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


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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300PM EDT TUESDAY JUN 30 2015

30-DAY OUTLOOK DISCUSSION FOR JULY 2015

THIS UPDATE TO THE 30-DAY OUTLOOK FOR JULY, 2015 IS BASED SUBSTANTIALLY ON
INFORMATION FROM SHORT-TERM WEATHER FORECASTS FOR THE FIRST 14 DAYS OF THE
MONTH. ENSEMBLE FORECASTS FROM THE GEFS, CANADIAN, AND ECMWF MODELS SHOW GOOD
CONSENSUS ON THE UPPER LEVEL CIRCULATION PATTERNS EXPECTED IN EARLY JULY. THE
ASSOCIATED SURFACE TEMPERATURE AND PRECIPITATION PATTERNS AGREE WELL WITH THE
JULY OUTLOOK ISSUED IN MID-JUNE. EL NINO CONDITIONS HAVE MAINTAINED AMPLITUDE
IN RECENT WEEKS AND CONTINUE TO BE ON TRACK WITH PREDICTIONS MADE IN THE LAST
MONTH OR TWO.

MODELS PREDICT A MEAN RIDGE OVER WESTERN NORTH AMERICA WITH A DOWNSTREAM TROUGH
FORECAST TO BE LOCATED NEAR THE EAST COAST OF THE CONUS DURING THE FIRST TWO
WEEKS OF JULY. THE GEFS PERSISTS THESE FEATURES INTO WEEKS 3 AND 4, ALTHOUGH
THE ECMWF ENSEMBLES SUGGEST THAT THE PATTERN MAY BREAK DOWN IN THE LATTER HALF
OF JULY. FORECASTS FOR THE FIRST HALF OF THE MONTH STRONGLY SUPPORT
ABOVE-NORMAL TEMPERATURES OVER THE PACIFIC NORTHWEST AND ALASKA, RESULTING IN
INCREASED CONFIDENCE FOR ABOVE-NORMAL MONTHLY MEAN TEMPERATURES RELATIVE TO THE
OUTLOOK RELEASED IN MID-JUNE. THE EXPECTED TROUGH OVER THE EASTERN CONUS SHOULD
FAVOR A COOL START TO THE MONTH FROM THE UPPER MISSISSIPPI VALLEY TO PARTS OF
THE NORTHEAST, RESULTING IN A NORTHEASTWARD EXTENSION OF THE AREA OF ENHANCED
CHANCES FOR BELOW-NORMAL TEMPERATURES INDICATED ON THE PREVIOUS OUTLOOK FOR
JULY. OTHERWISE THE REVISED TEMPERATURE OUTLOOK IS FAIRLY SIMILAR TO THE
OUTLOOK ISSUED AT MID-MONTH.

THE PRECIPITATION OUTLOOK IS HEAVILY INFLUENCED BY THE PRECIPITATION EXPECTED
IN THE FIRST WEEK OF THE MONTH. THE FOLLOWING CHANGES HAVE BEEN MADE TO THE
JULY, 2015 OUTLOOK ISSUED AT MID-MONTH. FORECASTS FOR THE FIRST FEW DAYS OF THE
MONTH INDICATE GOOD CHANCES FOR WET CONDITIONS FROM THE TENNESSEE VALLEY TO
PARTS OF THE NORTHEAST. THIS PROMPTED AN ADJUSTMENT OF THE AREA FAVORING
ABOVE-MEDIAN MONTHLY TOTAL PRECIPITATION EASTWARD TO THOSE REGIONS. THE CHANCES
FOR BELOW-MEDIAN PRECIPITATION APPEAR SOMEWHAT HIGHER FOR PARTS OF EASTERN
TEXAS THAN THEY DID ON THE OUTLOOK ISSUED A FEW WEEKS AGO ACCORDING TO THE
SHORT-TERM FORECASTS, EXCEPT FOR EXTREME SOUTHERN PARTS OF THE STATE WHERE SOME
PRECIPITATION IS EXPECTED EARLY IN THE MONTH. SHORT-TERM FORECAST FAVOR
ABOVE-MEDIAN RAINFALL THROUGHOUT MUCH OF THE WEST, EXCEPT FOR THE NORTHERN
ROCKIES AND THE PACIFIC NORTHWEST. THIS LEADS TO A SLIGHT WESTWARD EXPANSION OF
THE AREA FAVORING ABOVE-MEDIAN PRECIPITATION AMOUNTS INTO WESTERN NEVADA. AN
EXPECTED DRY START TO THE MONTH INCREASES CHANCES FOR BELOW-MEDIAN MONTHLY
PRECIPITATION TOTALS IN PARTS OF THE PACIFIC NORTHWEST. MODELS SUGGEST SOME
RIDGING OVER ALASKA IN THE EARLY PART OF THE MONTH, ELEVATING CHANCES FOR
BELOW-MEDIAN PRECIPITATION IN SOUTHEASTERN PART OF THE STATE.

BELOW IS THE DISCUSSION ISSUED WITH THE OUTLOOK ISSUED IN MID-JUNE.

SEA SURFACE TEMPERATURES (SSTS) IN EARLY JUNE ARE CURRENTLY MORE THAN ONE
DEGREE C ABOVE NORMAL ALONG THE EQUATOR IN THE PACIFIC OCEAN FROM THE SOUTH
AMERICAN COAST WESTWARD TO JUST EAST OF THE INTERNATIONAL DATE LINE. WITHIN
THIS AREA THERE ARE SOME PLACES WERE THE SST ANOMALIES ARE OVER +2.0 DEGREES C.
ABOVE NORMAL SSTS EXTEND NORTHWARD FROM THE EQUATOR TO COVER AN EXTENSIVE AREA
TO THE WEST OF NORTH AMERICA. SUBSURFACE OCEAN WATER TEMPERATURES ARE ALSO
CONSIDERABLY ABOVE NORMAL THROUGHOUT THE EASTERN EQUATORIAL PACIFIC OCEAN.
RECENT ATMOSPHERIC OBSERVATIONS OVER THE EASTERN AND CENTRAL TROPICAL PACIFIC
OCEAN SUGGEST STRONG OCEAN-ATMOSPHERE COUPLING, WITH UNUSUALLY ACTIVE
CONVECTION TOGETHER WITH LARGE SCALE WESTERLY WIND ANOMALIES AT LOW LEVELS, AND
EASTERLY ANOMALIES AT UPPER LEVELS. TOGETHER THESE SUGGEST THE DEVELOPMENT OF
MODERATE STRENGTH EL NINO CONDITIONS. STATISTICAL AND DYNAMIC MODELS FOR SST
PREDICTION SUGGEST THAT THE EL NINO CONDITIONS WILL PERSIST OR STRENGTHEN IN
THE COMING MONTHS. EL NINO APPEARS TO BE CONTRIBUTING TO CLIMATE ANOMALIES OVER
PARTS OF NORTH AMERICA IN THE PAST MONTH OR TWO, AND ARE EXPECTED TO CONTINUE
TO HAVE AN INFLUENCE IN JULY.

DYNAMICAL MODEL FORECASTS INITIALIZED IN THE LAST FEW MONTHS HAVE SHOWN
CONSIDERABLE CONSISTENCY IN THEIR PREDICTIONS FOR NORTH AMERICAN SURFACE
TEMPERATURE AND PRECIPITATION. THEIR PREDICTIONS HAVE BEEN QUITE SUCCESSFUL IN
SUGGESTING ELEVATED ODDS OF WET CONDITIONS IN MUCH OF WESTERN AND CENTRAL CONUS
IN THE LATE SPRING. THE MODEL PREDICTIONS AGREE REASONABLY WELL WITH THE
TEMPERATURE AND PRECIPITATION ANOMALIES OBSERVED IN ASSOCIATION WITH PAST EL
NINOS. THUS, THE OUTLOOK FOR JULY 2015 IS BASED HEAVILY ON THE FORECAST FROM
THE CFSV2, AND PROBABILITIES FROM THE MODEL CONSENSUS OF CLIMATE MODELS RUN AS
PART OF THE NMME AND IMME.

THE FORECAST SUGGESTS ELEVATED CHANCES OF ABOVE-NORMAL TEMPERATURES IN THE
WESTERN CONUS AND ALASKA. BELOW NORMAL TEMPERATURES ARE FAVORED IN AREAS THAT
HAVE EXPERIENCED RECENT SURPLUS RAINFALL IN THE CENTRAL AND SOUTHERN PORTIONS
OF THE ROCKY MOUNTAINS AND GREAT PLAINS, INCLUDING MUCH OF TEXAS. THIS AREA IS
LIKELY ASSOCIATED WITH THE COOLING EFFECTS OF ABOVE AVERAGE SOIL MOISTURE,
TOGETHER WITH INCREASED CHANCES FOR A CONTINUATION OF RELATIVELY WET CONDITIONS
IN THE NEXT MONTH. THERE IS A FAIR CONSENSUS AMONG CLIMATE MODELS FOR ABOVE
NORMAL TEMPERATURES IN THE EASTERN CONUS, HOWEVER THE CONFIDENCE IS LOW
CONSIDERING THAT PAST EL NINO SUMMERS GENERALLY FAVOR COOL CONDITIONS FOR MUCH
OF THE EAST AND NORTH CENTRAL CONUS. THE AREA FAVORING ABOVE NORMAL
TEMPERATURES WAS RESTRICTED TO AREAS EAST OF THE APPALACHAIN MOUNTAINS WHERE
THE YEAR-TO-YEAR TEMPERATURE VARIABILITY IS LOWER IN RELATION TO POSSIBLE
CLIMATE SIGNALS.

THERE CONTINUES TO BE A STRONG CONSENSUS AMONG MODELS FOR ABOVE-MEDIAN
PRECIPITATION AMOUNTS OVER A WIDE AREA OF THE CENTRAL AND WESTERN CONUS. SOME
EARLY TROPICAL STORM ACTIVITY HAS ALREADY BEEN OBSERVED IN EARLY JUNE IN THE
EASTERN PACIFIC OFF THE COAST OF MEXICO, AND HAS BEEN CONTRIBUTING TO ANOMALOUS
MOISTURE IN PARTS OF THE WESTERN CONUS. MODEL FORECASTS SUGGEST A CONTINUATION
OF ENHANCED CHANCES OF ABOVE MEDIAN PRECIPITATION THAT APPEARS AS A NORTHWARD
EXTENSION OF A LARGE AREA OF FORECAST ABOVE MEDIAN RAINFALL IN THE TROPICAL
EASTERN PACIFIC. ENSO COMPOSITES GENERALLY FAVOR A WEAK SOUTHWEST MONSOON IN
THE WESTERN PART OF THE MONSOON REGION, SO THE MODEL FORECASTS FOR ABOVE MEDIAN
PRECIPITATION AMOUNTS IN ARIZONA MAY DEPEND ON HIT-OR-MISS RESIDUAL MOISTURE
FROM TROPICAL STORMS, AND AS SUCH MAY BE UNRELIABLE IN WESTERN REGIONS OF THE
DESERT SOUTHWEST. THE CFSV2 MODEL INDICATES BELOW MEDIAN PRECIPITATION FOR
SOUTH TEXAS EXTENDING INTO PARTS OF THE SOUTHEASTERN CONUS. THIS AREA SEEMS A
REASONABLE EXTENSION OF DRY CONDITIONS EXPECTED OVER THE CARIBBEAN IN EL NINO
SUMMERS, HOWEVER MODEL CONSENSUS IN THE EASTERN PART OF THE AREA AND IN FLORIDA
WAS LOW. THERE IS ALSO SOME WEAK CONSENSUS AMONG THE NMME FOR BELOW MEDIAN
PRECIPITATION AMOUNTS OVER PARTS OF THE ALASKA PANHANDLE.

IN AREAS WHERE THERE ARE NO STATISTICALLY SIGNIFICANT CLIMATE SIGNALS, SUCH
THAT THE LIKELIHOODS OF MONTHLY MEAN TEMPERATURES OR MONTHLY ACCUMULATED
PRECIPITATION AMOUNTS ARE EQUAL 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: DAVID UNGER


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 AUG ... WILL BE ISSUED ON THU JUL 16 2015


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

$$

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