California and Nevada Drought is extreme to exceptional.

California and Nevada Drought is extreme to exceptional

Severe to Exceptional Drought conditions continue94% 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%).

Drought MonitorMay 19, 2015

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 DroughtThe 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 OutlookUpdated: 14 May 2015

The chance of El Niño is approximately 80-90% through 2015.

IRI/CPC Pacific Niño 3.4 SST Model

Outlook

Figure provided by the International Research Institute (IRI) for Climate and Society (updated 19 May 2015).

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.

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

Precipitation

Temperature

June – August 2015

The seasonal outlooks combine the effects of long-term trends, soil moisture, and, when appropriate, ENSO.