Out of Control --> Shooting Deep Shortwaves & Cold Air South
Posted by
JAC on 12/17/2009, 8:53 am
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/index_500_mu_loop.shtml
PRELIMINARY EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 818 AM EST THU DEC 17 2009 VALID 12Z MON DEC 21 2009 - 12Z THU DEC 24 2009 A REX-BLOCK EXTENDING FROM GREENLAND TO ONTARIO/QUEBEC AND A LARGE AMPLIFYING UPPER TROUGH OVER THE NORTHERN PACIFIC WILL SUPPORT AN UNUSUALLY HIGH-AMPLITUDE SPLIT-FLOW REGIME OVER THE CONUS THROUGH THE MEDIUM RANGE PERIOD. ONE SOURCE OF SHORTWAVE TROUGH DEVELOPMENT WILL OCCUR WITHIN AND AROUND THE LOW SEGMENT OF THE REX-BLOCK...WITH NORTHWESTERLY FLOW ALOFT LIKELY ALLOWING THESE SYSTEMS TO PERPETUATE COLD AND SOMEWHAT UNSETTLED CONDITIONS ACROSS THE DAKOTAS/GREAT LAKES/OHIO VALLEY/NORTHEAST. MEANWHILE...AN UPPER LOW NEARING THE PACIFIC NORTHWEST DAY 3 SHOULD REMAIN CUT OFF FROM THE MAIN FLOW AS IT DRIFTS OVER THE NORTHWEST BRINGING WET CONDITIONS TO THAT REGION DAYS 3-5 BEFORE SHIFTING EASTWARD AHEAD OF THE APPROACHING PACIFIC UPPER TROUGH. ALTHOUGH TIMING/PLACEMENT/INTENSITY DIFFERENCES ARE QUITE LARGE...SEVERAL DETERMINISTIC SOLUTIONS ALONG WITH MANY GEFS MEMBERS SHOW CYCLOGENESIS COMMENCING IN THE LEE OF THE SOUTHERN ROCKIES DAYS 5/6...ESPECIALLY AS THE UPPER TROUGH NEARS THE GULF COAST REGION BY DAY 7...WITH ALL MODELS HINTING TOWARD ANOTHER SIGNIFICANT WINTER STORM DEVELOPING. GENERALLY PREFER THE DETAILS OF THE ECMWF/GFS ENS MEANS WITH THIS SYSTEM...ESPECIALLY EARLY IN THE PERIOD ACROSS THE NORTHWEST WHERE THE GFS LIES NEAR THE FAST EDGE OF ALL THE GUIDANCE.
FINALLY...DEEPENING LOW PRESSURE OFF THE MID-ATLANTIC COAST AT THE START OF DAY 3 SHOULD BE ACCELERATING NORTHEASTWARD AFTER LEAVING BEHIND A SIGNIFICANT MID ATLC REGION SNOW EVENT. INTENSIFYING LOW MOVING ALONG THE GULFSTREAM EDGE LIKELY TO BE A SERIOUS MARINE THREAT. SEE OPC WARNINGS.
UPDATED MORNING MEDIUM RANGE PRESSURES/FRONTS WILL BEGIN WITH THE OPERATIONAL 00Z ECMWF DAYS 3-5 BEFORE SHIFTING TO A 70/30 BLEND OF THE ECMWF ENSEMBLE MEAN AND GFS ENSEMBLE MEAN DAYS 6/7. AT 6-7 DAYS OUT THESE MEANS TONE DOWN THE SIGNIFICANT MS VALLEY CYCLOGENESIS SEEN BY OP MODEL RUNS WITH LARGE DIFFERENCES LATE PERIOD. JAMES/ROSENSTEIN
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In this thread:
Major Snowstorm( Saturday) Mid-Atlantic??? -
Doorman,
12/15/2009, 6:59 pm- Look at those snowfall totals ! - CypressTX, 12/19/2009, 9:08 am
- Im gonna get smashed - DESteve, 12/18/2009, 7:33 am
- Re: Major Snowstorm( Saturday) Mid-Atlantic??? - Fred, 12/17/2009, 7:09 pm
- Re: Major Snowstorm( Saturday) - aquaRN, 12/17/2009, 4:52 pm
- Retrograding Rex Block over East Canada - JAC, 12/16/2009, 6:58 am
- Looks like it it staying out to sea - JAC, 12/16/2009, 6:50 am
- Re: Major Snowstorm( Saturday) Mid-Atlantic??? - Fred, 12/15/2009, 8:07 pm
- Re: Major Snowstorm( Saturday) Mid-Atlantic??? - aquaRN, 12/15/2009, 7:16 pm
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