PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU APR 21 2016

30-DAY OUTLOOK DISCUSSION FOR MAY 2016

THE MAY 2016 OUTLOOK IS CONSTRUCTED BASED ON THE LOW-FREQUENCY CLIMATE SIGNALS 
MANIFEST IN THE DYNAMICAL AND STATISTICAL GUIDANCE. MOST GUIDANCE IS IN GOOD 
AGREEMENT ON THE GENERAL STRUCTURE OF FORECAST PROBABILITIES, AND SHORTER TERM 
OUTLOOKS ARE CONSULTED TO REFINE THE FORECAST. THERE IS LITTLE IN THE WAY OF 
COHERENT MJO ACTIVITY TO INFLUENCE THE OUTLOOK; THE MJO'S INFLUENCE IS 
DIMINISHED IN THE WARM SEASON, AND PLAYS NO ROLE HERE IN INFORMING THE MONTHLY 
FORECAST. SOIL MOISTURE, HOWEVER, IS TAKEN INTO ACCOUNT, AS INCREASING INCIDENT 
SOLAR RADIATION ALLOWS IT TO EXERT MORE INFLUENCE ON LOCAL TEMPERATURES. 

THE CALIBRATED NMME TEMPERATURE PROBABILITIES INDICATE A FAIRLY WEAK TILT 
TOWARD WARMER-THAN-NORMAL TEMPERATURES ACROSS THE NORTHERN TIER OF THE CONUS, 
ALASKA, AND PARTS OF THE EASTERN CONUS. A NOTABLE WEAKNESS IS FORECAST OVER THE 
SOUTH-CENTRAL AND SOUTHWESTERN U.S. THIS IS GENERALLY CONSISTENT WITH LAGGED 
ENSO REGRESSIONS (USING LATE WINTER NINO 3.4 VALUES), OBJECTIVE COMPOSITE 
ANALOGS BASED ON THE RECENTLY OBSERVED SSTS IN THE TROPICAL AND NORTHERN 
PACIFIC AND ATLANTIC BASINS, AS WELL AS STATISTICALLY DERIVED LOCAL SOIL 
MOISTURE IMPACTS. THE SECULAR TREND EXPLAINS LESS VARIANCE ON MONTHLY 
TIMESCALES THAN ON SEASONAL TIMESCALES, BUT GENERALLY SUPPORTS THE SPATIAL 
STRUCTURE OF FORECAST TEMPERATURE PROBABILITIES. 

ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR MUCH OF 
THE WESTERN, NORTHERN, AND EASTERN CONUS, BASED ON THE ABOVE FACTORS. THE 
LOWEST PROBABILITIES ARE FORECAST OVER NORTHERN NEW ENGLAND AND THE NORTHERN 
PLAINS. THE FORMER IS DUE TO HIGHER-FREQUENCY PATTERNS THAT FAVOR ANOMALOUS 
NORTHERLY FLOW INTO EARLY MAY FOR THAT REGION, WHILE THE LATTER IS DUE TO 
TRENDS AND SOIL MOISTURE TOOLS. THE LATEST CFS FORECASTS, WEEK 3/4 GUIDANCE 
FROM BOTH THE CFS AND ECMWF, SOIL MOISTURE CONSIDERATIONS, AND LAGGED ENSO 
REGRESSIONS FAVOR ENHANCED PROBABILITIES OF BELOW-NORMAL TEMPERATURES ACROSS A 
PORTION OF THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS.

ALL OF THE AFOREMENTIONED OBJECTIVE GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE 
FORECAST PRECIPITATION OUTLOOK AS WELL. MODEST PROBABILITIES FAVORING 
ABOVE-MEDIAN PRECIPITATION ARE DEPICTED FOR MUCH OF THE CENTRAL AND SOUTHERN 
CONUS, EXTENDING WESTWARD TO PARTS OF CALIFORNIA AND THE GREAT BASIN.


FORECASTER: STEPHEN BAXTER


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.



AN UPDATED MONTHLY OUTLOOK... FOR MAY WILL BE ISSUED ON SAT APRIL 30 2016


THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.

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