690
FXUS10 KWNH 161625
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1223 PM EDT SAT MAY 16 2020
VALID MAY 16/1200 UTC THRU MAY 20/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SHORTWAVE AND SURFACE LOW TRACKING ACROSS THE NORTHERN TIER STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF/UKMET/ECENS
CONFIDENCE: LIMITED-MODERATE
A SHORTWAVE TROUGH CURRENTLY CROSSING THE NORTHERN PLAINS IS
EXPECTED TO AMPLIFY AND EVOLVE INTO A CLOSED LOW AS IT MOVES
TOWARD THE UPPER MIDWEST BY SUNDAY, WITH THE SHORTWAVE ENERGY
TAKING ON A MORE NEGATIVE TILT. IN THE INCREASING AMPLIFIED
PATTERN OVER THE NATION, OWING LARGELY TO THE DEVELOPING UPPER
RIDGE OVER THE WESTERN HIGH PLAINS, THIS LOW IS FORECAST TO BECOME
A CUT-OFF LOW BY THE TIME IT REACHES THE OHIO VALLEY EARLY NEXT
WEEK, AND SLOW DOWN CONSIDERABLY WITH THE OMEGA BLOCK PATTERN
DEVELOPING. THIS SYSTEM HAS THE GREATEST LEVEL OF UNCERTAINTY
ACROSS THE NATION GOING INTO EARLY IN THE WEEK AND BEYOND. THE
12Z NAM TAKES THE UPPER LOW FARTHEST SOUTHWEST ACROSS ILLINOIS AND
THEN WESTERN TENNESSEE, AND ON THE WESTERN EDGE OF THE ENSEMBLE
SPREAD. AN EVEN GREATER DIFFERENCE EXIST WITH THE 00Z CMC WHICH
HAS A MUCH WEAKER SYSTEM AND DISPLACED WELL TO THE NORTHEAST OF
THE MODEL CONSENSUS, AND DIFFERENCES WITH THE CMC EMERGE AS EARLY
AS 12Z SUNDAY. THERE IS RELATIVELY GOOD CLUSTERING WITH THE
GFS/ECMWF/UKMET, ALTHOUGH SOME DEPTH AND DETAIL DIFFERENCES STILL
EXIST. ONE OF THE THINGS LIMITING CONFIDENCE ARE RUN-TO-RUN
CONTINUITY CHANGES, WITH MOST TRENDING FARTHER WEST OVER THE PAST
COUPLE OF DAYS. THIS WILL HAVE IMPLICATIONS FOR POTENTIAL HEAVY
RAINFALL OVER THE APPALACHIANS FOR EARLY TO MID-WEEK.
DEEP UPPER LEVEL TROUGH DEVELOPING ALONG THE WEST COAST BY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
A LARGE CLOSED MID-UPPER LEVEL LOW IS FORECAST TO MOVE FROM THE
EASTERN PACIFIC TOWARD NORTHERN CALIFORNIA BY MONDAY EVENING, AND
THIS SHOULD SETTLE ACROSS THE INTERMOUNTAIN WEST BY THE END OF THE
FORECAST PERIOD TUESDAY EVENING. THIS WILL BECOME PART OF THE
DEVELOPING OMEGA BLOCK PATTERN THAT IS FORECAST TO BECOME FIRMLY
ESTABLISHED ACROSS THE U.S. BY THE MIDDLE OF THE WEEK. GIVEN THE
HIGHLY AMPLIFIED PATTERN, THE MODEL GUIDANCE SHOWS ABOVE AVERAGE
AGREEMENT THROUGH MONDAY NIGHT, AFTER WHICH THE CMC BECOMES
SLIGHTLY SLOWER WITH THE TROUGH AND A LITTLE MORE PRONOUNCED WITH
THE DOWNSTREAM RIDGE OVER THE PLAINS. HOWEVER, IT IS STILL WITHIN
THE ENSEMBLE SPREAD HERE SO THEREFORE A GENERAL MODEL BLEND CAN BE
USED FOR THE WESTERN U.S. FOR NOW.
SOUTHERN STREAM TROUGH TRACKING FROM TEXAS AND ALONG THE GULF COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/ECENS/UKMET
CONFIDENCE: MODERATE
A RELATIVELY WEAK SOUTHERN STREAM SHORTWAVE WILL MOVE ACROSS
SOUTHERN PLAINS AND THEN THE GULF COAST REGION THROUGH THIS
WEEKEND AND INTO MONDAY, WITH A SURFACE WAVE OF LOW PRESSURE AT
THE SURFACE. THIS DISTURBANCE WILL EVENTUALLY MERGE WITH THE
CLOSED LOW THAT SETTLES IN ACROSS THE SOUTHERN APPALACHIANS AND
OHIO VALLEY. THERE IS GOOD AGREEMENT ON THE MAGNITUDE OF THIS
TROUGH, BUT TIMING DIFFERENCES REMAIN WITH THE NCEP GUIDANCE
FASTER THAN THE NON-NCEP GUIDANCE, WITH THE CMC AND ECENS MEAN
HOLDING SOME OF THE SHORTWAVE ENERGY BACK FARTHER TO THE WEST.
ENSEMBLE SPAGHETTI PLOTS SUGGEST MORE SUPPORT FOR THE SLOWER
SOLUTION HERE, AND THEREFORE THE PREFERENCE LEANS TO THE
ECMWF/ECENS MEAN/UKMET FOR THIS REGION.
DEVELOPING LOW OVER THE NORTHERN BAHAMAS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z MONDAY, THEN 12Z
NAM/00Z ECMWF/00Z UKMET
CONFIDENCE: MODERATE
THE NATIONAL HURRICANE CENTER IS CONTINUING TO MONITOR AN AREA OF
LOW PRESSURE OVER THE NORTHERN BAHAMAS. THIS SYSTEM IS EXPECTED
TO DEVELOP FURTHER OVER THE NEXT COUPLE OF DAYS AS IT LIFTS
NORTHWARD AND TRACKS CLOSE TO THE SOUTHEAST U.S. COASTLINE. THERE
HAS BEEN SOME TREND OVER THE PAST COUPLE OF DAYS FOR THIS LOW TO
TRACK FARTHER WEST, THUS HAVING MORE POTENTIAL IMPLICATIONS FOR
COASTAL AREAS. THIS MAY BE DUE TO THE UPPER LEVEL LOW SETTLING IN
ACROSS THE OHIO VALLEY AND APPALACHIANS. THERE IS GOOD OVERALL
MODEL AGREEMENT IN THE TRACK THROUGH ABOUT 12Z MONDAY, AFTER WHICH
THE 12Z GFS/6Z GEFS IS A BIT TO THE WEST OF THE OTHER GUIDANCE AND
HAS THE LOW CROSSING THE OUTER BANKS OF NORTH CAROLINA, AND THE
OTHERS SHOWING AN OFFSHORE TRACK FOR THAT AREA. THE 12Z GFS DID
TRACK FARTHER OFFSHORE COMPARED TO ITS 6Z RUN ONCE IT PASSES THE
DELMARVA PENINSULA, AND THE CMC IS FASTER WITH THE LOW BY TUESDAY
OFF THE NEW ENGLAND COAST. ONCE THE SYSTEM BECOMES OFFICIALLY
IDENTIFIED AS A TROPICAL DEPRESSION BY NHC, THEN THEIR FORECAST
WILL BECOME THE OFFICIAL PREFERENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page