|
|
About Us
Contact Us
Official 90-day Outlooks are issued once each month near mid-month
at 8:30am Eastern Time. Please consult the of 30 & 90-day outlooks
for exact release dates.
Text Discussions
More Outlooks
Tools Used (see Discussion for explanation)
|
| |
|
| HOME> Outlook Maps>Seasonal Forecast Discussion |
| |
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THURSDAY APR 18 2013 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS WHICH USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH TOGETHER COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM 3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "ENSO COMPOSITES", WHICH ARE 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 - SOMETIMES CALLED MADDEN JULIAN OSCILLATION (MJO) - 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 CONSIDERED LESS PREDICTABLE ON A SEASONAL TIMESCALE THAN ENSO. 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 TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). AN EXPERIMENTAL MODEL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE, COMPRISED OF SEVERAL MODELS AND DESIGNATED NMME, MAY ALSO BE USED EXPERIMENTALLY AND SUBJECTIVELY UNTIL IT IS INCLUDED INTO THE CONSOLIDATION. AN INTERNATIONAL MODEL ENSEMBLE DESIGNATED IMME IS ALSO AVAILABLE. 9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE OCN, CCA, SMLR, ECCA, 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. ATMOSPHERIC AND OCEANIC OBSERVATIONS OVER THE LAST FEW MONTHS INDICATE ENSO-NEUTRAL CONDITIONS. PREDICTIONS OF SEA SURFACE TEMPERATURE (SST) IN THE NINO 3.4 REGION OF THE PACIFIC OCEAN FROM DYNAMICAL AND STATISTICAL MODELS INDICATE THAT SST WILL BE CLOSE TO THE CLIMATOLOGICAL MEAN THROUGH BOREAL SUMMER. THE OFFICIAL ENSO OUTLOOK IS FOR A CONTINUATION OF ENSO-NEUTRAL CONDITIONS AT LEAST THROUGH THE NORTHERN HEMISPHERE SUMMER 2013. CONFIDENCE IN PREDICTIONS FOR THE STATE OF ENSO IN LATE SUMMER 2013 AND BEYOND IS LOW AT THIS TIME. THE SEASONAL TEMPERATURE OUTLOOK FOR MJJ 2013 INDICATES ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR THE NORTHERN SECTIONS OF ALASKA, THE SOUTHWEST CONUS, THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL AND SOUTHERN PLAINS, AND MOST AREAS EAST OF THE MISSISSIPPI RIVER. TEMPERATURES IN HAWAII HAVE ENHANCED CHANCES TO BE IN THE BELOW NORMAL CATEGORY. THE MJJ 2013 PRECIPITATION OUTLOOK INDICATES THAT PROBABILITIES OF BELOW MEDIAN PRECIPITATION ARE ENHANCED FOR SECTIONS OF THE WESTERN CONUS FROM NW TEXAS TO WASHINGTON STATE. THE CHANCES FOR BELOW MEDIAN RAINFALL ARE ENHANCED FOR HAWAII, BUT STARTING ONLY IN JJA. IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) IS SHOWN. 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 EQUATORIAL SSTS ARE CLOSE TO LONG TERM AVERAGES THROUGHOUT THE PACIFIC. MOST OF THE SST ANOMALIES ARE WITHIN ONE-HALF DEGREE CELSIUS OF THE CLIMATOLOGICAL NORMALS. THE CURRENT WEEKLY NINO 3.4 INDEX IS -0.0 C, LESS NEGATIVE THAN IT WAS A MONTH AGO. HEAT CONTENT IN THE UPPER 300 METERS OF THE EQUATORIAL PACIFIC OCEAN HAS INCREASED AND IS NOW CLOSE TO LONG-TERM AVERAGE VALUES. LOW LEVEL EASTERLY WINDS AT 850 HPA WERE SLIGHTLY ENHANCED OVER THE CENTRAL TROPICAL PACIFIC OVER THE LAST FEW WEEKS. POSITIVE ANOMALIES IN OUTGOING LONG-WAVE RADIATION (OLR) NEAR AND TO EITHER SIDE OF THE DATE LINE INDICATE SUPPRESSED CONVECTION, AND NEGATIVE ANOMALIES IN OLR FARTHER WEST AND NEAR INDONESIA INDICATE ENHANCED CONVECTION FOR THE LAST 30 DAYS. EARLIER MJO ACTIVITY, FOR NOW MUCH WEAKENED, LIKELY CONTRIBUTED TO THESE ANOMALIES. PROGNOSTIC DISCUSSION OF SST FORECASTS ENSO-NEUTRAL CONDITIONS ARE LIKELY TO CONTINUE THROUGH THE NORTHERN HEMISPHERE SUMMER 2013. THE NINO 3.4 SST ANOMALY FORECAST FROM THE CFSV2, CA, MARKOV AND CCA ALL SHOW SLIGHT COOLING TO -0.5 BY EARLY FALL. MOST OTHER DYNAMICAL AND STATISTICAL MODELS PREDICT THE NINO 3.4 SST ANOMALY TO REMAIN BETWEEN -0.5 C AND +0.5 C THROUGH LATE 2013. SST FORECASTS SUPPORT ENSO NEUTRAL CONDITIONS THROUGH THE SPRING AND SUMMER WITH GREATER UNCERTAINTY FOLLOWING THE SPRING BARRIER. ENSO IS THUS NOT A FACTOR IN THE U.S. FORECAST FOR 2013. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS WERE MADE CONSIDERING ENSO-NEUTRAL CONDITIONS TO BE MOST LIKELY THROUGH NORTHERN HEMISPHERE SUMMER 2013. THE FORECASTS WERE BASED PRIMARILY ON DYNAMICAL MODEL OUTPUT FROM THE NMME AND IMME FOR MJJ THROUGH SON 2013, WITH SOME ADDITIONAL CONSIDERATION FROM STATISTICAL FORECAST TOOLS, SOIL MOISTURE CONDITIONS, DECADAL TRENDS AND THE CONSOLIDATION (CON) FORECAST. OUTLOOKS FOR OND 2013 ONWARD WERE BASED MOSTLY ON THE CONSOLIDATION, WHICH LARGELY REFLECTS TRENDS. PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2013 TO MJJ 2014 TEMPERATURE THE TEMPERATURE OUTLOOKS FOR MJJ THROUGH ASO 2013 INDICATE ENHANCED CHANCES FOR ABOVE NORMAL TEMPERATURES FOR NORTHERN ALASKA, THE SOUTHWEST, THE SOUTHERN AND CENTRAL PLAINS, AND THE EASTERN HALF OF THE CONUS. ENHANCED PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE NOT INDICATED ANYWHERE AT ANY TIME. THESE FORECASTS ARE SUPPORTED BY THE MODELS OF THE NMME AND IMME, AND ALSO LARGELY CONSISTENT WITH DECADAL TRENDS. SUBSTANTIAL SOIL MOISTURE DEFICITS OVER MUCH OF THE WEST AND CENTRAL CONUS ARE ALSO CONSISTENT WITH AN INCREASED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES DURING THE WARM SEASON. NORTHERN ALASKA IS MORE LIKELY TO EXPERIENCE ABOVE NORMAL TEMPERATURES FOR MJJ THROUGH OND 2013 AS INDICATED BY THE DECADAL TEMPERATURE TRENDS. THESE TEMPERATURE TRENDS ARE DUE IN PART TO REDUCED ARCTIC OCEAN SEA ICE COVER IN THIS REGION DURING RECENT YEARS FOR THE SPRING THROUGH AUTUMN SEASONS. INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES CONTINUE ACROSS MOST OF THE CONUS INTO SON 2013. FOR SON 2013 AND BEYOND, TEMPERATURE OUTLOOKS ARE PRIMARILY A RESULT OF SIGNALS RELATED TO DECADAL VARIABILITY AS DETERMINED BY THE CONSOLIDATION FORECAST. ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES CONTINUE FOR PORTIONS OF THE GREAT LAKES REGION, THE NORTHEAST, THE SOUTH AND THE SOUTHWEST THROUGHOUT THE YEAR INTO AMJ 2014. ENHANCED CHANCES FOR ABOVE NORMAL TEMPERATURES FOR NORTHERN ALASKA REAPPEAR FROM FMA 2014 FORWARD. IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF BELOW, NEAR AND ABOVE NORMAL SEASONAL MEAN TEMPERATURES IS INDICATED. PRECIPITATION THE PRECIPITATION OUTLOOK FOR MJJ 2013 INDICATES ELEVATED CHANCES FOR BELOW MEDIAN ACCUMULATED PRECIPITATION FOR SECTIONS OF THE WESTERN CONUS FROM NW TEXAS TO WASHINGTON STATE. THIS IS INDICATED BY A CONSENSUS OF STATISTICAL TOOLS AND DYNAMICAL MODEL FORECASTS FROM THE NMME AND IMME. ENHANCED CHANCES OF ABOVE MEDIAN PRECIPITATION ARE NOT INDICATED ANYWHERE AT ANY TIME. DURING JJA THROUGH SON, THERE ARE ENHANCED ODDS FOR BELOW-MEDIAN PRECIPITATION AT LOCATIONS WEST OF THE ROCKIES. DYNAMICAL MODELS INDICATE A CONTINUATION OF THE TENDENCY FOR BELOW MEDIAN PRECIPITATION IN PARTS OF THE SOUTHWEST MONSOON REGION THROUGH EARLY 2013. DECADAL TRENDS FOR BELOW MEDIAN PRECIPITATION ALSO EMERGE IN THE SOUTHEAST FOR NDJ 2013 THROUGH FMA 2014. IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF BELOW, NEAR AND ABOVE MEDIAN SEASONAL PRECIPITATION AMOUNTS IS INDICATED. FORECASTER: HUUG VAN DEN DOOL THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 COMPLETE DECADES AS THE CLIMATIC 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. 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 MAY 16 2013 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$
|
|
|
|