Prognostic Meteorological Discussion
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FXUS10 KWNH 181700
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1159 AM EST WED JAN 18 2017

VALID JAN 18/1200 UTC THRU JAN 22/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

...CLOSED UPPER LOW OVER CNTRL/SRN HIGH PLAINS TRACKING TO UPPER
MS VALLEY/GREAT LAKES FRI...
...ASSOCIATED SURFACE WAVE MOVING ACROSS THE MIDDLE MS VALLEY INTO
THE OHIO VALLEY FRI...

PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

THE CLOSED MID LEVEL LOW OVER THE HIGH PLAINS BROADENS AS IT LIFTS
ACROSS THE CENTRAL PLAINS THURSDAY...EVENTUALLY TRANSITIONING
TOWARD AN OPEN...NEGATIVELY TILTED TROUGH OVER THE UPPER MIDWEST
AND GREAT LAKES ON FRIDAY. THE 12Z NAM HAS CONTINUED ITS TREND
TOWARD MODEL CONSENSUS THROUGH DAY 3 ACROSS THE CENTRAL
PLAINS...AND NOW HANDLE THIS FEATURE SIMILARLY. GIVEN ONLY SUBTLE
TIMING/SPATIAL DIFFERENCES...WILL REFLECT A GENERAL MODEL
COMPROMISE. HOWEVER...GIVEN THESE SUBTLE DIFFERENCES...WILL
CONTINUE WITH ONLY AVERAGE FORECAST CONFIDENCE.

...LONG WAVE TROUGH DIGGING INTO THE SOUTHWEST US THU/THU NIGHT...
...DEVELOPING/CLOSING MID LEVEL LOW OVER THE CENTRAL PLAINS BY
EARLY SAT...

PREFERENCE: 12Z GFS AND 00Z ECMWF/00Z UKMET
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GENERALLY GOOD MODEL AGREEMENT WITH THE TIMING OF THE NEXT STRONG
LONG WAVE TROUGH DIGGING ACROSS THE WEST COAST INTO THE FOUR
CORNERS REGION BY LATER FRIDAY...WITH BOTH THE 12Z NAM AND 12Z GFS
CLOSE TO THE BEST CLUSTERING. 12Z/GFS AND 00Z ECMWF QUICKEST IN
CLOSING OFF IN THE MID LEVELS OVER THE CENTRAL HIGH PLAINS FRIDAY
NIGHT...BEFORE EJECTING TOWARD THE CENTRAL PLAINS ON SAT. THE
12Z/NAM AND 12Z/GFS REMAINS COMPARABLE TO THE 00Z/ECMWF AND
00Z/UKMET ON THE STRONG SIDE OF THE GUIDANCE ENVELOPE. ONLY
NOTABLE DIFFERENCE BETWEEN THE TWO IS THAT THE NAM IS A BIT
SLOWER/FARTHER WEST WITH THE CLOSED OFF MID LEVEL SYSTEM BY
SATURDAY AFTERNOON. IT SHOULD ALSO BE NOTED THAT THE 00Z/ECMWF
ENSEMBLE GUIDANCE IS MARRED BY A BIT MORE SPREAD THAN NORMAL BY
FRIDAY EVENING INTO EARLY SATURDAY...WITH QUITE A FEW MEMBERS
REMAINING A BIT FASTER WITH THIS SYSTEM.

WILL THEREFORE CONTINUE WITH PREVIOUS PREFERENCE UPDATED FOR THE
12Z GFS.

...SECONDARY HEIGHT FALLS ACROSS THE WEST FRIDAY/SATURDAY...

PREFERENCE: 12Z/GFS AND 00Z ECMWF ENSEMBLE
FORECAST CONFIDENCE: AVERAGE

NEXT STRONG SHORT WAVE DIGS ACROSS THE PAC NW INTO CA FRIDAY AND
FRIDAY NIGHT. MODELS STILL HANDLING THE UPPER FEATURE SIMILARLY
THROUGH DAY 2...WITH THE GFS AND GEFS A BIT STRONGER/SLOWER THAN
THE NON-NCEP PROBABILISTIC GUIDANCE BY DAY 3. AT THE SFC, 12Z/GFS
IS A BIT WEAKER WITH THE SFC LOW OVER THE PAC NW DAY 3. TO THE
SOUTH, THE SOUTHERN STREAM SFC LOW OVER THE SOUTHERN HIGH PLAINS
IS HANDLED SIMILARLY, WITH FURTHER CLUSTERING OF THE EXPECTED SFC
LOW OVER THE SOUTHERN HIGH PLAINS LATE SATURDAY. GIVEN THAT SOME
ADDITIONAL ECMWF ENSEMBLE MEMBERS HAVE TRENDED TOWARDS A SLOWER
SOLUTION WITH THE MID LEVEL SYSTEM, WILL TREND THE PREFERENCE
TOWARD A GFS/ECMWF ENSEMBLE BLEND, WITH ONLY AVERAGE FORECAST
CONFIDENCE.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

MONTEFUSCO

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