PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU JUL 19 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 A FEW TENTHS BELOW 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 STRAIGHTFORWARDLY IN THE CENTRAL PACIFIC... INTRASEASONAL VARIATIONS HAVE CAUSED CONSIDERABLE VARIATIONS. 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 MORE SLOWLY DOWNWARD... INDICATING NEUTRAL ENSO OR ONLY VERY WEAK LA NINA CONDITIONS. THUS... AT THIS TIME NEUTRAL ENSO CONDITIONS ARE ANTICIPATED THROUGH ASO WITH THE DEVELOPMENT OF LA NINA CONDITIONS POSSIBLE LATER IN THE FALL. THE TEMPERATURE OUTLOOK FOR AUGUST-SEPTEMBER-OCTOBER (ASO) 2007 CALLS FOR ABOVE NORMAL TEMPERATURES OVER MOST OF THE U.S. AMPLE SOIL MOISTURE AND PERSISTENT TROUGHS SHOULD HELP MODERATE TEMPERATURES IN THE SOUTHERN 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 NEVADA AND CALIFORNIA AND THE GREAT BASIN FOR ASO 2007. ALONG THE EASTERN SEABOARD AND THE GULF COAST WE EXPECT SLIGHTLY ENHANCED PROBABILITIES OF ABOVE MEDIAN PRECIPITATION. 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 140W... AND BELOW NORMAL FROM 140W TO THE SOUTH AMERICAN COAST. SST ANOMALIES IN ALL FOUR NINO REGIONS HAVE BEEN SUBJECT TO INTRASEASONAL VARIATION. 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 A MONTH AGO FOLLOWED BY A SMALLER DECREASE. COLLECTIVELY... THE ATMOSPHERIC AND OCEANIC CONDITIONS INDICATE A NEUTRAL ENSO CLASSIFICATION. 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 - WITH EXCEPTIONS - CONTINUE TO PREDICT A MORE 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 SEASONALLY AVERAGED NINO 3.4 SST ANOMALIES TO DROP TO NEAR -0.5 C BY ASO 2007 AND REMAINING NEARLY STEADY FOR THE REMAINDER OF THE YEAR. THERE IS THE USUAL UNCERTAINTY IN THIS PREDICTION... AND CHANCES FOR THE ABOVE - NEAR NORMAL AND BELOW CATEGORIES FOR NINO34 TO BE REALIZED ARE ON THE ORDER OF 2% - 45% AND 53% RESPECTIVELY WITH ONLY SLIGHT VARIATIONS ALL THE WAY OUT TO THE END OF THE YEAR. WE PRACTICALLY EXCLUDE A WARM EVENT BUT A WEAK LA NINA FOR NEXT WINTER IS A DISTINCT POSSIBILITY. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOK FOR ASO 2007 IS BASED MAINLY ON THE CONSOLIDATION TOOL... WHICH IS A SKILL-WEIGHTED OBJECTIVE BLEND OF CFS... CCA... SMLR... AND OCN. THE IRI.. CDC AND CAS TOOLS WERE ALSO USED IN ASO. 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 ASO 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 HAS INFLUENCED THE OUTLOOKS FROM NDJ TO JFM... ALTHOUGH ONLY SLIGHTLY BUT MORE SO THAN A MONTH AGO. PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2007 TO ASO 2008 TEMPERATURE: THE TEMPERATURE OUTLOOK FOR ASO 2007 CALLS FOR ELEVATED CHANCES OF ABOVE NORMAL SEASONAL AVERAGE TEMPERATURE OVER MUCH OF THE CONUS - EXCEPT IN THE CENTER - 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-JULY ABOVE AVERAGE SOIL MOISTURE WAS OBSERVED IN THE SOUTHERN GREAT PLAINS - SOME PLACES ARE EXTREMELY WET 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 ASO 2007 IN MOST OF THE GREAT PLAINS. WE ENLARGED THE AREA LABELLED EC IN THE CENTER OF THE COUNTRY TO ACCOMODATE WEAK INDICATION OF BELOW NORMAL TEMPERATURES BY ASSORTED TOOLS. OUTLOOKS FOR SON 2007 THROUGH ASO 2008 ARE BASED PRIMARILY ON THE CONSOLIDATION TOOL WHICH IS OFTEN DOMINATED BY THE TREND. THE POSSIBILITY OF WEAK LA-NINA CONDITIONS HAS BEEN INCORPORATED PROPORTIONALLY INTO THE FORECASTS FOR NDJ 2007 THROUGH FMA 2008 MAINLY BY SLIGHTLY INCREASING THE CHANCES OF ABOVE NORMAL TEMPERATURES IN THE SOUTHEASTERN CONUS AND REDUCING PROBABILITIES FOR ABOVE NORMAL IN THE NORTHWEST. PRECIPITATION: THE OUTLOOK FOR ASO 2007 CALLS FOR BELOW-MEDIAN PRECIPITATION FROM PARTS OF NEVADA.. IDAHO AND CALIFORNIA INTO THE INTERIOR 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 SON AND OND IN THE IOWA AND MISSOURI AREA ARE SUPPORTED MAINLY BY TREND. THE DRY CONDITIONS PREDICTED FOR THE SOUTHEAST FROM NDJ THROUGH FMA ARE STRONGLY INDICATED BY THE CON... AND WOULD BE CONSISTENT WITH LA NINA... WE EXTENDED THE AREAL COVERAGE OF THE BELOW MEDIAN PREDICTION - BOTH SOUTHWARD INTO FLORIDA AND WESTWARD ACROSS THE SOUTH. EQUAL CHANCES OF BELOW - NEAR - AND ABOVE MEDIAN PRECIPITATION ARE INDICATED FOR MUCH OF SPRING AND SUMMER 2008... WITH THE TREND SIGNAL FOR BELOW MEDIAN PRECIPITATION NEAR THE PACIFIC NORTHWEST AND ABOVE MEDIAN PRECIPITATION FOR FLORIDA AGAIN APPEARING IN THE OUTLOOK FOR JAS AND ASO 2008. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: HUUG VAN DEN DOOL 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 AUG 16 2007 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$