PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300 PM EDT THU MAY 31 2018 30-DAY OUTLOOK DISCUSSION FOR JUNE 2018 THE UPDATED MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR JUNE 2018 ARE BASED ON THE LATEST DYNAMICAL MODEL GUIDANCE, WPC TEMPERATURE AND PRECIPITATION FORECASTS DURING THE FIRST WEEK OF THE MONTH, THE CPC 6-10/8-14 DAY TEMPERATURE AND PRECIPITATION OUTLOOKS, CLIMATE LINKAGES TO CURRENT SOIL MOISTURE CONDITIONS, AND THE POTENTIAL INFLUENCE FROM AN ATMOSPHERIC KELVIN WAVE (KW). THE ENHANCED PHASE OF THE MADDEN-JULIAN OSCILLATION (MJO) PROPAGATED EAST ACROSS THE INDIAN OCEAN DURING LATE MAY. ALTHOUGH THE MJO TYPICALLY PROVIDES LITTLE IF ANY INFLUENCE ON THE CIRCULATION PATTERN AT THE MID-LATITUDES OF NORTH AMERICA DURING JUNE, A KW IS CURRENTLY CROSSING THE WEST PACIFIC. THE CFS MODEL INDICATES THAT THIS KW CONTINUES TO PROPAGATE EAST THROUGH THE BEGINNING OF JUNE AND MAY HELP TO INITIATE A TROPICAL CYCLONE (TC) ACROSS THE EAST PACIFIC OR WESTERN CARIBBEAN SEA DURING EARLY TO MID-JUNE. THIS INCREASING CHANCE OF TC DEVELOPMENT BY MID-JUNE IS A FACTOR IN SUPPORT OF ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTHEAST. THE CFS 500-HPA MONTHLY FORECAST FEATURES ANOMALOUS RIDGING, CENTERED OVER THE SOUTHWEST AND SOUTHERN GREAT PLAINS, WITH THE LARGEST 500-HPA HEIGHT ANOMALIES OVER THE WEST-CENTRAL U.S. THE REVISED TEMPERATURE AND PRECIPITATION OUTLOOKS ARE GENERALLY CONSISTENT WITH THIS PREDICTED LONGWAVE PATTERN. ONLY MINOR REVISIONS TO THE TEMPERATURE OUTLOOK ARE NECESSARY AS ABOVE-NORMAL TEMPERATURES CONTINUE TO BE FAVORED FOR A MAJORITY OF THE CONUS. SOIL MOISTURE REMAINS A FACTOR IN THE JUNE TEMPERATURE OUTLOOK. DURING THE PAST 30 DAYS, PRECIPITATION AVERAGED MORE THAN 4 INCHES ABOVE NORMAL ACROSS THE SOUTHEAST AND MID-ATLANTIC WITH SOME AREAS RANKING ABOVE THE 70TH PERCENTILE IN SOIL MOISTURE. IN CONTRAST TO THE RECENT EXCESSIVE WETNESS, SOIL MOISTURE RANKS IN THE LOWEST 30TH PERCENTILE ACROSS PARTS OF THE CENTRAL AND SOUTHERN GREAT PLAINS ALONG WITH THE SOUTHWEST. THE GEFS AND ECMWF ENSEMBLE MEANS INDICATE AN AMPLIFYING UPPER-LEVEL TROUGH EARLY IN THE MONTH ALONG THE EAST COAST. GIVEN THIS EXPECTED START TO THE MONTH, ONGOING HIGH SOIL MOISTURE CONTENT, AND UNCERTAINTY ON THE LONGWAVE PATTERN EVOLUTION DURING THE LATTER HALF OF THE MONTH, EQUAL CHANCES (EC) OF BELOW, NEAR, OR, ABOVE-NORMAL TEMPERATURES ARE FORECAST ALONG THE EAST COAST. TEMPERATURE TOOLS THROUGHOUT THE MONTH ARE IN GOOD AGREEMENT FOR ABOVE-NORMAL TEMPERATURES ACROSS THE CENTRAL AND WESTERN U.S. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE SOUTHERN GREAT PLAINS AND SOUTHWEST DUE IN PART TO LOW SOIL MOISTURE AND THE ONGOING DROUGHT CONDITIONS ALONG WITH LONG-TERM TRENDS. A DRY START TO JUNE AND A STRONG UPPER-LEVEL RIDGE PREDICTED FOR AT LEAST THE FIRST HALF OF THE MONTH ENHANCES ODDS FOR BELOW-NORMAL PRECIPITATION ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS ALONG WITH THE WESTERN U.S., EXCLUDING THE DRY CLIMATOLOGY AREAS OF CALIFORNIA. WEEK-2 PRECIPITATION TOOLS ALONG WITH RECENT DAILY RUNS OF THE CFS MONTHLY INDICATE ENHANCED ODDS OF ABOVE-NORMAL PRECIPITATION ACROSS PARTS OF ARIZONA AND NEW MEXICO. ON JUNE 1 AND 2, FORECAST HEAVY RAINFALL (LOCALLY MORE THAN 2 INCHES), ASSOCIATED WITH A VIGOROUS SHORTWAVE TROUGH AND MESOSCALE CONVECTIVE SYSTEM, INCREASES CHANCES FOR ABOVE-NORMAL PRECIPITATION ACROSS NORTH DAKOTA. ALTHOUGH A WET START TO THE MONTH IS ALSO LIKELY ACROSS THE MIDDLE TO UPPER MISSISSIPPI VALLEY AND MUCH OF THE CORN BELT, RAINFALL AMOUNTS ARE EXPECTED TO BE SLIGHTLY LOWER THAN NORTH DAKOTA. DURING THE REMAINDER OF THE MONTH, ONLY WEAK SIGNALS EXIST AMONG THE PRECIPITATION TOOLS. THEREFORE, EQUAL CHANCES OF BELOW, NEAR, OR ABOVE-NORMAL PRECIPITATION ARE FORECAST FOR THE MIDDLE TO UPPER MISSISSIPPI VALLEY AND CORN BELT. ENHANCED ODDS FOR ABOVE-NORMAL PRECIPITATION ARE MAINTAINED ACROSS THE SOUTHEAST, BASED LARGELY ON GOOD CONSISTENCY AMONG DAILY CFS MODEL RUNS. DURING THE FIRST WEEK OF JUNE, A CLOSED 500-HPA LOW IS EXPECTED TO DEVELOP AND RESULT IN HEAVY RAINFALL (1 TO 3 INCHES) ACROSS THE NORTHERN MID-ATLANTIC. THEREFORE, INCREASED CHANCES FOR ABOVE-NORMAL PRECIPITATION ARE FORECAST FOR THIS REGION. A SLIGHT TILT IN THE ODDS FOR BELOW-NORMAL PRECIPITATION IS FORECAST FOR THE EASTERN GREAT LAKES AND NEW ENGLAND WHERE DAILY CFS MODEL RUNS FEATURE A CONSISTENT DRY SIGNAL. THE HIGHEST PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE FORECAST ACROSS THE ALEUTIANS AND WESTERN COASTAL MAINLAND ALASKA WHERE SEA SURFACE TEMPERATURE ANOMALIES ARE AVERAGING MORE THAN 1.5 DEGREES C ABOVE NORMAL. SINCE TEMPERATURES ARE FORECAST TO AVERAGE NEAR TO BELOW-NORMAL ACROSS SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE DURING THE FIRST TWO WEEKS OF JUNE, EC IS THE PREFERRED TEMPERATURE FORECAST FOR THESE AREAS. A REVISION TO THE PRECIPITATION OUTLOOK IS NECESSARY TO EASTERN MAINLAND ALASKA WHERE RECENT CFS DAILY MODEL RUNS INDICATE ENHANCED ODDS FOR BELOW-NORMAL PRECIPITATION. ----------- PREVIOUS MESSAGE (FROM MAY 17) IS SHOWN BELOW ------------ THE JUNE 2018 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL MODEL GUIDANCE, STATISTICAL TOOLS, CURRENT SOIL MOISTURE CONDITIONS, AND POTENTIAL INFLUENCES FROM MODES OF TROPICAL VARIABILITY. ENSO IS NOT A FACTOR IN THESE OUTLOOKS SINCE IT IS IN A NEUTRAL STATE AND IS PREDICTED TO REMAIN NEUTRAL. THE MADDEN-JULIAN OSCILLATION (MJO) WAS QUITE ACTIVE DURING THE PAST SIX MONTHS. AFTER A BRIEF WEAKENING DURING LATE APRIL, THE MJO STRENGTHENED BY EARLY MAY WITH ITS ENHANCED PHASE OVER THE WESTERN HEMISPHERE. DURING MID-MAY, THE ENHANCED PHASE OF THE MJO PROPAGATED EAST OVER AFRICA, WHILE A VERY ROBUST EQUATORIAL ROSSBY WAVE (ERW) SHIFTED WEST ACROSS THE INDIAN OCEAN. DYNAMICAL MODELS VARY ON THE AMPLITUDE OF THE MJO DURING THE NEXT TWO WEEKS. GIVEN THE CURRENT 200-HPA VELOCITY POTENTIAL ANOMALY FIELD, AN MJO SIGNAL IS EXPECTED TO CONTINUE ITS EASTWARD PROPAGATION BUT ITS INTERACTION WITH THE ERW INCREASES UNCERTAINTY ON ITS EVOLUTION THROUGH THE BEGINNING OF JUNE. DUE TO THIS UNCERTAINTY AND TIME OF YEAR, THE MJO IS EXPECTED TO PLAY LITTLE IF ANY ROLE IN THE LONGWAVE PATTERN ACROSS THE MID-LATITUDES OF NORTH AMERICA. THE DYNAMICAL MODEL CONSENSUS, INCLUDING THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME), SUPPORTS A BROAD AREA OF INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES THROUGHOUT THE CONTINENTAL U.S. A STRONG INVERSE RELATIONSHIP EXISTS BETWEEN SOIL MOISTURE AND SURFACE TEMPERATURE DURING JUNE. SOIL MOISTURE CURRENTLY RANKS IN THE LOWEST 20TH PERCENTILE ACROSS THE SOUTHWESTERN U.S. AND MUCH OF THE CENTRAL AND SOUTHERN GREAT PLAINS WHERE RELATIVELY HIGH PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE FORECAST. DECADAL TRENDS ALSO STRONGLY SUPPORT ABOVE-NORMAL TEMPERATURES ACROSS THESE AREAS. IN CONTRAST TO THE DROUGHT-STRICKEN SOUTHERN GREAT PLAINS, SOIL MOISTURE RANKS IN THE HIGHEST 70TH OR EVEN 90TH PERCENTILE ACROSS MUCH OF THE GREAT LAKES REGION. GIVEN THIS HIGH SOIL MOISTURE CONTENT ALONG WITH SUPPORT FROM THE ECMWF MODEL, EQUAL CHANCES (EC) FOR BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS PARTS OF THE GREAT LAKES REGION. EC IS ALSO FORECAST FOR MUCH OF FLORIDA AND SOUTH GEORGIA, BASED ON DYNAMICAL MODELS AND THE EXPECTATION FOR ABOVE-NORMAL RAINFALL. ABOVE (BELOW)-NORMAL PRECIPITATION ACROSS THE SOUTHEAST, MID-ATLANTIC, AND PARTS OF THE GULF COAST (PACIFIC NORTHWEST, NORTHERN GREAT BASIN, AND NORTHERN ROCKIES) IS BASED ON DYNAMICAL MODELS AND DECADAL TRENDS. IF THE ENHANCED PHASE OF THE MJO CONTINUES ITS EASTWARD PROPAGATION TO THE WESTERN HEMISPHERE DURING JUNE AND/OR AN ATMOSPHERIC KELVIN WAVE EMERGES, THEN THE LARGE SCALE ENVIRONMENT COULD BE FAVORABLE FOR AN EARLY SEASON TROPICAL CYCLONE (TC) ACROSS THE GULF OF MEXICO. THE MJO EVOLUTION AND ITS POTENTIAL INFLUENCE ON TC FORMATION WILL BE CLOSELY MONITORED DURING THE REMAINDER OF MAY. THE LARGE COVERAGE OF EQUAL CHANCES FOR BELOW-, NEAR-, OR ABOVE-NORMAL PRECIPITATION IS DUE TO THE LOWER CONFIDENCE IN THE PRECIPITATION OUTLOOK AT A HALF MONTH LEAD AND THE LACK OF PREDICTABILITY OF CONVECTIVE RAINFALL ON A MONTHLY TIME SCALE. MODIFICATIONS TO THE COVERAGE AND PROBABILITIES IN THE PRECIPITATION OUTLOOK ARE ANTICIPATED WITH THE UPDATED OUTLOOK RELEASED ON MAY 31. THE DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES ACROSS MOST OF ALASKA. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS WESTERN ALASKA AND THE ALEUTIANS, BASED IN PART ON SEA SURFACE TEMPERATURES AVERAGING 1 TO 2 DEGREES C ABOVE NORMAL. THE NMME INDICATES ENHANCED ODDS FOR ABOVE-NORMAL PRECIPITATION THROUGHOUT MAINLAND ALASKA WITH THE HIGHEST ODDS ACROSS WESTERN ALASKA. FORECASTER: BRAD PUGH 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 JUL ... WILL BE ISSUED ON THU JUN 21 2018 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$