High Amplitude Omega Block Sets In
Posted by
JAC on 12/15/2010, 6:48 am
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
239 AM EST WED DEC 15 2010
VALID 12Z SUN DEC 19 2010 - 12Z WED DEC 22 2010
DETERMINISTIC AND ENSEMBLE GUIDANCE AGREE IN ALLOWING THE
ANOMALOUSLY STRONG UPPER HIGH NEAR GREENLAND TO RETROGRADE INTO
CENTRAL CANADA DURING THE MEDIUM RANGE PERIOD HELPING TO COMPLETE
AN OMEGA-BLOCK CONFIGURATION OF UNUSUALLY HIGH AMPLITUDE.
THUS...PERSISTENCE WILL BE A LARGE COMPONENT OF THE FORECAST
PHILOSOPHY THIS PACKAGE. REGARDING SYSTEM DETAILS...THE 00Z ECMWF
IS CONSIDERED AN OUTLIER WITH AN UPPER LOW RETROGRADING ACROSS
SOUTHERN CANADA DAYS 3-6 WHILE OTHER MODELS CONTINUE TO ALLOW
PERTURBATIONS TO ROTATE AROUND THE NEW ENGLAND UPPER LOW.
THUS...THE ECMWF SCENARIO WILL BE IGNORED UNTIL STRONGER SUPPORT
DEVELOPS. OTHERWISE...THE ECMWF IS A LITTLE FASTER THAN THE 00Z
GFS IN REPLACING THE UPPER CYCLONE OFF THE NORTHWEST COAST WITH A
NEWLY FORMED LOW DROPPING SOUTHWARD FROM ALASKA BY DAY 7...AND IS
A LITTLE FARTHER SOUTH THAN THE GFS IN DEVELOPING A SECOND LOW
CENTER OFF THE CALIFORNIA COAST AT THE SAME TIME. IN THE
EAST...THE GFS HAS SLOWLY BACKED OFF ITS MOST WESTWARD LOW TRACK
ALONG THE EAST COAST DAYS 3/4...WITH THE ECMWF FARTHER OUT TO SEA
UNTIL ABOUT DAY 5 WHEN THEY BOTH SHOW THE CYCLONE RETROGRADING
INTO NOVA SCOTIA. HOWEVER...THE 00Z UKMET/CANADIAN AND THE GLOBAL
ENSEMBLE MEANS ARE FARTHER EAST...WITH A CONSENSUS APPROACH STILL
RECOMMENDED. THUS...THE PRELIMINARY PRESSURES/FRONTS WILL CONSIST
OF 70 PERCENT 12Z ECMWF ENSEMBLE MEAN TO 30 PERCENT 00Z GEFS
MEANS.
JAMES
|
46
In this thread:
Post A Reply
This thread has been archived and can no longer receive replies.