198
FXUS10 KWNH 041830
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 PM EST TUE FEB 04 2020
VALID FEB 04/1200 UTC THRU FEB 08/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~
..EVOLVING FULL LATITUDE TROUGH OVER THE CENTRAL US THROUGH THU
..SURFACE WAVE DEVELOPING OVER THE LOWER MS VALLEY
MOVING INTO
THE INTERIOR MID ATLANTIC LATE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~
PREFERENCE: 12Z ECMWF/UKMET/CMC/GEFS AND 00Z ECENS MEAN
CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE
07Z UPDATE: THE 12Z UKMET SLOWED A BIT, WHILE KEEPING A VERY
SIMILAR EVOLUTION (PARTICULARLY, THE STRONGER COMPACT SHORTWAVE
ROUNDING THE BASE OF THE MAIN TROF THURS/FRI). THE 12Z CMC AND
ECMWF CONTINUE TO BE SLOWER ALLOWING FOR A MUCH SHARPER SOUTHERN
PORTION OF THE TROF AS A WHOLE. THIS CONTINUES TO BE FAVORED BY
THE ENSEMBLES THROUGH THE GEFS WAS EVEN SLOWER THAN THE ECENS
MEAN. AS SUCH WILL CONTINUE TO FAVOR A UKMET/ECMWF/CMC BLEND WITH
INCORPORATION OF THE 12Z GEFS/00Z ECENS MEAN. WHILE THE LARGE
SCALE PATTERN/SYSTEM IS AGREED THE DIFFERENCES IN THE TIMING LEAD
TO THE AVERAGE TO SLIGHTLY BELOW AVERAGE CONFIDENCE IN THE
PREDICTABILITY AT THIS POINT.
---PRIOR DISCUSSION---
GOES-EAST WV DEPICTS THE FULL LATITUDE TROUGH ACROSS THE CENTER TO
SOUTHWESTERN PORTION OF THE CONUS. THE NORTHERN STREAM SHORTWAVE
IS ALREADY DEPARTING/SEVERING CONNECTION TO THE MAIN ELONGATED
UPPER LEVEL TROF. AS SUCH THE SURFACE PATTERN DEPICTS A WELL
DEFINED BUT STATIONARY FRONT FROM THE EASTERN GREAT LAKES TOWARD
THE SOUTHERN PLAINS AND HIGH PLAINS OVER NEW MEXICO. THE
SHORTWAVE AT THE BASE OF THE ELONGATED TROF WILL EMERGE LATER
TODAY AND ALONG WITH INSTABILITY OFF THE WESTERN GULF, WILL
SUPPORT A SURFACE WAVE THAT LIFTS THROUGH THE LOWER MS VALLEY
TOMORROW (WED) AND THROUGH THE UPPER OHIO VALLEY BY THURSDAY
MORNING. THIS EVOLUTION IS FAIRLY WELL AGREED UPON, WITH
EXCEPTION OF THE 12Z GFS, WHICH CONTINUES FAVOR STRONGER INFLUENCE
OF THE CENTRAL US SHORTWAVE ENERGY OVER THE BASE ENERGY ROTATING
NORTH, LEADING TO GREATER RIDGING ACROSS THE OHIO VALLEY AND
THEREFORE GREATER INSTABILITY/MOISTURE FLUX ACROSS THE CUMBERLAND
PLATEAU.
THIS MAY BE KEYED ON THE APPROACH/INTERACTION WITH THE LEADING
SHORTWAVE EMERGING FROM THE STRONG PACIFIC FLOW OVER-TOPPING THE
PACIFIC/WEST COAST RIDGE. THE GFS AND LESSER SO 12Z NAM, BOTH
SUGGEST SLIGHTLY FASTER AND MORE ELONGATED JET EXIT REGION AND
MID-LEVEL STRETCHING INTO THE WESTERN SIDE OF THE FULL-LATITUDE
TROF. THE 06Z GEFS THOUGH IS MORE IN-LINE WITH THE ECENS MEAN,
UKMET, CMC AND OPERATIONAL ECMWF, SO WOULD CONTINUE TO FAVOR THIS
DIRECTION, THOUGH THE SPREAD IS STILL FAIRLY SMALL.
IT IS AFTER THIS SHORTWAVE ENTERS THE BASE OF THE MAIN TROF, LATE
THURSDAY, THAT THE SPREAD SIGNIFICANTLY CHANGES, MAINLY ON THE
SHAPE, TIMING OF THE WAVE AND ASSOCIATED JET STREAK ROUNDING THE
BASE. HERE, THE 00Z UKMET IS MOST COMPACT AND VERY STRONG WITH
THE JET AND TYPICAL OF ITS BIAS IS FASTER MOVING THROUGH AND
LIFTING ACROSS THE SOUTHEAST INTO THE CENTRAL EAST COAST FRI
(THOUGH STILL SLOWER THAN THE 12Z GFS). THE ECMWF/ECENS MEAN AND
CMC ARE SLOWEST TO ENTER THE BASE AND DIG A BIT FURTHER SOUTH THAN
THE OTHER GUIDANCE, THIS IS SIMILAR TO THE 12Z NAM AND HOW IT
BROKE FROM THE GFS. OVERALL, THERE IS SIZABLE SPREAD/UNCERTAINTY
BUT WILL CONTINUE A NON-GFS BLEND FAVORING THE ECMWF/ECENS MEAN
AND GEFS MEAN. SO AVERAGE TO SLIGHTLY BELOW AVERAGE AFTER FRIDAY
12Z.
..PULSES ALONG ATMOSPHERIC RIVER WED-FRI INTO PACIFIC NW
...APPROACHING RAPIDLY DEEPENING CYCLONE TOWARD PACIFIC NW BY END
OF DAY 3...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: 12Z ECMWF/UKMET/NAM BLEND
CONFIDENCE: AVERAGE
07Z UPDATE: THE 12Z ECMWF/UKMET BOTH TRENDED MUCH FASTER, BOTH
CONTINUE TO BE MORE VERTICALLY STACKED AND COMPACT, BUT HAVE
REDUCED THE SPREAD OVERALL PARTICULARLY WITH THE GFS/NAM. THE CMC
TRENDED EVEN FURTHER EAST THAN THE GFS/NAM, TO MAKE IT STAND OUT.
AT THIS POINT WILL CONTINUE TO FAVOR THE STRONGER, MORE COMPACT
SOLUTIONS OF THE UKMET/ECMWF BUT HAVE SOME INCORPORATION OF THE
NAM TO ACCOUNT FOR THE SLIGHTLY WEAKER SOLUTIONS WHICH MATCH THE
GEFS/ECENS MEAN CLUSTERS BETTER THAN THE FASTEST CMC/GFS.
---PRIOR DISCUSSION---
UPSTREAM, THE WESTERN RIDGE REMAINS DOMINANT THROUGH THE FORECAST
PERIOD, WITH STRONG SUPERGEOSTROPHIC FLOW OVER THE RIDGE DIRECTING
A WEAKER BUT STILL SLIGHTLY ABOVE AVERAGE MOISTURE STREAM/AR
ACROSS THE PACIFIC NW INTO THE SNAKE RIVER VALLEY AND CENTRAL
ROCKIES THURS-FRI. THIS IS FINALLY DISRUPTED BY THE STRONG
SHORTWAVE ENERGY AT THE BASE OF THE BERING SEA CLOSED LOW, THAT
RAPIDLY EVOLVES/OCCLUDES LATE FRIDAY. THE UNCERTAINTY, HERE IS
THE PLACEMENT AND JUST LIKE FURTHER EAST THE GFS IS FURTHER EAST
HAVING A LESS AMPLIFIED RIDGE ACROSS BRITISH COLUMBIA. THE NAM IS
SIMILAR BUT WITH GREATER RIDGING AND TYPICAL LATE DAY 3
AMPLIFICATION BIAS, IT SLOWS AND MATCHES THE 06Z GEFS MEAN AND
CMC. THE 00Z ECMWF SHOWS MUCH GREATER AMPLIFICATION OF THE RIDGE
ALLOWING FOR A DEEPER VERTICALLY STACKED LOW WHICH IS MUCH SLOWER.
INTERESTINGLY, THE ECENS SOLUTIONS SUGGEST THIS MAY BE A BIT
FASTER THAN THE BULK OF ENSEMBLE SOLUTIONS. THE UKMET IS CLEARLY
THE SLOWEST/GREATEST AMPLIFIED AND STICKS OUT SIGNIFICANTLY FROM
THE ENSEMBLES TO HAVE MUCH CONFIDENCE IN IT. AS SUCH WILL FAVOR
AN ECMWF/CMC/NAM BLEND FOR THIS SYSTEM, THOUGH THE AR/MOISTURE
TRANSPORT INTO THE PACIFIC NW PRIOR TO THIS SYSTEM MAY BE BEST
SUITED WITH A NON-GFS BLEND.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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