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    Henry Margusity

    The Cold Weather and Sustained Cold Coming

    1/10/2013, 7:43:22 AM

    Comment

    Below is a nice writeup from the NWS office in Buffalo regarding the stratospheric warming and the implications. I wanted to share that writeup with you because I thought the forecaster who wrote it did a nice job explaining what it is and what the impacts are.

    We have been talking about the cold weather coming the end of January into February and this may be a situation of sustained cold into the Great Lakes and Northeast. For some, it will be the coldest weather in years.


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    "A MAJOR SUDDEN STRATOSPHERIC WARMING EVENT IS UNDERWAY AND NEARING COMPLETION. SUDDEN STRATOSPHERIC WARMING EVENTS ARE FAVORED TO OCCUR DURING AN EASTERLY PHASE OF THE QUASI-BIENNIAL OSCILLATION /QBO/...WHICH IS THE PHASE THE STRATOSPHERE IS IN THIS WINTER. THE SUDDEN STRATOSPHERIC WARMING CAUSES A DRAMATIC WEAKENING...AND SOMETIMES ENTIRE BREAKDOWN OF THE STRATOSPHERIC POLAR VORTEX...AND A GREAT WEAKENING OR EVEN REVERSAL OF THE STRATOSPHERIC POLAR NIGHT JET. THE GFS FORECASTS THIS TO OCCUR OVER THE NEXT WEEK AT THE 2MB LEVEL.

    THE RESULT OF ALL OF THIS IS THE GENERATION OF STRONG HIGH LATITUDE BLOCKING AS THE DRAMATIC CHANGES IN THE STRATOSPHERE FEED DOWN INTO THE TROPOSPHERE. HIGH LATITUDE BLOCKING FORCES THE COLDEST AIR SOUTH OUT OF THE HIGH ARCTIC AND TOWARDS THE MID LATITUDES...AND ALSO FAVORS LASTING STRONGLY NEGATIVE EPISODES OF ARCTIC OSCILLATION /AO/ AND NORTH ATLANTIC OSCILLATION /NAO/. THIS TYPICALLY BEGINS TO TAKE PLACE 10-15 DAYS AFTER THE SUDDEN STRATOSPHERIC WARMING EVENT. HOW LONG IT LASTS CAN VARY...BUT TYPICALLY THE COLD PATTERN LASTS FOR AT LEAST A FEW WEEKS...AND OCCASIONALLY CAN PERSIST THROUGH THE REST OF WINTER.

    AS ALL OF THIS IS OCCURRING...THE MJO IS FORECAST BY THE GEFS ENSEMBLES TO WEAKEN AND FADE AWAY IN ABOUT 10 DAYS. THE PACIFIC NORTH AMERICAN PATTERN /PNA/ IS FORECAST TO REMAIN NEGATIVE OVER THE NEXT 10 DAYS...WHICH WILL DIRECT THE FIRST BATCHES OF COLD INTO THE WESTERN AND EVENTUALLY CENTRAL UNITED STATES. GEFS ENSEMBLE MEMBERS SUPPORT A TREND TOWARDS A NEUTRAL OR POSITIVE PNA BY THE MIDDLE OF THE MONTH...WHICH SHOULD ALLOW THE GROWING COLD TO SPREAD EASTWARD.

    WHAT ALL OF THIS TECHNICAL JARGON MEANS IS THAT THERE IS MODERATE TO HIGH CONFIDENCE IN A PATTERN CHANGE TOWARDS MUCH COLDER WEATHER FOR THE CENTRAL AND EASTERN UNITED STATES STARTING AROUND THE MIDDLE OF JANUARY...WITH COLD LIKELY PEAKING IN LATE JANUARY INTO EARLY FEBRUARY. THERE IS THE POTENTIAL FOR THE COLDEST AIR WE HAVE SEEN IN AT LEAST SEVERAL YEARS DURING THIS PERIOD. WHAT SNOW POTENTIAL THIS WILL BRING IS MUCH MORE UNCERTAIN DUE TO UNKNOWN DETAILS WITH SYNOPTIC STORM TRACK AND LAKE EFFECT POTENTIAL."


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    This is the same map I issued yesterday for the snowfall. I don't have any changes at this time on the storm. I will add that the combination of wind, very cold weather and snow will create blizzardlike conditions across the Dakotas into northern Minnesota. The next wave of low pressure will produce another swath of snow in the Midwest Sunday followed by another swath of possible snow from Tennessee to Maine Tuesday.

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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    Henry Margusity