August 2017 Discussion

Discussion in 'General Weather Discussion' started by JayF, Aug 7, 2017.

  1. JayF

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    PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
    NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
    300 PM EDT MON JUL 31 2017

    30-DAY OUTLOOK DISCUSSION FOR AUGUST 2017

    THE UPDATED MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR AUGUST 2017 ARE
    BASED ON THE LATEST DYNAMICAL MODEL GUIDANCE, WPC TEMPERATURE AND PRECIPITATION
    FORECASTS DURING THE FIRST WEEK OF THE MONTH, THE CPC 6-10/8-14 DAY TEMPERATURE
    AND PRECIPITATION OUTLOOKS, CLIMATE LINKAGES TO CURRENT SOIL MOISTURE
    CONDITIONS, AND POTENTIAL INFLUENCE FROM AN ATMOSPHERIC KELVIN WAVE (KW).
    ALTHOUGH THE MADDEN-JULIAN OSCILLATION (MJO) STRENGTHENED DURING LATE JULY WITH
    ITS ENHANCED PHASE OVER THE MARITIME CONTINENT AND WEST PACIFIC, IT IS FORECAST
    TO WEAKEN. A ROBUST KW EMERGED FROM THE WEST PACIFIC RECENTLY AND IS CURRENTLY
    PROPAGATING EAST ACROSS THE WESTERN HEMISPHERE. THIS KW IS EXPECTED TO PROVIDE
    A FAVORABLE ENVIRONMENT FOR TROPICAL CYCLONE (TC) DEVELOPMENT OVER THE EAST
    PACIFIC DURING THE FIRST WEEK OF AUGUST. TCS ACROSS THE EAST PACIFIC MAY
    ENHANCE MOISTURE ACROSS THE SOUTHWESTERN U.S. DURING EARLY AUGUST.

    THE MAJOR REVISION TO THE TEMPERATURE OUTLOOK IS A LARGE REDUCTION IN THE
    COVERAGE OF INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES ACROSS THE CENTRAL
    AND EASTERN U.S. THE GFS AND ECMWF ENSEMBLE MEANS INDICATE AN AMPLIFYING
    500-HPA TROUGH DEVELOPING OVER THE EAST-CENTRAL U.S. DURING THE FIRST WEEK OF
    AUGUST WITH NEAR- TO BELOW-NORMAL 500-HPA HEIGHTS PERSISTING THROUGH AT LEAST
    THE FIRST TEN DAYS OF THE MONTH. BELOW-NORMAL TEMPERATURES ARE MOST LIKELY
    ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS WHERE TEMPERATURES ARE FORECAST TO
    AVERAGE NEAR 10 DEGREES F BELOW NORMAL DURING THE FIRST WEEK OF AUGUST AND
    WEEK-2 TEMPERATURE TOOLS HAVE THE HIGHEST PROBABILITIES FOR BELOW-NORMAL
    TEMPERATURES ACROSS THIS REGION. INCREASED CHANCES FOR ABOVE-NORMAL
    TEMPERATURES ARE FORECAST ACROSS THE WESTERN U.S. DUE TO ANOMALOUS RIDGING
    EARLY IN THE MONTH ALONG WITH A CONSISTENT SIGNAL AMONG RECENT MONTHLY
    TEMPERATURE FORECASTS FROM THE CFS MODEL. PROBABILITIES FOR ABOVE-NORMAL
    TEMPERATURES ARE HIGHEST ACROSS THE PACIFIC NORTHWEST SINCE TEMPERATURES ARE
    FORECAST TO AVERAGE NEAR 15 DEGREES F ABOVE NORMAL THROUGH THE FIRST WEEK OF
    AUGUST. ELEVATED CHANCES FOR ABOVE-NORMAL TEMPERATURES INCLUDE THE NORTHERN
    HIGH PLAINS, BASED IN PART ON EXCEPTIONALLY LOW SOIL MOISTURE. AS OF JULY 30,
    SOIL MOISTURE IS BELOW THE 5TH PERCENTILE ACROSS EASTERN MONTANA AND WESTERN
    NORTH DAKOTA. ACCORDING TO THE U.S. DROUGHT MONITOR VALID ON JULY 25, NEARLY
    ALL OF WESTERN NORTH DAKOTA IS DESIGNATED WITH EXTREME (D3) TO EXCEPTIONAL (D4)
    DROUGHT.

    ENHANCED ODDS FOR ABOVE-MEDIAN PRECIPITATION ARE MAINTAINED ACROSS THE
    SOUTHWESTERN U.S. AND EXPANDED TO INCLUDE PARTS OF THE CENTRAL AND SOUTHERN
    GREAT PLAINS, GULF COAST, AND SOUTHEASTERN U.S. THE HIGHEST ODDS FOR
    ABOVE-MEDIAN PRECIPITATION ARE FORECAST FOR SOUTHEAST NEW MEXICO AND THE RIO
    GRANDE VALLEY DUE TO SHORT-TERM RAINFALL AND A CONSISTENT SIGNAL AMONG RECENT
    MONTHLY PRECIPITATION FORECASTS FROM THE CFS MODEL. THE EXPANSION OF INCREASED
    CHANCES FOR ABOVE-MEDIAN PRECIPITATION ACROSS PARTS OF THE CENTRAL AND SOUTHERN
    GREAT PLAINS, GULF COAST, AND SOUTHEASTERN U.S. IS BASED ON LOCALLY HEAVY
    RAINFALL EXPECTED DURING THE FIRST WEEK OF AUGUST ALONG WITH GOOD AGREEMENT
    AMONG PRECIPITATION TOOLS AT ALL TIME RANGES. AS OF 11AM ON JULY 31, TROPICAL
    STORM EMILY IS NEAR TAMPA BAY, FLORIDA. EMILY IS FORECAST TO CROSS THE FLORIDA
    PENINSULA AND TRACK AWAY FROM FLORIDA AT THE BEGINNING OF THE MONTH. ALTHOUGH
    MOST OF THE RAINFALL ASSOCIATED WITH EMILY IS EXPECTED TO OCCUR BEFORE THE
    START OF THE MONTH, THE MOST RECENT DAILY RUN OF THE CFS MODEL INDICATES
    ENHANCED ODDS FOR ABOVE-MEDIAN PRECIPITATION ACROSS FLORIDA. LITTLE OR NO
    PRECIPITATION IS LIKELY ACROSS THE PACIFIC NORTHWEST, NORTHERN ROCKIES, AND
    NORTHERN HIGH PLAINS DURING THE FIRST WEEK OF AUGUST. SINCE THE PAST THREE
    DAILY RUNS OF THE CFS MODEL HAVE A DRY SIGNAL, ENHANCED ODDS FOR BELOW-MEDIAN
    PRECIPITATION WERE ADDED TO THESE AREAS IN THIS UPDATED OUTLOOK. DUE TO
    CONFLICTING OR WEAK PRECIPITATION SIGNALS AT DIFFERENT TIME RANGES, EQUAL
    CHANCES FOR BELOW-, NEAR-, OR ABOVE-MEDIAN PRECIPITATION ARE NECESSARY FOR THE
    MIDWEST AND NORTHEAST.

    ONLY MINOR CHANGES ARE REQUIRED TO THE PREVIOUS TEMPERATURE AND PRECIPITATION
    OUTLOOKS ACROSS ALASKA. THE HIGHEST CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE
    FORECAST ACROSS NORTHWEST ALASKA WHERE SEA SURFACE TEMPERATURE ANOMALIES ARE
    AVERAGING MORE THAN 2.5 DEGREES C ABOVE NORMAL. ENHANCED ODDS FOR ABOVE-MEDIAN
    PRECIPITATION ARE EXPANDED TO INCLUDE MORE OF THE ALASKA MAINLAND BASED ON THE
    LATEST PRECIPITATION TOOLS.

    ----------- PREVIOUS MESSAGE (FROM JULY 20) IS SHOWN BELOW ------------
    THE AUGUST 2017 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL
    MODEL GUIDANCE, STATISTICAL TOOLS, CURRENT SOIL MOISTURE CONDITIONS, AND
    POTENTIAL INFLUENCES FROM MODES OF TROPICAL VARIABILITY. ENSO IS NOT A FACTOR
    IN THESE OUTLOOKS SINCE IT IS IN A NEUTRAL STATE AND IS PREDICTED TO REMAIN
    NEUTRAL. PLEASE SEE THE ENSO DIAGNOSTIC DISCUSSION AT:
    HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/ANALYSIS_MONITORING/ENSO_ADVISORY/ENSODISC
    .SHTML FOR A MORE DETAILED ANALYSIS OF SEA SURFACE TEMPERATURES ACROSS THE
    EQUATORIAL PACIFIC. THE MADDEN-JULIAN OSCILLATION (MJO) BECAME MORE COHERENT
    DURING MID-JULY WITH ITS ENHANCED PHASE OVER THE WESTERN MARITIME CONTINENT. A
    COHERENT MJO SIGNAL IS FAVORED TO PROPAGATE EASTWARD DURING THE NEXT TWO WEEKS,
    BUT ITS EFFECTS ON THE EXTRATROPICS ARE EXPECTED TO BE MINIMAL GIVEN THE TIME
    OF YEAR. THE CFS MODEL INDICATES AN ATMOSPHERIC KELVIN WAVE (KW) CROSSING THE
    WESTERN HEMISPHERE DURING LATE JULY INTO THE BEGINNING OF AUGUST. THIS KW COULD
    PROVIDE A FAVORABLE ENVIRONMENT FOR TROPICAL CYCLONE DEVELOPMENT OVER THE EAST
    PACIFIC AND CONTRIBUTE TO A CONTINUATION OF ENHANCED MOISTURE ACROSS THE
    SOUTHWESTERN U.S.

    THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) DEPICTS INCREASED PROBABILITIES
    FOR ABOVE-NORMAL TEMPERATURES ACROSS NEARLY ALL OF THE CONTINENTAL U.S. THE
    LARGEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES IN THE OFFICIAL OUTLOOK ARE
    FORECAST ACROSS THE NORTHERN GREAT PLAINS WHERE CURRENT SOIL MOISTURE VALUES
    RANK BELOW THE 10TH PERCENTILE. ALSO, THE GFS, ECMWF, AND CANADIAN ENSEMBLE
    MEANS INDICATE THAT THE ANOMALOUS 500-HPA RIDGE IS LIKELY TO PERSIST AT LEAST
    THROUGH THE BEGINNING OF AUGUST. ALTHOUGH MANY OF THE DYNAMICAL MODELS FAVOR
    ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHWESTERN U.S., EQUAL CHANCES FOR
    BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE FORECAST FOR THIS REGION BASED
    ON A CONSISTENT SIGNAL AMONG DAILY RUNS OF THE NCEP CLIMATE FORECAST SYSTEM
    (CFS) MODEL, DEPICTING NEAR TO BELOW-NORMAL TEMPERATURES, AND THE ENHANCED ODDS
    FOR ABOVE-MEDIAN PRECIPITATION FORECAST IN THE PRECIPITATION OUTLOOK.

    THE PROBABILITY ANOMALY CORRELATION (PAC) CALIBRATED PROBABILITY FORECAST FROM
    THE NMME FEATURES LITTLE IF ANY SIGNAL THROUGHOUT MOST OF THE FORECAST DOMAIN
    WITH ONLY A SLIGHT TILT IN THE ODDS (36 TO 40 PERCENT) FOR THE ABOVE NORMAL
    TERCILE FROM THE RIO GRANDE VALLEY NORTH TO THE CENTRAL ROCKIES. THE MOST
    CONSISTENT SIGNAL AMONG DAILY CFS MODEL RUNS IS A FAVORED AREA OF ABOVE-MEDIAN
    PRECIPITATION OVER THE RIO GRANDE VALLEY AND PARTS OF THE WESTERN U.S. BASED ON
    THESE TWO PRECIPITATION TOOLS ALONG WITH POTENTIAL INFLUENCES FROM AN EXPECTED
    ACTIVE PERIOD OF EAST PACIFIC TROPICAL CYCLONE ACTIVITY, ABOVE-MEDIAN
    PRECIPITATION IS FAVORED FOR THE RIO GRANDE VALLEY, MOST OF THE MONSOON REGION
    OF THE SOUTHWESTERN U.S., AND THE CENTRAL ROCKIES. FORECAST CONFIDENCE IN THE
    PRECIPITATION OUTLOOK IS LIMITED DUE TO THE LACK OF PREDICTABILITY OF
    CONVECTIVE RAINFALL ON A MONTHLY TIME SCALE.





    FORECASTER: BRAD PUGH
     
    #1 JayF, Aug 7, 2017
    Last edited: Aug 7, 2017
  2. Taylor Campbell

    PerryW Project Supporter

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    Funny how a flash flood watch gets canceled before it should be.
     
  3. Taylor Campbell

    PerryW Project Supporter

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    Just keep it out for the next 14 days.
     

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