA CONDITIONS BY LATE SUMMER... ALTHOUGH STATISTICAL MODELS PREDICT THAT CENTRAL PACIFIC SSTS WILL DRIFT ONLY SLIGHTLY DOWNWARD... INDICATING NEUTRAL ENSO OR ONLY VERY WEAK LA NINA CONDITIONS. THUS... AT THIS TIME NEUTRAL ENSO CONDITIONS ARE ANTICIPATED THROUGH JAS WITH THE DEVELOPMENT OF LA NINA CONDITIONS POSSIBLE LATER IN THE FALL... ALTHOUGH AT THIS TIME IT APPEARS THAT LA NINA CONDITIONS WILL BE WEAK. THUS ENSO HAS A LIMITED IMPACT ON THIS SERIES OF FORECASTS. THE TEMPERATURE OUTLOOK FOR JULY-AUGUST-SEPTEMBER (JAS) 2007 CALLS FOR ABOVE NORMAL TEMPERATURES OVER MOST OF THE U.S. AMPLE SOIL MOISTURE SHOULD HELP MODERATE TEMPERATURES IN THE GREAT PLAINS AND BRING THE TEMPERATURES MORE IN LINE WITH LONG TERM CLIMATOLOGY... WITH EQUAL CHANCES OF BELOW - NEAR - OR ABOVE NORMAL TEMPERATURES. THE CHANCES OF ABOVE NORMAL TEMPERATURES ARE SUBSTANTIALLY HIGHER THAN NORMAL THROUGHOUT THE SOUTHWESTERN CONUS... HOWEVER SSTS ALONG THE SOUTHERN CALIFORNIA COAST ARE NEAR OR SLIGHTLY BELOW NORMAL AND SHOULD REDUCE THE CHANCES OF ABOVE NORMAL TEMPERATURES IN ADJACENT AREAS TO THEIR LONG TERM AVERAGES. BELOW MEDIAN PRECIPITATION IS EXPECTED IN PORTIONS OF THE PACIFIC NORTHWEST AND THE GREAT BASIN FOR JAS 2007. ELSEWHERE THERE ARE EQUAL CHANCES OF ABOVE- BELOW- OR NEAR-MEDIAN PRECIPITATION. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE: HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS THE PATTERN OF ANOMALOUS SEA SURFACE TEMPERATURES (SSTS) IN RECENT WEEKS IS CONSISTENT WITH ENSO-NEUTRAL CONDITIONS IN THE TROPICAL PACIFIC... WITH SSTS AVERAGING ABOUT .5 DEGREES C ABOVE NORMAL ALONG THE EQUATOR WEST OF THE DATE LINE... AVERAGING WITHIN .5 DEGREES C OF NORMAL FROM NEAR THE DATE LINE TO ABOUT 120W... AND BELOW NORMAL FROM 120W TO THE SOUTH AMERICAN COAST. THE LATEST WEEKLY SST DEPARTURES IN THE NINO REGIONS ARE -1.0 C (NINO 1+2)... -0.5 C (NINO 3)... +0.2 C (NINO 3.4)... AND +0.4C (NINO 4). SST ANOMALIES IN ALL FOUR NINO REGIONS WERE HIGHER IN MID-JUNE THAN AT THE END OF MAY. UPPER-OCEAN HEAT CONTENT IN THE CENTRAL AND EASTERN EQUATORIAL PACIFIC (AVERAGE TEMPERATURE IN THE UPPER 300 METERS OF THE OCEAN) REMAINED BELOW AVERAGE... BUT INCREASED MARKEDLY IN THE LAST FEW WEEKS. SUB-SURFACE OCEAN TEMPERATURE ANOMALIES IN THE CENTRAL PACIFIC HAVE ALSO INCREASED SUBSTANTIALLY IN RECENT WEEKS WITH ABOVE NORMAL OCEAN TEMPERATURES PREDOMINATING ALONG THE EQUATOR WESTWARD OF 160W LONGITUDE FROM THE SURFACE TO ABOUT 200 M DEPTH. LOW-LEVEL EASTERLY WINDS REMAINED ABOVE AVERAGE OVER THE CENTRAL EQUATORIAL PACIFIC AND CONVECTION WAS ENHANCED OVER THE WESTERN EQUATORIAL PACIFIC AND SUPPRESSED EAST OF THE DATE LINE. COLLECTIVELY... THESE ATMOSPHERIC AND OCEANIC CONDITIONS INDICATE A NEUTRAL ENSO CLASSIFICATION. WITH POSITIVE SST ANOMALIES HOLDING ON IN THE CENTRAL PACIFIC... AND EVEN MIGRATING EASTWARD IN RECENT WEEKS... IT NOW APPEARS LIKELY THAT DYNAMIC MODEL PREDICTIONS EARLIER IN THE YEAR WERE TOO AGGRESSIVE IN PREDICTING A TRANSITION TO LA NINA CONDITIONS BY SUMMER AND THAT ENSO WILL REMAIN NEUTRAL IN THE NEXT FEW MONTHS. PROGNOSTIC DISCUSSION OF SST FORECASTS MOST STATISTICAL FORCASTS INDICATE NEAR... OR SLIGHTLY BELOW-NORMAL SST DURING THE NEXT SEVERAL MONTHS. MANY DYNAMICAL MODELS CONTINUE TO PREDICT A RAPID TRANSITION TO LA NINA... WITH THE CFS PREDICTING NINO 3.4 SSTS TO BE MORE THAN 1 DEGREE C BELOW NORMAL BY AUGUST 2007. IN VIEW OF THE RECENT EVOLUTION OF SSTS IN THE CENTRAL PACIFIC... A FORECAST BASED ON A CONSOLIDATION OF STATISTICAL AND DYNAMIC MODELS IS FAVORED. THE CONSOLIDATED SST FORECAST BASED ON THE CFS... CANONICAL CORRELATION... CONSTRUCTED ANALOG... AND MARKOV MODEL PREDICTS NINO 3.4 SST ANOMALIES TO DROP TO ABOUT -.3 C BY JAS 2007 AND REMAINING STEADY FOR THE REMAINDER OF THE YEAR. THERE IS A LARGE AMOUNT OF UNCERTAINTY IN THIS PREDICTION... AND THERE REMAINS A SUBSTANTIAL POSSIBLILITY THAT WEAK LA NINA CONDITIONS COULD DEVELOP IN THE FALL. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOK FOR JAS 2007 IS BASED MAINLY ON THE CONSOLIDATION TOOL... WHICH IS A SKILL-WEIGHTED OBJECTIVE BLEND OF CFS... CCA... SMLR... AND OCN. THE IRI AND CAS TOOLS WERE ALSO USED IN JAS. CON IS NOT AVAILABLE FOR ALASKA... SO THE FORECAST THERE IS BASED ON A SUBJECTIVE COMBINATION OF THE CFS - IRI- CCA - OCN - AND TO A LESSER EXTENT THE SMLR. SST ANOMALIES WERE CONSIDERED FOR COASTAL CALIFORNIA. THE OUTLOOKS FOR ASO 2007 THROUGH JAS 2008 ARE BASED PRIMARILY ON THE CONSOLIDATION TOOL... LONG-TERM TRENDS... AND THE POSSIBLE INFLUENCE OF WEAK LA NINA CONDITIONS. TEMPERATURE TRENDS ARE POSITIVE AND SUBSTANTIAL FOR THE SOUTHWESTERN U.S. IN MOST OF THE YEAR AND OVER MUCH OF THE COUNTRY IN THE WINTER. PRECIPITATION TRENDS HAVE MOST SKILL DURING THE JAS SEASON... AND ARE EMPHASIZED IN THAT... AND ADJACENT SEASONS. THE POSSIBILITY OF WEAK LA NINA CONDITIONS HAVE INFLUENCED THE OUTLOOKS FROM NDJ TO JFM... ALTHOUGH ONLY SLIGHTLY. PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2007 TO JAS 2008 TEMPERATURE: THE TEMPERATURE OUTLOOK FOR JAS 2007 CALLS FOR ELEVATED CHANCES OF ABOVE NORMAL SEASONAL AVERAGE TEMPERATURE OVER MUCH OF THE CONUS AS WELL AS FOR MUCH OF ALASKA. THIS IS BASED LARGELY ON THE CON TOOL AND ITS COMPONENT INPUTS... WITH SUPPORT FROM THE IRI AND CAS TOOLS. NEAR TO BELOW NORMAL SSTS OFF THE SOUTHERN CALIFORNIA COAST ARE EXPECTED TO INFLUENCE AIR TEMPERATURES IN COASTAL AREAS. AS OF MID-JUNE ABOVE AVERAGE SOIL MOISTURE WAS OBSERVED IN THE GREAT PLAINS AND THIS SHOULD HELP MODERATE TEMPERATURES IN THE NEXT MONTH OR TWO... SO THE CHANCES OF BELOW- NEAR- OR ABOVE NORMAL TEMPERATURES ARE ABOUT EQUAL IN JAS 2007 IN MOST OF THE GREAT PLAINS. OUTLOOKS FOR ASO 2007 THROUGH JAS 2008 ARE BASED PRIMARILY ON THE CONSOLIDATION TOOL WHICH IS OFTEN DOMINATED BY THE TREND. THE POSSIBILITY OF WEAK LA-NINA CONDITIONS HAVE BEEN INCORPORATED INTO THE FORECASTS FOR NDJ 2007 THROUGH FMA 2008 MAINLY BY SLIGHTLY INCREASING THE CHANCES OF ABOVE NORMAL TEMPERATURES IN THE SOUTHERN CONUS. PRECIPITATION: THE OUTLOOK FOR JAS 2007 CALLS FOR BELOW-MEDIAN PRECIPITATION FROM THE NORTHERN GREAT BASIN TO THE PACIFIC NORTHWEST. THIS IS SUPPORTED BY OCN- CCA- SMLR- CFS- CAS AND ECCA. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE INDICATED IN COASTAL AREAS OF THE EAST AND THE GULF COAST FOR THE LATE SUMMER AND EARLY FALL... REFLECTING TREND AND/OR THE MULTI-DECADAL VARIABILITY IN ATLANTIC TROPICAL ACTIVITY... HOWEVER THIS SHOULD NOT BE INTERPRETED AS AN INDICATION OF HURRICANE STRIKE PROBABILITIES. THE DRY CONDITIONS PREDICTED FOR THE SOUTHEAST FROM NDJ THROUGH FMA IS STRONGLY INDICATED BY THE CON... AND IS CONSISTENT WITH LA NINA... AS IS THE WEAK SIGNAL INDICATED BY THE CONSOLIDATION FORECAST FOR ABOVE MEDIAN PRECIPITATION NEAR THE GREAT LAKES. EQUAL CHANCES OF BELOW - NEAR - AND ABOVE MEDIAN PRECIPITATION ARE INDICATED FOR SPRING AND SUMMER 2008... WITH THE TREND SIGNAL FOR BELOW MEDIAN PRECIPITATION NEAR THE PACIFIC NORTHWEST AGAIN APPEARING IN THE OUTLOOK FOR JAS 2008. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: DAVID UNGER FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML (USE LOWER CASE LETTERS) INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIOD. WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM RANGE FORECASTS SHOULD BE CONSULTED. THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT MONTH ON THU JUL 19 2007 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$