Gale WindSat case off NW California – Mel Nordquist

During the morning of October 31 we had a gale event over the coastal waters just off the Northern California Coast. This presented a good opportunity to evaluate the operational usefulness of the WindSat data. During late spring and summer, strong gale to near gale conditions develop within a few miles off shore over the Northern California and Southern Oregon waters. On most days the wind peaks during the late afternoon or evening hours. The core of the northwesterly low level jet that forms is usually just beyond the buoy locations and hence not well sampled by surface obs. Even though this case occurred during October it has many of the characteristics of the summer gale events. Note the core of the low level jet off Cape Mendocino in light green with 35kt wind barbs indicating gale winds. This is a warning condition for Marine concerns (Figure 1).  Note the area of  > 34Kt wind indicated by yellow wind barbs (Figure 2). We see in this case very good correlation with the WFO forecast. Also provided is the GFS 12Z initialization of the surface winds with buoy data overlaid for comparison. The Marine forecast valid for that time frame is also provided for operational context.

Figure 1 - The 15Z surface wind forecast grid issued by the Eureka WFO overnight.

Figure 2 – The WindSat data for the same time frame, 15Z in the morning.

 

Figure 3 – Surface winds from the GFS for 12Z.

PT ST GEORGE TO CAPE MENDOCINO 10 TO 60 NM-
310 AM PDT MON OCT 31 2011

…SMALL CRAFT ADVISORY IN EFFECT UNTIL 10 AM PDT THIS
MORNING…
…GALE WARNING IN EFFECT FROM 10 AM PDT THIS MORNING THROUGH
TUESDAY EVENING…

.TODAY…N WIND 15 TO 20 KT…RISING TO 20 TO 30 KT WITH GUSTS TO 45 KT. WIND WAVES 4 FT…BUILDING TO 8 TO 10 FT. NW SWELL 5 FT AT 9 SECONDS…BECOMING N 5 TO 7 FT AT 10 SECONDS. PATCHY FOG AND SLIGHT CHANCE OF RAIN BEFORE SUNRISE.
.TONIGHT…N WIND 30 TO 35 KT WITH GUSTS TO 45 KT. WIND WAVES 12 TO 13 FT. N SWELL 7 TO 8 FT AT 10 SECONDS…BUILDING TO 11 TO 12 FT AT 10 SECONDS AFTER MIDNIGHT.
.TUE…N WIND 25 TO 35 KT WITH GUSTS TO 45 KT. WIND WAVES 11 TO 13 FT. N SWELL 10 TO 12 FT AT 13 SECONDS.

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