PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT TUE JUL 31 2007 30-DAY OUTLOOK DISCUSSION FOR AUGUST 2007 ENSO-NEUTRAL CONDITIONS HAVE PERSISTED INTO LATE JULY. DURING LATE JULY THERE HAS BEEN A SLIGHT COOLING OF EQUATORIAL PACIFIC SSTS EAST OF 150 W LONGITUDE PRODUCING NEGATIVE ANOMALIES OF 0.5 TO 1.5 DEGREES CELSIUS... AND ATMOSPHERIC CONDITIONS ARE NOW SLIGHTLY CLOSER TO LA NINA THAN THEY WERE SEVERAL WEEKS AGO. THE CFS FORECASTS THE ONSET OF LA NINA WITHIN THE NEXT TWO MONTHS... HOWEVER THERE IS STILL SIGNIFICANT UNCERTAINTY... AND ENSO-NEUTRAL CONDITIONS SHOULD PERSIST THOUGH AUGUST. THE GFS MODEL PREDICTS A WARM DRY PATTERN FOR THE EASTERN U.S. AND BELOW NORMAL OR NEAR NORMAL TEMPERATURES FOR THE WEST IN THE NEXT TWO WEEKS. IN THE FIRST WEEK OF AUGUST... THE SOUTHWEST MONSOON IS EXPECTED TO BRING PRECIPITATION AS FAR WEST AS ARIZONA AND NEVADA. HOWEVER... THERE IS SOME INDICATION THAT TOWARDS THE END OF THE FIRST TWO WEEKS OF AUGUST THE RIDGE OVER THE CENTRAL PLAINS WILL BUILD AGAIN BRINGING WARMER TEMPERATURES AND DRIER CONDITIONS TO THE WEST. ONLY SMALL CHANGES HAVE BEEN MADE IN THE OUTLOOK FOR AUGUST IN THIS UPDATE. THE AREA OF ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES IN THE EASTERN U.S. HAS BEEN EXPANDED NORTHWARD INTO THE OHIO VALLEY DUE TO ABOVE NORMAL TEMPERATURES EXPECTED DURING THE FIRST TWO WEEKS OF AUGUST AND SUPPORT FROM THE OCN AND CCA. THE AREA OF ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES IN THE WEST HAS BEEN REMOVED FROM THE PACIFIC COAST WHERE A TROUGH IS FORECAST TO BE IN PLACE DURING THE NEXT TWO WEEKS. SMALL ADJUSTMENTS TO THE AREA IN THE SOUTHERN PLAINS OF ENHANCED PROBABILITY OF BELOW NORMAL TEMPERATURES AND ABOVE NORMAL PRECIPITATION HAVE BEEN MADE TO REFLECT RECENT CFS AND GFS MODEL PREDICTIONS. THE AREA IN THE WEST OF ENHANCED PROBABILITY OF BELOW NORMAL PRECIPITATION HAS BEEN MOVED SLIGHTLY TO THE SOUTHWEST AND REMOVED FROM PARTS OF MONTANA AND WYOMING IN AGREEMENT WITH RECENT CFS AND GFS MODEL PREDICTIONS. THE AREA OF ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES OVER ALASKA HAS BEEN EXPANDED TO INCLUDE MOST OF THE STATE THOUGH REMOVED FROM THE ALASKAN PANHANDLE IN AGREEMENT WITH THE GFS MODEL FORECASTS FOR THE FIRST TWO WEEKS OF AUGUST. FOLLOWING IS THE TEXT FROM THE ORIGINAL 30-DAY OUTLOOK FOR AUGUST RELEASED ON JULY 19. SEA SURFACE TEMPERATURES (SSTS) HAVE PERSISTENTLY REMAINED FROM 0.5 TO 1.5 DEGREES CELSIUS BELOW NORMAL IN THE EQUATORIAL PACIFIC OCEAN FROM ABOUT 120 W LONGITUDE TO THE SOUTH AMERICAN COAST. AFTER A BRIEF WARMING OF MOST OF THE EASTERN EQUATORIAL PACIFIC DURING LATE MAY AND EARLY JUNE... SSTS HAVE COOLED SLIGHTLY IN RECENT WEEKS. SSTS AND ATMOSPHERIC CIRCULATION PATTERNS ARE CONSISTENT WITH NEUTRAL ENSO CONDITIONS AND ARE EXPECTED TO PERSIST THROUGH AUGUST. THE POSSIBLE DEVELOPMENT OF LA NINA CONDITIONS AFTER AUGUST IN THE EQUATORIAL PACIFIC SHOULD NOT HAVE MUCH INFLUENCE ON AUGUST CLIMATE ANOMALIES OVER THE U.S. THERE IS GOOD AGREEMENT AMONG THE TRADITIONAL TOOLS FOR THE MONTHLY FORECAST OVER THE WESTERN STATES AND THE SOUTHEAST AND TO A LESSER EXTENT ALASKA. THERE HAS BEEN A PERSISTENT PATTERN OF ABOVE NORMAL RAINFALL IN THE SOUTHERN CENTRAL PLAINS AND DRYNESS IN THE WEST AND SOUTHEAST AND ASSOCIATED STRONG SOIL MOISTURE ANOMALIES OVER THE LAST SEVERAL MONTHS. THE RELATIONSHIP OF TEMPERATURE AND SOIL MOISTURE IN AUGUST AND THE PERSISTENCE OF TEMPERATURE ANOMALIES FROM JULY TO AUGUST ARE RELATIVELY STRONG CLIMATE INDICATORS FOR THE GREAT PLAINS. TOOLS THAT INCLUDE SOIL MOISTURE AS A PREDICTOR ARE EMPHASIZED SOMEWHAT FOR THE AUGUST FORECAST. THE SMLR CCA AND OCN SUPPORT THE PREDICTION OF WARMER THAN NORMAL TEMPERATURES IN THE WEST... SOUTHEAST AND THE SOUTH COAST OF ALASKA. THERE IS SOME SUPPORT FOR THE WEST AND SOUTHEAST TO HAVE ABOVE NORMAL TEMPERATURES FROM THE CFS AND CAS THOUGH THESE TOOLS HAVE LIMITED AREAS OF SKILL. PROBABILITIES OF ABOVE NORMAL ARE HIGHEST IN THE WEST AND SOUTHEAST WHERE TEMPERATURE TRENDS INDICATED BY OCN HAVE THE LARGEST POSITIVE VALUES. AN AREA OF ENHANCED PROBABILITY OF BELOW NORMAL TEMPERATURES IS PREDICTED FOR THE SOUTHERN PLAINS CENTERED OVER OKLAHOMA. THE CFS AND CAS PREDICT LARGE NEGATIVE TEMPERATURE ANOMALIES OVER A LARGE AREA OF THE CENTER OF THE COUNTRY... THOUGH THEIR SKILL IS LIMITED FOR MOST OF THIS REGION. THE AREA PREDICTED TO HAVE BELOW NORMAL TEMPERATURES IS EXPERIENCING THE HIGHEST POSITIVE SOIL MOISTURE ANOMALIES IN THE U.S. AND A COLD AND WET PATTERN THAT HAS BEEN IN PLACE FOR SOME TIME. ABOVE MEDIAN PRECIPITATION IS PREDICTED FOR A SIMILAR AREA OF THE SOUTHERN PLAINS SUPPORTED BY THE CAS AND CFS. SMLR CCA OCN CFS AND CAS ALL INDICATE BELOW MEDIAN PRECIPITATION FOR SOME PORTION OF THE WEST. AN AREA OF ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION IS PREDICTED FOR THE WEST WITH THE GREATEST PROBABILITY IN PARTS OF IDAHO... MONTANA AND WYOMING WHERE CCA SMLR AND CAS HAVE THEIR LARGEST SKILL. NEGATIVE PRECIPITATION TRENDS INDICATED BY OCN ARE MOST SIGNIFICANT IN NEVADA. THE TWO WEEK NUMERICAL WEATHER MODEL FORECASTS BRING VERY WARM TEMPERATURES TO THE NORTHERN PLAINS AND THIS PATTERN IS EXPECTED TO BE IN PLACE AT THE BEGINNING OF AUGUST. THERE IS ONLY WEAK SUPPORT AT THIS TIME FROM THE CCA OCN AND SMLR FOR THE PERSISTENCE OF THIS WARMTH THROUGH AUGUST. THE AUGUST UPDATE AT THE END OF JULY WILL CONSIDER ANY CHANGES IN THE TOOLS SUCH AS THE CFS AND CAS WHICH ARE UPDATED DAILY. IN ADDITION... THE NUMERICAL WEATHER PREDICTION FOR THE FIRST TWO WEEKS WILL BE USED TO ADJUST THE AUGUST PREDICTIONS. FORECASTER: DAN COLLINS NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). THE NEXT MONTHLY OUTLOOK...FOR SEPTEMBER 2007...WILL BE ISSUED ON THU AUG 16 2007 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. $$