576
FXUS10 KWNH 161830
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
229 PM EDT WED OCT 16 2019
VALID OCT 16/1200 UTC THRU OCT 20/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GREAT LAKES CLOSED LOW TRANSFERRING TO DEVELOPING NORTHEAST
COASTAL SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: THE 12Z CMC SHIFTED TOWARD BETTER OVERALL AGREEMENT IN
DEPTH, SHAPE AND TIMING. THIS MADE SMALLER VARIATIONS AFTER THE
SYSTEM MOVES INTO THE ST. LAWRENCE SEAWAY A BIT MORE OBVIOUS WITH
THE ECMWF AND GFS WOBBLING NORTH AND EAST A BIT FASTER THAN THE
OTHER GUIDANCE. STILL, IT IS MINOR SO A GENERAL MODEL BLEND CAN
BE EMPLOYED WITH ABOVE AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
THIS MORNING'S SUITE OF GUIDANCE APPEARS TO HAVE LATCHED ON TO A
COMMON EVOLUTION INCLUDING THE PLACEMENT/INTERSECTION OF THE WARM
CONVEYOR BELT AND ACTIVE CONVECTION THAT FEEDS BACK ON THE ALREADY
STRONG BAROCLINIC CYCLOGENESIS. THE ONLY DIFFERENCES APPEAR TO
THE BE THE MAGNITUDE OF THE DEEPENING. GIVEN THE
ORIENTATION/INTERSECTION OF THE WARM CONVEYOR TO THE NEGATIVE
TILT/DIFFLUENT UPPER LEVEL PATTERN, EXTREMELY DEEP (SUB 973MB)
SOLUTIONS MAY BE A BIT TOO AGGRESSIVE. STILL, THIS IS BECOMING
MORE LIKELY TO BREAK NON-TROPICAL CYCLONE PRESSURE OCTOBER RECORDS
ACROSS NEW ENGLAND. ON THE WEAKER SIDE OF THE GUIDANCE IS THE 00Z
CMC; ITS SOLUTION BECOMES EVOLUTIONARILY OUT OF PLACE AFTER 42HRS
WOBBLING OUT OF THE CONUS INTO SE CANADA A BIT TOO FAST AND MORE
ELONGATED IN SHAPE. AS SUCH, A NON-CMC BLEND IS SUPPORTED AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE. PRESSURE RECORDS CAN BE VIEWED
AT WWW.WPC.NCEP.NOAA.GOV/RESEARCH/ROTH/SLPRECORDS.HTML .
SHORT WAVE ENERGY AFFECTING TEXAS THROUGH MIDWEEK SHEARING DRAWING
TROPICAL ENERGY, DEVELOPING SURFACE WAVE INTO THE CENTRAL GULF
STATES AND SOUTHEAST FRI/SAT.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/ECMWF/CMC BLEND
CONFIDENCE: BELOW AVERAGE
19Z UPDATE: FURTHER UNCERTAINTY IS CAST WITH THE 12Z UKMET AND
ECMWF, BOTH TRENDING MUCH STRONGER WITH THE UKMET MUCH FASTER THAN
INITIALLY PREFERRED. THE ECMWF ALSO TRENDED STRONGER WITH THE
SHORTWAVE IN THE NORTHERN STREAM/TX ALLOWING FOR A SLIGHTLY FASTER
PROGRESSION OF THE DEVELOPING TROPICAL/SUBTROPICAL SYSTEM EASTWARD
AS WELL AS STRONGER THAN THE 00Z RUN. THE ECWMF ALSO REMAINS
NORTH OF THE REMAINING NAM/CMC AND 06Z GEFS, BUT AT LEAST SHOWS
MORE FAVORABLE TIMING. THE 12Z GEFS FURTHER EXPANDED THE
POTENTIAL SPEED/TIMING OF THE DEVELOPING WAVE, SO WITH A FEW
MEMBERS CLOSE TO THE OPERATIONAL GFS AND A FEW LAGGING NEAR THE
NAM/ECMWF/CMC, THE GEFS IS NO LONGER VIABLE AS A BLENDING MEMBER,
BUT CAN HELP WITH WITH DETERMINING PREFERENCE. AS SUCH WILL
REPLACE THE UKMET AND GEFS WITH THE 12Z CMC/ECMWF IN THE
PREFERENCE BUT CONFIDENCE REMAINS LOW (BELOW AVERAGE) GIVEN THE
UNCERTAINTY AND INTERACTIONS BETWEEN TWO STREAMS.
---PRIOR DISCUSSION---
NORTHERN PORTIONS OF THE TROPICAL WAVE THAT SPAWNED TROPICAL
DEPRESSION 17E, ARE LIFTING NORTH ACROSS THE BAY OF CAMPECHE INTO
THE WESTERN GULF UNDER THE INFLUENCE OF THE REMAINING SMALL BUT
COMPACT SHORTWAVE ENERGY NEAR THE BIG BEND OF TX. GUIDANCE HAS
COME INTO BETTER AGREEMENT IN THE PLACEMENT AND EVOLUTION OF THE
SHORTWAVE AS IT SLIDES SOUTHEAST DOWN THE RIO GRANDE, INCLUDING
THE GENERAL WEAKENING IN FAVOR OF THE PORTION OF THE TROPICAL
WAVE. THE 12Z GFS CONTINUES TO BE THE STRONGEST/BROADEST WITH THE
WAVE AND MELDS IT WITH THE TROPICAL ENERGY OVER THE NW GULF BY
EARLY FRIDAY, GIVEN A SLIGHTLY FASTER BASE TO THE NORTHERN STREAM
LONGWAVE TROF APPROACHING FROM THE SOUTHWEST FRI (SEE SECTION
BELOW), THIS SHORTWAVE AMPLIFIES AND EJECTS MUCH FASTER THAN ANY
OTHER GUIDANCE MEMBER, EVEN INCREASING STRENGTH AND SPEED FROM THE
06Z RUN WHICH WAS ALREADY WELL DISPLACED FROM THE BULK OF 06Z GEFS
MEMBERS. AS SUCH THE GFS IS NOT FAVORED IN THIS REGION. ON THE
OTHER SIDE OF THE GUIDANCE SUITE, THE 00Z ECMWF AND BULK OF ECENS
MEMBERS SUPPORT A FULL SHEARING OF THE NORTHERN STREAM SHORTWAVE
INTO THE TROPICAL WAVE, THIS ALLOWS FOR A WESTWARD ADJUSTMENT OF
THE LOWER LEVEL WAVE (INCLUDING THE DEVELOPING SURFACE REFLECTION)
BACK WEST TOWARD THE CENTRAL GULF COAST FRI INTO SAT FEELING THE
APPROACH OF THE BASE OF THE NORTHERN STREAM TROUGH. WHILE THIS IS
MORE IN LINE WITH THE OTHER REMAINING GUIDANCE (INCLUDING THE 06Z
GEFS MEAN), IT DOES APPEAR TO HAVE SOME TYPICAL KNOWN NEGATIVE
SLOW BIAS SO SUGGEST EITHER REMOVING THE EC/ECENS OR WEIGHTING
MUCH LOWER IN ANY BLEND. THE 12Z NAM, LOOKS THE BEST COMPROMISE
AND METEOROLOGICALLY SOUND IN THE INTERACTION OF THE TWO STREAMS,
SUPPORTED STRONGLY BY A FAIRLY CONSISTENT UKMET (THOUGH MAY BE A
BIT TOO AGGRESSIVE WITH THE CONVECTIVE COVERAGE AND MAGNITUDE, AS
IT IS APT TO DO). AGAIN, BOTH ARE SUPPORTED BY THE BULK OF GEFS
SOLUTIONS. THE CMC IS ALSO GENERALLY FAVORABLE BUT IS ON THE
SOUTHEAST SIDE OF THE ENSEMBLE SUITE TO HAVE HIGH CONFIDENCE FOR
INCLUSION AT THIS POINT. SO OVERALL A 12Z NAM, 06Z GEFS AND 00Z
UKMET BLEND IS PREFERRED AT SLIGHTLY BELOW AVERAGE CONFIDENCE.
WESTERN U.S. LONGWAVE TROUGH (WED-THURS) SHIFTS INTO ROCKIES WITH
NORTHERN PLAINS CYCLOGENESIS THURS INTO FRI AND SOUTHERN PLAINS
SURFACE CYCLONE BY EARLY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: THE 12Z CMC TRENDED A BIT STRONGER AND THEREFORE A BIT
NORTH WITH THE NORTHERN STREAM SHORTWAVE WITHIN THE DEEP LATITUDE
LONG WAVE TROF. WHILE STILL GENERALLY FAVORABLE IN THE
SOUTHERN/BASE OF THE LARGER WAVE, IT BECOME A BIT OFFSET NORTH OF
THE CONUS AFTER ABOUT 19.00Z. STILL, A GENERAL MODEL BLEND COULD
BE EMPLOYED ACROSS THE CONUS AS THE TIMING OF THE FRONT IS NOT TOO
DELAYED BY THE NORTHWARD SHIFT NORTH OF THE BORDER.
--PRIOR DISCUSSION---
DEEP LATITUDINAL LONG WAVE TROF IS ENTERING THE WEST CURRENTLY,
THIS WAVE USHERS IN A WELCOME CHANGE OF PATTERN WITH BROAD FLAT
BUT STRONG WESTERLY PACIFIC JET PUSHING THE TROUGH ALONG.
OVERALL, THE GUIDANCE IS IN SOLID AGREEMENT IN ORIENTATION, TIMING
AND STRENGTH THROUGH THE WAVE FOR THE BULK OF THE FORECAST PERIOD.
THE NORTHERN PORTION OF THE WAVE HAS TRENDED WEAKER OVER THE LAST
FEW CYCLES BUT THE GUIDANCE IS ALSO MUCH TIGHTER IN TIMING WITH
ONLY SMALL TYPICAL TIMING BIASES (NAM/UKMET/GFS FAST: ECMWF/CMC
SLOW).
AS FOR THE BASE OF THE TROF, THERE WAS A TREND TOWARD SLIGHTLY
SOUTHWARD TREND, SHARPER BASE OF THE TROF. THERE IS STILL VERY
GOOD AGREEMENT IN THE EVOLUTION INCLUDING SPURRING SOUTHERN PLAINS
SURFACE CYCLOGENESIS BY EARLY SAT. THE ONLY DEPARTURE/DIFFERENCE
IS THE 12Z GFS HAS TRENDED MUCH FASTER ON DAY 3, LIKELY IN
COMBINATION WITH THE STRONGER SHORTWAVE LINGERING ACROSS THE GULF
COAST INTO THE SOUTHEAST. THIS IS A NEGATIVE AFFECT FOR THE
SOUTHEAST, AND WOULD BE NEGATIVE FOR PORTIONS OF THE MIDDLE TO
LOWER RED RIVER VALLEY ON DAY 3, PARTICULARLY ALOFT. THIS IS
FAIRLY MINOR SO MUCH LIKE THE NORTHERN STREAM A GENERAL MODEL
BLEND IS SUPPORTED AT ABOVE AVERAGE CONFIDENCE.
PACIFIC NORTHWEST REINFORCING SHORTWAVE(S) LATE THURS/FRI AND
EARLY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET TRENDED A BIT SOUTH, WHILE POTENTIALLY A
BIT SLOWER THAN NORMAL, THE OVERALL EVOLUTION OF THE ELONGATED NW
TO SE TROF/SHORTWAVE IS AGREED UPON WITH MODEST UNCERTAINTY GIVEN
THE FAST GENERALLY ZONE FLOW PRECEDING IT AND THE SHEAR AXIS
BREAKDOWN OCCURRING ACROSS THE GULF OF AK INTO NW CANADA...AS SUCH
A GENERAL MODEL BLEND IS PREFERRED.
---PRIOR DISCUSSION---
IN THE WAKE OF THE INITIAL LONGWAVE TROUGH ACROSS THE PACIFIC
NORTHWEST, A STRONGER/COMPACT SHORTWAVE PIECE OF ENERGY PUSHES
INTO THE REGION LATE THURSDAY INTO FRIDAY. IN THE PRIOR FEW
CYCLES THIS WAVE CONTINUES TO COME INTO BETTER AGREEMENT AND WHILE
THERE ARE SOME SHARPER/DEEPER SOLUTIONS, THE SPREAD IS FAIRLY
MINOR TO SUPPORT A GENERAL MODEL BLEND FOR THIS WAVE.
BY DAY 3, THE ELONGATED SHEAR AXIS ACROSS THE BERING SEA/GULF OF
AK INTO NORTHWEST CANADA IS BREAKING DOWN WITH VORTICAL ROLL-UP IN
LAMINAR FLOW. THIS ALLOWS FOR A COUPLET ALONG THE JET TO AMPLIFY
INTO A MORE SOLID WAVE. AS IT APPROACHES THE EASTERN EDGE OF THE
INFLUENCE OF THE MULTIPLE SMALLER CLOSED LOWS ALONG THE SHEAR
AXIS, IT DEEPENS SLIGHTLY WITH A HIGH NEGATIVE TILT ANGLE ENTERING
THE PACIFIC NORTHWEST. THIS IS FAIRLY WELL AGREED UPON IN THE
GUIDANCE, THOUGH THE 12Z GFS IS A BIT FLATTER THAN THE PRIOR RUN,
BUT STILL ORIENTED CLOSELY TO THE CONSENSUS. THE 00Z UKMET
HOWEVER, IS FURTHER NORTH AND EAST, AND FAVORS ORIENTATION OF
ONSHORE FLOW TO THE N WA CASCADES WHILE THE REMAINING GUIDANCE
FAVORS FURTHER SOUTH IN THE S WA AND OREGON CASCADES. AS SUCH A
NON-UKMET BLEND IS FAVORED AFTER 19.00Z AT SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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