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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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More Outlooks
    0.5mn AMJ 2015
    1.5mn MJJ 2015
    2.5mn JJA 2015
    3.5mn JAS 2015
    4.5mn ASO 2015
    5.5mn SON 2015
    6.5mn OND 2015
    7.5mn NDJ 2015
    8.5mn DJF 2015
    9.5mn JFM 2016
   10.5mn FMA 2016
   11.5mn MAM 2016
   12.5mn AMJ 2016
    0.5mn Apr 2015


Tools Used (see Discussion for explanation)
   CCA
   OCN
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   SMT
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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY MAR 19 2015

30-DAY OUTLOOK DISCUSSION FOR APRIL 2015

EQUATORIAL SEA-SURFACE TEMPERATURE (SST) ANOMALIES REMAIN ABOVE-NORMAL ACROSS
MUCH OF THE WESTERN AND CENTRAL EQUATORIAL PACIFIC AND THE OCEAN HAS BEGUN
TO SHOW BETTER COUPLING WITH THE ATMOSPHERE OVER THE LAST 1-2 MONTHS. CONSEQUENTLY, AN
EL NINO ADVISORY WAS ISSUED EARLIER THIS MONTH. THE LATEST NINO 3.4 INDEX IS
+0.5 C, WHILE THE NINO 4 INDEX IS +1.0 C. A STRONG MJO IS ALSO EVIDENT WITH THE
ENHANCED CONVECTIVE PHASE LOCATED ACROSS THE WESTERN HEMISPHERE AND MOVING
EASTWARD. BOTH OF THESE FACTORS PLAY A ROLE TO SOME DEGREE IN THE APRIL MONTHLY
OUTLOOK, ALTHOUGH TELECONNECTIONS AND IMPACTS FROM THESE MODES OF CLIMATE
VARIABILITY BEGIN TO RAPIDLY DECREASE DURING THE MONTH OF APRIL. ANOMALOUS SNOW
COVER AND SOIL MOISTURE ALSO PLAYED A ROLE IN THE FORECAST FOR APRIL IN SEVERAL
AREAS OF THE UNITED STATES.

THE APRIL TEMPERATURE OUTLOOK SHOWS AN ENHANCED LIKELIHOOD OF ABOVE-NORMAL
TEMPERATURES FOR THE FAR WEST AND ALL OF ALASKA, WITH THE HIGHEST PROBABILITIES
LOCATED ALONG THE COAST OF THE PACIFIC NORTHWEST AND THE SOUTHERN AREAS OF
ALASKA. CONSIDERATIONS OF BELOW AVERAGE SNOW COVER, ONGOING DROUGHT CONDITIONS
AND DYNAMICAL MODEL GUIDANCE ALL SUPPORT VARIOUS REGIONS OF THIS FORECAST AREA.

BELOW AVERAGE TEMPERATURES ARE FAVORED IN TWO AREAS WITHIN THE CONUS, AN AREA
CENTERED ACROSS WESTERN TEXAS AND ANOTHER SPANNING THE EASTERN GREAT LAKES,
NORTHEAST AND NORTHERN MID-ATLANTIC. THE REGION NEAR TEXAS IS SUPPORTED BY EL
NINO CONSIDERATIONS IN WHICH COMPOSITES AND REGRESSIONS INDICATE A BELOW NORMAL
SIGNAL IN THAT REGION. PROBABILISTIC NMME AND IMME DYNAMICAL MODEL GUIDANCE AND
TO SOME DEGREE MJO COMPOSITES FOR RMM PHASES 2 AND 3 ALSO SUPPORT THIS REGION.

DYNAMICAL MODEL GUIDANCE CONTINUES TO INDICATE A MEAN TROUGH ACROSS EASTERN
NORTH AMERICA AS HAS BEEN OBSERVED THROUGHOUT MUCH OF FEBRUARY AND MARCH. THE
CFS, PROBABILISTIC NMME AND IMME GUIDANCE FAVOR ELEVATED ODDS FOR BELOW NORMAL
TEMPERATURES IN THIS AREA. POSITIVE SNOW COVER AND DEPTH ANOMALIES IN SOME OF
THESE AREAS ALSO FAVORS BELOW NORMAL TEMPERATURES AS DO MJO COMPOSITES FOR
FORECAST MJO EVOLUTION FOR THE REMAINDER OF MARCH INTO EARLY APRIL.

THE APRIL PRECIPITATION OUTLOOK DEPICTS ELEVATED PROBABILITIES FOR ABOVE MEDIAN
PRECIPITATION ACROSS THE SOUTHWEST, SOUTHERN AND CENTRAL ROCKIES AND FROM
SOUTHERN TEXAS TO THE SOUTHEAST CONUS. DYNAMICAL MODEL GUIDANCE FROM THE CFS,
PROBABILISTIC NMME AND IMME ARE IN GOOD AGREEMENT ACROSS THE SOUTHWEST FOR
ANOMALOUS WETNESS WHILE EL NINO CONDITIONS, THE MJO (EARLY IN THE MONTH), AND
DYNAMICAL MODEL GUIDANCE SUPPORT THE FORECAST IN THE SOUTHEAST. THE FAVORED
UPPER-AIR HEIGHT PATTERN AT THE CURRENT TIME ESPECIALLY DURING THE FIRST HALF
OF THE MONTH IS FOR RIDGING (TROUGHING) ACROSS WESTERN (EASTERN) NORTH AMERICA
WHICH SUPPORTS ELEVATED ODDS FOR BELOW MEDIAN PRECIPITATION FOR PARTS OF THE
NORTHERN PLAINS AND WESTERN GREAT LAKES. BELOW MEDIAN PRECIPITATION IS ALSO
FAVORED BY DYNAMICAL MODEL GUIDANCE FOR THE FAR PACIFIC NORTHWEST.

IN AREAS WHERE CLIMATE SIGNALS ARE WEAK, SUCH THAT THE LIKELIHOODS OF MONTHLY
MEAN TEMPERATURES OR MONTHLY ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO
CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) IS 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: JON GOTTSCHALCK


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 APR WILL BE ISSUED ON TUE MARCH 31 2015


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

$$

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