410
FXCN01 CWAO 292100
MAIN WX DISCUSSION
UPPER LEVEL PATTERN
HI AMPLITUDE BUT RPDLY CHGG UPR PATN PREVAILS DURG PD.
QS UPR LO IS FOUND VCNTY NR 72N 120-130W THRUT PD. UPR LO OVR FXBSN
RELOCATES TO NRN GRNLD WHILE NRN AK UPR LO RETROGRESSES TO WRN AK FORCING
ALUTNS AND GLFALSK UPR LOS TO DUMBBELL ARND EACHOTHER, EVENTUALLY SENDING
SOME ENERGY NWD ACROSS NWRN CAN BY END PD. ALL THIS ACTION ALLOWS FOR BC/NWRN
USA AND ON/NERN USA UPR LARGE TROFS/LOS TO SPLIT FM THE NRN PORTION OF THE L/W
TROFS. HENCE SWRN BC UPR LO SLIPS SEWD TO SWRN PRAIRIES/NWRN USA. MEANWHILE
MORE OR LESS N-S ERN NAM UPR TROF/LO REALINES ITSELF ALG A NE-SW AXIS AS TWO
NEW UPR LOS FORM OVR SRN HSNBA AND GLFME WITH UPR TROF LINKING THOSE TWO
FEATS.
WHILE MDLS AGREE ON OVRALL EVOLUTION OF CIR, NUMRS FEATS EMBDD ARND THESE LARGE
SCALE CIR LEAD TO SLIGHT DIFF AMONG MDLS. MORE BELOW.
ARTC...
MDLS ARE IN EXCELLENT AGREEMENT OVR AREAS AND SHUD CONT TO VERIFY WELL.
LTL WX IS ASOCTD TO NRLY QS N OF ARTC CIRCLE.
SOME MXD PCPN WILL AFFECT SRN YKN ON DY1. PCPN WILL THEN PUSH NWD ALG YK/AK
BORDER AS UPR SUPRT DOES SAME. NIL SIG SNW ACCUM XPCD XPC PSBLY OVR HIER TRRN.
SOME LGT SNW IS XPCD OVR BAFISLD WITH HIER ACCUM LCLY VCNTY WKNG QS SYS OVR NRN
FXBSN AND NR FNTL WV FCST TO TRACK ACROSS XTRM SRN PORTION OF ISLD ON DY1. A
SLIGHT RISK OF ZR IS TIED TO WRM FROPA. BY DY2 A WK LO HAS DVLPD OVR BAFBA. AS
IS OFTEN THE CASE WITH SUCH SYS, CAN MDLS ARE LKLY A FEW HPA TOO DEEP WITH THAT
FEAT.
BC/PRAIRIES...
00Z ENS MEAN AS WELL AS ECMWF WERE A SUGGESTING A SLIGHTLY MORE SLY TRAJ FOR
THAT SYS. NEW MDL HAS ADJUSTED IN THAT DIR. AGREEMENT AMONG MDLS IS QUITE GOOD
OUT TO 24HR BUT ONCE SYS BEGINS TO BACKTRACK WWD, MDLS DIFFER. RGNL MDL IS
FURTHEST W, FOLLOWED BY GBL. WRF-NAM, GFS AND UKMET ALL KEEP THEIR LO VCNTY
AB/SK BORDER (I.E. KEEP SYS QS AFTER 24HR). ONLY ONE OF THE 00Z ENS MEMBER WAS
ADVERTIZING A LO AS FAR W AS SUGGESTED BY 12Z RGNL MDL. ALL OTHER MEMBERS ARE
FURTHER E OR SE. NONE OF THE 12Z ENS MEMBERS ARE SUPRTG THE RGNL MDL
SCENARIO. IN FACT THEY HV ADJUSTED EVEN FURTHER TO THE SE. 12Z ENS MEAN CLOS
ELY RESSEMBLE THE 12Z ECMWF MDL. THEIR ONLY SHOW AN INVRTD SFC TROF POKING
INTO SRN AB AT 48HR. THUS WUD TEND TO LEAN TWD USA-UKMET SCENARIO ... A
COMPROMISE BTN RGNL/GBL AND ECMWF HENCE WUD XPC THAT RGNL MDL AND EVEN GBL MDLS
PCPN MAX ARE FCST TOO FAR W BUT UNCERTAINTY IN FCST REMAINS QUITE HI ON DY2 WITH
THIS FEAT AND WILL NEED CLOSE MONITORING IN COMING RUNS.
SYS UNDERGOES SLO DPNG ERLY IN PD BUT THEN GRADLY WKNS AS UPR SUPRT DOES SAME.
SYS HAS SIG MID LVL DYNAMICS ASOCTD AS 700HPA UPR LO REMAINS WELL-DEFINED THRUT
PD. THAT ALLOWS FOR EASIER TRACKING OF PCPN MAX ASOCTD TO SYS. SOME
THUNDERSHOWERS ARE FCST WITH SYS (SEE OBJCTV CVCTV CHARTS). MAIN THREAT AREAS
WILL BE ASOCTD TO SFC LO AND JUST N OF WRM FNT AFFECTG SERN AB/SRN SK LTR TDY
(ASOCTD TO LO FURTHER S OVR NRN PLAINS). DIRECTIONAL SHEAR IS PRESENT AS WELL AS
DIFFLUENCE ALF BUT PW IS RATHER SMALL (10 TO 15MM). THUS THREAT FOR SVR WX WITH
TO THOSE CELLS APPEARS SMALL, ESPLY SINCE CB'S ASOCTD TO SRN SYS WILL BE
HI-BASED.
ERN AND ATLC CAN...
MDLS ARE NOW IN GOOD AGREEMENT IN TREATMENT OF MAIN LO TO TRACK NEWD TWD
HSNBA. AS DISCUSSED IN ERLY FX, RGNL MDL IS NOW WKR AND A BIT FURTHER N WITH SYS
AT 36HR AND IS NOW IN LN WITH MAJORITY OF DETERMINISTIC AS WELL AS ENS GUIDANCE.
THERE CONTS TO BE SOME DIFF WITH TRAILING TROF/LO OVR MRTMS ON DY2. CAN AND
EUROPEAN MDLS AS WELL AS 12Z ENS RUN ARE SIMILAR AT 500HPA WHILE USA MDLS ARE
SUGGESTING A WKR TROF OVR GLFME AT 48HR. THUS AS SFC, USA MDLS ARE FURTHER E
THAN ALL OTHER MDLS AND ARE REJECTED IN FAVOR OF BLEND BTN DEEPER RGNL/ENS AND
WKR GBL/UKMET/ECMWF SCENARIO. HENCE SUSPECT THAT THERE WILL BE LESSER QPF ALG E
CST OF NB AND OVR PEI THAN CURRENTLY ADVERTIZED BY RGNL MDL. PREFER GBL MDL QPF
ATTM.
SOME PCPN IS FCST TO SPILL OVR SRN ON BY END PD. SUSPECT THAT CAN MDLS ARE TOO
PROGRESSIVE AND TOO WK WITH RDG AHD OF THAT PCPN BAND THUS XPC THAT IN COMING
RUNS PCPN WILL BECOME ORIENTED MORE NW-SE AND BE SLOWER TO COME OVR RGN.
END MARCHAND
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