Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5
000
FXUS10 KWNH 180649
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 AM EDT FRI AUG 18 2017

VALID AUG 18/0000 UTC THRU AUG 21/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH
PREFERENCES/FORECAST CONFIDENCE...

...700 MB WAVE CROSSING THE CENTRAL PLAINS TO MID MS VALLEY FRI
AND OH VALLEY SAT...

PREFERENCE: BLEND OF THE GFS/ECMWF
FORECAST CONFIDENCE: AVERAGE

ANOTHER DISTURBANCE IS FORECAST TO PUSH THROUGH THE CENTRAL PLAINS
TO THE MIDDLE MS VALLEY FRI  AND OH VALLEY SAT.  THE 00Z NAM HAS A
BULLSEYE IN 700 MB CONVERGENCE AND ASCENT THAT DISTORTS THE WAVE
FIELD 00-06Z SUN OVER NORTH CENTRAL KS...WHICH CARRIES DOWNSTREAM
INTO THE MID MS VALLEY AND THEN OH VALLEY AFTERWARD.  WITH GOOD
CLUSTERING AMONG THE GFS/UKMET/ECMWF...RECOMMEND BLENDING THESE
SOLUTIONS INSTEAD.

...COLD FRONT CROSSING THE NORTHERN HIGH PLAINS FRI TO THE UPPER
MS VALLEY AND CENTRAL PLAINS BY SUN MORNING..WITH WAVY LOW
PRESSURE OVER THE CENTRAL PLAINS SUN NIGHT TO MON MORNING...

PREFERENCE: BLEND OF THE 00Z GFS/ECMWF
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE MODELS SHOW A SLOW MOVING UPPER TROUGH DRIFTING OUT OF THE
NORTHERN ROCKIES ONTO THE NORTHERN PLAINS.  SHORTWAVES EJECT EAST
NORTHEAST ACROSS THE NORTHERN PLAINS TOWARDS THE UPPER MS VALLEY.
THE EXTREME AMONG THE SUITE OF MODELS IS THE 12-00Z UKMET...WHOSE
PATTERN OVER THE UPPER GREAT LAKES AND UPPER MS VALLEY BECOMES
DISTORTED IN RESPONSE TO AGGRESSIVE AMPLIFICATION OF A WAVE
CROSSING NORTHERN MANITOBA...NORTHWEST ONTARIO...AND HUDSON BAY.

A BLEND OF THE 00Z GFS/00Z ECMWF SHOULD SUFFICE HERE GIVEN
SOMEWHAT SIMILAR FORECASTS...AND UNCERTAINTIES OF THE WAVE
AMPLITUDE/TIMING IN FAST CONFLUENT FLOW.

...IMPULSE LIFTING OUT OF NORTHERN MX REACHING SOUTHWESTERN NM BY
20/0000Z...

PREFERENCE: BLEND OF 12Z ECMWF/00Z NAM
FORECAST CONFIDENCE: ABOVE AVERAGE

LIKE YESTERDAY...THE GFS IS MORE ASSERTIVE THAN OTHER MODELS IN
DEVELOPING A COMPACT 500 MB CIRCULATION CENTER WITH HIGH ABSOLUTE
VORTICITY ORIGINATING FROM CONVECTION IN NORTHERN MEXICO AND THEN
MOVING IT DOWNSTREAM NEAR THE MEXICO/TX/NM BORDER AND NORTHEAST
ACROSS NM ON DAY 3.
THE WAVE IS SHOWN IN SEVERAL OTHER MODELS BUT WITH LESS
CONCENTRATION THAN THE GFS.

THE 00Z ECMWF ALSO DEVELOPS A COMPACT CIRCULATION WITH HIGH
ABSOLUTE VORTICITY TAKING A DIFFERENT TRACK NEAR THE AZ/NM BORDER
SUNDAY INTO CO AND SPLITTING BY 12Z MON.  CONFIDENCE IS LOW IN THE
00Z RUN OF THE ECMWF UNTIL BETTER CONTINUITY DEVELOPS AND
AGREEMENT WITH OTHER SOLUTIONS.

...LOW PRESSURE MOVING ACROSS QUEBEC WITH FRONTAL SYSTEMS CROSSING
NEW YORK/NEW ENGLAND FRI AND MOVING OFF THE COAST SAT...

FINAL PREFERENCE: MODEL CONSENSUS
FORECAST CONFIDENCE: AVERAGE

MODELS SHOW LOW PRESSURE MOVING NORTHEAST OUT OF ONTARIO IN QUEBEC
FRI NIGHT. A WARM FRONT AHEAD OF THE SYSTEM CROSSES NY/NEW
ENGLAND...FOLLOWED BY A TRAILING COLD FRONT.  GOOD AGREEMENT
EXISTS AMONG THE MODELS TO SUPPORT A MODEL CONSENSUS.

www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

PETERSEN


$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.