30 Day Narrative

587 
FXUS07 KWBC 311900
PMD30D
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.
$$