719
FXUS10 KWNH 291627
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 AM EST SUN DEC 29 2019
VALID DEC 29/1200 UTC THRU JAN 02/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DOMINANT CENTRAL PLAINS THROUGH GREAT LAKES AND NORTHEAST
CLOSED LOW/SURFACE CYCLONE(S) INCLUDING COASTAL LOW TUES/WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MATURE/VERTICALLY STACKED LOW OVER IA/MN WILL GIVE WAY TO THE
SHORTWAVE STARTING TO TAKE SHAPE/AMPLIFY ACROSS NE TX AT THIS
TIME. THIS WAVE TAKES OVER THE LARGER CLOSED LOW AS IT DEVELOPS
THE NEW TRIPLE POINT LOW THROUGH THE MS VALLEY, CENTRAL OHIO
VALLEY INTO THE GREAT LAKES LATE TOMORROW. THE 12Z GFS CONTINUES
TO BE SLIGHTLY OFF-BALANCE FAVORING A NORTHERN/EASTERN TRACK
RELATIVE TO THE OVERALL GUIDANCE, ADDITIONALLY THE THERMAL
PROFILES SHOW CONTINUED WARMER SOLUTIONS PARTICULARLY INT THE
TRANSITION BETWEEN THE NEXT SHORTWAVE LIFTS UP AND STARTS TO
DEVELOP A COASTAL SURFACE WAVE ON LATE MONDAY INTO TUESDAY, WHICH
AFFECTS PRECIPITATION TYPE ACROSS PA INTO THE NORTHEAST MON INTO
TUESDAY. THE MASS FIELDS ARE NOT TOO BAD EVEN AS THE FORMER INNER
CORE ROTATES THROUGH SUPPORTING THE COASTAL LOW INTO THE NEXT
PERMUTATION OF THE CLOSED LOW CENTER HUB IN MAINE/SOUTHEAST CANADA
BY MIDDAY WED. HERE, THE GFS IS VERY AGREEABLE IN A TIGHTLY
PACKED SOLUTION AT THE LOWEST LAYERS. SO GENERALLY, MASS FIELDS
COULD BE GENERALLY BLENDED TOGETHER, BUT GIVEN THE THERMALS A
STILL MORE IMPORTANT A NON-GFS BLEND IS PREFERRED THROUGH THE
FORECAST PERIOD AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
..PACIFIC SHORTWAVE DIVING ALONG THE WEST COAST SUN-WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
GOES-W WV DENOTES COMPACT CLOSED LOW CORE OFF THE NW TIP OF
VANCOUVER ISLAND WITH AN ELONGATING WARMING ASSOCIATED WITH THE
STRETCHING SHORTWAVE ALOFT, A FEW DEGREES WEST OF THE US COAST.
THIS AREA CONTINUES TO ELONGATE/STRETCH AND THE BASE IS EXPECTED
TO REORGANIZE TO THE NEW CLOSED LOW OFF THE CA COAST BY LATER
TODAY/EARLY TOMORROW WITH AN ASSOCIATED SURFACE LOW. GUIDANCE
CONTINUES TO BE VERY STRONG WITH THE EVOLUTION AND TIMING ALONG
THE CONUS AREA TO SUPPORT A GENERAL MODEL BLEND. HOWEVER, BY
01.00Z THERE IS SOME MODEL DIFFERENCES THAT WILL PLAY A ROLE IN
LONGER TERM FORECAST DIFFERENCES AS IT ROTATES INTO THE SEA OF
CORTEZ/NORTHERN MEXICO (SO PLEASE REFER TO WPC PMDEPD FOR MORE
DETAILS).
..ATMOSPHERIC RIVER SINKING INTO PAC NW BY LATE TUES
...AMPLIFYING INTO BROAD TROF ACROSS NORTHERN ROCKIES/NORTHERN
PLAINS BY LATE WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF W/12Z NAM @ LOWER WEIGHT
CONFIDENCE: SLIGHTLY BELOW AVERAGE
IN THE WAKE OF THE CLOSED LOW NEAR THE COAST CURRENTLY, VERY
VIGOROUS PACIFIC FLOW, NOTED UPSTREAM IN THE GOES-WEST WV SUITE,
BECOMES VERY ZONAL INTO THE PACIFIC NW BUT IS VERY STRONG WITH
INTERNAL SMALLER SCALE WAVES RIPPLING FAST THROUGH IT. COMBINE
THIS WITH DEEP ANOMALOUS MOISTURE TAPPED FROM THE WARM CENTRAL
PACIFIC AIDS A STRONG ATMOSPHERIC RIVER THAT SLOWLY DROPS SOUTH
INTO THE CONUS BY EARLY TUESDAY. AS SUCH, PREDICTABILITY IS QUITE
DIFFICULT ESPECIALLY WITH TIMING. YET, THE LARGER EVOLVING
PATTERN AS THE MAIN WAVE/JET ENERGY ENTERS THE PACIFIC NORTHWEST
AND BLEEDS OVER INTO THE NORTHERN ROCKIES IS TAKING SHAPE FAIRLY
AGREEABLY AS A BROAD BUT MODESTLY DEEP LONGER WAVELENGTH INTO THE
NORTHERN PLAINS BY 00Z THURSDAY. HERE THE ENSEMBLE SUITE SHOWS
THE BROAD PATTERN BUT GIVEN THE SPREAD, EFFECTIVELY LOSES THE
SIGNAL AND WASHES IT OUT. STILL, DETERMINISTICALLY, THE 12Z GFS
AND 00Z ECMWF ARE VERY CENTRAL TO THE ENSEMBLE SUITE PROVIDING
CONFIDENCE BUT ALSO SHOW A MORE REALISTIC DEPTH OF THE WAVE AND
SURFACE LOW TRACK TO SUGGEST A BLEND OF THE TWO. THE 00Z
UKMET/CMC ARE BOTH MUCH TO STRONG WITH STRONG SURFACE REFLECTIONS
IN THIS STREAM THAT TRANSFERS INTO S CANADA WELL BROADER AND WELL
NORTH OF CURRENT PREFERENCE/THINKING. THE 12Z NAM IS A BIT
SLOWER AND STRONGER THEREFORE ENCAPSULATE SOME OF UNCERTAINTY IN
THE ENSEMBLE SUITE AND WILL BE INCLUDED IN THE BLEND TO HELP
ACCOUNT FOR SOME OF THAT "POSITIVE" UNCERTAINTY, EVEN IF NOT
IDEALLY DESIRED...PERHAPS SHOWING SOME TYPICAL DAY 3 MORE
AMPLIFIED TYPICAL NEGATIVE BIAS. OVERALL CONFIDENCE IS SLIGHTLY
BELOW AVERAGE.
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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