# Changes are coming



## FISHERBOY (Aug 13, 2007)

THE SECOND PATTERN CHANGE WILL BEGIN TO SHOW ITS CARDS BY THE MIDDLE
OF THE MONTH. 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.Thumbs Up payup


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## Charles (Dec 21, 1999)

I would think the Lake effect would be high since they aren't frozen


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## unit28 (Jan 1, 2007)

just curious to see how this really pans out


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