California Climate

Outcome Likelihood Tool

Nina Oakley, Kelly Redmond, Grant Kelly, Britta Daudert

Western Regional Climate Center

USDM Forum

April 22 2015 – Reno, NV

Motivations How might this year turn out?

NCDC “Amelioration” tool (PHDI) 1

M. Dettinger “ESP” analysis

P. Iñiguez PRISM simulations

What water managers want:

Better seasonal forecasts, monitoring, communication2

Constrain decision-making

Tool that is customizable, daily resolution

Tool that is graphical, explains caveats3

1ncdc.noaa.gov/temp-and-precip/drought/recovery/2Steinemann 2014, BAMS 3Pulwarty 2003, Water Resources

Data Source NWS COOP via ACIS

Daily, long record

Decision makers often state climate forecasts unreliable1

Suggest stations with record 1920 or better-present

Any station, any record

in US

Provisions for how

much missing data

acceptable

COOP at Manzanita Lake, CA1Pulwarty 2003, Water Resources

3 Data Options “Observed” data in station record

Distribution built from all past periods equal to “recovery period”in station record

“Analog” Periods

Identify periods in station record of date range equal to observed period that are within +/- 1, 2, or 3 deciles of current observed total

Take their corresponding future “recovery” periods and create distribution

Random sampling of station record

Sample each day of “recovery period” from station record, build “synthetic accumulations”, repeat 1000x

Apr 13 2001 + Apr 14 1934 + Apr 15 1901 + ... Sept 30 1996

Doesn’t account for multiple day precipitation streaks

2 “Analysis” Options

Amelioration

Likelihood of reaching normal, recovering deficit by end of

“recovery period”

Custom Threshold

Likelihood of receiving a user-specified amount of

precipitation by end of “recovery period”

At RENO

2014-10-01 to

2015-04-12

2.93 in accum.

0 missing days

2.43 in deficit

11.87 in needed

by 09-30-2016

to recover deficit,

reach normal

15.6% chance

of recovering

based on 77 of

78 possible

periods in record

1937-03-01 to

2015-04-12

“Observed”

optionDeciles

Amount needed

Normal

for period

Probability of

occurrence

“Analog”

optionAt RENO

2014-10-01 to

2015-04-12

2.93 in accum.,

falls between

10th - 20th

percentile

2.43 in deficit

11.87 in needed

by 09-30-2016 to

recover deficit,

reach normal

13% chance

of recovering

using +/- 1

decile analog

(10th-30th

percentile),

23 periods

Probability of

occurrence

Amount needed

Normal

for period

Example graph + table for Sacramento, CA

Likelihood of exceeding threshold of 3 inches

by end of WY 2015 (20% chance)

Spaghetti Plot (coming soon)

Observed Precipitation

10-01-2014 through

04-12-2015

+Selected precipitation

traces 04-13-2015

through 09-30-2016

=Range of outcomes

based on climatology

Hypothetical Station

Observed period 10-01-2014 to 04-12-2015,

Future period ending 09-30-2016 10 traces shown

pre

cip

ita

tio

n

time

Limitations and Future Work

Using historic record, does not account for future trends

Point rather than areal data

Test on target audience, implement feedback

http://wrcc.dri.edu/col/

Expand to other accumulating quantities

snowfall, HDD, CDD, GDD

Thank you!

South Yuba River, Sierra Nevada, CA

Feb 7/8 2015 Atmospheric River event

Bad for skiing, good for kayakingPhoto credit: Ben Hatchett nina.oakley@dri.edu

@WRCCclimate

Connect with WRCC!

Random

Sampling

2014-10-01 to

2015-03-18

3.09 in

0 missing

0.15 in deficit

6.65 in needed

to recover deficit

by 09-30

28.6% chance

of recovering

based on 1000

random daily

samples from

record

1892-01-01 to

2015-03-19