
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
719 AM EST THU JAN 13 2005
VALID 12Z MON JAN 17 2005 - 12Z THU JAN 20 2005
12Z DISCUSSION...
THE 00Z GFS REMAINS A VALID CHOICE FOR THE MEDIUM RANGE PERIOD.
THE 06Z RUN SLOWED DOWN THE TROUGH MOVG ACRS THE NRN PLAINS/EAST
...AND SINCE THE GFS HAS BEEN BOUNCING ARND IN THE LOCATION OF THE
TROF AXIS FOR 3 DAYS NOW... DID NOT FEEL THE NEED TO JUMP TO ITS
06Z SOLN. DEFINITELY HAD TO THINK ABOUT THE INCREASED
AMPLIFICATION SEEN SINCE YESTERDAY AS THE ALL THE GUIDANCE HAD
TRENDED FLATTER WITH THE FLOW FOR THE 48 HR PERIOD GOING INTO WED
WHICH HAD BEEN GENERALLY SUPPORTED BY THE AO AND TELECONNECTIONS.
THE ENSEMBLE MEAN DEPTH WAS NOT TOO MEANINGFUL THIS MORNING AS IT
HAS BEEN DEEPER FOR THE PAST 3 DAYS. HOWEVER...THE APEX OF THE
RIDGE IN AK HAS FAR LESS SPREAD IN THE ENSEMBLE MEAN TODAY...AND
IT IS STILL TO THE NORTHWEST ACRS NRN AK...SO A DEEPER ERN TROF
APPEARS MORE PROBABLE. ANOTHER GOOD SIGN WAS A CHANGE IN THE
ARCTIC OSCILLATION...AS VALUES ARE PLUNGING TWDS ZERO AFTER BEING
STRONGLY POSITIVE FOR A COUPLE WEEKS. HENCE...AMPLIFICATION IS
LOOKING INCREASINGLY PSBL.