30 Day Narrative

189 
FXUS07 KWBC 181230
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU AUG 18 2016
30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2016
THE SEPTEMBER 2016 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON 
DYNAMICAL MODEL GUIDANCE AND, TO A LESSER EXTENT, STATISTICAL TOOLS. THE IMPACT 
OF CURRENT SOIL MOISTURE CONDITIONS ON THE TEMPERATURES DURING THE FOLLOWING 
MONTH BEGINS TO WANE IN THE AUTUMN, BUT THERE IS STILL A RESPECTABLE 
CORRELATION OVER THE SOUTHERN GREAT PLAINS BETWEEN AUGUST SOIL MOISTURE AND 
SEPTEMBER TEMPERATURES.  ENSO IS NOW IN ITS NEUTRAL PHASE ACROSS THE TROPICAL 
PACIFIC. LA NINA IS SLIGHTLY FAVORED TO DEVELOP DURING AUGUST - OCTOBER 2016, 
WITH ABOUT A 55-60% CHANCE OF LA NINA DURING THE FALL AND WINTER 2016-17. 
PLEASE REFER TO THE ENSO DIAGNOSTIC DISCUSSION AT: 
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/ENSO_ADVISORY/ FOR A 
MORE DETAILED ANALYSIS OF ENSO CONDITIONS ACROSS THE EQUATORIAL PACIFIC.
DURING THE FIRST HALF OF AUGUST, ABOVE AVERAGE CONVECTION HAS DEVELOPED OVER 
THE WESTERN PACIFIC, WITH MULTIPLE TROPICAL CYCLONES FORMING. MOST MJO INDICES 
HAVE AMPLIFIED IN A DIRECTION INDICATING ENHANCED CONVECTION OVER THE WESTERN 
PACIFIC. GOING FORWARD, MOST MODELS CONTINUE TO INDICATE CONVECTION OVER THE 
WESTERN PACIFIC, WHICH COULD HAVE A DOWNSTREAM IMPACT ON THE CIRCULATION OVER 
NORTH AMERICA, ALTHOUGH THAT CONNECTION IS MORE ROBUST LATER IN THE MONTH 
BECAUSE OF THE DYNAMICS OF THE SEASONAL PROGRESSION OF THE EAST ASIAN JET 
STREAM. DYNAMICAL MODELS ARE LIKELY THE BEST TOOLS TO CAPTURE THIS POTENTIAL 
IMPACT. THEREFORE, THE OUTLOOKS RELY PRIMARILY UPON THE LATEST DYNAMICAL MODEL 
GUIDANCE FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS), THE NORTH AMERICAN 
MULTI-MODEL ENSEMBLE (NMME), THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME), AND 
MODEL GUIDANCE FOR WEEKS 3 AND 4 FROM THE CFS, JAPAN METEOROLOGICAL AGENCY 
(JMA), AND ECMWF, WITH LESSER INPUTS FROM TOOLS BASED ON CURRENT SOIL MOISTURE 
CONDITIONS.
MOST DYNAMICAL MODELS FROM THE NMME SUITE INDICATE GENERALLY ABOVE AVERAGE 
TEMPERATURES FOR SEPTEMBER 2016. ANY AREAS WHERE NEAR OR BELOW AVERAGE 
CONDITIONS ARE INDICATED ARE OVER THE CENTRAL PORTIONS OF THE CONUS. CURRENTLY 
HIGH SOIL MOISTURE OVER THE SOUTHERN GREAT PLAINS WOULD FAVOR NEAR TO BELOW 
AVERAGE TEMPERATURES OVER THAT REGION, WHILE UNCERTAINTY AMONG THE MODELS (NMME 
AND IMME) PROHIBITS THE DEPICTION OF A SIGNAL FROM THE NORTHERN GREAT PLAINS TO 
THE GREAT LAKES REGION. MORE AGREEMENT RETURNS OVER THE NORTHEAST, WHERE TOOLS 
INDICATE ABOVE AVERAGE TEMPERATURES ARE FAVORED, AND OVER THE WESTERN CONUS 
FROM THE ROCKIES TO THE WEST COAST, WHERE MODELS AND TRENDS FAVOR ABOVE AVERAGE 
TEMPERATURES. SSTS 1.5-3.5 DEGREES C ABOVE AVERAGE IN THE VICINITY OF ALASKA 
FAVOR ABOVE AVERAGE TEMPERATURES FOR SOUTHERN AND WESTERN ALASKA, WHILE TRENDS 
FAVOR ABOVE AVERAGE TEMPERATURES FOR THE NORTH SLOPE.
THE PRECIPITATION OUTLOOK FOR SEPTEMBER CONTAINS A HIGH AMOUNT OF UNCERTAINTY. 
MODEL SIGNALS ARE SPARSE IN COVERAGE, AND WEAK EVEN WHERE SIGNALS PASS THROUGH 
THE CALIBRATION METHODS. TRENDS FAVOR BELOW AVERAGE PRECIPITATION OVER THE 
SOUTHWEST WHILE MOST MODELS IN THE NMME SUITE FAVOR ABOVE AVERAGE 
PRECIPITATION. THE OFFICIAL OUTLOOK FAVORS ABOVE AVERAGE PRECIPITATION, BUT 
OVER A SMALLER AREA THAN WHAT THE DYNAMICAL MODELS INDICATE TO ACCOUNT FOR THE 
UNCERTAINTY RAISED BY CONFLICTING GUIDANCE. OVER THE NORTHERN GREAT PLAINS, 
ABOUT HALF OF THE MODELS DEPICT ABOVE AVERAGE PRECIPITATION AND TRENDS FROM THE 
SEASONAL OPTIMAL CLIMATE NORMALS HAVE LITTLE TO NO SIGNAL, SO NO SIGNAL IS 
DEPICTED. TRENDS AND MODELS DEPICT BELOW AVERAGE PRECIPITATION FOR THE 
NORTHWEST AND FROM THE SOUTHERN GREAT PLAINS TO THE SOUTHEAST. MODEL FORECASTS 
SUPPORT ABOVE AVERAGE PRECIPITATION FOR SOUTHERN ALASKA, ALTHOUGH THEY VARY IN 
WHERE THE HIGHEST AMOUNTS ARE LIKELY TO OCCUR, SO THE OFFICIAL FORECAST COVERS 
ALL OF THE AREAS WHERE THE NMME MODELS FAVOR ABOVE AVERAGE PRECIPITATION.
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.
AN UPDATED MONTHLY OUTLOOK... FOR SEP WILL BE ISSUED ON WED AUGUST 31 2016
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.
$$