HPC model Diagnostic disc. - underestimating strength

[Stormsfury]

of the current mid-level and SFC cyclogenesis ... includes ALL of the models, even the RUC which was 3 MB too weak ... the trends continue to support a slower, and stronger SFC cyclone, and more indications of a northern/southern stream phase to occur... and places far south along the GOM coast, could see some other form of precip other than just rain, and into GA, and the Carolinas ... in fact, all the models continue to play catch up with this developing winter storm ...

(Entire HPC Model Diagnostic Discussion below)
MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1229 PM EST SAT DEC 25 2004

VALID DEC 25/1200 UTC THRU DEC 28/0000 UTC

MODEL INITIALIZATION...

...S/WV TROF/CYCLOGENESIS IN GULF OF MEXICO...

THE ETA AND GFS ARE HAVING TROUBLE HANDLING THE DETAILS OF
THE STG UPR TROF/CLOSED LOW FEATURE EJECTING INTO THE GULF
OF MEXICO THIS MORNING. INITIALIZATION ERRORS ARE MOST
NOTABLE AT THE SFC UP TO NR 700 MB AND AT 250 MB WITH THE
CHARACTER DEGREE OF JET LVL WINDS.

THE ETA IS ABOUT 3 MB TOO WEAK WITH THE SFC LOW STRENGTH IN
THE W CNTRL GULF OF MEX AT 12Z. THE GFS IS ABOUT 5 MB TOO WEAK
AND THE GFS IS ALSO HAS ITS SFC LOW PLACED TOO FAR TO THE
NORTHEAST FRM THE ACTUAL LOCATION. LOOKED AT THE 12Z RUC
AND EVEN THE RUC IS ABOUT 3 MB TOO WEAK...THE CMC 4 MB TOO
WEAK AND THE UKMET 2 MB TOO WEAK. SAT IR/WV IMAGERY AND HIGH
DENSITY WIND DATA ARE ALSO SUGGESTING A MORE ORGANIZED 700
MB TROF AND CLOSED LOW THAT NEITHER THE ETA AND GFS HAVE
INITIALIZED.

THIS STRONGER DEEP LYR REPRESENTATION SEEMS CORRELATED TO
VRY STG 250 MB JET WINDS THAT THE ETA AND GFS ARE ALSO BOTH
MISHANDLING. 12Z UPR AIR RAOB DATA AND GOES-E HIGH DENSITY SAT
WINDS SHOW A STG JET COUPLET IN THE W CNTRL GULF. 250 MB
WINDS OF 160 TO 180 KTS ARE NOTED DOWNWIND OVR THE INTERIOR
OF THE MID-ATL STATES. MEANWHILE 120 TO 130 KT JET MAXIMA WINDS
ARE SEEN UNDERCUTTING THE UPR TROF/CLOSED LOW IN THE SWRN
GULF OF MEXICO. THE ETA AND GFS ARE UNDERDONE LOCALLY BY 20
TO 30 KTS WITH THESE MAXIMA...AND NEITHER MDL DEPICTS THE
SHARPNESS OF THE JET COUPLET AS DEPICTED BY THE SAT DERIVED
WINDS. CONSEQUENTLY...STRONGER LFQ AND RRQ JET FORCING
SEEMS TO AT PLAY HERE.

...UPR TROF OVR GRT LAKES REGION...

THE ETA AND GFS ARE BOTH A LITTLE UNDERDONE WITH THE
STRENGTH OF THE UPR TROF OVR THE GRT LAKES REGION. THEY ARE
ALSO BOTH NOT HANDLING THE LOWER SFC PRESSURES/INVERTED
TROFFING OVR THE LAKES AS BEING DICTATED BY THE DIABATIC HEAT
FLUX.

...CLOSED LOW OFF PAC NW...

THE ETA WAS A BIT BETTER IN HANDLING THE LOWER SFC PRESSURES
INVOF B.C ASSOC WITH THE UPR TROF MOVING SSEWD. THE ERRORS
ON THE GFS DO NOT APPEAR TO BE THAT SIGNIFICANT THOUGH. NOT
SEEING ANY SIGNIFICANT ERRORS WITH THE UPR TROF/CLOSED LOW
FEATURE OFF THE B.C. COAST.


MODEL TRENDS...

...GULF OF MEXICO/EAST COAST CYCLOGENESIS...

THE ETA AND GFS CONTINUE TO TREND SLOWER AND STRONGER WITH
THE CYCLOGENESIS ALREADY OCCURRING OVR THE CNTRL GULF OF
MEXICO. THIS TREND IS NOTABLE OUT TO 24 HRS. THEREAFTER THE
ETA AND GFS BOTH BEGIN TO PLACE MORE EMPHASIS ON THE
DEVELOPMENT OF A SECONDARY SFC LOW OFF ILM/HSE AHEAD OF THE
MAIN BATCH OF 500/700 MB HEIGHT FALLS BUT ALONG A STG
BAROCLINIC ZONE ENHANCED BY THE GULF STREAM. THE ETA AND GFS
AFTER 36 HRS HAVE TRENDED CONSIDERABLY STRONGER AND
CLOSER TO THE MID-ATL COAST/NEW ENGLAND COASTS WITH THE
LOW EVOLUTION. THE GFS AND ESP THE ETA ALSO SUGGEST
SOMEWHAT STRONGER PHASING OF ARCTIC/POLAR STREAM ENERGY
INVOF THR ERN LAKES/UPR OH VLY WITH THE EJECTING SRN STREAM
ENERGY UP THE COAST.

...UPR TROF OVR GRT LAKES REGION...

NOT SEEING ANY APPRECIABLE BREAKS IN CONTINUITY REGARDING
THE EVOLUTION OF THE GRT LAKES REGION TROF ATTM. GRADUAL
HEIGHT RISES ARE STILL PROGGED ON BOTH THE ETA AND GFS AND
ESP IN THE DAY 2 PERIOD. THIS MAY ACTUALLY OCCURRING A LITTLE
FASTER AS THE ETA SUGGESTS GIVEN THE SHARPER PHASING OF
NRN/SRN STREAM VORT ENERGY ALONG THE MID-ATL/NEW ENGLAND
COAST AT 36 HRS AND BEYOND.

...CLOSED LOW OFF PAC NW...

THE ETA SHOWS VRY GOOD RUN TO RUN CONTINUITY SFC AND ALOFT
WITH THE SWD PUSH OF HEIGHT FALLS OFF B.C ON DAY ONE AND THEN
OFF THE PAC NW ON DAY TWO. BY 60 HRS MUCH OF THIS ENERGY IS
PROGGED TO BE OFF NRN CA/SRN OR. THE GFS MDL HAS TRENDED
SLIGHTLY FARTHER OFF SHORE WITH THE 500 MB LOW TRACK BUT HAS
ALSO TRENDED A LITTLE STRONGER AT THE SFC WITH THE LOW
CENTER JUST OF SRN B.C. BY 24 HRS


MODEL DIFFERENCES AND PREFERENCES...

...GULF OF MEXICO/EAST COAST CYCLOGENESIS...

VRY INTERESTING 24 TO 48 HRS EXPECTED FOR THE SERN STATES AND
NEWD UP THE COAST INTO ESP COASTAL NEW ENGLAND. THE ETA AND
GFS APPEAR TO PLAYING CATCH UP WITH THE STRENGTH OF THE
HEIGHT FALLS/JET ENERGY/CYCLOGENESIS CURRENTLY OVR THE GULF
OF MEXICO AND THE ENERGY STREAMING DOWNWIND ACRS THE
SOUTHEAST. THE GFS HAD ONE OF THE POOREST INITIALIZATIONS OF
ANY MDL WITH THE SYS AND CAN ALMOST BE THROWN OUT AT LEAST
FOR THE FIRST 12 TO 24 HRS.

THE ETA MAINTAINS A STRONGER MID/UPR LVL TROF OUT TO 36 HRS VS
THE GFS/CMC AND UKMET MDLS WHICH SEEMS TO HAVE SUPPORT FRM
12Z RAOB AND CURRENT IR/WV TRENDS. THIS ALSO SUPPORTS A MORE
ORGANIZED SFC LOW AFFECTING THE FL PENINSULA THRU 24 HRS.
THEREAFTER...THE ETA ATTEMPTS TO GRADUALLY THROW MORE
ENERGY TO A NEW SFC LOW JUST OFF SERN NC. NOT COMPLETELY
SURE THAT THIS IS GOING TO HAPPEN GIVEN THAT A STRONGER MORE
ORGANIZED UPR TROF WL FAVOR A MORE CONCENTRATED/ORGANIZED
SFC LOW EJECTING NEWD ALONG THE COAST. THE GFS FAVORS THE
IDEA OF LEAD VORT ENERGY DEVELOPING THE SFC LOW...BUT THIS
SEEMS TO BE SOMEWHAT RELATED TO CONVECTIVE FEEDBACK. IF ANY
SFC LOW AHEAD OF THE MAIN BATCH OF HEIGHT FALLS DEVELOPS IT
SHD BE WEAK AND DOMINATED BY THE MAIN LOW ATTM IN THE GULF
OF MEXICO.

PREFER TO GO WITH A SOLN LIKE THE ETA WITH THE LOW TRACK ESP
ON DAY ONE AND AT LEAST LEANING ETA AFTER 36 HRS WITH A
RAPIDLY DEEPENING LOW OFF THE MID-ATL COAST AND THEN OFF
NEW ENGLAND AROUND 48 HRS. THIS IS ALL BASED ON THE MDL
TRENDS OF THE ETA AND GFS OF A STRONGER SFC LOW AND A TRACK
NOW A BIT TOO THE LEFT. WORRIED THAT THE MDLS ARE NOT STG
ENOUGH STILL WITH THE LOW INTENSITY AND WUD NOT ARGUE
AGAINST A STRONGER SOLN THAN ANY MDL CURRENTLY HAS. THIS
MATCHES WELL WITH CURRENT IR/WV SAT TRENDS WHICH SHOW A
STG COMMA-HEAD DEVELOPING OVR THE NWRN GULF OF MEXICO AND
AN IMPRESSIVE JET COUPLET IMPLYING A MORE AGGRESSIVE SOLN.

...UPR TROF OVR GRT LAKES REGION...

PREFER TO LEAN TWD AN ETA/GFS BLEND HERE OVR THE LAKES
REGION REGARDING THE TRANSITIONING OF HEIGHT FALLS
GRADUALLY THE EAST AND PHASING WITH SRN STREAM ENERGY
CUTTING UP OFF THE EAST COAST. NO MAJOR MDL DISCREPANCIES
SEEN HERE IN COMPARISON THE TO CMC OR UKMET EITHER WHICH
FURTHER SUPPORTS AN ETA/GFS BLEND.

...CLOSED LOW OFF PAC NW...

IN GENERAL THE ETA HAS HAD BETTER MDL CONTINUITY AND THE GFS
APPEARS TO BE TRENDING TWD THE ETA WITH THE TRACK OF THE 500
MB CENTER. THE GFS APPEARS TO ALSO BE A BIT OF AN OUTLIER WITH
ITS STRONGER SFC LOW SOLN JUST OFF THE WA COAST THRU 24 HRS.
THERE IS A LOT OF STG JET ENERGY OFFSHORE AND A STRONGER
SOLN CANNOT BE RULED OUT...BUT FOR NOW WUD NOT PREFER TO GO
AGAINST THE VRY CONSISTENT ETA AND A SOMEWHAT WEAKER SFC
REFLECTION. PREFER TO BLEND THE ETA/GFS THRU 24 HRS AND LEAN
TWD THE ETA THEREAFTER GIVEN ITS SUPPORT FRM THE UKMET AND
CMC.

ORRISON

MODEL BIASES AT http://WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML

[Wannabewxman79]

Well Storm let us know if you hear anything for us coastal folks! I guess we will be breathing cold smoke and having a 33 degree rain as usual.