811
FXUS06 KWBC 161909
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT TUE OCTOBER 16 2018
6-10 DAY OUTLOOK FOR OCT 22 - 26 2018
THE ENSEMBLE MEANS AND THEIR DETERMINISTIC MODEL RUNS REMAIN CONSISTENT THAT AN
AMPLIFIED UPPER-LEVEL TROUGH SHIFTS EAST TOWARDS THE WEST COAST DURING LATE
OCTOBER. DOWNSTREAM, A RIDGE (TROUGH) IS ALSO FORECAST TO PROGRESS EAST OVER
THE CENTRAL (EASTERN) CONUS. THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS ARE IN GOOD
AGREEMENT THAT A HIGHLY ANOMALOUS 500-HPA RIDGE DEVELOPS TO THE SOUTHEAST OF
GREENLAND. THESE ENSEMBLE MEANS INDICATE A 500-HPA HEIGHT ANOMALY CENTER OF
+300 METERS WITH THIS RIDGE. FOR THE SECOND CONSECUTIVE DAY, THE DETERMINISTIC
6Z GFS AND 0Z ECMWF MODEL RUNS ARE INCLUDED IN CREATING THE 500-HPA BLEND,
GIVEN THEIR GOOD AGREEMENT WITH THEIR RESPECTIVE ENSEMBLE MEANS.
LARGE NEGATIVE TEMPERATURE ANOMALIES (AROUND -10 DEGREES F) ON DAYS 6 AND 7
ACROSS THE EASTERN CONUS CONTINUE TO INCREASE CHANCES THAT TEMPERATURES WILL
AVERAGE BELOW NORMAL DURING THIS 5-DAY PERIOD. A SHORTWAVE TROUGH IN THE
SOUTHERN STREAM AND LIKELIHOOD FOR WIDESPREAD RAINFALL FAVOR BELOW NORMAL
TEMPERATURES ACROSS MUCH OF TEXAS AND THE LOWER MISSISSIPPI VALLEY. AN INCREASE
IN PACIFIC FLOW INCREASES CHANCES FOR ABOVE NORMAL TEMPERATURES ACROSS THE
WESTERN CONUS ALONG WITH THE NORTHERN AND CENTRAL GREAT PLAINS.
ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION FORECAST ACROSS THE SOUTHWESTERN
CONUS ARE DUE TO A SHORTWAVE TROUGH IN THE SOUTHERN STREAM. THIS SHORTWAVE
TROUGH IS FORECAST TO CAUSE SURFACE CYCLOGENESIS IN THE WESTERN GULF OF MEXICO
BY DAY 8. DURING THIS 5-DAY PERIOD, THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS
INDICATE A WIDESPREAD AREA OF MORE THAN 1 INCH OF PRECIPITATION FROM TEXAS EAST
TO THE LOWER MISSISSIPPI VALLEY AND ALONG THE GULF COAST. THEREFORE, RELATIVELY
HIGH PROBABILITIES FOR ABOVE NORMAL PRECIPITATION COINCIDE WITH THIS > 1 INCH
AREA. THE DETERMINISTIC 0Z ECMWF MODEL FEATURES 2 TO 4 INCHES (LOCALLY MORE) OF
RAINFALL ALONG THE TEXAS GULF COAST, SUPPORTING A GREATER THAN 70 PERCENT
CHANCE OF ABOVE NORMAL PRECIPITATION. BELOW-NORMAL PRECIPITATION IS FAVORED
ACROSS THE MIDWEST DUE TO RIDGING ALOFT, WHILE THE ONSET OF PACIFIC FLOW
INCREASES CHANCES FOR ABOVE NORMAL PRECIPITATION ACROSS THE PACIFIC NORTHWEST
AND NORTHERN CALIFORNIA.
THE MODEL SOLUTIONS DEPICT A LARGE SURFACE CYCLONE CENTERED SOUTH OF THE KENAI
PENINSULA OF ALASKA. SOUTHERLY SURFACE FLOW, ASSOCIATED WITH THIS LOW PRESSURE
SYSTEM, FAVORS ABOVE NORMAL TEMPERATURES ACROSS ALASKA AND ABOVE NORMAL
PRECIPITATION ACROSS SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE. BEHIND
THIS LOW PRESSURE SYSTEM, AN INCREASED CHANCE FOR BELOW NORMAL PRECIPITATION IS
FORECAST ACROSS THE ALEUTIANS AND SOUTHWEST MAINLAND ALASKA.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 30% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 20% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON
DAY 8, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 20% OF
TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO GOOD
AGREEMENT BETWEEN THE GFS AND ECMWF ENSEMBLE MEANS AND THEIR DETERMINISTIC
MODEL RUNS IN AN AMPLIFIED LONGWAVE PATTERN. HOWEVER, FORECAST CONFIDENCE IS
REDUCED DUE TO UNCERTAINTY ON THE TRACKS OF PREDICTED LOW PRESSURE SYSTEMS OVER
THE GULF OF MEXICO AND NEAR THE EAST COAST.
8-14 DAY OUTLOOK FOR OCT 24 - 30 2018
THE STRENGTHENING RIDGE OVER THE NORTH ATLANTIC COUPLED WITH BELOW NORMAL
HEIGHTS AT 500-HPA ACROSS THE EASTERN TROPICAL ATLANTIC IS FORECAST TO RESULT
IN A NEGATIVE NORTH ATLANTIC OSCILLATION (NAO) INDEX LATER IN WEEK-2. THIS
EVOLVING LONGWAVE PATTERN IS LIKELY TO MAINTAIN BELOW NORMAL TEMPERATURES
ACROSS MUCH OF THE EASTERN CONUS DURING WEEK-2. WIDESPREAD PRECIPITATION,
ASSOCIATED WITH A LOW PRESSURE SYSTEM EARLY IN WEEK-2, TILTS THE ODDS TOWARDS
BELOW NORMAL TEMPERATURES ACROSS THE WESTERN GULF COAST. ENHANCED PACIFIC FLOW
FAVORS ABOVE NORMAL TEMPERATURES ACROSS THE WESTERN AND NORTH-CENTRAL CONUS.
INCREASED CHANCES FOR ABOVE NORMAL TEMPERATURES ACROSS ALASKA ARE BASED ON:
PREDICTED SOUTHERLY SURFACE FLOW, LACK OF SNOW COVER IN SOUTHEAST MAINLAND
ALASKA, AND ABOVE NORMAL SEA SURFACE TEMPERATURES CURRENTLY OBSERVED IN THE
BERING SEA.
ABOVE NORMAL PRECIPITATION IS LIKELY TO ACCOMPANY THE LOW PRESSURE SYSTEM THAT
IS FORECAST TO TRACK ACROSS THE NORTHERN GULF OF MEXICO EARLY IN WEEK-2.
THEREFORE, THE HIGHEST PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE
FORECAST FROM SOUTHEAST TEXAS EAST TO THE FLORIDA PANHANDLE. TROPICAL STORM
TARA IS CURRENTLY LOCATED NEAR THE SOUTHWEST COAST OF MEXICO AND A SECOND
TROPICAL CYCLONE IS LIKELY TO FORM IN THE EAST PACIFIC PRIOR TO WEEK-2. DEEP
MOISTURE ASSOCIATED WITH THESE TROPICAL CYCLONES MAY SPREAD NORTH AND INTERACT
WITH THE SHORTWAVE TROUGH IN THE SOUTHERN STREAM, FURTHER ENHANCING RAINFALL
AMOUNTS ACROSS THE SOUTHERN TIER OF THE CONUS.
THE DETERMINISTIC 6Z GFS AND 0Z ECMWF MODELS FEATURE A STRENGTHENING LOW
PRESSURE SYSTEM NEAR COASTAL NEW ENGLAND ON DAY 8. ITS PROXIMITY TO THE EAST
COAST IS UNCERTAIN, BUT THE STRENGTHENING RIDGE DOWNSTREAM OVER THE NORTH
ATLANTIC SUPPORTS THIS LOW PRESSURE SYSTEM. ABOVE-NORMAL PRECIPITATION, ALBEIT
WITH LOW PROBABILITIES, IS FORECAST ACROSS THE PACIFIC NORTHWEST, NORTHERN
ROCKIES, AND MUCH OF THE CENTRAL U.S. GIVEN ENHANCED PACIFIC FLOW. BASED ON THE
PREDICTED STORM TRACK ACROSS THE NORTH PACIFIC, BELOW NORMAL PRECIPITATION IS
FAVORED FOR A MAJORITY OF CALIFORNIA AND THE GREAT BASIN. NEAR NORMAL
PRECIPITATION IS MOST LIKELY ACROSS SOUTHEAST MAINLAND ALASKA AND THE ALASKA
PANHANDLE AS A WET START TO WEEK-2 BECOMES INCREASINGLY DRIER AS THE STORM
TRACK SHIFTS SOUTH FROM ALASKA.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 50% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, AND 50% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO GOOD
AGREEMENT BETWEEN THE GFS AND ECMWF ENSEMBLE MEANS OFFSET BY UNCERTAINTY ON THE
TRACK OF A LOW PRESSURE SYSTEM THAT IS LIKELY TO DEVELOP ACROSS THE GULF OF
MEXICO AND THE POTENTIAL FOR A STRONG LOW PRESSURE SYSTEM NEAR COASTAL NEW
ENGLAND.
FORECASTER: BRAD PUGH
NOTES:
AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OCCASIONALLY MANUAL
INTERVENTION IS NECESSARY TO ADDRESS QUALITY CONTROL AND CONSISTENCY ISSUES. IN
THESE CASES, FORECASTS ARE MANUALLY DRAWN BUT A FULL DISCUSSION IS NOT ISSUED.
THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS THE SAME AS
THAT IN THE TABLES: A-ABOVE N-NEAR NORMAL B-BELOW
THE TEMPERATURE MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WARMER (ORANGE,
"A"), COLDER (BLUE, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL AVERAGE
VALUES FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "F"). LABELS ON THE
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).
PROBABILITY OF N IS ALWAYS < 40%.
THE PRECIPITATION MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WETTER (GREEN,
"A"), DRIER (TAN, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL MEDIAN VALUES
FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "INCHES"). LABELS ON THE
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).
PROBABILITY OF N IS ALWAYS < 40%.
IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL BE A
GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY EVEN A NORMAL
(I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY SEASONS. IN SUCH CASES
A FORECAST OF NEAR NORMAL IS EFFECTIVELY A FORECAST OF LITTLE OR NO
PRECIPITATION.
THE CLIMATE PREDICTION CENTER USES 1981-2010 BASE PERIOD MEANS FOR
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE
OUTLOOKS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON
OCTOBER 18.
ANALOGS TO THE 5 DAY MEAN OBSERVED PATTERN CENTERED 3 DAYS AGO (D-3)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 5 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19861009 - 19511030 - 20011004 - 19811019 - 19541028
ANALOGS TO THE 7 DAY MEAN OBSERVED PATTERN CENTERED 4 DAYS AGO (D-4)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 7 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19861010 - 19511029 - 19811018 - 19541028 - 19861005
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 22 - 26 2018
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A A
SRN CALIF A N IDAHO A A NEVADA A A
W MONTANA A A E MONTANA A N WYOMING A A
UTAH A A ARIZONA A A COLORADO A A
NEW MEXICO A A N DAKOTA A B S DAKOTA A B
NEBRASKA A A KANSAS A A OKLAHOMA B A
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA A B IOWA B B MISSOURI B B
ARKANSAS B A LOUISIANA B A WISCONSIN B B
ILLINOIS B B MISSISSIPPI B A MICHIGAN B B
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B B ALABAMA B A NEW YORK B B
VERMONT B B NEW HAMP B N MAINE B N
MASS B N CONN B N RHODE IS B N
PENN B B NEW JERSEY B B W VIRGINIA B B
MARYLAND B B DELAWARE B B VIRGINIA B B
N CAROLINA B B S CAROLINA B N GEORGIA B A
FL PNHDL N A FL PENIN A A AK N SLOPE A A
AK ALEUTIAN A N AK WESTERN A N AK INT BSN A A
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 24 - 30 2018
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A B
SRN CALIF A B IDAHO A A NEVADA A B
W MONTANA A A E MONTANA A N WYOMING A A
UTAH A N ARIZONA A B COLORADO A A
NEW MEXICO N A N DAKOTA A N S DAKOTA A A
NEBRASKA A A KANSAS B A OKLAHOMA B A
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA A A IOWA N A MISSOURI B A
ARKANSAS B A LOUISIANA B A WISCONSIN N A
ILLINOIS B A MISSISSIPPI B A MICHIGAN N A
INDIANA B A OHIO B A KENTUCKY B A
TENNESSEE B A ALABAMA B A NEW YORK B A
VERMONT B A NEW HAMP B A MAINE B N
MASS B A CONN B A RHODE IS B A
PENN B A NEW JERSEY B A W VIRGINIA B A
MARYLAND B A DELAWARE B A VIRGINIA B A
N CAROLINA B A S CAROLINA B A GEORGIA B A
FL PNHDL N A FL PENIN N A AK N SLOPE A N
AK ALEUTIAN A B AK WESTERN A B AK INT BSN A N
AK S INT A B AK SO COAST A N AK PNHDL A N
LEGEND
TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN
A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN
B - BELOW B - BELOW
THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE.
FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS
PMDMRD.
$$