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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 2018
    1.5mn JJA 2018
    2.5mn JAS 2018
    3.5mn ASO 2018
    4.5mn SON 2018
    5.5mn OND 2018
    6.5mn NDJ 2018
    7.5mn DJF 2018
    8.5mn JFM 2019
    9.5mn FMA 2019
   10.5mn MAM 2019
   11.5mn AMJ 2019
   12.5mn MJJ 2019
    0.5mn May 2018


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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 APR 19 2018


30-DAY OUTLOOK DISCUSSION FOR MAY 2018

THE MAY 2018 IS ISSUED AGAINST THE BACKDROP OF A TRANSITIONING ENSO STATE (TO
ENSO-NEUTRAL) AND FOLLOWING A PROLONGED STRETCH (INCLUDING FORECASTS THAT
EXTEND THROUGH THE END OF APRIL) OF BELOW-NORMAL TEMPERATURES ACROSS MANY PARTS
OF THE CONUS. AS WITH ANY CLIMATE FORECAST, WE MUST BE COGNIZANT OF LONG-TERM
TRENDS; BOTH A 15-YEAR OCN AND A LEAST-SQUARES LINEAR FIT REVEAL STRONG WARMING
TRENDS ACROSS THE SOUTHERN AND EASTERN CONUS DURING LATE SPRING AND EARLY
SUMMER. SLIGHTLY NEGATIVE TEMPERATURE TRENDS ARE OBSERVED FOR A SMALL PORTION
OF THE NORTHERN HIGH PLAINS AND NORTHERN ROCKIES. PRECIPITATION TRENDS ARE NOT
NEGLIGIBLE THIS TIME OF YEAR EITHER; AN INCREASING (DECREASING) TREND IN LATE
SPRING AND EARLY SUMMER PRECIPITATION HAS BEEN OBSERVED ACROSS MUCH OF THE
NORTHERN AND EASTERN CONUS (SOUTHWESTERN CONUS). THESE LONG-TERM TRENDS FORM
THE STARTING POINT FOR THE MAY 2018 OUTLOOK, AT WHICH POINT WE CONSIDER
SUBSEASONAL TO SEASONAL CLIMATE VARIABILITY, INCLUDING ENSO, SOIL MOISTURE, AND
VARIOUS STATE-OF-THE-ART DYNAMICAL MODEL FORECASTS.

THE TEMPERATURE OUTLOOK IS CONSTRUCTED WITH THE AFOREMENTIONED TRENDS IN MIND,
BUT TWEAKED COLDER ACROSS PARTS OF THE EAST-CENTRAL CONUS CENTERED ON THE
MISSISSIPPI RIVER. THIS IS DUE TO VERY HIGH SOIL MOISTURE CONTENT AND THE
LATEST MODEL GUIDANCE FROM THE NMME AND ECMWF. OVER THE MID-ATLANTIC AND
NORTHEAST THE OBJECTIVE GUIDANCE, TAKEN IN ITS ENTIRETY, STILL EXHIBITS A
SLIGHT TILT TOWARD ABOVE-NORMAL TEMPERATURES DESPITE DYNAMICAL MODEL WEEK 3-4
GUIDANCE, FOR EXAMPLE, THAT TILTS COLD THROUGH THE FIRST HALF OF MAY.
PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES ARE HIGHEST OVER THE
SOUTHWEST, WHERE LONG-TERM TRENDS, NEGATIVE SOIL MOISTURE ANOMALIES, LAGGED
ENSO REGRESSIONS, AND DYNAMICAL MODEL GUIDANCE ARE ALL IN AGREEMENT. OVER THE
NORTHERN HIGH PLAINS, A SIMILAR ALIGNMENT OF GUIDANCE POINTS MORE TOWARD
BELOW-NORMAL TEMPERATURES. THERE IS BROAD CONSENSUS FAVORING ABOVE-NORMAL
TEMPERATURES FOR ALASKA, WITH THE HIGHEST PROBABILITIES NEAR THE NORTHERN AND
WESTERN COASTS, WHERE ICE BREAKUP IS LIKELY TO OCCUR EARLIER THAN NORMAL.

THE PRECIPITATION OUTLOOK IS CONSTRUCTED IN SIMILAR FASHION TO THE TEMPERATURE
OUTLOOK, STARTING WITH LONG-TERM TRENDS AND ADJUSTING FOR SUBSEASONAL TO
SEASONAL VARIABILITY MANIFEST IN EITHER STATISTICAL OR DYNAMICAL GUIDANCE.
LAGGED ENSO REGRESSIONS AND THE PREPONDERANCE OF DYNAMICAL GUIDANCE
CONSTRUCTIVELY INTERFERE WITH LONG-TERM TRENDS OVER MUCH OF THE WEST, SO
BELOW-NORMAL PRECIPITATION IS MODESTLY FAVORED FOR PARTS OF THE WEST EXTENDING
FROM THE NORTHWEST COAST SOUTHEASTWARD TO PARTS OF THE SOUTHERN HIGH PLAINS.
ABOVE-NORMAL PRECIPITATION IS FAVORED SLIGHTLY OVER THE NORTHERN HIGH PLAINS
WHERE LONG-TERM TRENDS ARE FAIRLY STRONG, AND CALIBRATED GUIDANCE FROM THE NMME
HAS A COHERENT WET SIGNAL. OVER THE EASTERN CONUS THERE ARE SOME CONFLICTING
SIGNALS, BUT THE MAJORITY OF FORECAST GUIDANCE, INCLUDING THE NMME, LONG-TERM
TRENDS, AND THE ECWMF, TILTS SLIGHTLY TOWARD ABOVE-NORMAL PRECIPITATION. THE
VARIOUS TOOLS ARE IN QUITE GOOD AGREEMENT OVER ALASKA, BROADLY FAVORING
ABOVE-NORMAL PRECIPITATION, WITH THE BEST ODDS IN SOUTHWESTERN ALASKA.

FORECASTER: STEPHEN BAXTER

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 MAY WILL BE ISSUED ON MON APRIL 30 2018

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

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