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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 ASO 2017
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    6.5mn FMA 2018
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    0.5mn Aug 2017


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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUL 20 2017

30-DAY OUTLOOK DISCUSSION FOR AUGUST 2017

THE AUGUST 2017 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. PLEASE SEE THE ENSO DIAGNOSTIC DISCUSSION AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/ENSO_ADVISORY/ENSODISC
.SHTML FOR A MORE DETAILED ANALYSIS OF SEA SURFACE TEMPERATURES ACROSS THE
EQUATORIAL PACIFIC. THE MADDEN-JULIAN OSCILLATION (MJO) BECAME MORE COHERENT
DURING MID-JULY WITH ITS ENHANCED PHASE OVER THE WESTERN MARITIME CONTINENT. A
COHERENT MJO SIGNAL IS FAVORED TO PROPAGATE EASTWARD DURING THE NEXT TWO WEEKS,
BUT ITS EFFECTS ON THE EXTRATROPICS ARE EXPECTED TO BE MINIMAL GIVEN THE TIME
OF YEAR. THE CFS MODEL INDICATES AN ATMOSPHERIC KELVIN WAVE (KW) CROSSING THE
WESTERN HEMISPHERE DURING LATE JULY INTO THE BEGINNING OF AUGUST. THIS KW COULD
PROVIDE A FAVORABLE ENVIRONMENT FOR TROPICAL CYCLONE DEVELOPMENT OVER THE EAST
PACIFIC AND CONTRIBUTE TO A CONTINUATION OF ENHANCED MOISTURE ACROSS THE
SOUTHWESTERN U.S.

THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) DEPICTS INCREASED PROBABILITIES
FOR ABOVE-NORMAL TEMPERATURES ACROSS NEARLY ALL OF THE CONTINENTAL U.S. THE
LARGEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES IN THE OFFICIAL OUTLOOK ARE
FORECAST ACROSS THE NORTHERN GREAT PLAINS WHERE CURRENT SOIL MOISTURE VALUES
RANK BELOW THE 10TH PERCENTILE.  ALSO, THE GFS, ECMWF, AND CANADIAN ENSEMBLE
MEANS INDICATE THAT THE ANOMALOUS 500-HPA RIDGE IS LIKELY TO PERSIST AT LEAST
THROUGH THE BEGINNING OF AUGUST. ALTHOUGH MANY OF THE DYNAMICAL MODELS FAVOR
ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHWESTERN U.S., EQUAL CHANCES FOR
BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST FOR THIS REGION BASED
ON A CONSISTENT SIGNAL AMONG DAILY RUNS OF THE NCEP CLIMATE FORECAST SYSTEM
(CFS) MODEL, DEPICTING NEAR TO BELOW-NORMAL TEMPERATURES, AND THE ENHANCED ODDS
FOR ABOVE-MEDIAN PRECIPITATION FORECAST IN THE PRECIPITATION OUTLOOK.

THE PROBABILITY ANOMALY CORRELATION (PAC) CALIBRATED PROBABILITY FORECAST FROM
THE NMME FEATURES LITTLE IF ANY SIGNAL THROUGHOUT MOST OF THE FORECAST DOMAIN
WITH ONLY A SLIGHT TILT IN THE ODDS (36 TO 40 PERCENT) FOR THE ABOVE NORMAL
TERCILE FROM THE RIO GRANDE VALLEY NORTH TO THE CENTRAL ROCKIES. THE MOST
CONSISTENT SIGNAL AMONG DAILY CFS MODEL RUNS IS A FAVORED AREA OF ABOVE-MEDIAN
PRECIPITATION OVER THE RIO GRANDE VALLEY AND PARTS OF THE WESTERN U.S. BASED ON
THESE TWO PRECIPITATION TOOLS ALONG WITH POTENTIAL INFLUENCES FROM AN EXPECTED
ACTIVE PERIOD OF EAST PACIFIC TROPICAL CYCLONE ACTIVITY, ABOVE-MEDIAN
PRECIPITATION IS FAVORED FOR THE RIO GRANDE VALLEY, MOST OF THE MONSOON REGION
OF THE SOUTHWESTERN U.S., AND THE CENTRAL ROCKIES. FORECAST CONFIDENCE IN THE
PRECIPITATION OUTLOOK IS LIMITED DUE TO THE LACK OF PREDICTABILITY OF
CONVECTIVE RAINFALL ON A MONTHLY TIME SCALE.

THE DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT WITH INCREASED CHANCES OF
ABOVE-NORMAL TEMPERATURES ACROSS ALASKA. THE HIGHEST PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE ALASKA PENINSULA ALONG WITH
PARTS OF WESTERN AND SOUTHERN ALASKA, BASED IN PART ON SEA SURFACE TEMPERATURES
AVERAGING 1 TO 3 DEGREES C ABOVE NORMAL. THE DYNAMICAL MODEL CONSENSUS FAVORS A
RELATIVELY WET AUGUST 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.



AN UPDATED MONTHLY OUTLOOK... FOR AUG WILL BE ISSUED ON MON JULY 31 2017


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

$$

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