Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4
000
FXUS10 KWNH 280700
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT FRI JUL 28 2017

VALID JUL 28/0000 UTC THRU JUL 31/1200 UTC

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

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


...STAGNANT CIRCULATION LINGERING OFF THE GA/FL COAST...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: HIGH

A REMNANT CIRCULATION SPINNING OFF THE NORTHEASTERN FL COAST
SHOULD LINGER A BIT LONGER BEFORE AN UPSTREAM SYNOPTIC-SCALE
TROUGH SHUNTS IT OUT TO SEA. AT THIS POINT IT BECOMES ABSORBED
WITHIN THE SOUTHERN FRINGE OF THIS AFOREMENTIONED LONGWAVE TROUGH.
MODELS ARE IN GOOD AGREEMENT SO A GENERAL MODEL COMPROMISE IS THE
RECOMMENDATION.


...INITIAL HEIGHT FALLS EXITING UPPER NEW ENGLAND...
...COMPACT UPPER LOW TRACKING THROUGH QUEBEC AND CROSSING NORTHERN
MAINE BY 29/0600Z...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

WITH THE INITIAL UPPER TROUGH BEGINNING TO EXIT THE NORTHEASTERN
U.S...A SECOND MORE POTENT SYSTEM LURKS TO THE NORTHWEST.
COMPARISON OF THE LAST SEVERAL ENSEMBLE SPAGHETTI PLOTS...MOST
NOTABLY AT 570-DM...THERE HAS BEEN A DECIDED SHIFT TOWARD
DE-AMPLIFICATION. BY 30/0000Z...THIS PARTICULAR CONTOUR IS SEVERAL
HUNDRED MILES NORTHWARD OF WHERE IT WAS YESTERDAY.
ADDITIONALLY...AGREEMENT IS MUCH STRONGER WHICH WARRANTS A GENERAL
MODEL COMPROMISE HERE.


...STRENGTHENING SHORTWAVE PUSHING THROUGH THE LOWER GREAT LAKES
MIDDAY FRIDAY...
...RESULTANT ELONGATED UPPER LOW SPINNING OVER THE
MID-ATLANTIC/DELMARVA PENINSULA...
...DEEP SURFACE LOW TRACKING THROUGH THE AFOREMENTIONED REGIONS...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

WATER VAPOR IMAGERY EARLY THIS MORNING SHOWS A BROAD TROUGH
PUSHING THROUGH THE UPPER GREAT LAKES. THIS SYSTEM IS FORECAST TO
CONTINUE TO INTENSIFY WHILE DEVELOPING A CLOSED CENTER. THE
FORWARD PROGRESSION WILL SLOW CONSIDERABLY WHEN REACHING THE
MID-ATLANTIC WHILE BECOMING MORE STRETCHED OUT AS IT SPINS ALONG
THE MID-ATLANTIC COAST OVER THE WEEKEND. MODELS SEEM TO SETTLE
INTO THEIR RESPECTIVE CAMPS LIKE YESTERDAY WITH THE 00Z NAM/CMC
BECOMING QUICKER WITH THE SURFACE LOW TRACK. BETTER CLUSTERING
EXISTS AMONG THE 00Z GFS/ECMWF/UKMET WHILE THE LATTER TWO
SOLUTIONS ARE QUITE A BIT DEEPER AT THE SURFACE...I.E. AROUND 1000
MB OR LOWER CYCLONE CENTERS ON 29/1200Z. GIVEN DOWNSTREAM RIDGING
ACROSS THE ATLANTIC...THIS SYSTEM DOES NOT MOVE APPRECIABLY AS THE
FRONTAL ZONE/SURFACE WAVES LINGER OVER THE WESTERN ATLANTIC. THIS
IS WHERE FURTHER DIVERGENCE IN THE GUIDANCE IS NOTED AS THE 00Z
ECMWF TRENDED MUCH QUICKER AND TAKES THE BOUNDARY OUT TO SEA.
GIVEN THE AMOUNT OF MOVEMENT AMONG THE MODELS...DAY 3 WILL BE A
MORE CHALLENGING FORECAST. WILL LOWER THE CONFIDENCE ACCORDINGLY
IN THIS UPDATE BUT UTILIZE THE 00Z RUNS OF THE GFS/ECMWF/UKMET TO
MAINTAIN A SENSE OF CONTINUITY.


...MODEST IMPULSE OVER WESTERN WY GRADUALLY SHEARING ACROSS THE
GREAT PLAINS...
...TRAILING LOW-AMPLITUDE WAVE INITIALLY APPROACHING THE OR
COASTLINE...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

ALONG THE LEADING EDGE OF A BROAD TROUGH EXTENDING ACROSS THE
NORTHWESTERN U.S...A PAIR OF WEAK TO MODEST IMPULSES ARE WORTH
NOTING. THE LEAD FEATURE CURRENTLY PUSHING INTO WESTERN WY WILL
EVENTUALLY SHEAR AS THE SYSTEM ENTERS THE VICINITY OF SD/NE. THE
00Z CMC MADE PROPER ADJUSTMENTS FROM ITS PREVIOUS STRONGER
FORECAST WHICH BRINGS IT BACK TO THE CONSENSUS.

CONSIDERING THE TRAILING IMPULSE...THIS PARTICULAR SYSTEM IS
FORECAST TO REACH COASTAL OR BY FRIDAY MORNING WHILE GRADUALLY
BECOMING STRETCHED SOUTHWEST/NORTHEAST ACROSS THE STATE.
THEREAFTER...MODELS WEAKEN THE VORTICITY CENTERS TO THE POINT OF
BEING SHEARED OUT. OVERALL...CONSIDERING BOTH SYSTEMS HERE...THERE
IS SOLID ENOUGH AGREEMENT TO SUPPORT A GENERAL MODEL COMPROMISE.


...DEEP UPPER TROUGH AFFECTING THE NORTHEASTERN PACIFIC THIS
WEEKEND...
...WEAK HEIGHT FALLS GRAZING NORTHERN SECTIONS OF WA...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

A PERSISTENT NEGATIVE HEIGHT ANOMALY APPEARS TO HAVE ANCHORED
ITSELF TO THE NORTHEAST PACIFIC. WHILE THE INITIAL LONGWAVE TROUGH
EXITS DOWNSTREAM...A MUCH MORE PRONOUNCED SYSTEM TRACKS TOWARD
COASTAL BRITISH COLUMBIA BY EARLY SATURDAY. COMPARED TO
YESTERDAY...SOLUTIONS ARE MUCH MORE STABLE AFTER NOTING THE VAST
QUICKER TREND IN PREVIOUS GUIDANCE. THE CORE OF LOWER HEIGHTS
STAYS IN WESTERN CANADA WITH LITTLE TO NO IMPACTS ACROSS THE
PACIFIC NORTHWEST. GRADUALLY BROAD MID-LEVEL RIDGING SETS UP IN
THE WAKE WITH MODEL DIFFERENCES GENERALLY MINIMAL. AS SUCH...A
GENERAL MODEL COMPROMISE IS THE PREFERRED SOLUTION.


...SERIES OF MID-LEVEL PERTURBATIONS TRACKING THROUGH THE FOUR
CORNERS REGION...

FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

WITH A MID-LEVEL ANTICYCLONE CONTINUING TO SIT ACROSS THE FOUR
CORNERS REGION/ADJACENT HIGH PLAINS...A SERIES OF PERTURBATIONS
WILL TRACK NORTHWARD INTO THE SOUTHWESTERN U.S./SOUTHERN TO
CENTRAL ROCKIES. WHILE A NUMBER OF IMPULSES ARE SCATTERED ABOUT IN
THE MODELS...ONE PARTICULAR SYSTEM STICKS OUT EMERGING INTO
EASTERN CO/WESTERN KS ON SATURDAY NIGHT/SUNDAY MORNING. BY
31/0000Z...THERE IS SOME NORTH/SOUTH SCATTER ACROSS THE OZARKS
WITH THE 00Z NAM/CMC ON THE NORTHERN END OF THE SPREAD. PLAN ON
STAYING FARTHER SOUTH WHERE THERE IS BETTER ENSEMBLE SUPPORT WHICH
CONSISTS OF THE 00Z GFS/ECMWF/UKMET.



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