California and Nevada Drought is extreme to exceptional
Drought Monitor
May 19, 2015
Severe to Exceptional Drought conditions continue
94% of California in severe to exceptional (D2-D4) drought conditions (one year
ago the coverage was 100%). Over Nevada the D2-D4 area covers 87% of the state
(one year ago the coverage was also 87%).
It’s been dry for 3 years: the percent of average precipitation from late May
2012-2015 shows much of the west below normal (100%). Much of California is
below 70% of normal and much of Nevada is below 90% of normal.
The Northern Sierra Precipitation 8-station index is at
74% of normal.
How warm has it been?
May 2014-May 2015 was the warmest period on record (1895-2015) for
maximum (left) and minimum (right) average statewide temperatures for
extreme western states. Other states in the west were much above average.
May 1st: California state conditions
For 2003 (left) to 2015 (right)
this graph shows the percent of
average for snowpack (open
bars), precipitation (hatched
bars), runoff (black bars) and
reservoir storage (line with
triangles).
2015 shows the lowest
snowpack (2% of average) and
lowest reservoir storage (65%
of normal)
From California Department of
Water Resources Bulletin 120 for
May 2015
Sacramento River Basin: wet and dry periods
Large (blue) and small (red) amounts of precipitation over the past
century aggregated over periods of one month to 3 years (y-axis)
NOAA releases a
service assessment on
the California Drought
The principal purpose of this report is
for NOAA to identify resource
management decisions that were
affected by the current drought in
California and to assess the use and
effectiveness of forecasts, indices,
monitoring data, and services that are
available to decision makers and
stakeholders
Find a copy of this report at:
http://cnap.ucsd.edu
Sea Surface Temperatures have been
above normal off the west coast and
over the equatorial Pacific
for the past week,
for the past month,
and for the past season
CPC/IRI Probabilistic ENSO Outlook
Updated: 14 May 2015
The chance of El Niño is approximately 80-90% through 2015.
IRI/CPC Pacific Niño
3.4 SST Model Outlook
Almost all of the models indicate
Niño 3.4 SST anomalies will
remain greater than or equal to
+0.5C through the end of 2015.
However, there is a large
amount of spread in the
potential strength of El Niño.
Figure provided by the International Research
Institute (IRI) for Climate and Society
(updated 19 May 2015).
SST Outlook: NCEP CFS.v2 Forecast (PDF corrected)
Issued: 26 May 2015
The CFS.v2 ensemble mean (black dashed line) predicts El Niño through
DJF 2015-16.
U. S. Seasonal Outlooks
June – August 2015
The seasonal outlooks combine the effects of long-term trends, soil moisture,
and, when appropriate, ENSO.
Precipitation
Temperature