National Weather Service United States Department of Commerce

Snow Will Persist in the Northeast and Great Lake States

Heavy Lake Effect snow will continue to the lee of the Great Lakes for the next couple of days. Snow will also return to the Northeast by Tuesday as another front moves in. Bitter cold wind chills can be expected in the Upper Mississippi Valley. Freezing temperatures will even impact central Florida. Meanwhile, elevated fire weather conditions will persist in southern California. Read More >

PHILADELPHIA/MT HOLLY WINTER ANALOGS FOR 2014-2015

 

CLIMATE…

WITH THANKSGIVING UPON US AND METEOROLOGICAL WINTER KNOCKING ON

OUR DOOR, ITS OUR ANNUAL LOOK TO SEE HOW PAST WINTERS HAVE FARED

BASED ON PRECEDING FALL PATTERNS AND TRENDS.

 

OUR FORAY LAST FALL ABOUT THE WINTER OF 2013-14 WAS AN

UNMITIGATED BUST AS THE NEGATIVE EASTERN PACIFIC OSCILLATION

PATTERN (EPO) TOOK HOLD IN NOVEMBER AND NEVER LET GO THE ENTIRE

WINTER. WHILE THE COLDER NOVEMBER TRENDED DOWN OUR WINTER

TEMPERATURE ANALOGS TO ABOUT NORMAL, IT WAS NOWHERE NEAR ENOUGH.

IT WAS ALSO ONLY THE SIXTH TIME (OUT OF FORTY SIX OCCURRENCES)

THAT A BOTTOM THIRD WINTER FOLLOWED A WARM OCTOBER.

 

ONCE AGAIN WE ARE HEADING INTO THIS WINTER WITH A RARER

COMBINATION OF A WARM OCTOBER AND COLDER NOVEMBER JUST LIKE THE

TWO PREVIOUS AUTUMNS.

 

IN TERMS OF ENSO, THE LATEST CONSENSUS OF ALL DYNAMICAL AND

STATISTICAL MODELS FOR THE WINTER SEASON IS FOR A WEAK EL NINO TO

OCCUR. OF LATE THE EL NINO HAS LOOKED HEALTHIER AS A KELVIN WAVE

AND A CURRENTLY ROBUST MJO CYCLE HAVE/WILL HELP BOOST SEA SURFACE

TEMPERATURE ANOMALIES (SSTA). AS CPC HAS STATED, THERE IS STILL A

SSTA AND ATMOSPHERIC RESPONSE DISCONNECT THAT EXISTS. THE LATEST

GLOBAL WIND OSCILLATION READINGS, OUR ATMOSPHERE IS STILL IN AN

ENSO NEUTRAL STATE EVEN IF WATER EASTERN TROPICAL PACIFIC

TEMPERATURE ANOMALIES HAVE BECOME WARMER.

 

WEAK EL NINOS SINCE 1950 IN PHILADELPHIA HAVE HAD AN AVERAGE

TEMPERATURE OF 33.2 DEGREES AND AVERAGE SNOWFALL OF 21.8 INCHES.

WEAK EL NINOS, LIKE MOST NON-UBER EL NINOS, FAVOR HAVING MORE

MAJOR SNOW STORMS THAN THE CLIMATOLOGICAL AVERAGE. IN THE TEN WEAK

EL NINOS SINCE 1950, PHILADELPHIA HAS HAD EIGHT SNOWFALL EVENTS OF

SIX INCHES OR MORE, FOUR OF WHICH WERE TEN INCHES OR MORE. THE

MOST COMMON MONTH FOR MAJOR SNOWS DURING WEAK EL NINOS IS JANUARY,

BUT THEY HAVE OCCURRED IN EVERY MONTH FROM NOVEMBER THROUGH MARCH.

 

LOOKING AT THE MIDDLE AND HIGH LATITUDES, ONCE AGAIN SNOW

COVERAGE IN EURASIA WAS OFF TO THE RACES IN SEPTEMBER AND OCTOBER,

EVEN FASTER THAN AUTUMN OF 2013. OCTOBER 2014 ONLY TRAILED OCTOBER

1976 FOR TOTAL SNOW COVERAGE. IN THE SATELLITE ERA WHEN BOTH

SEPTEMBER AND OCTOBER HAVE HAD ABOVE AVERAGE SNOW COVERAGE, 64

PERCENT OF THE ENSUING PHILADELPHIA WINTERS HAVE BEEN SNOWIER THAN

THE CURRENT AVERAGE AND HAD A 50/50 SPLIT WITH TEMPERATURES BEING

EITHER ABOVE OR BELOW NORMAL. WHILE 64 PERCENT MAY NOT SOUND

DEFINITIVE, SNOWFALL IS NOT A NORMAL DISTRIBUTION BECAUSE SEASONS

LIKE 2013-14 SKEW UPWARD THE STATISTICAL AVERAGE. SINCE 1967 (THE

START OF THE SATELLITE ERA AND OUR LOOK AT THE DR. JUDAH COHEN

STUDY) ONLY 1 IN 3 WINTERS HAS HAD ABOVE AVERAGE SNOWFALL. THE

STATISTICAL MEDIAN FOR SNOWFALL IN PHILADELPHIA SINCE 1967 IS

ABOUT 18 INCHES.

 

BEYOND SIBERIA, THE ARCTIC OSCILLATION AVERAGED NEGATIVE DURING

THE MONTH OF OCTOBER. WHEN IT HAS, 70 PERCENT OF ENSUING WINTERS

HAS AVERAGED NEGATIVE. THANK-YOU METEOROLOGIST MATT LANZA FOR THIS

INFORMATION. ANOTHER PHENOMENON THAT FAVORS A NEGATIVE ARCTIC

OSCILLATION FOR THIS UPCOMING WINTER IS THAT WE ARE IN THE

EASTERLY PHASE OF THE QUASI-BIANNUAL OSCILLATION STRATOSPHERIC

WINDS OVER THE TROPICS. WHEN WE ARE IN THIS PHASE, HISTORICALLY WE

HAVE HAD MORE SUDDEN STRATOSPHERIC WARMING EVENTS WHICH OFTEN

SPLITS AND DISPLACES EVERYBODY`S FAVORITE POLAR VORTEX FROM NEAR

THE NORTH POLE. THERE IS NO GUARANTEE THE WESTERN HEMISPHERE WOULD

BE THE SO CALLED BENEFICIARY OF THIS ARCTIC DISPLACEMENT, BUT A

HIGHER CHANCE EXISTS THIS WINTER VS NO CHANCE AT ALL.

 

THE ARCTIC OSCILLATION`S COUSIN, THE NORTH ATLANTIC OSCILLATION

(NAO), WE HAVE SEEN BEEN THE DRIVER (WINTER OF 2010-11) OR THE

CRICKET CHIRPING (LAST WINTER) RECENTLY. UNFORTUNATELY THIS

IMPORTANT TELECONNECTION INDEX IS TOUGH TO OUTLOOK MORE THAN WEEKS

IN ADVANCE. WHILE THE ARCTIC OSCILLATION AND NORTH ATLANTIC

OSCILLATION NORMALLY WORK IN TANDEM, ITS NOT ALWAYS THE CASE.

SINCE 1950, 60 PERCENT OF ALL WINTERS HAVE AVERAGED A NEGATIVE

ARCTIC OSCILLATION, BUT ONLY 42 PERCENT OF ALL WINTERS HAVE

AVERAGED A NEGATIVE NORTH ATLANTIC OSCILLATION. THE LATE JACK

ORDILLE POINTED US TO A RESEARCH PAPER USING NEWFOUNDLAND REGION

SPRING-SUMMER SEA SURFACE TEMPERATURE ANOMALIES AS A PREDICTOR OF

THE NAO FOR THE ENSUING WINTER. IT HAS WORKED WELL THE LAST COUPLE

OF WINTERS (HERE COMES THE JINX) AND IT FAVORS A NEGATIVE NAO FOR

THIS UPCOMING WINTER.

 

THIS BRINGS US TO OUR LAST (BUT NOT LEAST) OSCILLATION INDEX, THE

PACIFIC DECADAL OSCILLATION (PDO). CURRENTLY THE OSCILLATION IS IN

TEXTBOOK POSITIVE POSITION. SO MUCH SO, THAT WHEN ITS BEEN THIS

POSITIVE DURING THE MONTH OF OCTOBER, IT HAS NEVER AVERAGED

NEGATIVE (HERE COMES ANOTHER ANNOUNCER`S JINX: 15 OF 15 TIMES

SINCE 1900) DURING THE UPCOMING WINTER. ELEVEN OF THOSE WINTERS

HAVE AVERAGED COLDER THAN THE CURRENT AVERAGE (AND AVERAGED AROUND

20 INCHES OF SNOW) IN PHILADELPHIA. HISTORICALLY ABOUT 2/3RDS OF

ALL WINTERS SINCE 1900 HAVE AVERAGED COLDER THAN NORMAL IN

PHILADELPHIA WHEN THE PDO HAS AVERAGED POSITIVE. IN FACT, THE

GREATEST POINT OF FAILURE WHEN WARM OCTOBERS HAVE NOT BEEN

FOLLOWED BY WARMER WINTERS HAS BEEN WHEN THE PDO HAS BEEN STRONGLY

POSITIVE IN THE AUTUMN.

 

LOCALLY, OF THE 46 WARMEST WINTERS IN PHILADELPHIA ON RECORD,

HALF OF THEM HAVE OCCURRED AFTER A WARM OCTOBER. GIVEN THE STATE

OF THE PDO, WE DON`T HAVE A WARM FEELING ABOUT THAT THIS WINTER.

THIS NOVEMBER WILL END AGAIN CLOSE TO THE CUSP BETWEEN THE

UNSEASONABLY COLD AND NORMAL TERCILES. REGARDLESS THIS IS A RARER

OCCURRENCE AND A CONTRADICTION IN THE STUDY FIRST DONE IN WHICH

THE STRONGEST CORRELATOR FOR A WARM WINTER IS A WARM OCTOBER WHILE

THE STRONGEST CORRELATOR FOR A COLD WINTER IS A COLD NOVEMBER. IN

2012 OCTOBER WON, LAST YEAR NOVEMBER WON. UNLIKE THE LAST TWO

WINTERS, WE ARE EXPECTING A WEAK EL NINO AND NOT ENSO NEUTRAL

NEGATIVE. WHILE THE PACIFIC FAVORS COLD AGAIN, THE TYPE OF COLD

LOOKS DIFFERENT AS POSITIVE SEA SURFACE TEMPERATURE ANOMALIES ARE

FARTHER EAST THAN THEY WERE LAST AUTUMN.

 

 

 

 

 

 

 

 

 

SO HERE ARE OUR ANALOGS FOR THE UPCOMING WINTER. THEY ARE BASED

ON WARMER THAN CURRENT NORMAL OCTOBERS AND COLDER THAN CURRENT

NORMAL NOVEMBERS. THE ANALOGS ARE A COMBINATION OF MODERATE, WEAK

AND ENSO POSITIVE WINTERS. SEVEN OF THESE ALSO HAD POSITIVE PDO(S)

DURING THE WINTER, THE ONE EXCEPTION (1953-4) WE KEPT BECAUSE IT

WAS A WEAK EL NINO AND IT ALSO WAS A SNOWY NOVEMBER. AS ALWAYS

PAST PERFORMANCE MAY NOT BE AN INDICATOR OF FUTURE TRENDS....AND

NOW TO THE GREAT EIGHT:

 

 

 

SEASON         DEC      JAN      FEB    WINTER    SEASONAL   WINTER

               AVG      AVG      AVG      AVG     SNOWFALL   PCPN

 

 

1905-06        39.2     39.4     33.6     37.4       20.5    8.61

1914-15        33.3     36.6     38.6     36.2       32.5   19.64

1939-40        38.1     25.3     34.8     32.7       22.3    7.77

1941-42        38.3     30.5     30.8     33.2       10.3    9.24

1951-52        38.7     37.3     38.2     38.1       16.2   12.21

1953-54        39.4     31.7     41.7     37.6       22.6    7.58

1986-87        37.9     31.9     32.5     34.1       25.7   11.64

2002-03        35.4     28.6     29.9     31.3       46.3   11.02

 

AVG            37.5     32.7     35.0     35.1       24.6   11.59

1981-2010 NML  37.5     33.0     35.7     35.4       22.4    9.24

 

THE OFFICIAL CPC OUTLOOK FOR THE WINTER IS FOR EQUAL CHANCES OF

IT BEING EITHER WARMER OR COLDER THAN NORMAL AND A GREATER CHANCE

OF IT BEING WETTER THAN NORMAL.

 

WE HOPE EVERYONE HAD A GREAT THANKSGIVING AND WE HOPE YOU WILL

HAVE A HAPPY UPCOMING HOLIDAY SEASON. MAY THIS WINTER BE BEYOND

YOUR WILDEST EXPECTATIONS.