957  
FXCN01 CWAO 270930  
 
MAIN WX DISCUSSION  
 
EASTERN REGIONS SYSTEM.  
PREFERRED MODEL: GFS  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
AS MENTIONED IN THE EARLY FX, THE RDPS IS ON THE SLOW SIDE WITH THE TROUGH  
MOVING THROUGH EASTERN CANADA INITIALLY, AND GFS OVERALL HAD A BETTER HANDLING  
ON IT. ON DAY 2, GFS CONTINUES TO LEAD THE PACK WITH A SLIGHTLY MORE PROGRESSIVE  
SYSTEM, AND IT IS WELL-SUPPORTED BY THE ECMWF. MEANWHILE, THE REST OF THE  
GUIDANCE ISN'T FAR BEHIND. QPF-WISE, GFS LOOKS GOOD WITH MORE ADVANCED  
PRECIPITATION INTO LABRADOR DURING THE PERIOD. LOCALLY HIGHER AMOUNTS ARE  
HOWEVER POSSIBLE WITH CONVECTION.  
 
NORTHEASTERN USA LOW.  
PREFERRED MODEL: GDPS  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
BY T+48H, MODELS ARE IN GOOD AGREEMENT WITH THE UPPER LOW NEAR LAKE ERIE, BUT  
NAM/UKMET ARE ON THE DEEP SIDE WITH IT WHILE RDPS IS ON THE FAST SIDE COMPARED  
TO THE REST OF THE GUIDANCE. AT THE SURFACE, THE RDPS IS FARTHEST SOUTH, WITH  
SUPPORT FROM GEPS-MEAN. MEANWHILE, NAM/GFS/UKMET AGREE ON A POSITION FARTHEST  
NORTH, ALTHOUGH WE NOTE UKMET IS THE DEEPEST. GDPS IS PREFERRED HERE OVERALL  
WITH A SOLUTION IN THE MIDDLE OF THE GUIDANCE AND IS SUPPORTED BY ECMWF.  
 
HIGH ARCTIC LOW.  
PREFERRED MODEL: GDPS  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
ON DAY 2, MODELS AGREE IN A GENERAL SENSE TO CURL THE SURFACE LOW TOWARD THE  
NORTHWEST. THE GDPS/GFS ARE IN GOOD AGREEMENT WITH THE POSITION AND INTENSITY  
THROUGH THE PERIOD AND FALL IN THE MIDDLE OF THE OTHER SOLUTIONS OFFERED BY  
RDPS/NAM/UKMET/ECMWF/GEPS-MEAN. THE GFS HAS SHOWN GOOD CONSISTENCY RUN-TO-RUN,  
SO CONFIDENCE HAS BEEN GOOD WITH IT, HOWEVER, GFS, ALONG WITH NAM/ECMWF, SEEMS A  
BIT ON THE DEEP SIDE WITH THE ASSOCIATED SURFACE TROUGH OVER BAFFIN ISLAND  
DURING THE PERIOD. MEANWHILE, RDPS/GDPS/UKMET AGREE ON A WEAKER FEATURE. THE GFS  
HAS THE HIGHEST QPF OVER SOUTHERN BAFFIN ISLAND AND NORTHERN QC DURING THE  
PERIOD DUE TO THIS, AND IS LIKELY OVERDONE. SO OVERALL, GDPS IS RECOMMENDED  
HERE.  
 
LOW COMPLEX TRACKING THROUGH SOUTHERN NT/NU AND PRAIRIES SYSTEM.  
PREFERRED MODEL: RDPS  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
ON DAY 2, THE NAM IS THE FASTEST MOVING THE LEADING LOW INTO SOUTHERN NU,  
FOLLOWED BY GFS AND ECMWF. RDPS/GDPS/UKMET AGREE ON A POSITION FARTHER WEST. IN  
TERMS OF CENTRAL PRESSURE, UKMET IS AN OBVIOUS OUTLIER WITH A DEEPER FORECAST  
VALUE. THE CANADIAN MODELS HAVE MAINTAINED FAIRLY GOOD CONSISTENCY HERE, AND AS  
MENTIONED IN THE EARLY FX, THEY INITIALIZED WELL WITH A STRONGER SURFACE RIDGE  
TO THE NORTH OF THE LOW OVER NT. DUE TO THESE REASONS WE RECOMMEND RDPS HERE.  
FARTHER SOUTH, THERE ARE SOME DISCREPANCIES WITH THE TIMING OF THE SURFACE  
TROUGH MOVING THROUGH THE PRAIRIES ON DAY 2, BUT THE SPREAD IS FAIRLY SMALL  
AMONG ALL OF THEM, SO RDPS SHOULD BE OK IN A GENERAL SENSE HERE AS WELL. THE  
MODEL IS SUGGESTING SOME VERY HIGH PRECIPITATION MAXIMA BUT CONFIDENCE IS NOT  
HIGH IN THESE DETAILS DUE TO THE EXPECTED CONVECTION. HOWEVER, RDPS HAS SHOWN  
GOOD CONSISTENCY WITH THE AREAL EXTENT OF THE QPF, AND THAT ASPECT IS SUPPORTED  
BY GDPS/UKMET. AS FAR AS SEVERE WEATHER, THE CMC SUMMER SEVERE WEATHER CHART IS  
SUGGESTING SEVERE THUNDERSTORM POTENTIAL ON DAY 2 FOR SK/MB/NORTHERN ON.  
 
BC.  
PREFERRED MODEL: RDPS  
SCENARIO CONFIDENCE LEVEL: MEDIUM  
BY T+48H, THE NAM/GFS ARE FARTHEST SOUTH WITH THE EASTERN PACIFIC LOW WHILE  
ECMWF IS FARTHEST NORTH. THE RDPS/GDPS/UKMET AGREE WITH A MIDDLE POSITION WITH  
SOME SUPPORT FROM GEPS/NAEFS. HERE WE RECOMMEND RDPS AS A GOOD MID-PACK  
CANDIDATE. THERE IS SUPPORT FOR THE RDPS LIGHT PRECIPITATION PATTERN OVER THE  
NORTHERN BC COAST AT T+48H FROM GDPS/UKMET AS WELL.  
 
END/HARTT  
 
 
 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab CANADA Page Main Text Page