WCN April 2020 Draft E

Table 1: Note: Some stations were excluded because of data quality concerns.
a. Biggs, Durham, Williams, Gerber (except 2013, for which Biggs and Williams were not available)
b. Twitchell Island, Winters, Verona, Woodland, Davis
c. Kesterson, Los Banos, Merced, Manteca, Denair, Modesto, Oakdale
d. Coalinga, Firebaugh, Five Points USDA, Fresno State, Parlier, Westlands, Arvin-Edison, Belridge, Blackwells Corner, Shafter, Stratford, Delano
Continued from Page 14
ary 19 th for chill accumulation at all the
CIMIS stations in the Central Valley
(Nov 1-Feb 19), the average for the
whole valley is 2 percent below the average
of the last five years when counted
in Chill Portions. As you can see in
Table 1(see above), regional averages
ranged from 8 percent below average in
the southern Sacramento Valley (5 chill
portions) to 2 percent above average
in the southern San Joaquin Valley (2
chill portions). Note that the year listed
is the year in which the winter started.
For example, this winter is shown
below as 2019. Chill hours, on the other
hand, indicates we are 11 percent above
the average of the last five years for the
whole Central Valley.
How Does This Year Compare?
Another way to look at this winter is
to compare it with the winters of 2013
and 2014, the last couple of low chill
winters that resulted in unusual (in
some cases, yield-decreasing) spring
bloom timing. Compared with the
winter of 2014, across the whole Central
Valley, chill is 7 percent higher this
winter when counted using chill portions.
This ranges from just 2 percent
higher (1 chill portion) in the southern
Sacramento Valley to 13 percent higher
(7 chill portions) in the southern San
Joaquin Valley. Winter chill accumulation
this year is fairly equal across
regions. The relative difference is due to
2014 being a much warmer winter for
the southern San Joaquin. Compared to
the winter of 2013, we’ve accumulated
8 to 11 percent more chill (5 to 7 chill
portions) this year. On the other hand,
Central Valley-wide, this winter was
34 percent higher when counting using
chill hours.
Looking both relative to average
recent conditions and relative to warm
recent years, while it was not a boom
winter for chill accumulation, it does
not look like a bust winter either. When
counted using the chill portions method,
this winter’s chill accumulation has
squeaked through above the yield-decreasing
winters of 2013 and 2014. I
would not expect the flash bloom we
saw in almond this year to play out
in other crops. But the chill portions
numbers indicate we have (narrowly?)
avoided yield-decreasing bloom and
I’VE LARGELY EMPHASIZED CHILL PORTIONS ABOVE. THIS IS A WIN-
TER TO HIGHLIGHT THE DIFFERENCES AMONG THE TWO MODELS,
BECAUSE DEPENDING ON WHICH TOOL YOU USE TO COUNT CHILL,
THIS WINTER WAS EITHER WARM BUT NOT DISASTROUSLY WARM
(CHILL PORTIONS) OR COOLER THAN AVERAGE (CHILL HOURS).
leaf-out problems this season.
I’ve largely emphasized chill portions
above. This is a winter to highlight
the differences among the two
models, because depending on which
tool you use to count chill, this winter
was either warm but not disastrously
warm (chill portions) or cooler than
16 West Coast Nut April 2020