Dodging a Bullet

The Bay Area office of the National Weather Service is starting to compare the upcoming rain chances to the epic October storm that brought half a foot or more of rain, along with windy conditions, to parts of Northern California. But confidence continues to grow that any such madness will ensue post-race, perhaps not even until the middle of next week.

Like the Sacto crew, the SF NWS overnighters note the Canadian and the Euro (ECMWF) snuggling each other while poor GFS stands forlorn in a corner. SF thinks it won't be long until GFS makes it a menage a trois, however: "Expect to see new runs of the GFS trend more in line with the Euro." Fine with me, as long as they continue to have the storm arriving after, say, 10 a.m. on Sunday.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
445 AM PST TUE DEC 1 2009

... EXTENDED FORECAST...THE CANADIAN (GEM) AND ECMWF MODELS ARE IN REASONABLY GOOD AGREEMENT WITH THE LONG RANGE FORECAST AND WE`VE FOLLOWED THEIR WETTER SOLUTIONS. THE GFS MODEL CONTINUES TO STRUGGLE WITH AN ARCTIC INTRUSION THAT IT DROPS DOWN FROM PACIFIC NORTHWEST INTO THE NORTHERN GREAT BASIN. MORE REASONABLE SOLUTION THERE WILL KEEP THAT ASSOCIATED TROUGH AND COLD AIR FARTHER EAST OVER MONTANA.

FOLLOWING THE GEM AND ECMWF WOULD BRING RAIN CHANCES TO NORTHERN CALIFORNIA BY SUNDAY...ESPECIALLY LATER IN THE DAY AND HAVE KEPT POPS IN THE CHANCE CATEGORY. MODEL SOLUTIONS ACTUALLY BRING WARM ADVECTION RAINS ONSHORE SOMETIME SUNDAY EVENING BUT ENOUGH UNCERTAINTY TO AT LEAST MENTION RAIN CHANCES DURING THE DAY SUNDAY. RAIN CHANCES THEN INCREASE OVERNIGHT SUNDAY INTO MONDAY. THE EURO HASN`T REALLY WAVERED OVER THE LAST THREE MODEL RUNS WITH TWO RELATIVELY WEAKER STORMS SUNDAY NIGHT THROUGH TUESDAY WITH THE REMNANTS OF FORMER SUPER-TYPHOON NIDA ARRIVING ON WEDNESDAY. AGAIN THE GEM MODEL IS VERY SIMILAR TO THE EURO IN TIMING AND INTENSITY WITH AT LEAST TWO ~980-985 MB LOWS PASSING WEST OF CAPE MENDOCINO MONDAY THROUGH WEDS OF NEXT WEEK. THE ONLY THING KEEPING CONFIDENCE DOWN SLIGHTLY IS THE FACT THAT THE GFS MODEL KEEPS THINGS DRY UNTIL WEDS. CONSENSUS IN HOUSE AND WITH NEIGHBORING OFFICES IS TO DISREGARD THIS AND WOULD EXPECT TO SEE NEW RUNS OF THE GFS TREND MORE IN LINE WITH THE EURO. ITS GETTING HARD NOT TO START DRAWING ANALOGIES TO THE OCTOBER EVENT WITH ANOTHER RE-CURVING FORMER TYPHOON TAKING AIM AT THE CENTRAL COAST AND NORTHERN CALIFORNIA. TO GIVE AN IDEA ON RAINFALL POTENTIAL...AND THESE ARE VERY COARSE AND PRELIMINARY AT THIS TIME THE ECMWF GIVES 4 DAY STORM TOTALS OF 5-7 INCHES IN THE HILLS WITH WIDESPREAD 3 TO 5 INCH RAIN TOTALS FOR THE VALLEYS. OVER IN THE SIERRA THE LATEST RUNS GIVE STORM TOTAL QPF OF NEARLY 19 INCHES OF LIQUID PRECIP.