Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12
000
FXUS10 KWNH 231851
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT WED JUL 23 2014

VALID JUL 23/1200 UTC THRU JUL 27/0000 UTC

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

...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...UPPER LOW SPINNING OVER SOUTHEASTERN LA...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

BASED ON THE LATEST WATER IMAGERY...A MID/UPPER LOW WAS SEEN
SPINNING IN THE VICINITY OF SOUTHEASTERN LA. IT HAS BECOME MORE
ELONGATED IN NATURE COMPARED TO PREVIOUS DAYS BUT STILL REMAINS A
FOCUS FOR CONVECTION...PRIMARILY DURING THE PEAK DIURNAL HEATING.
THE GUIDANCE SHOWS THE SYSTEM CONTINUING TO SHEAR AS IT FEELS THE
INFLUENCE OF A BROAD MID-LEVEL RIDGE ACROSS THE FOUR CORNERS
REGION/SOUTHERN PLAINS. NOW THAT THE 12Z CMC HAS COME ON BOARD
WITH THE OTHER MODELS IN TERMS OF PLACEMENT...A GENERAL MODEL
COMPROMISE CAN BE RECOMMENDED.


...DEEP AND ANOMALOUS CLOSED LOW MOVING FROM THE PACIFIC NORTHWEST
TO SOUTHERN SASKATCHEWAN...
...SURFACE LOW TRACKING THROUGH THE GREAT PLAINS ON
THURSDAY/FRIDAY...

FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF WITH THE 12Z GEFS/00Z
ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

A RATHER STRONG UPPER LOW CURRENTLY APPROACHING THE PACIFIC
NORTHWEST COAST WILL MOVE ONSHORE BY THIS AFTERNOON. THE 12Z NAM
INDICATED THIS FEATURE IS AT LEAST 2 TO 2.5 STANDARDIZED ANOMALIES
BELOW CLIMATOLOGY BASED ON 500-MB HEIGHTS. SUCH ANOMALIES ARE
FORECAST TO PERSIST THROUGHOUT THE SHORT RANGE PERIOD EXTENDING
THROUGH SATURDAY. SOLUTIONS VARY WITH THE SPEED OF THIS FEATURE
WITH THE 12Z NAM BEING THE QUICKEST BY AS EARLY AS THURSDAY
MORNING. THIS ARTIFACT OF THE FORECAST CONTINUES ONWARD WITH
ENSEMBLE MEANS SUGGESTING A MUCH SLOWER EASTWARD PROGRESSION.
GIVEN THE FORECAST INVOLVES A COMPACT CLOSED LOW...WOULD LIKE TO
ERR ON THE WESTERN SIDE HERE. OVERALL...THE 12Z GFS/ECMWF CONTINUE
TO BE BEST SUPPORTED BY THE ENSEMBLE MEANS. THE 576-DM SPAGHETTI
PLOT SHOWS A RELATIVELY WELL BEHAVED PLOT WITH THE MODELS SUBTLY
IN AGREEMENT. THE 00Z ECMWF ENSEMBLE MEMBERS DO SHOW HINTS AT A
FASTER/MORE AMPLIFIED PROGRESSION BY SATURDAY ACROSS THE MIDDLE MS
VALLEY/UPPER GREAT LAKES. IN SPITE OF THE SIMILARITY BETWEEN THE
12Z GFS/ECMWF WITH THE CORE OF THE LOWER HEIGHTS ACROSS SOUTHERN
CANADA...THEY DIFFER WITH THE DETAILS OF JET ENERGY CROSSING THE
NORTHERN TIER OF THE U.S. THIS HAS RAMIFICATIONS ON UNCERTAINTY
WITH THE EVOLUTION OF THE SURFACE FEATURES...PARTICULARLY OVER THE
REALM OF THE MESOSCALE. WILL MAINTAIN THE PREVIOUS SOLUTION BUT
WILL INCORPORATE THE NEWER CYCLES OF THE ECMWF/GEFS MEAN.


...MEAN UPPER TROF OVER NORTHEASTERN NORTH AMERICA...
...ASSOCIATED COLD FRONT...

FINAL PREFERENCE: A NON-12Z NAM SOLUTION
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

A PERSISTENT NEGATIVE HEIGHT ANOMALY ACROSS THE NORTHEASTERN
SECTOR OF NORTH AMERICA WILL BE FEATURED DURING THE PERIOD. A
SERIES OF IMPULSES TRAVERSING WITHIN THE CYCLONIC FLOW WILL MOVE
THROUGH OH VALLEY AND MID-ATLANTIC/NEW ENGLAND. THROUGH
25/1200Z...THE MODELS ARE NOW IN GENERAL AGREEMENT WITH THE HEIGHT
PATTERN ANCHORING THE EASTERN U.S. MORE UNCERTAINTY LOOMS UPSTREAM
WITH A RATHER POTENT IMPULSE SLIDING THROUGH THE UPPER GREAT LAKES
ON FRIDAY EVENING. THE GUIDANCE HAS TENDED TO WAVER WITH THE
DETAILS AND ADDITIONALLY DO NOT SHOW MUCH AGREEMENT WITH ONE
ANOTHER. THE 12Z NAM APPEARS TO BE THE OUTLIER BEING QUICKER OFF
TOWARD THE SOUTHEAST BY 26/0000Z WHILE THE 12Z GFS/CMC/UKMET ARE
IN THE VICINITY OF THE MI/IN BORDER. MEANWHILE...THE 12Z ECMWF HAS
TRENDED TOWARD A MORE SUPPRESSED SOLUTION WHICH ENDS UP
DIMINISHING THE QPF AMOUNTS RELATIVE TO ITS PREVIOUS CYCLE. WILL
TEND TO STAY AWAY FROM THE 12Z NAM AND FAVOR SOME SORT OF
COMPROMISE OF THE REMAINING DETERMINISTIC GUIDANCE UNTIL BETTER
AGREEMENT ARISES.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

RUBIN-OSTER

$$





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