Prognostic Meteorological Discussion
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FXUS07 KWBC 311900
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300PM EDT THURSDAY JUL 31 2014

30-DAY OUTLOOK DISCUSSION FOR AUGUST 2014

THE UPDATED 30-DAY OUTLOOK FOR AUGUST 2014 DEPICTS SIGNIFICANT CHANGES FROM THE
0.5-MONTH LEAD OUTLOOK ISSUED JULY 17. THIS IS PARTLY DUE TO SUBSTANTIAL
VARIATIONS IN DAY-TO-DAY RUNS OF THE CFS, POTENTIALLY RELATED TO TWO WESTERN
PACIFIC TYPHOONS AND THEIR ASSOCIATED INFLUENCE ON THE MID-LATITUDE CIRCULATION
UPSTREAM OF THE UNITED STATES. RECENTLY, A WESTERN PACIFIC TYPHOON WAS ABSORBED
INTO THE MID-LATITUDE CIRCULATION OFF EAST ASIA, AND MAY HAVE BEEN RELATED TO
AN AMPLIFICATION OF THE FLOW PATTERN DOWNSTREAM OVER THE UNITED STATES,
FAVORING A WESTERN RIDGE AND EASTERN TROUGH. IT IS CONCEIVABLE THAT THIS
SITUATION COULD OCCUR AGAIN AS TWO WESTERN PACIFIC TYPHOONS ARE PREDICTED TO
GET CAUGHT UP IN THE WESTERLIES AND USHERED DOWNSTREAM TOWARDS THE UNITED
STATES. THE UPDATED 30-DAY OUTLOOK IS BASED PRIMARILY ON FORECASTS OF
TEMPERATURE AND PRECIPITATION PATTERNS OUT THROUGH THE EXTENDED-RANGE (THROUGH
THE FIRST HALF OF AUGUST), AND RECENT RUNS OF THE CFS. THE ANTICIPATED
BACKGROUND 500-HPA CIRCULATION PATTERN THROUGH AT LEAST THE MIDDLE OF AUGUST
FAVORS A TROUGH NEAR THE ALEUTIANS, A RIDGE OVER THE FAR WESTERN CONUS, AND
ANOTHER TROUGH OVER THE EAST-CENTRAL CONUS. ENSO COMPOSITES PLAYED A VERY SMALL
ROLE IN THIS OUTLOOK. IT IS IMPORTANT TO POINT OUT THAT THE LATEST RUNS OF THE
GFS (AS OPPOSED TO CFS) MODEL PREDICT A RELAXATION OF THE SOUTHWEST MONSOON
DURING WEEK 2, AFTER AN ACTIVE WEEK 1 PERIOD. HOWEVER, THIS RELAXATION APPEARS
SHORT-LIVED AND IT WAS DECIDED NOT TO MODIFY THE 30-DAY PRECIPITATION OUTLOOK
AS IT NOW STANDS.



THE UPDATED MONTHLY TEMPERATURE OUTLOOK FOR AUGUST 2014 FAVORS ABOVE-NORMAL
MEAN TEMPERATURES OVER THE FAR WESTERN CONUS, FLORIDA AND ADJACENT PORTIONS OF
BOTH GEORGIA AND ALABAMA, AND ALASKA. BELOW-NORMAL MONTHLY MEAN TEMPERATURES
ARE FAVORED OVER THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND MIDDLE
MISSISSIPPI VALLEY, AND THE WESTERN GREAT LAKES REGION. SINCE THE RELEASE OF
THE 0.5-MONTH LEAD TEMPERATURE OUTLOOK ON JULY 17TH, THE CFS HAS TRENDED COLDER
OVER MOST OF THE CONUS, ESPECIALLY OVER THE WEST-CENTRAL AND NORTH-CENTRAL
STATES. THE LARGE AREAS OF FAVORED ABOVE-NORMAL MONTHLY MEAN TEMPERATURES ON
THE PREVIOUS OUTLOOK HAVE BEEN REDUCED IN SIZE TO INCLUDE ONLY THE FAR WEST,
FLORIDA. THE CFS PREDICTIONS FOR ALASKA HAVE BEEN FAIRLY STABLE, WITH THE BEST
CHANCES FOR RELATIVE WARMTH OVER THE SOUTHERN AND SOUTHWESTERN PORTIONS OF
ALASKA, WITH DECREASING PROBABILITIES FARTHER NORTH. IN AREAS WHERE CLIMATE
SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND
ABOVE-NORMAL MONTHLY MEAN TEMPERATURES IS INDICATED.



THE UPDATED MONTHLY PRECIPITATION OUTLOOK INDICATES ELEVATED ODDS OF
ABOVE-MEDIAN PRECIPITATION FROM EASTERN ARIZONA AND COLORADO EASTWARD TO
INCLUDE NEW MEXICO AND THE SOUTH-CENTRAL PLAINS. THERE ARE ELEVATED ODDS OF
BELOW-MEDIAN PRECIPITATION OVER SOUTHERN TEXAS. THESE TWO SIGNALS ARE
REASONABLY CONSISTENT WITH PRECIPITATION DYNAMICAL MODEL GUIDANCE OUT THROUGH 2
WEEKS. IT IS THOUGHT THAT MONSOONAL ACTIVITY WILL BE MORE CONCENTRATED IN THE
EASTERN MONSOON REGION (NEW MEXICO, COLORADO, WEST TEXAS), THOUGH AREAS FARTHER
WEST ARE ALSO EXPECTED TO RECEIVE MONSOONAL MOISTURE. IN ADDITION, A MEAN
FRONTAL BOUNDARY IS PREDICTED TO BE POSITIONED SOMEWHERE IN THE VICINITY OF
COLORADO AND WYOMING SOUTHEASTWARD TOWARDS ARKANSAS. RECENT RUNS OF THE CFS
CONTINUE TO FAVOR ABOVE-MEDIAN PRECIPITATION ACROSS MOST OF THE INTERIOR WEST,
AS WELL AS BELOW-MEDIAN PRECIPITATION IN THE GENERAL VICINITY OF THE GULF
COAST. IT IS THOUGHT THAT THE CFS IS OVERDOING BOTH OF THESE SIGNALS,
ESPECIALLY THE FAVORED WETNESS IN THE INTERIOR WEST. THE SIGNAL FOR ENHANCED
CHANCES OF BELOW-MEDIAN PRECIPITATION IN SOUTHERN TEXAS IS FAIRLY ROBUST. A
FINAL CONSIDERATION INVOLVES DROUGHT IN THE SOUTHEAST. WIDESPREAD DETERIORATION
OF DROUGHT CONDITIONS APPEARS TO HAVE BEEN PREVENTED BY THE PERSISTENT PRESENCE
OF AN AMPLIFIED UPSTREAM TROUGH OVER THE EAST-CENTRAL STATES. THIS IN TURN
APPEARS TO BE RELATED TO THE INCORPORATION OF A WESTERN PACIFIC TYPHOON INTO
THE WESTERLIES WELL UPSTREAM OF THE U.S. SINCE WE COULD SEE A SIMILAR SITUATION
RECUR IN THE NEXT WEEK, IT IS DEEMED TOO RISKY TO FORECAST ANY BELOW-MEDIAN
PRECIPITATION NEAR MOST OF THE GULF COAST AND SOUTHEAST. IN AREAS WHERE CLIMATE
SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND
ABOVE-MEDIAN PRECIPITATION AMOUNTS IS INDICATED.



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PREVIOUS DISCUSSION FROM 7/17 IS BELOW.

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RECENT OCEANIC CONDITIONS ACROSS THE TROPICAL PACIFIC CONTINUE TO SUPPORT THE
FAVORED TRANSITION FROM ENSO-NEUTRAL TO EL NINO LATER THIS SUMMER. HOWEVER, THE
ATMOSPHERE REMAINS SOMEWHAT DECOUPLED WITH THE RELATIVELY WARM SEA SURFACE
TEMPERATURES (SST) AND THE SUBSURFACE WARMTH OF THE TROPICAL PACIFIC. THESE
OBSERVATIONS SUGGESTS THAT THE ENSO PHASE IS STILL NEUTRAL. IT NOW APPEARS THAT
THE PREDICTED EL NINO MAY PEAK AT WEAK TO MODERATE STRENGTH BY LATE
AUTUMN/EARLY WINTER, COMPARED TO PREVIOUS EXPECTATIONS OF FAVORED MODERATE
INTENSITY PEAKING DURING THE SAME PERIOD.



DURING THE PAST FEW WEEKS, POSITIVE SST ANOMALIES PERSISTED (THOUGH WEAKENED
SLIGHTLY) IN THE EASTERN EQUATORIAL PACIFIC, AND ANOMALIES ARE CLOSE TO ZERO IN
THE CENTRAL PACIFIC (180W-150W). THE LATEST WEEKLY SST DEPARTURE IN THE
EAST-CENTRAL PACIFIC (NINO 3.4 REGION) IS +0.3C. THE OCEANIC HEAT CONTENT
(SUBSURFACE TEMPERATURE ANOMALIES IN THE UPPERMOST 300-METERS OF THE EASTERN
AND CENTRAL EQUATORIAL PACIFIC) DECLINED FAIRLY RAPIDLY IN THE LAST FEW MONTHS,
AND ANOMALIES ARE NOW CLOSE TO ZERO. DURING THIS SAME PERIOD, THE LARGE
RESERVOIR OF SUBSURFACE WARMTH OVER THE CENTRAL AND EASTERN EQUATORIAL PACIFIC
HAS DIMINISHED SIGNIFICANTLY IN COVERAGE AND MAGNITUDE, AND IS NOW CONFINED
FROM ABOUT 145W-85W, AND EXTENDS DOWN TO A DEPTH OF ABOUT 75 METERS. DURING THE
PAST 30-DAYS, TROPICAL RAINFALL WAS SLIGHTLY ABOVE-AVERAGE IN INDONESIA AND THE
WESTERN EQUATORIAL PACIFIC, AND LOW-LEVEL (850-HPA) WINDS WERE NEAR LONG-TERM
AVERAGES ACROSS MOST OF THE EQUATORIAL PACIFIC.



MONTHLY MEAN TEMPERATURES FOR AUGUST 2014 ARE FAVORED TO BE ABOVE-NORMAL ACROSS
THE SOUTHERN HALVES OF BOTH THE LOWER GREAT PLAINS AND MISSISSIPPI VALLEY, THE
SOUTHEAST, TENNESSEE VALLEY, AND MUCH OF THE MID-ATLANTIC REGION, AS WELL AS IN
THE PACIFIC NORTHWEST, MOST OF NEVADA AND CALIFORNIA, AND ALASKA. BELOW-NORMAL
MONTHLY MEAN TEMPERATURES ARE MOST LIKELY OVER PORTIONS OF THE NORTHERN GREAT
PLAINS, UPPER MISSISSIPPI VALLEY, AND UPPER GREAT LAKES REGION. THIS OUTLOOK IS
BASED PRIMARILY ON RECENT RUNS OF THE CFS DYNAMICAL MODEL, NMME, IMME, AND
THEIR CONSTITUENT CLIMATE MODELS. IT IS ALSO BASED ON, TO A LESSER DEGREE, THE
CAS, SMLR, CCA, AND OCN STATISTICAL TOOLS, AS WELL AS SOIL MOISTURE
CONSIDERATIONS. AREAS OF DIMINISHED CONFIDENCE INCLUDE THE FOUR CORNERS MONSOON
REGION (WHERE THE CFS IN PARTICULAR PREDICTS ENHANCED ODDS OF BELOW-NORMAL
TEMPERATURES, AS OPPOSED TO THE EUROPEAN AND OTHER CLIMATE MODELS WHICH FAVOR
NEAR OR EVEN ABOVE-NORMAL TEMPERATURES), AND NORTHERN ALASKA. IN THIS LATTER
AREA, RECENT RUNS OF THE CFS APPEAR TO BE TOO COLD, ESPECIALLY GIVEN THE
ANOMALOUSLY LOW ICE COVER OBSERVED OVER THE BEAUFORT SEA. IN AREAS WHERE
CLIMATE SIGNALS ARE WEAK AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-,
NEAR-, AND ABOVE-NORMAL MONTHLY MEAN TEMPERATURES IS INDICATED.



PRECIPITATION FOR AUGUST 2014 IS ANTICIPATED TO BE ABOVE-MEDIAN OVER MUCH OF
THE INTERIOR WEST. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE SLIGHTLY FAVORED FOR
MOST OF THE GULF COAST REGION, AND PORTIONS OF GEORGIA AND SOUTH CAROLINA.

THE OUTLOOK IS BASED PRIMARILY ON THE SAME TOOLS NOTED ABOVE FOR TEMPERATURE.

FOR THE SOUTHWEST, IT IS CONSISTENT WITH THE EXPECTATION OF BOTH AN ENHANCED
MONSOON AND AN ENHANCED EASTERN PACIFIC HURRICANE SEASON. IN THE NORTHERN HIGH
PLAINS AND NORTHERN ROCKIES, IT IS MOST LIKELY DUE TO FRONTAL ACTIVITY. PERHAPS
THE MOST UNCERTAIN PART OF THIS FORECAST IS THE ANTICIPATED REGION OF FAVORED
BELOW-MEDIAN RAINFALL OVER THE GULF COAST STATES AND ADJACENT PORTIONS OF
GEORGIA AND SOUTH CAROLINA. THE CFS AND IMME SUPPORT SOME EXTENSION OF THIS
AREA OF RELATIVE DRYNESS THROUGH NORTH CAROLINA AND PARTS OF THE MID-ATLANTIC
REGION, WHILE THE NMME INCLUDES ONLY TEXAS AND LOUISIANA. THIS IS COMPLICATED
BY WHAT APPEARS TO BE THE EARLY STAGES OF A FLASH DROUGHT TRYING TO DEVELOP
FROM ALABAMA AND THE FLORIDA PANHANDLE NORTHEASTWARD INTO SOUTHWESTERN
VIRGINIA. THE PRECIPITATION FORECAST FOR THE UPCOMING 7-DAYS CALLS FOR
SIGNIFICANT RAINFALL (RANGING FROM 0.5 TO 4 INCHES) TO OCCUR ACROSS THE GULF
COAST REGION AND SOUTHEAST, WHICH MAY (AT LEAST TEMPORARILY) HELP TO OFFSET THE
RAPIDLY DETERIORATING SOIL MOISTURE CONDITIONS NOW SETTING UP IN THE SOUTHEAST.
THE OFFICIAL CPC PRECIPITATION OUTLOOK IS THOUGHT TO BE A REASONABLE COMPROMISE
BETWEEN VARIOUS COMPETING FACTORS. IN AREAS WHERE CLIMATE SIGNALS ARE WEAK
AND/OR UNRELIABLE, EQUAL CHANCES (EC) OF BELOW-, NEAR-, AND ABOVE-MEDIAN
PRECIPITATION AMOUNTS 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: ANTHONY ARTUSA


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 SEP ... WILL BE ISSUED ON THU AUG 21 2014


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

$$


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