The Ensembles

[aggiecutter]

continue to look very impressive in the 15th to 20th time frame.
http://www.cdc.noaa.gov/map/images/ens/ ... times.html

[cctxhurricanewatcher]

What is it saying?

[aggiecutter]

It continues to show a deep trough in the central and eastern part of the country, with the possibilty for phasing. This is the 4th day in a row the model has been showing basically the same output, which is pretty remarkable for a long range model.

[WindRunner]

I've noticed a lot of the models have been consistent in the long-range recently, but not so much the short-term.

[conestogo_flood]

Do explain to those who have no idea what is being mentioned. Is it atmosphereic temps?

[aggiecutter]

During this time frame, 15th-20th, is when the southern plains and Texas will get a major winter storm. The models have been hinting at this for the past 4 or 5 days.

"ENSEMBLE MEANS FROM THE MODEL SUITE ARE IN EXCELLENT AGREEMENT REGARDING THE LONGWAVE PATTERN ACROSS NORTH AMERICA BUT PHASING BETWEEN THE NORTHERN AND SOUTHERN STREAMS WILL DICTATE PRECIPITATION AMOUNTS ACROSS THE SOUTH AND EAST. CYCLOGENESIS ALONG THE GULF COAST AND AN EVENTUAL TRACK ALONG THE EAST COAST REMAINS PROBABLE SOMETIME DURING THE OUTLOOK PERIOD."


PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST TUE DEC 06 2005

6-10 DAY OUTLOOK VALID FOR DEC 12 - 16 2005 TODAYS NUMERICAL MODEL GUIDANCE IS IN REASONABLY GOOD AGREEMENT AND CONSISTENT FROM YESTERDAYS RUN DEPICTING A PERSISTENT HIGH AMPLITUDE TROUGH ACROSS EASTERN NORTH AMERICA AND A RIDGE ACROSS WESTERN NORTH AMERICA. THE ENSEMBLE MEANS ARE IN EXCELLENT AGREEMENT FORECASTING A SIGNIFICANT POSITIVE 500-HPA HEIGHT ANOMALY CENTERED IN WESTERN CANADA. HOWEVER... MODEL GUIDANCE DIFFERS IN THE ORIENTATION OF THE EASTERN NORTH AMERICA TROUGH. THE CANADIAN MODEL IS LESS AMPLIFIED RELATIVE TO THE GFS AND ECMWF. IN ADDITION... THE CANADIAN MODEL CALLS FOR THE TROUGH AXIS TO BE MORE TOWARDS THE EAST COMPARED TO THE GFS AND ECMWF. THE ECMWF IS PREFERRED AGAIN TODAY FOR THE FOLLOWING REASONS... SUPERIORITY DURING THE COLD SEASON... RECENT MODEL PERFORMANCE... AND SUPPORT FROM THE GFS SUPERENSEMBLE. ELSEWHERE... ALL MODELS FORECAST A POSITIVE 500-HPA HEIGHT ANOMALY NEAR GREENLAND AND THE NAO IS FORECAST TO REMAIN SLIGHTLY NEGATIVE. THE NEGATIVE NAO INDEX COUPLED WITH A HIGHLY NEGATIVE AO INDEX STRONGLY FAVORS BELOW NORMAL TEMPERATURES FROM THE MISSISSIPPI VALLEY TO THE EAST COAST. POSITIVE 500-HPA HEIGHT ANOMALIES IN WESTERN CANADA MAY LEAD TO A STRONG ANTICYCLONE OVER THE CANADIAN PRARIES AND RESULT IN BELOW NORMAL TEMPERATURES FOR THE INTERIOR PACIFIC NORTHWEST. ELSEWHERE IN THE CONUS... ABOVE NORMAL TEMPERATURES WILL BE LIMITED TO CALIFORNIA AND THE DESERT SOUTHWEST. THE PRECIPITATION FORECAST REMAINS MORE UNCERTAIN TODAY ACROSS THE CONUS. ENSEMBLE MEANS FROM THE MODEL SUITE ARE IN EXCELLENT AGREEMENT REGARDING THE LONGWAVE PATTERN ACROSS NORTH AMERICA BUT PHASING BETWEEN THE NORTHERN AND SOUTHERN STREAMS WILL DICTATE PRECIPITATION AMOUNTS ACROSS THE SOUTH AND EAST. CYCLOGENESIS ALONG THE GULF COAST AND AN EVENTUAL TRACK ALONG THE EAST COAST REMAINS PROBABLE SOMETIME DURING THE OUTLOOK PERIOD. THEREFORE... ABOVE NORMAL PRECIPITATION IS HIGHLIGHTED FOR PARTS THE GULF COAST AND EAST. ACROSS THE REMAINDER OF THE CONUS... ABOVE NORMAL PRECIPITATION IS EXPECTED FOR THE CENTRAL ROCKIES AND PLAINS WITH BELOW NORMAL PRECIPITATION FOR THE OHIO VALLEY AND PACIFIC NORTHWEST. ELSEWHERE... BELOW NORMAL HEIGHTS ARE FORECAST BY ALL THE MODELS FROM EAST ASIA AND INTO THE PACIFIC. IN ADDITION... ENSEMBLE MEANS SHOW A 500-HPA TROUGH CENTERED ACROSS THE ALEUTIANS. THIS LONGWAVE PATTERN ACROSS THE PACIFIC STRONGLY SUGGESTS ABOVE NORMAL PRECIPITATION FOR MUCH OF ALASKA. ABOVE NORMAL TEMPERATURES SHOULD ACCOMPANY THE WETTER-THAN-NORMAL CONDITIONS. TODAYS OFFICIAL 500-HPA BLEND CONSISTS OF 20 PERCENT OF TODAY'S 0Z GFS ENSEMBLE MEAN CENTERED ON DAY 8...30 PERCENT OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8...AND 50 PERCENT OF TODAY'S EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 7. MODEL(S) OF THE DAY: ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD IS ABOVE AVERAGE...4 ON A SCALE OF 1 TO 5....DUE TO GOOD CONSISTENCY FROM THE ECMWF IN THE HIGH AMPLITUDE LONGWAVE PATTERN AND REASONABLY GOOD AGREEMENT AMONG THE MODEL GUIDANCE. THE 6-10 DAY TEMPERATURE PROG IS BASED ON THE CPC AUTO BLEND FORECAST...KLEIN SPECIFICATIONS FROM THE ECMWF AND GFS MEAN... AND KLEIN AND ANALOG SPECIFICATIONS TO THE OFFICIAL BLEND. THE 6-10 DAY PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL BLEND... THE CPC AUTO BLEND PRECIPITATION FORECAST... THE CPC CALIBRATED PRECIPITATION FROM THE VARIOUS INDIVIDUAL MODEL RUNS... AND THE CDC PRECIPITATION FORECAST. 8-14 DAY OUTLOOK FOR DEC 14 - 20 2005: DURING THE WEEK 2 PERIOD... THE GFS ENSEMBLE MEAN SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT IN MAINTAINING A HIGHLY AMPLIFIED LONGWAVE PATTERN ACROSS THE CONUS. 500-HPA HEIGHT ANOMALIES ARE FORECAST TO BE BELOW NORMAL FOR MUCH OF THE CONUS EXCLUDING THE PACIFIC NORTHWEST. THE HIGH AMPLITUDE TROUGH CENTERED OVER EASTERN NORTH AMERICA AND A POSITIVE HEIGHT ANOMALY NEAR GREENLAND STRONGLY FAVORS BELOW NORMAL TEMPERATURES FOR THE EASTERN CONUS. THE ENSEMBLE MEANS SUGGEST THAT THE LONGWAVE PATTERN MAY RETROGRADE... IMPLYING THAT BELOW NORMAL TEMPERATURES COULD BE MORE EXPANSIVE COMPARED TO THE 6-10 DAY PERIOD. ABOVE NORMAL TEMPERATURES ARE ONLY EXPECTED FOR CALIFORNIA AND THE DESERT SOUTHWEST. THE LONGWAVE PATTERN REMAINS FAVORABLE FOR CYCLOGENESIS ALONG THE GULF AND EAST COASTS WHERE ABOVE NORMAL PRECIPITATION IS ANTICIPATED. THE POSITIVE 500-HPA HEIGHT ANOMALY CENTERED IN WESTERN CANADA DURING THE 6-10 DAY PERIOD IS FORECAST TO REMAIN STRONG BY THE GFS ENSEMBLE MEAN. THE PRESENCE OF THIS FEATURE SHOULD MAINTAIN BELOW NORMAL PRECIPITATION FOR THE PACIFIC NORTHWEST AND GREAT BASIN. ELSEWHERE... NEGATIVE 500-HPA HEIGHT ANOMALIES CENTERED SOUTH OF THE ALEUTIANS SHOULD LEAD TO ABOVE NORMAL PRECIPITATION FOR SOUTHERN ALASKA AND THE ALASKAN PANHANDLE. TEMPERATURES SHOULD REMAIN ABOVE NORMAL FOR ALASKA. THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF 30 PERCENT OF TODAY'S 0Z GFS ENSEMBLE MEAN CENTERED ON DAY 11...20 PERCENT OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 11...AND 50 PERCENT OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11. FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS ABOVE AVERAGE TODAY... 4 ON A SCALE OF 1 TO 5....DUE TO FAIRLY GOOD MODEL AGREEMENT. THE 8-14 DAY TEMPERATURE PROG IS BASED ON THE KLEIN AND ANALOG SPECIFICATIONS TO THE BLENDED HEIGHT FIELD...KLEIN PROBABILITIES TO THE GFS SUPERENSEMBLE MEAN...THE CDC TEMPERATURE TOOL...AND THE CPC AUTO BLEND TEMPERATURE FORECAST. THE 8-14 DAY PRECIPITATION PROG IS BASED ON THE NEURAL NET AND ANALOG SPECIFICATIONS TO THE BLENDED HEIGHT FIELD...THE CPC AUTO BLEND PRECIPITATION FORECAST...CPC AND EMC CALIBRATED PRECIPITATION PERCENTAGES FROM THE GFS ENSEMBLES...AND THE CDC PRECIPITATION TOOL. FORECASTER: B. PUGH