708
FXUS10 KWNH 201904
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EST MON JAN 20 2020
VALID JAN 20/1200 UTC THRU JAN 24/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
..AMPLIFYING SHORTWAVE CROSSING THE MIDWEST THROUGH MONDAY
..CLOSED LOW EVOLUTION OVER THE SOUTHEAST BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: NEAR AVERAGE
A SHORTWAVE IMPULSE CURRENTLY OVER THE MIDWEST IS TRACKING
SOUTHEASTWARD ON THE EAST SIDE OF AN UPPER LEVEL RIDGE OVER THE
ROCKIES. THIS IS FORECAST TO EVOLVE INTO A CLOSED LOW NEAR THE
SOUTHEAST U.S. COAST BY TUESDAY MORNING AND THEN TRACK EASTWARD
OUT TO SEA. THIS WILL INDUCE SURFACE CYCLOGENESIS ALONG A FRONTAL
BOUNDARY SITUATED WELL OFFSHORE. EXCEPT FOR SOME LIGHT RAIN NEAR
COASTAL AREAS, THIS SHOULD MAINLY BE A MARINE IMPACT. THE 12Z NAM
IS CONSIDERABLY FARTHER WEST THAN THE OTHER GUIDANCE, AND ALSO
STRONGER WITH THE SURFACE LOW. THIS BECOMES APPARENT MAINLY AFTER
TUESDAY AFTERNOON.
..SOUTHERN STREAM SHORTWAVE CROSSING CALIFORNIA BY MONDAY
..ENERGY CROSSING THE SOUTHWEST/PLAINS TUESDAY AND WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A SOUTHERN STREAM UPPER LEVEL TROUGH IS CURRENTLY APPROACHING
SOUTHERN CALIFORNIA AND WILL QUICKLY TRACK EASTWARD ACROSS THE
SOUTHERN ROCKIES AND THEN REACH THE SOUTH-CENTRAL U.S. BY
WEDNESDAY MORNING. THE 12Z GFS/NAM APPEAR SLIGHTLY MORE
PROGRESSIVE AND MORE AMPLIFIED WITH THE SHORTWAVE TROUGH COMPARED
TO THE NON-NCEP GUIDANCE AS IT CROSSES THE SOUTHWEST THROUGH
TUESDAY. THERE IS NOW ENOUGH AGREEMENT AMONG THE GUIDANCE TO
MERIT A GENERAL BLEND OF THE DETERMINISTIC GUIDANCE WITH THIS
SHORTWAVE PERTURBATION.
..UPPER TROUGH/CLOSED LOW OVER THE PACIFIC NORTHWEST BY TUESDAY
...ENERGY EJECTING OUT ACROSS THE NORTHERN PLAINS WEDNESDAY
NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET/GFS
CONFIDENCE: SLIGHTLY BELOW AVERAGE
A CLOSED UPPER LOW CURRENTLY OVER THE NORTHEAST PACIFIC IS
FORECAST TO REACH BRITISH COLUMBIA TUESDAY NIGHT AND THEN REACH
THE NORTHERN HIGH PLAINS AND SOUTH-CENTRAL CANADA BY THE MIDDLE OF
THE WEEK. THE LATITUDINAL DIFFERENCES ARE NOW MINIMAL AS IT
APPROACHES THE PACIFIC NORTHWEST ON TUESDAY COMPARED TO EARLIER
MODEL RUNS. AS THE UPPER LEVEL ENERGY EMERGES OVER THE NORTHERN
HIGH PLAINS, THE 12Z GFS AND THE 12Z GEFS MEAN ARE SLIGHTLY
FARTHER SOUTH WITH THE UPPER LOW CENTER, AND MORE SPREAD EXISTS BY
84 HOURS ON THURSDAY EVENING OVER THE CENTRAL-NORTHERN PLAINS,
WITH THE 12Z CMC INDICATING THE MOST AMPLIFIED UPPER LEVEL PATTERN
BY THAT TIME.
...UPSTREAM MID-LEVEL TROUGH OFFSHORE OF THE PACIFIC NORTHWEST
EARLY THURSDAY ALONG WITH ACCOMPANYING SURFACE CYCLONE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~
PREFERENCE: 12Z GEFS MEAN/00Z EC MEAN
CONFIDENCE: AVERAGE
TIMING DIFFERENCES APPEAR TO BE THE SIGNIFICANT REASON FOR MODEL
DIFFERENCES WITH AN UPSTREAM, SHALLOW AMPLITUDE LONGWAVE TROUGH
APPROACHING THE PACIFIC NORTHWEST WEDNESDAY NIGHT. THE NAM APPEARS
FLATTER WITH THIS WAVE COMPARED TO THE MODEL CONSENSUS, AND THE
GFS MORE PROGRESSIVE. THERE ARE MODEST DIFFERENCES REFLECTED IN
THE ENSEMBLE SPREAD AND GIVEN THE SOURCE REGION FOR THIS SYSTEM IS
AN AREA OF HIGHER UNCERTAINTY, WILL PREFER TO GO IN THE MIDDLE OF
THE SPREAD TOWARD THE ENSEMBLE MEANS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page