PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300PM EDT MONDAY MAR 31 2014

30-DAY OUTLOOK DISCUSSION FOR APRIL 2014

ADJUSTMENT ON MARCH, 31 IS BASED MAINLY ON THREE TOOLS, AND ALL THREE REFLECT 
THE IMPACT OF THE MOST RECENT ATMOSPHERIC CONDITIONS ON THE WEATHER OF THE 
FIRST SEVERAL DAYS OF APRIL 2014. THE FIRST TOOL IS THE GFS ENSEMBLE. SECOND 
TOOL IS THE WPC 5-DAY PRECIPITATION FORECAST, WHICH USES NWP MODELS FROM 
OUTSIDE NCEP AS WELL. THIRD TOOL IS THE 16 MEMBER CFS USING INITIAL CONDITIONS 
FROM MARCH 30 6Z THROUGH MARCH, 31 0Z. THE LATTER TOOL, AN AVERAGE FOR ALL OF 
APRIL, IS IN THEORY IDEAL IN COMBINING SHORT RANGE WEATHER INFORMATION AND 
SHORT-TERM CLIMATE SIGNALS. 

FOR THE MOST PART THE TEMPERATURE FORECAST NEEDED ONLY SLIGHT ADJUSTMENTS. 
BECAUSE OF WARMTH IN THE EARLY DAYS OF APRIL IN EAST-CENTRAL AND SOUTHEASTERN 
U.S., WE MOVED THE SOUTHERN BOUNDARY OF THE AREA OF FAVORED BELOW AVERAGE 
TEMPERATURE CENTERED IN THE GREAT LAKES A LITTLE TO THE NORTH. 

PRECIPITATION IS MORE COMPLICATED. THE EXPECTED PRECIPITATION DURING APRIL 1-2 
ALONG THE WEST COAST AND EVEN IN COASTAL SOUTHERN CALIFORNIA MADE US REMOVE THE 
AREA OF PREDICTED BELOW MEDIAN PRECIPITATION, INDICATED AT MID-MONTH, FROM MUCH 
OF THE MAP, ESPECIALLY ALONG THE IMMEDIATE WEST COAST. THE ONLY SURVIVING 
FORECAST FOR ENHANCED CHANCES FOR BELOW MEDIAN PRECIPITATION IS IN SOUTHEASTERN 
CA, AND PARTS OF AZ, NV, UT AND CO. IN THE FIRST FEW DAYS OF APRIL THERE WILL 
BE SEVERAL PRECIPITATION EVENTS IN THE TENNESSEE AND OHIO VALLEY SO WE ADDED 
ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION IN THAT AREA. 

THE APRIL TEMPERATURE OUTLOOK INDICATES AN AREA OF FAVORED BELOW NORMAL MONTHLY 
MEAN TEMPERATURES FOR PORTIONS OF THE NORTHERN PLAINS, GREAT LAKES, AND 
NORTHEAST. SOME OF THE COLD MAY BE AMPLIFIED NEAR THE SHORES AROUND THE GREAT 
LAKES SINCE ICE COVER IS PRESENTLY HIGH AND, ONCE UNFROZEN, WATER TEMPERATURE 
WILL LIKELY BE BELOW NORMAL FOR SOME TIME. TOOLS FAVOR ABOVE NORMAL 
TEMPERATURES FOR MUCH OF THE SOUTHWEST QUARTER OF THE CONUS WITH A WEAK 
EXTENSION ACROSS TEXAS INTO THE COASTAL AREAS OF THE SOUTHEAST. MUCH OF ALASKA 
HAS ENHANCED PROBABILITY FOR ABOVE NORMAL TEMPERATURE.

THE APRIL OUTLOOK FAVORS BELOW-MEDIAN PRECIPITATION IN THE SOUTHEASTERN PART OF 
CALIFORNIA, AND SOME OF NEVADA, ARIZONA, UTAH AND COLORADO. ABOVE MEDIAN 
PRECIPITATION IS FAVORED IN PARTS OF THE TENNESSEE AND OHIO VALLEY. THE REST OF 
CONUS AND ALASKA IS DESIGNATED EC.





THE TWO-WEEK OLD MID-MONTH MESSAGE IS BELOW:

ENSO-NEUTRAL CONDITIONS REMAIN IN PLACE AND ARE NOT DIRECTLY CONSIDERED FOR 
APRIL. THE FIRST GUESS FOR APRIL IS THE 0.5 MONTH LEAD MAM SEASONAL FORECAST 
ISSUED ONE MONTH AGO. THERE IS STRONG SUPPORT FOR CONTINUATION OF THE 
TEMPERATURE PATTERN THAT RESEMBLES WHAT WE HAVE SEEN ALL WINTER. DYNAMICAL 
TOOLS AND SOME OF THE EMPIRICAL TOOLS SUPPORT THE CONTINUATION OF THIS PATTERN 
FOR AT LEAST APRIL. THE IMPACT ON THE APRIL OUTLOOK WOULD BE WARMTH IN THE 
SOUTHWEST AND COLD IN THE NORTHERN PLAINS AND NORTHEAST.  COVERAGE AND 
PROBABILITIES ARE QUITE HIGH FOR A MONTHLY TEMPERATURE FORECAST.

THE APRIL TEMPERATURE OUTLOOK INDICATES AN AREA OF FAVORED BELOW NORMAL MONTHLY 
MEAN TEMPERATURES FOR PORTIONS OF THE NORTHERN PLAINS, GREAT LAKES, TENNESSEE 
AND OHIO VALLEYS AND NORTHEAST. SOME OF THE COLD MAY BE AMPLIFIED NEAR THE 
SHORES AROUND THE GREAT LAKES SINCE ICE COVER IS PRESENTLY HIGH AND, ONCE 
UNFROZEN, WATER TEMPERATURE WILL BE BELOW NORMAL FOR SOME TIME. TOOLS FAVOR 
ABOVE NORMAL TEMPERATURES FOR MUCH OF THE SOUTHWEST QUARTER OF THE CONUS WITH A 
WEAK EXTENSION ACROSS TEXAS INTO THE COASTAL AREAS OF THE SOUTHEAST. 
ANTICIPATED RIDGING ACROSS PORTIONS OF WESTERN NORTH AMERICA INTO ALASKA 
SUPPORT ABOVE NORMAL TEMPERATURES FOR MUCH OF ALASKA. BELOW AVERAGE SEA ICE 
EXTENT AND ABOVE AVERAGE SEA SURFACE TEMPERATURES IN THE BERING SEA ALSO 
SUPPORT THIS FORECAST.  

IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR NOT RELIABLE, EQUAL CHANCES (EC) 
OF BELOW-, NEAR- AND ABOVE-NORMAL MEAN MONTHLY TEMPERATURES ARE INDICATED.

THE CONFIDENCE IN THE PRECIPITATION OUTLOOK IS MUCH LESS THAN THAT FOR 
TEMPERATURE, WHICH IS OFTEN THE CASE. THE NMME, CFS, AS WELL AS THE CCA 
STATISTICAL TOOL, FAVOR BELOW-MEDIAN PRECIPITATION IN THE SOUTHWEST FOR ALL OF 
CALIFORNIA, AND SOME OF NEVADA, ARIZONA AS WELL AS ALONG THE WEST COAST INTO 
THE ALASKA PANHANDLE. THE REST OF CONUS IS DESIGNATED EC.

ALL OF THE ABOVE WILL BE REVISITED WHEN DOING THE MONTHLY UPDATE OM MARCH 31.   
 

IN AREAS WHERE CLIMATE SIGNALS ARE WEAK AND/OR NOT RELIABLE, EQUAL CHANCES (EC) 
OF BELOW-, NEAR- AND ABOVE-MEDIAN TOTAL MONTHLY PRECIPITATION ARE INDICATED.

THE MAIN FACTORS THAT USUALLY INFLUENCE THE MONTHLY CLIMATE OUTLOOK INCLUDE:
1) EL NINO AND LA NINA - WHICH COMPRISE ENSO. IMPACTS OF THESE EVENTS ARE 
SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM THREE OR MORE DECADES INTO 
EL NINO, NEUTRAL AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN 
COMPUTING ANOMALIES. THESE ARE CALLED "COMPOSITES" AND 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 - CALLED THE MADDEN JULIAN OSCILLATION 
(MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS.
4) THE ARCTIC OSCILLATION (AO), THE SIMILAR NORTH ATLANTIC OSCILLATION (NAO), 
AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE 
ANOMALY PATTERN ESPECIALLY DURING BOREAL WINTER AND ARE GENERALLY CONSIDERED TO 
HAVE LOW PREDICTABILITY.
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 MODELS - CANONICAL CORRELATION ANALYSIS (CCA), 
SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOG (CA), AND 
ENSEMBLE CCA (ECCA).
8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM 
VERSION 2 (CFS) AND FOR THE ZERO-LEAD UPDATE FORECASTS THE NCEP GLOBAL ENSEMBLE 
FORECAST SYSTEM (GEFS).  AN EXPERIMENTAL FORECAST SYSTEM, THE NATIONAL 
MULTI-MODEL ENSEMBLE (NMME), COMPRISED OF SEVERAL DYNAMICAL MODELS IS ALSO USED.


FORECASTER: HUUG VAN DEN DOOL


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 MAY ... WILL BE ISSUED ON THU APR 17 2014


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

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