Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000 FXUS10 KWNH 301900 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 PM EDT THU OCT 30 2014 VALID OCT 30/1200 UTC THRU NOV 03/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 12Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...TROUGH AMPLIFYING ACROSS EASTERN NORTH AMERICA... PREFERENCE: BLEND OF 12Z ECMWF/CANADIAN CONFIDENCE: AVERAGE COASTAL CYCLOGENESIS IS FORECAST TO START RAMPING UP LATE FRIDAY. OVER THE WEEKEND THIS INITIAL LOW LIFTS TOWARD COASTAL NORTHERN NEW ENGLAND...WHILE A SECOND LOW FORMS BENEATH A STRONGLY ANOMALOUS VORTICITY MAXIMUM THAT DIVES TOWARD THE CAROLINA COAST. THE TWO SYSTEMS MAY CONSOLIDATE BY SUNDAY EVENING. GEFS STANDARD ANOMALIES FOR 500 MB HEIGHTS REACH AN IMPRESSIVE 4.5 DEVIATIONS FROM CLIMATOLOGY OVER SOUTH CAROLINA ON SATURDAY. THERE IS FAIRLY GOOD MODEL CLUSTERING ON A LARGE SCALE...BUT A NUMBER OF SMALLER SCALE DIFFERENCES. RUN TO RUN VARIABILITY WITHIN THE GEFS IS EVEN A LITTLE GREATER THAN USUAL...ESPECIALLY TOWARD NORTHERN NEW ENGLAND ON DAYS 2/3. THE 12Z GFS MOVED SIGNIFICANTLY LEFT OF THE PREVIOUS 00Z/06Z GFS RUNS. NOT TOO SURPRISINGLY...THE 12Z GEFS MEAN SHOWED THE SAME TREND. EVIDENCE IN THE VALIDITY OF THIS TREND IS STRENGTHENED...HOWEVER...BY THE UKMET AND CANADIAN SHOWING SOMETHING SIMILAR...ALTHOUGH TO A LESSER DEGREE. THIS ALLOWS US TO HEDGE A LITTLE TOWARD A TRACK FARTHER TO THE LEFT...AND PERHAPS AN INCREASE TO THE AMOUNT OF PRECIPITATION REACHING NORTHERN NEW ENGLAND...ESPECIALLY EASTERN MAINE...ON DAYS 2/3. THE OPERATIONAL GFS...THOUGH...APPEARS TO SPIN UP THE INITIAL LOW MORE STRONGLY AND FARTHER LEFT THAN MOST GUIDANCE...SO WE STILL RECOMMEND SOLUTIONS OTHER THAN THE 12Z GFS. THE 12Z NAM WAS SIMILAR TO THE ECMWF...BUT THE NAM WAS EVEN MORE ROBUST/DEEP WITH THE ANOMALOUS SHORTWAVE INTO THE CAROLINAS ON DAY 2...RESULTING IN A MORE ROBUST SURFACE CYCLONE. THE NAM IS ALSO PARTICULARLY AGGRESSIVE AT RAISING HEIGHTS ON THE BACK SIDE OF THE TROUGH BY DAY 3. THE MODELS HAVE TRENDED TOWARD NARROWING THE BREADTH OF THE TROUGH...BUT THE AMPLIFYING PATTERN ACROSS NORTH AMERICA WOULD ARGUE TOWARD MORE PERSISTENT CYCLONIC FLOW ALONG THE EAST COAST...MORE LIKE THE NON-NAM SOLUTIONS. ...AMPLIFIED TROUGH/CLOSED LOW MOVING INTO THE WEST... PREFERENCE: BLEND OF 12Z NAM/ECMWF/CANADIAN CONFIDENCE: AVERAGE THE MODELS CLUSTER FAIRLY WELL HERE...ESPECIALLY AS THE NAM/GFS TRENDED SLOWER WITHIN THE BASE OF THE POSITIVELY TILTED TROUGH OVER THE SOUTHWEST U.S. ON DAY 3. REGARDING THE LEAD SHORTWAVE THAT EJECTS INTO MT/ND...THE GFS MAY BE SLIGHTLY FAR TO THE EAST...AND THE UKMET SLIGHTLY FAST TO LIFT NORTHWARD. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE $$

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