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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 MJJ 2017
    1.5mn JJA 2017
    2.5mn JAS 2017
    3.5mn ASO 2017
    4.5mn SON 2017
    5.5mn OND 2017
    6.5mn NDJ 2017
    7.5mn DJF 2017
    8.5mn JFM 2018
    9.5mn FMA 2018
   10.5mn MAM 2018
   11.5mn AMJ 2018
   12.5mn MJJ 2018
    0.5mn May 2017


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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SUN APR 30 2017

30-DAY OUTLOOK DISCUSSION FOR MAY 2017

ENSO NEUTRAL CONDITIONS CONTINUED ACROSS THE PACIFIC OCEAN. THE SEA-SURFACE
TEMPERATURES IN THE NINO 1+2, NINO4, AND NINO 3.4 REGIONS INCREASED. THE MJO
REMAINED WEAK, THOUGH SOME MODELS DO INDICATE A STRENGTHENING SIGNAL ACROSS THE
WESTERN HEMISPHERE, SO THERE COULD BE SOME RELATED IMPACTS DURING THE LATTER
HALF OF MAY. UNCERTAINTY ABOUT THE DEVELOPMENT OF AN MJO, THEN THE ATTENDANT,
LAGGED IMPACTS, RESULTS IN THE MJO BEING OF MINIMAL CONSEQUENCE IN THE UPDATED
OUTLOOK. THE OUTLOOKS ARE CONSISTENT WITH SOME OF THE MJO LAGGED COMPOSITES
CENTERED ON MAY.

THE UPDATED TEMPERATURE OUTLOOK REFLECTS GUIDANCE FOR EARLY IN THE MONTH WHERE
TEMPERATURES ARE FORECAST TO BE BELOW AVERAGE ACROSS THE GREAT PLAINS, MIDWEST,
AND MISSISSIPPI VALLEY. THAT PREDICTED COOLER AIR IS THEN LIKELY TO SLIDE SOUTH
AND EAST, SO THE UPDATED OUTLOOK NOW REFLECTS THAT LIKELY COOLER FIRST HALF OF
THE MONTH FROM THE SOUTHERN GREAT PLAINS TO THE OHIO VALLEY AND ACROSS TO THE
MID-ATLANTIC. ACROSS THE SOUTHWEST AND GREAT BASIN, THE OUTLOOK IS RELATIVELY
UNCHANGED, WITH THE HIGHEST ODDS OF ABOVE NORMAL TEMPERATURES SHIFTED NORTHWARD
SLIGHTLY, GIVEN A PREDICTED COOLER PERIOD, MID-MONTH, OVER ARIZONA. UNCERTAINTY
ACROSS THE NORTHERN GREAT PLAINS, NORTHERN ROCKIES, AND PACIFIC NORTHWEST, IS
HIGH, SO NO TILT IN THE ODDS IS INDICATED FOR THOSE REGIONS. TEMPERATURES OVER
MUCH OF ALASKA ARE PREDICTED TO BE ABOVE NORMAL, WITH A WARMER START TO THE
MONTH. UNCERTAINTY IS HIGHEST OVER SOUTHEAST ALASKA AND THE ALASKA PANHANDLE.

THE PRECIPITATION OUTLOOK HAS BEEN REVISED CONSIDERABLY, GIVEN THE STRONG
SIGNALS IN SHORT-TERM MODEL GUIDANCE AND OFFICIAL PRODUCTS. AN ACTIVE PERIOD IS
FORECAST EARLY IN THE MONTH FROM THE GULF COAST TO THE NORTHEAST. A RELATIVELY
SHORT WAVELENGTH AND A PREDICTED TROUGH OVER THE ROCKIES FOR THE MIDDLE OF THE
MONTH SUPPORTS A BROAD SWATH OF FAVORED ABOVE MEDIAN PRECIPITATION FROM THE
NORTHERN ROCKIES TO FOUR CORNERS REGION, WHERE MEDIAN PRECIPITATION AMOUNTS ARE
LOW, SO EVEN A SHORT PERIOD OF WETNESS WOULD FAVOR ABOVE MEDIAN PRECIPITATION
FOR THE ENTIRE MONTH. MODEL GUIDANCE AND OFFICIAL OUTLOOKS COVERING MOST OF
MAY, FAVORS DRIER THAN MEDIAN CONDITIONS FOR THE PACIFIC NORTHWEST COAST, AND
PORTIONS OF THE MIDDLE AND UPPER MISSISSIPPI VALLEY.

----------- THE FORECAST MESSAGE FOR THE MAY TEMPERATURE AND PRECIPITATION
OUTLOOKS ISSUED ON APRIL 20 IS BELOW. -------------------

ENSO NEUTRAL CONDITIONS ARE PRESENT ACROSS THE PACIFIC OCEAN.  SOME ATMOSPHERIC
VARIABLES, SUCH AS LOW-LEVEL WINDS AND OUTGOING LONGWAVE RADIATION (OLR) STILL
HAVE SOME RESEMBLANCE TO CANONICAL LA NINA PATTERNS, THOUGH OTHERS (UPPER-LEVEL
WINDS) ARE LESS COHERENT. OLR STILL INDICATES SUPPRESSED (ENHANCED) CONVECTION
NEAR THE DATE LINE (MARITIME CONTINENT). A KEY DIFFERENCE THIS MONTH, IS THAT
THE SUPPRESSED CONVECTION EXTENDS NORTHEASTWARD, RATHER THAN BEING SYMMETRIC
ALONG THE EQUATOR. THIS ASYMMETRY HAS ALLOWED SOME CONVECTION TO DEVELOP FROM
160W TO 120W, JUST SOUTH OF THE EQUATOR.

THE MJO PLAYED A SMALL ROLE IN THE TROPICAL PACIFIC DURING MARCH. SOME SHORTER
PERIOD VARIABILITY WAS EVIDENT ACROSS THE EASTERN PACIFIC, BUT THE PATTERN OVER
THE CENTRAL PACIFIC WAS HIGHLY LINKED TO THE LONG-TERM PATTERN. FORECASTS OF
THE MJO INDICATE AN AMPLIFICATION OVER THE WESTERN PACIFIC, THOUGH THE
INCOHERENCE OF THE OBSERVED SIGNAL INCREASES UNCERTAINTY. THE MJO IS NOT LIKELY
TO PLAY A LARGE ROLE IN THE MONTHLY VARIABILITY OVER NORTH AMERICA DURING MAY.

OTHER FACTORS, SUCH AS ANTECEDENT SOIL MOISTURE AND SNOW PACK, WERE CONSIDERED.
SOIL MOISTURE IS ANOMALOUSLY HIGH OVER PORTIONS OF THE MIDWEST, WHICH HAS A
LAGGED RELATIONSHIP WITH BELOW NORMAL TEMPERATURES. ABOVE NORMAL SNOW PACK OVER
THE CENTRAL AND NORTHERN ROCKIES WAS ALSO CONSIDERED IN THE TEMPERATURE OUTLOOK.

DYNAMIC MODELS FROM THE NMME SUITE GENERALLY INDICATED ABOVE NORMAL
TEMPERATURES FOR MOST OF THE CONUS AND ALASKA. PROBABILITIES WERE WEAKEST FROM
CALIFORNIA TO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. MORE RECENT TRENDS IN
MODEL GUIDANCE (CFS FOR THE MONTH OF MAY, GUIDANCE FOR THE WEEK 3-4 PERIOD,
AND THE LAST FEW DAYS OF THE 8-14 DAY PERIOD) INDICATE A COOL START TO THE
MONTH OVER THE NORTHERN ROCKIES AND GREAT PLAINS. THE OUTLOOK REFLECTS THE
COMBINATION OF NMME MODELS AND MORE RECENT MODEL INPUTS, AS WELL AS THE
ANTECEDENT CONDITIONS MENTIONED ABOVE. THE OUTLOOK INDICATES ABOVE NORMAL
TEMPERATURES ARE FAVORED FOR THE SOUTHWEST, TEXAS, AND FROM THE SOUTHEAST TO
THE GREAT LAKES AND NORTHEAST.

SIGNALS FOR PRECIPITATION ANOMALIES IN THE INDIVIDUAL NMME MODELS ARE QUITE
STRONG, BUT SIGNALS IN THE MEAN ARE QUITE A BIT WEAKER AS THE MODELS EXHIBIT
POOR AGREEMENT IN THE OVERALL PATTERN. AFTER CALIBRATION, WEAK SIGNALS REMAIN
OVER WESTERN ALASKA, THE NORTHERN HIGH PLAINS, THE GREAT LAKES, AND NORTHEAST.
SOME OF THE MODELS IN THE NMME SUITE INDICATED EXTREME ANOMALIES (IN BOTH
TEMPERATURE AND PRECIPITATION), SO THOSE MODELS WERE CONSIDERED OUTLIERS. TO
BROADEN THE MODEL INPUTS AND LESSEN THE IMPACT OF THE EXTREME ANOMALIES, THE
IMME WAS ALSO USED AS AN INPUT FOR THE PRECIPITATION OUTLOOK. THE OFFICIAL
OUTLOOK INDICATES BELOW MEDIAN PRECIPITATION IS FAVORED FOR WESTERN ALASKA, THE
ALASKA PANHANDLE, AND THE GREAT LAKES, ALL CONSISTENT WITH MODEL OUTPUT. ABOVE
MEDIAN PRECIPITATION IS FAVORED OVER THE NORTHERN HIGH PLAINS AND ALONG THE
GULF COAST, CONSISTENT WITH MODEL OUTPUT AND IN SOME CASES, TRENDS.


FORECASTER: MATTHEW ROSENCRANS


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 JUN ... WILL BE ISSUED ON THU MAY 18 2017


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

$$

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