#450 Postby HockeyTx82 » Mon Jan 03, 2011 1:08 pm
FT. WORTH NWS
.PREV DISCUSSION... /ISSUED 418 AM CST MON JAN 3 2011/
/AND NOW A DISSERTATION ON A LIKELY COLD SPELL NEXT WEEK/
ALL THE MEDIUM TO LONG RANGE MODELS CONTINUE TO ADVERTISE A MAJOR
PATTERN SHIFT OCCURRING OVER THE NORTHERN LATITUDES...WITH BLOCKED
UPPER FLOW SETTING UP AND PERSISTING ACROSS CANADA. MODELS FORECAST
THE UPPER LEVEL RIDGE NOW OVER WESTERN CANADA TO BREAK DOWN AND BE
REPLACED BY A STATIONARY UPPER LEVEL LOW THIS WEEKEND. AS THIS
OCCURS...SURFACE TEMPS COOL AND PRESSURES GRADUALLY RISE. IN SHORT
THIS MEANS WESTERN CANADA WILL BE THE GENESIS REGION OF THE COLD
AIR MASS FORECAST TO ARRIVE IN 7 TO 8 DAYS.
THE ASTUTE OBSERVER WOULD NOTICE TEMPS ACROSS WESTERN CANADA AND
ALASKA ARE NOT THAT COLD NOW. I KNOW IT IS A HABIT FOR MANY OF US
TO THROW A MAP OF SURFACE TEMPS UP AND TRY TO SEE WHERE THE COLD
AIR IS AND WHERE IT IS COMING FROM. BUT THIS IS SORT OF A RULE OF
THUMB AND IS PARTIALLY FLAWED THINKING FOR A COUPLE REASON. FIRST
COLD AIR AT THE SURFACE IS NOT A CONSERVED QUANTITY...IT DEVELOPS
AND IS ALSO DESTROYED BY COMPLEX DYNAMIC MOTIONS ALOFT. THE SECOND
REASON IS AN ANALYSIS OF WHERE OUR PAST BIG ARCTIC OUTBREAKS
ORIGINATE USING BACKWARD TRAJECTORIES SHOWS US THAT THE NORTH POLE
REGION IS PREFERRED...BUT OUR SURFACE PARCELS HERE ACTUALLY
ORIGINATE AT LEVELS BETWEEN 500MB-700MB. THUS AN ANALYSIS OF
500MB-700MB TEMPS AND ANOMALIES IN THE NORTHERN LATITUDES CAN GIVE
US A GOOD PROXY TO COMPARE AND JUDGE THE STRENGTH OF FUTURE ARCTIC
EPISODES. THESE CURRENT MID-UPPER LEVEL TEMPS ARE CHILLY...BUT NOT
TOO UNUSUAL. SO THE FRONT THAT ARRIVES IN A WEEK MAY BE
SIGNIFICANT BUT NOT RECORD BREAKING...AT LEAST NOT INITIALLY.
WHAT IS INTERESTING ABOUT THE FORECAST UPPER PATTERN IS THAT BY
7-10 DAYS AN UNUSUALLY STRONG UPPER LEVEL HIGH IS FORECAST TO
DEVELOP OVER ALASKA...WITH A STRENGTHENING UPPER LOW ACROSS
NORTHERN CANADA. THESE POLAR LOWS ARE RESPONSIBLE FOR THE MAJOR
ARCTIC OUTBREAKS WHEN THEY MOVE SOUTH...AND THAT IS WHAT THE GFS
HAS BEEN FORECASTING TO OCCUR IN THE 10-15 DAY TIME RANGE. WHETHER
THIS ACTUALLY OCCURS REMAINS TO BE SEEN. REGARDLESS...THE BLOCKING
UPPER PATTERN WILL KEEP A PROLONGED FETCH OF CANADIAN/ARCTIC AIR
COMING INTO THE REGION FOR THE 2ND WEEK OF JANUARY. TOO EARLY TO
TELL WHETHER ANY MOISTURE WILL BE AVAILABLE...BUT NONETHELESS ITS
SHAPING UP TO BE AN INTERESTING WEEK WEATHER-WISE.
TR.92
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Don't hold me accountable for anything I post on this forum. Leave the real forecasting up to the professionals.
Location: Ponder, TX (all observation posts are this location unless otherwise noted)