423
FXCN01 CWAO 312100
MAIN WX DISCUSSION
UPPER LEVEL PATTERN
PROGRSSV PATTRN OF UPR TROUGHS OVR MID LTTDS; MODLS ENCOUNTER PROBLEMS FM MID PD
ONWD WITH SYS BECOMG MATURE OVR CNTR OF CONTINENT, EVRY MODL ACTG DIFFRNTLY
WITH PHASG OF S/W ENRGY STREAMG ACRS SRN PRAIRIES AND FM U.S. PLAINS.
PROBLMS TOO WITH AS NEWLY FORMED T.S. CHANTAL ENTERS THE MID LTTD CIRCLTN NR
NF. GEM MODLS TENDENCY IS TO INTEGRATE RAPDLY CHANTAL TO FORM ONE POWRFL N
ATLNTC STORM NE OF NF BY T+36, AND NRLY VRTCL S OF GRNLD BY END OF PD. FOREIGN
MODLS KEEP UPR CENTR ASOCTD WITH MID LATTD UPR TROF DISTNCT FM REMNT OF
TROPCL STORM, THIS IS THE WAY TO GO.
OVR THE ARCTC THE SITTN IS EASIER, WITH UPR LO MOVG PLACIDLY N OF VICTORIA
ISLD. MODL DIFFR WITH DEGREE OF INTRUSION OF COLD AIR ACRS VICTORIA ISLD AND
POSN OF DFZN ACRS WRN BAFFIN.
T.S. CHANTAL..
COMPARSN OF SATPIX WITH GEMREG OUTGOING FLUX SHOWS GEMREG TO BE A TAD ON THE
SLOW SIDE WITH CHANTAL, THUS KEEPG THE STORM LONGER OVR WARMR WTRS. YET GEMREG
RENDERS REALISTCLY THE STORM'S EVLTN AS OF NOW. ALSO ON THE SIDE OF GEMREG IN
THE SHORT TERM WE NOTE GOOD CONCRDNC BTN CURRNT SAT PIX AND AREAS OF MODL CVCTV
FORCG ELSW OFF ATLNTC CST. GFS AND NAM/WRF TRACKG CHANTAL FRTHR W THAN EURPNS
AND GEM'S BUT BCS OF THEIR INTLZTN OF THE STORM, FRTHR WEST THAN THAT OF GEM
MODLS AT 12Z THIS MORNG.
OVRALL OUR THINKG HASN'T CHANGED, CURRNT INTGRTN OF GEM MODLS GIVE A
GOOD IDEA OF TRACK AND ASOCTD PPCN UP TO 24H, BUT UNDERGOES XTRATRPCL TRNSTN TOO
RAPDLY WITH OVRDEEPNG AND ENLARGING OF THE TROPICAL FEAT AT EXPENSE OF LARGER
NON-INTNSFYG LO TO THE NORTH. HENCE BY T+36 GEMS TOO DEEP, AND TOO SLOW AND FAR
WEST WITH THE REMANTS OF THE TROPCL STORM. A BLEND OF UKMET/NAM APPEARS A BETTR
CHOICE NOW BYD T+24.
COLD FNT ERN QC..
CURRNT WV/IR SAT PIX FIT WELL GEMREG UPR CIRCLTN AND PATTRN OF CVTV PCPN OVR
QC'S N/SHORE AND SRN LABDR, WHICH GIVES SM CONFDNC IN FCST FOR LATR EVLTN OF
REMNANTS OF T.S. CHANTAL, AS BAROCLNC FORCNG WILL BEGIN TO ACT DECISVRLY EARLY
WED OVR SERN NF.
SRN QC..
CURRNT TSTM VC MTL WAS A BIT OF A SURPRISE.. MODL HAD THE INSTBLTY AND THE ENRGY
BUT WAS DFNTLY TOO DRY WITH FCST DWPTS OF 15C OR LESS.. NOT UNLIKE WHAT WE SEE
IN WRM SCTR OVR PRAIRIES MORE OFTEN THAN NOT.
SYS DEEPNG AND OCCLDG OVR PRAIRIES/HDSNBA..
MODLS AGREE STGLY ON ONE ASPECT OF THIS STORM.. BY END OF PD THEY ALL END UP
WITH A DEEP OCCLUDED SYS, VERTCLY STACKED OVR WRN PORTN OF HDSNBA. YET THEY
DISPLY QUITE A RANGE OF TRACK EARLY IN PD AND FINAL POSNS BY T+48. BCS OF
APPRNTLY BETTER INTLZTN OF NRN AB UPR LO BY ECMWF, SUGGSTG DOUBL UPR LO
STRCTR, WE LEAN TWD MORE SLY TRACK OF THIS MODL BY T+24, EVN THOUGH IT
APPEARS AS AN OUTLIER, AND A BLEND OF ECMWF/GEMREG BY END OF PD, ABOUT AS
DEEP AS GEMREG WITH A POSN FURTHR W THAN UKMET/GFS (DEEPEST MODLS, FRTHR
EAST) AND FRTHR S THAN GEMREG. SVR WX NOT REALLY DEVLPG YET OVR SRN PRAIRIES
UNDR THRML RDG, BUT IS ADVRTZD BY MODL OBJCTV ASSESSMNT. SAME SCNRIO FOR NWRN
ONTARIO WED.
ARCTC..
MODLS NOT AS DIFFRNT THAN OVR PRAIRIES/HDSNBA. BLV IN SLGTLY DEEPR SRN PORTION
OF UPR LO OVR NUNAVUT AND DFZN FRTHR EAST TWD BAFFIN, WITH SHIFT IN QPF ACCRDG
TO ADJSTMNT.
PAC CST..
NEAR UNANIMITY OF MODLS WITH APPROACHG UPR LO, WITH XCPN OF SLOWR NAM WRF. GEM
GUIDNC FINE ALG CST AND NRN BC INTRR; SIMILARLY OVR YUKON/NWT WITH WDSPRD
INSTBLTY BUT WEAK DYNMCS.
END/GIGUERE
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