Fall 2011 Outlook; Warmer with 'Average' precipitation

The Climate Prediction Center (CPC) has released the seasonal outlooks for the meteorological fall. Across the Northern Plains, the months of September through November comprise the transition from consistently milder weather to much colder by the end of the season.There are several factors that are considered for this outlook period, including the state of the El Niño Southern Oscillation (ENSO), recent climate trends, a near term Pacific oscillation called the Madden-Julian Oscillation and much more. A detailed technical discussion is included at the bottom of this article.

Based on the available information, forecast tools and other related information the fall [across our region] should have the tendency to be warmer than normal. Precipitation, on balance, should be within the normal bounds of climatology, perhaps favoring above normal rainfall in parts of southeast North Dakota .

La Niña Watch has been issued by the CPC in anticipation that the waters in the Equatorial Pacific will continue the slow cooling trend. Depending on the speed with which the cooling occurs, the later part of the fall season could see an increase in precipitation. Using statistical data from the CPC, there is a tendency towards increasing precipitation from west to east across the region during La Niña fall seasons. Looking at the graphics below, one can see the distribution of temperature and precipitation patterns during La Niña events. As of this writing, the Pacific, wild cooler than average, was not yet in La Niña mode. So while the Official Outlook suggests climatologically normal precipitation patterns, history suggests a wetter bias. This would be particularly true later in the season if La Niña develops

Box and Whisker plot of temperature and precipitation during ENSO events

Distribution of precipitation (left) and temperature (right) for Eastern North Dakota during ENSO events. (Courtesy NOAA Climate Prediction Center)

Box and Whisker plots of temperature and precipitation for ENSO events

Distribution of precipitation (left) and temperature (right) for Northwest Minnesota during ENSO events. (Courtesy NOAA Climate Prediction Center)

 Normal Maximum, Minimum temperature, and total precipitation / snowfall for selected cities in the September - November time frame.

Fargo Max Min
Sep.   1 77 53
Sep. 15 71 48
Oct.    1 64 41
Oct. 15 57 36
Nov.   1 47 28
Nov. 15 38 21
Total Precipitation 5.72
Total Snowfall   8.9
   
UND/NWS Max Min
Sep.  1 76 52
Sep. 15 70 47
Oct.    1 62 40
Oct. 15 55 35
Nov.   1 44 27
Nov. 15 35 19
Total Precipitation 4.87
Total Snowfall 6.5

Average Maximum and minimum temperatures for Fargo and the UND/NWS climate station on the 1st and 15th of September, October and November. Precipitation and snowfall totals for the entire 3 month period. Data from the NOAA Regional Climate Center/ACIS.

Updated Outlooks will be issued on September 15th and October 20th. Below is the Long-Lead Technical Description from the CPC as of August 18th 2011

PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830AM EDT THURSDAY AUG 18 2011

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE MAIN FACTORS WHICH USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE:
1) EL NINO AND LA NINA - WHICH COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO.
IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM
3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH
SEPARATELY, AND THEN COMPUTING ANOMALIES.  THESE ARE CALLED "ENSO COMPOSITES",
AND ARE 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 - SOMETIMES CALLED MADDEN JULIAN
OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS.
4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA)
PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE
COLD SEASONS. THESE PHENOMENA ARE LESS PREDICTABLE BEYOND A WEEK OR TWO IN THE
FUTURE.
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 TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING
MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA
(ECCA).
8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM
(CFS). THE UPGRADED PARALLEL VERSION OF THE CFS (CFSV2) BECAME OPERATIONAL IN
LATE MARCH OF 2011. BOTH VERSIONS OF CFS ARE CURRENTLY RUN IN PARALLEL.
9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE OCN,
CCA, SMLR, ECCA, AND CFS FORECASTS IS USED AS A FIRST GUESS IN PREPARING THE
FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF OUR
FORECAST TOOLS.

WEEKLY SEA SURFACE TEMPERATURE (SST) OBSERVATIONS HAVE BEEN VERY CLOSE TO
CLIMATOLOGICAL MEAN VALUES ALONG THE EQUATOR ACROSS MOST OF THE PACIFIC OCEAN,
DURING THE LAST MONTH. A SMALL AREA OF BELOW NORMAL TEMPERATURES HAS APPEARED
IN THE EAST-CENTRAL PACIFIC IN THE LAST TWO WEEKS. ATMOSPHERIC CIRCULATION
ANOMALIES OVER THE TROPICAL PACIFIC ASSOCIATED WITH LAST WINTER'S LA NINA WHILE
WEAKER THAN IN PRIOR MONTHS HAVE CONTINUED THROUGH THE SUMMER. OVERALL,
OBSERVATIONS INDICATE ENSO NEUTRAL CONDITIONS. THE CONSENSUS OF FORECASTS FOR
THE MEAN SST IN THE NINO 3.4 REGION OF THE PACIFIC INDICATES THAT SST ANOMALIES
ARE MOST LIKELY TO REMAIN NEUTRAL THROUGH THE AUTUMN, THOUGH THE CHANCE OF LA
NINA CONDITIONS IS ELEVATED TO APPROXIMATELY 50% AFTER THE AUTUMN OF 2011.

THE SEASONAL TEMPERATURE OUTLOOK FOR SON 2011 INDICATES ENHANCED PROBABILITIES
OF ABOVE NORMAL TEMPERATURES FOR A LARGE PART OF THE U.S. FROM THE SOUTHWEST
THROUGH THE GREAT PLAINS TO THE GREAT LAKES AND THE NORTHEAST. THE OUTLOOK
RESULTS FROM A COMBINATION OF FACTORS INCLUDING DECADAL TRENDS, ESPECIALLY IN
THE SOUTHWEST, AND STATISTICAL AND DYNAMICAL MODEL FORECASTS. PROBABILITIES OF
ABOVE NORMAL TEMPERATURES ARE INCREASED IN NORTHERN ALASKA, PRIMARILY DUE TO
DECADAL TEMPERATURE TRENDS, RECENT TEMPERATURE OBSERVATIONS, AND THE
OBSERVATION OF NEAR-RECORD LOW SEA-ICE EXTENT OVER THE ARCTIC.

THE SEASONAL PRECIPITATION OUTLOOK FOR SON 2011 PREDICTS ENHANCED PROBABILITIES
OF BELOW MEDIAN PRECIPITATION IN THE SOUTHWEST AND SOUTHERN PLAINS RESULTING
FROM DECADAL TRENDS IN PRECIPITATION RELATIVE TO THE CLIMATOLOGY, AS WELL AS
INITIALLY DRY SOIL MOISTURE CONDITIONS IN THE SOUTHERN PLAINS. ENHANCED
PROBABILITIES OF ABOVE MEDIAN PRECIPITATION IN THE NORTHERN PLAINS ARE ALSO DUE
TO DECADAL TRENDS IN PRECIPITATION. DYNAMICAL MODEL FORECASTS AND THE SLIGHTLY
ENHANCED PROBABILITY OF LA NINA CONDITIONS RESULTS IN INCREASED PROBABILITIES
OF ABOVE MEDIAN PRECIPITATION ALONG THE PACIFIC NORTHWEST COAST.

IN LOCATIONS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL
PRECIPITATION AMOUNTS ARE SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL
CHANCES (EC) OF BELOW, NEAR, AND ABOVE ARE INDICATED.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

CENTRAL EQUATORIAL PACIFIC SST ANOMALIES WERE NEAR ZERO OR SLIGHTLY NEGATIVE IN
EARLY AUGUST. SUBSURFACE OCEAN TEMPERATURES ALONG THE EQUATOR ARE ABOVE NORMAL
IN THE WESTERN PACIFIC AT A DEPTH OF 50 TO 200 METERS, AND BELOW NORMAL FROM
NEAR THE SURFACE TO A DEPTH OF 150 METERS IN THE EAST-CENTRAL PACIFIC. THE
SUBSURFACE OCEAN HEAT CONTENT MEASURED BY THE MEAN TEMPERATURE ANOMALY IN THE
UPPER 300 METERS OF THE EASTERN EQUATORIAL PACIFIC DROPPED BELOW ZERO IN LATE
JULY AND EARLY AUGUST.

AS OF EARLY AUGUST, THE ATMOSPHERIC CIRCULATION CONTINUED TO EXHIBIT TRAITS OF
WEAK LA NINA CONDITIONS. THESE TRAITS INCLUDE ENHANCED CONVECTION JUST NORTH OF
THE EQUATOR FROM EASTERN INDONESIA TO THE DATE LINE, SUPPRESSED CONVECTION
SOUTH OF THE EQUATOR NEAR THE DATE LINE, SLIGHTLY ENHANCED LOW-LEVEL EASTERLY
WINDS, AND SLIGHTLY ENHANCED UPPER LEVEL WESTERLY WINDS OVER THE CENTRAL
EQUATORIAL PACIFIC OCEAN.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE AVERAGE OF STATISTICAL AND DYNAMICAL MODEL FORECASTS PREDICTS SST ANOMALIES
JUST BELOW ZERO IN THE NINO 3.4 REGION THROUGH THE AUTUMN OF 2011 WITH
ANOMALIES DROPPING SLIGHTLY TO ABOUT -0.2 TO -0.3 CELSIUS IN THE WINTER. THE
MAJORITY OF MODEL SOLUTIONS PREDICT SST ANOMALIES TO REMAIN WITHIN HALF A
DEGREE C OF THE CLIMATOLOGICAL MEAN, WHILE THE CFSV2 IN PARTICULAR PREDICTS A
GREATER LIKELIHOOD OF THE RE-EMERGENCE OF LA NINA BY THIS BOREAL WINTER. THE
CPC NINO 3.4 CONSOLIDATION FORECAST WHICH INCLUDES FORECASTS FROM THE CFSV2,
CONSTRUCTED ANALOG, MARKOV MODEL AND ENSO CCA, PREDICTS NEUTRAL ENSO CONDITIONS
TO BE MOST LIKELY FOR THE REMAINDER OF 2011. CONSIDERING PERSISTENT WEAK
CHARACTERISTICS OF LA NINA IN THE TROPICAL ATMOSPHERE, BELOW NORMAL SUBSURFACE
OCEAN TEMPERATURES IN THE EAST-CENTRAL PACIFIC, AND THE LATEST CFS SST
FORECASTS FROM VERSIONS 1 AND 2, THE CHANCE OF LA NINA TO RE-EMERGE HAS
INCREASED TO APPROXIMATELY 50%.

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

OUTLOOKS FOR SON 2011 THROUGH SON 2012 WERE BASED PRIMARILY ON A CONSOLIDATION
(CON) OF FORECASTS AND THE CLIMATE FORECAST SYSTEM VERSION TWO (CFSV2) COUPLED
OCEAN-ATMOSPHERE MODEL FORECASTS, WITH CONSIDERATION OF COMPOSITES FOR LA NINA
CONDITIONS, ESPECIALLY FOR WINTER OUTLOOKS. THE CON COMBINES SMLR, CCA, OCN,
ECCA AND CFS VERSION 1 FORECASTS. INITIAL SOIL MOISTURE CONDITIONS WERE
CONSIDERED FOR SON 2011.

THE 1981-2010 CLIMATOLOGICAL NORMALS ARE USED FOR THIS SET OF OUTLOOKS.
ANOMALIES RELATIVE TO THE 1981-2010 NORMALS ARE USED TO ASSESS DECADAL TRENDS
AND FORECAST ANOMALIES THAT PREVIOUSLY WERE REPRESENTED AS ANOMALIES RELATIVE
TO THE 1971-2000 PERIOD. THE USE OF MORE RECENT 1981-2010 NORMALS GENERALLY
REDUCES THE ANOMALIES ASSOCIATED WITH DECADAL TRENDS RELATIVE TO OUTLOOKS FOR
CORRESPONDING SEASONS RELEASED PRIOR TO MAY 2011. THIS IS ESPECIALLY TRUE FOR
THE TEMPERATURE OUTLOOKS IN ALASKA WHERE THE 1981-2010 NORMALS ARE
SUBSTANTIALLY WARMER THAN THE 1971-2000 NORMALS FOR MANY STATIONS AND SEASONS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2011 TO SON 2012

TEMPERATURE

ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR SON AND OND 2011 ARE
INDICATED IN THE SOUTHWEST, THE GREAT PLAINS AND PARTS OF THE NORTHEAST BY THE
CON. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR NORTHERN ALASKA ARE
ENHANCED IN THE FIRST TWO LEADS, PRIMARILY AS A RESULT OF DECADAL TIMESCALE
TRENDS IN TEMPERATURES RELATED TO A DECREASE IN SEA-ICE EXTENT. ABOVE NORMAL
TEMPERATURES ARE MOST LIKELY FOR THE SOUTHWEST AND SOUTHERN PLAINS IN NDJ
2011-2012, AND EXPAND EASTWARD INTO THE SOUTHEAST AND PARTS OF THE MID-ATLANTIC
THROUGH THE FOLLOWING SEASONS INTO MAM 2012. AREAS WHERE THE PROBABILITIES OF
BELOW NORMAL TEMPERATURES ARE SLIGHTLY INCREASED APPEAR IN THE PACIFIC
NORTHWEST, THE NORTHERN PLAINS AND WESTERN GREAT LAKES REGION, AS WELL AS
SOUTHERN ALASKA AND THE ALASKAN PANHANDLE FROM THE DJF 2011-2012 TO THE MAM
2012 SEASON. THE OUTLOOKS FOR NDJ 2011-2012 THROUGH MAM 2012 ARE IMPACTED BY A
RELATIVE INCREASE IN THE PROBABILITY OF THE REEMERGENCE OF LA NINA CONDITIONS
AFTER AUTUMN. BECAUSE THE LIKELIHOOD OF LA NINA CONDITIONS FOR THESE SEASONS IS
CONSIDERED TO BE APPROXIMATELY 50%, THE PROBABILITIES ASSOCIATED WITH IMPACTS
TO TEMPERATURE AND PRECIPITATION ARE ONLY SLIGHTLY ABOVE CLIMATOLOGY.

ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES CONTINUE FOR VARIOUS
REGIONS OF THE U.S. FOR LONGER LEADS FROM AMJ THROUGH SON 2012 AS A RESULT OF
DECADAL TRENDS RELATIVE TO CLIMATOLOGY.

PRECIPITATION

PRECIPITATION OUTLOOKS FOR SON 2011 INDICATE INCREASED PROBABILITIES OF BELOW
MEDIAN PRECIPITATION FOR THE SOUTHWEST EASTWARD ACROSS TEXAS REACHING THE LOWER
MISSISSIPPI VALLEY BY OND 2011, DUE TO INITIAL DRY SOIL MOISTURE CONDITIONS AND
TRENDS. A SMALL AREA OF INCREASED CHANCES OF ABOVE MEDIAN PRECIPITATION IN THE
NORTHERN PLAINS IN SON 2011 IS ALSO DUE TO TRENDS. ABOVE MEDIAN PRECIPITATION,
INDICATED IN THE PACIFIC NORTHWEST, BEGINNING IN SON 2011 AND CONTINUING
THROUGH JFM 2012 APPEARS IN DYNAMICAL MODEL FORECASTS FROM THE CFSV2 IN
PARTICULAR, DUE IN PART TO THE FORCING OF THE INCREASING LIKELIHOOD OF LA NINA
CONDITIONS IN THE MODEL EQUATORIAL PACIFIC. THE PROBABILITY OF ABOVE MEDIAN
PRECIPITATION IS SLIGHTLY INCREASED ABOVE CLIMATOLOGY IN AN AREA FROM THE OHIO
VALLEY TO THE GREAT LAKES IN THE DJF 2011-2012 AND JFM 2012 OUTLOOKS AS A
RESULT OF THE INCREASED CHANCE OF LA NINA CONDITIONS BY THIS WINTER.  AREAS OF
ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION IN THE SOUTHWEST AND
SOUTHEAST CONTINUE INTO MAM 2012 SUPPORTED PRIMARILY BY TRENDS IN PRECIPITATION
FOR RECENT DECADES.

ASSOCIATED WITH INCREASED CHANCES OF BELOW NORMAL TEMPERATURES, BELOW MEDIAN
PRECIPITATION IS MOST LIKELY FOR THE INTERIOR OF ALASKA FROM NDJ 2011-2012
THROUGH FMA 2012.

DECADAL TRENDS IN PRECIPITATION RELATIVE TO THE CLIMATOLOGY LEAD TO ENHANCED
PROBABILITIES OF BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND ABOVE
MEDIAN PRECIPITATION IN THE FLORIDA PENINSULA IN JAS AND ASO 2012. IN SON 2012,
TRENDS INDICATE INCREASED CHANCES OF ABOVE MEDIAN PRECIPITATION IN THE CENTRAL
PLAINS AND OF BELOW MEDIAN PRECIPITATION IN SOUTHERN ARIZONA.

FORECASTER: DAN COLLINS

THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATIC 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.

FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT
HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML
(USE LOWER CASE LETTERS)
INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS)
NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR
VALID PERIOD.  WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM
RANGE FORECASTS SHOULD BE CONSULTED.

THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT
MONTH ON SEP 15 2011


1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011
FORECAST RELEASE.
$$

 

 

 



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