Le météogramme de 12 z du GEMGB est-il correct ?

[Pierre]

Si oui d'après les températures prévues par lui les précipitations risque d'être plus sous forme solide ou en PV ?! Il fait passer les températures de surface en dessous de 0 °C presque avant le début des précipitations abondante....

 

Y a t-il une explication.....?

 

Pierre

CPCQ

[beachcp31]

En fait, la résolution du GEMGLB est de 0.9 degrés, soit environ 100km.

De plus, la température à ce niveau est la température au premier niveau du modèle, et n'est pas ajustée (comme celle du GEMREG), ce sont les sorties brutes. Donc il faut faire attention à la précision qu'on donne à la température, surtout avec une situation avec un tel gradient de température...

Tout n'est pas joué, même les américains ne sont pas sûr entre 5cm de neige ou bien 25cm pour Plattsburgh (CPV). Ce sera une ligne est-ouest bien tranchée!

 

Aussi:

SCENARIO IS FOR A FIRST LO TO TRACK FM WRN MI AT 18Z TWD CNTRL QC TO

BRING SOME SNOW N OF TRACK (10CM RANGE) AND RAIN IN WRM SCTR WITH RISK

FZRA NR BNDRY. STRNG S/W IN SWLY FLO AHD UPR TROF WILL SUPPRT

DEVELOPMENT OF A SECOND LO ON ERN SEABOARD. THIS LO WILL REALLY BE THE

WX MAKER AS AN EXPLOSIVE DEVELOPMENT IS EXPECTED BY ALL MDLS ON

THIS. UKMET AND GEMREG ARE A BIT FRTHE E THN US MDLS WITH POSN OF LO

AT T+48H ... GEMREG BRINGS MORE WRM AIR INTO ERN QC THN US MDLS IN THE

30-48H TIME RANGE. THIS IS REALLY PROBLEMEATIC AS LARGE AMOUNT OF PCPN

ARE AT STAKES: WE ARE LOOKING AT 20-30 CM OF SNOW IN A BAND E OF LO

STRTCHNG FM ERN ONT - SWRN QC TO NR WABUSH; GEMREG FCST RAIN FOR THE S

SHORE OF STLWRNC AND MRTMS AND THE AREA IN BETWEEN (CORRIDOR

TROIS-RIVIERE - SEPT-ILES) IS EXPECTED TO EXPERIENCE A MIX OF SNOW AND

RAIN WITH MAX PCPN AMOUNT (OVR 50 MM OF WTR EQUIVALENT IN THE 36-48H

TIME RANGE.

 

AT THIS POINT GEMREG SEEMS TO PUSH WRMR AIR TOO FAR E OVR QC WHILE

GFS SEEMS TOO COLD. GFS ALSO FRTHR E WITH MAX PCPN CORE.

 

 

et encore :

 

WED: NRN LOW CONTINUES TO WEAKEN AS IT MOVES ACRS ONT INTO QUE.

ATTENTION SHIFTS TO LOW WHICH WL BE DVLPG IN MID ATLC RGN AND

INTENSIFY AS IT TRACKS NORTH INTO NEW ENG WED NITE. DIFFERENCES IN

TRACK OF SFC LOW CONTINUE BETWEEN THE MODELS...WITH EACH MODEL

REMAINING FAIRLY CONSISTENT WITH ITSELF OVR PREVIOUS FEW RUNS. ETA

CONTINUES WITH A MORE EASTERN TRACK...UP THRU ERN NEW ENGLAND. GFS

CONTINUES WITH A MORE WEST TRACK...UP INTO CT VLY. IMPRESSIVE INFLUX

OF MSTR ON ALL MODELS...WITH WDSPRD 1-2 INCHES OF QPF BEING

GENERATED. MAIN DIFFICULTY IS DETERMINING PTYPE...ESPECIALLY FROM

CHMPLN VLY EAST. ETA INDICATING MORE SNOW...WHILE WARMER GFS

 

SNOW THREAT: HAVE UPGRADED WATCHES THAT WERE IN EFFECT FOR NRN NY TO

WARNINGS FOR SNOW AMOUNTS ANYWHERE FROM 6 TO 14 INCHES BY THURS AM.

DUE TO THE MAGNITUDE OF THE EVENT AND CONTINUED UNCERTAINTY AS TO

HOW MUCH PCPN WILL FALL IN FORM OF SNOW...HAVE DECIDED TO ISSUE

WINTER STORM WATCH FOR REST OF NRN ZONES (CHMPLN VLY AND NRN VT) FOR

WED NITE INTO THURS. ALTHOUGH THERE WILL BE CHANGEOVER TO SNOW IN

SC VT LATER WED NITE...ACCUUMULATIONS IN THIS RGN EXPECTED TO BE

BELOW WATCH CRITERIA.