CW3E AR Update: 5-7 March 2016 Outlook

CW3E AR Update – 5-7 March 2016 Outlook

March 4, 2016

A storm predicted to make landfall over northern California on 5 March 2016 has characteristics of an Atmospheric River. The AR is showing moderate strength with an average landfall duration of 12-24 hours. The storm has the potential for R-Cat 1 rainfall in favored mountain areas. For up to date AR forecasts visit the CW3E AR Portal.

CW3E AR Update: 3 March 2016 Outlook

CW3E AR Update: 3 March 2016 Outlook

March 3, 2016

CW3E gives an outlook on current and upcoming Atmospheric River (AR) events along the U.S. West Coast. A moderate AR is currently impacting central California producing light precipitation over the northern Sierra Nevada and Central Valley. Two ARs are expected to make landfall over the Pacific Northwest in the next seven days, with both propagating south over California prior to dissipation. Long range forecasts also show the potential for another strong AR to make landfall in the Pacific Northwest next week.

For the latest river and precipitation forecasts and observations visit the California Nevada River Forecast Center (CNRFC) or the U.S. Geological Survey (USGS). For the latest AR forecasts visit the CW3E AR Portal.

Click here for a pdf file of this information.


Current Conditions: 3/3/2016
Northeast Pacific SSMI IWV: 1400 UTC 29 Feb 2016 – 1400 UTC 3 March 2016

GPS Integrated Water Vapor: 1515 UTC 3 March 2016
IWV values greater than 2 cm
throughout central California
-Current AR conditions

Current California Precipitation Conditions
The North Sierra 8-Station and Tulare Basin 6-Station Precipitation Indices are average for this time of year.


AR Landfall Probability Tool: Initialized 0000 UTC 3 March 2016
Hover mouse over description below to see forecast product or click to open. Images courtesy Jason Cordeira; Plymouth State University

IVT >250 kg m-1 s-1
IVT >500 kg m-1 s-1
Inland IVT >250 kg m-1 s-1
Inland IVT >500 kg m-1 s-1

  • Periods of AR conditions forecasted along most the U.S. West Coast on forecast days 0-1, 1-2, 2-5 and 4-5
  • Strong probability of AR event on forecast days 7-8
  • All forecasted ARs are expected to penetrate inland over Oregon and northern California


CNRFC River Forecasts
2000 UTC 3 March 2016

  • 1 river forecasted above flood stage
     -Navarro River
  • 7 rivers forecasted above monitor stage

    Russian River CNRFC Forecast

    GFS Ensemble MJO Index Forecast; 3 March 2016 – 17 March 2016


    • A continuation of MJO activity is expected
    • Propagation through Phases 8 and 1 and possibly 2
    • Significant decrease in amplitude

    GFS IWV: 0600 UTC 3 March 2016 – 1800 UTC 10 March 2016

    • AR currently impacting northern and central California
    • AR to make landfall at 1800 UTC 4 March 2016 over NW Pacific
    • AR to make landfall at 0600 UTC 9 March 2016 over NW Pacific
    • All three ARs propagate south over California prior to dissipation

    GFS IVT: 0600 UTC 3 March 2016 – 1800 UTC 10 March 2016

    CNFRC Precipitation Forecasts: Produced 3 March 2016

    Max 72-h precip >6 inches over Northern Sierra Nevada and California Coastal Range
    Max 6-day precip ~11 inches over Northern Sierra Nevada and California Coastal Range

    7-day Precipitation Forecasts: Ending 4:00 am PST 10 March 2016

    Max 7-day precip ~290 mm over Northern Sierra Nevada, Olympic Mountains and Vancouver Island
    Max 7-day precip ~270 mm over Northern Sierra Nevada, Olympic Mountains and Vancouver Island




    • Current dissipating AR impacting central California
    • Two moderate strength ARs expected to make landfall along the U.S. West Coast over the next five days
    • Another AR may potentially make landfall late next week
    • 7-day precipitation totals up to 300 mm in multiple locations over the U.S. West Coast

    For more information about AR updates or forecast products visit the CW3E Home Page or contact Brian Kawzenuk, Marty Ralph, or Scott Sellars at CW3E.

    The Washington Post Capital Weather Gang features CW3E and Atmospheric River Field Mission

    The Washington Post Capital Weather Gang features CW3E and Atmospheric River Field Mission

    February 18, 2016

    The Washington Post Capital Weather Gang today (18 February 2016) featured the current observing missions happening over the eastern Pacific as coordinated by CW3E director Dr. F. Martin Ralph. Current missions are starting from Hickam Air Force Base in Hawaii and include some 800-mile transects. Critical information about water vapor distribution and winds are gathered during these flights and are used as initial conditions in global forecast models. The article highlights several quotes from CW3E director Ralph including the importance of pin-pointing the landfall of an Atmospheric River. Regarding forecast uncertainty: “Where it hits is off by an average of plus or minus 500 kilometers,” Ralph said. “An atmospheric river is 500 kilometers wide, so the error can mean the difference of whether you’re hit or not.”

    Find the full article at The Washington Post Capital Weather Gang page: here.

    State-of-the-art WC-130J aircraft for weather reconnaissance missions. The aircraft is a C-130J transport configured with palletized weather instrumentation for penetration of tropical disturbances and storms, hurricanes and winter storms to obtain data on movement, size and intensity.The WC-130J carries a minimal crew of five: pilot, co-pilot, navigator, aerial reconnaissance weather officer and weather reconnaissance loadmaster. (U.S. Air Force photo/Tech. Sgt. Ryan Labadens)

    Odds of Reaching 100% Water Year Precipitation – February Update

    Odds of Reaching 100% of Normal Precipitation for Water Year 2016 in California (February update)

    February 8, 2016

    Contribution from Dr. M.D. Dettinger, USGS

    The January 2016 precipitation observations are now in, and have allowed calculation of the odds of reaching 100% of normal for the water year across three key climate divisions of California. These odds have increased slightly in Northern California, and decreased slightly in Southern California. The previous estimate had been based on observations only through December 2015. The state was affected by a series of storms in January, including atmospheric river events, such as the one highlighted in an earlier CW3E storm summary (see the storm summaries posted on 5, 8 and 15 January 2016 under “What’s New” on the CW3E web page – The odds of reaching 100% of normal Water Year precipitation in the key northern California climate division that encompasses the Sacramento River, and the State’s largest water supply reservoirs, increased from 32% as of the end of December 2015, to 52% as of the end of January 2016.

    Sonoma County Water Agency and CW3E — Monitoring sites expected to improve forecast capability

    Sonoma County Water Agency and CW3E — Monitoring sites expected to improve forecast capability<

    September 2013

    South end of Lake Mendocino; September 2013 (photo by Kent Porter / Press Democrat)

    The Santa Rosa Press Democrat (Sean Scully) published an article: “Weather forecasting a key concern for Sonoma County Water Agency”. CW3E is working with the Sonoma County Water Agency and the Hydrometeorology Testbed (HMT) data to improve forecasts in the region. The data being gathered from HMT will lead to improved forecasting of Atmospheric River (AR) events. These events are significant rain producers in the region and strongly impact how water is managed. Better management would lead to storage that could help prevent extremely low lake levels (as shown at Lake Mendocino above). Please find the full Press Democrat article here.

    Test Beds Linking Research and Forecasting

    Test Beds Linking Research and Forecasting

    September 10, 2013

    TestBeds Linking Research and Forecasting

    A new article written by Marty Ralph and colleagues was recently published in the Bulletin of the American Meteorological Society focusing on the emergence of weather-related test beds. The paper provides a brief background on how these test beds successfully bridged the gap between research and forecasting operations; summarizes test bed origins, methods and selected accomplishments; and provides a perspective on the future of test beds. A personal use copy of the paper can be obtained here.

    Publication Notice: Chemical properties of insoluble precipitation residue particles

    CW3E Publication Notice

    Chemical properties of insoluble precipitation residue particles

    Jessie Creamean posing for a photo while clearing snow from the top of the NOAA trailer at Sugar Pine Dam after the storm on 2/25/11.

    This article provides an in-depth analysis of resuspended residues from precipitation samples collected at a remote site in the Sierra Nevada Mountains in California during the 2009-2011 winter seasons. These residues may be used as a benchmark for classification of insoluble precipitation. Knowledge of the precipitation chemistry of insoluble residues coupled with meteorological and cloud microphysical measurements will ultimately improve our understanding of the link between aerosols, clouds, and precipitation.

    This paper represents a significant milestone from the CalWater experiment, which is led by members of UCSD/Scripps’ new Centers on aerosols (CAICE) and extreme events (CW3E), as well as NOAA, DOE, NASA, USGS. It also highlights the multi-disciplinary research stimulated by CalWater, and the partnerships between key researchers across organizations. The lead author, Jessie Creamean, received her PhD in atmospheric chemistry from UCSD under Kim Prather using CalWater data, and is now bringing that expertise to a primarily meteorological group in NOAA as she pursues emerging topics in aerosol-precipitation interactions in collaboration with CW3E scientists.

    A personal use copy of the article is available here.

    CalWater-ACAPEX 2015 Planning Workshop

    CalWater-ACAPEX 2015 Planning Workshop

    Scripps Institution of Oceanography

    La Jolla, California

    CalWater 2 Co-Leads: Marty Ralph, Kim Prather, Dan Cayan (Scripps)

    Organizing Committee: Chris Fairall (NOAA), Ruby Leung (PNNL), Andrew Martin (Scripps), Ryan Spackman (NOAA/STC)

    CalWater2 – ACAPEX Observational Strategy Winter 2014-15

    CalWater-2 took major steps from vision to reality on 22-24 April 2014 at Scripps Institution of Oceanography when roughly 40 key individuals (scientists, engineers, aircraft and ship managers, and students) met to plan for major field deployments in 2015. The following facilities are committed (or nearly so) to a field campaign between roughly 10 January and 10 March 2015:

    • DOE – G-1 aircraft
    • DOE AMF-2 ocean-atmosphere facility on the NOAA Research Vessel (ship) Ron Brown
    • NOAA G-IV aircraft
    • NOAA P-3 aircraft
    • ATOFMS mobile, land-based aerosol-sensor suite
    • EFREP hydrometeorological Mesonetwork in California

    The DOE facilities are part of the ARM Cloud Aerosol Precipitation Experiment (ACAPEX) experiment addressing (1) aerosol impacts on clouds and precipitation and (2) atmospheric rivers. The NOAA facilities were requested also based on the CalWater vision, with an emphasis on atmospheric-river science questions.

    The workshop concluded with a plan for specific start and end dates for each facility, narrowed options for where to operate them, a plan for a field operations center (and a specific possible location), strategies for developing coordinated ship and aircraft operations, and plans for the forecasting capabilities needed to guide missions. In addition, the 12-member CalWater Core Scientific Steering Group met afterword and reviewed plans for 2016-2018 and strategies to advance the longer term Calwater Vision. The Steering Group committed to organizing two special sessions and a side meeting (for last minute coordinations of the 2015 CalWater and ACAPEX activities) at the Fall Meeting of AGU in December 2014, and a journal article describing the program. The proposed AGU sessions are:

    1. CalWater Theme 1: Cloud-Aerosol-Precipitation Interactions in California (Conveners: Daniel Rosenfeld, Kimberly Prather),
    2. Atmospheric Rivers: Observations, Dynamics, Modeling, Impacts and Applications (Conveners: Marty Ralph, Duane Waliser, Jason Cordeira).

    The presentations from the Workshop are available here.

    Workshop Sponsored by:

    • Scripps, Center for Western Weather and Water Extremes (CW3E)
    • Scripps Center for Aerosol Impacts on Climate and the Environment (CAICE)
    • Science and Technology Corporation (STC)

    Workshop Sponsored by:Workshop Participants

    Photo of most workshop participants at the CalWater 2015 – ACAPEX workshop at Scripps, April 2014.

    CalWater2 Workshop Participants

    Likelihood of Drought Ending, updated

    Drought Recovery by end of Water Year?

    The most recent figures can be found on Mike Dettinger’s web page.

    Drought Recovery Odds

    Updated March 21, 2014

    Researcher Mike Dettinger has updated his analysis examining the likelihood of the California drought ending by the end of the current water year on Sept 30, 2014. This new analysis utilizes the just released February precipitation totals for California’s climatic divisions as well as best guess estimates for March 2014 precipitation. Visit the CW3E Drought Info Page to see updated projections for all seven of California’s climatic divisions.

    Drought Recovery Odds

    February 12, 2014

    CW3E researcher Mike Dettinger was interested in knowing the likelihood of California recovering from the drought by the end of the current water year on Sept 30, 2014. The method he came up with starts with the precipitation deficit from last water year (Oct 2012 – Sept 2013). Observed precipitation for Oct 2013 thru Jan 2014 was used to determine what has been added to this previous water year deficit, depicted in the above figure by the black squares. Here negative precipitation refers to the carryover deficit from the period extending back to October 2012.

    Projections into the future of cumulative precipitation since Oct 2012 were computed by adding observed monthly precipitation from each year in the historical record, 1931-2013, or a total of 83 projections. For each future month (Feb-Sep 2014) the red dots in the above figure represent each of the 83 projections.

    The example shown above is for the Sacramento Drainage region (CA Climate Division 2). For this region, only 2 of the 83 projections make it above the 75%-tile level by the end of Sept 2014. None of the projections show the 24-month cumulative precipitation reaching “normal” levels by the end of this water year.

    Visit the CW3E Drought Info Page to see projections for all seven of California’s climatic divisions.

    Scripps Researchers Take Flight

    Scripps and NOAA Researchers Take Flight to Observe Atmospheric River

    IWV Feb 5-10, 2014

    Integrated Water Vapor GFS Analysis Feb 5-10, 2014.

    Researchers from Scripps Institution of Oceanography at UC San Diego, and NOAA are taking part in research flights to observe a distinctive type of storm system that has historically provided significant precipitation to California.

    Scientists tracked the evolution of “atmospheric rivers,” narrow corridors of strong water vapor transport that can extend thousands of miles, as they made landfall in central California in early February. Atmospheric rivers (ARs), identified by researchers only in recent decades, can provide beneficial water supply and snowpack to the West Coast as well as create conditions for dangerous floods that affect lives and property. NOAA, Scripps, USGS, and other agency/institution researchers, working with water managers for the state, Sonoma County, and elsewhere, are studying them with the goal of providing better information for earlier and more accurate extreme weather forecasts. Scripps and USGS scientists are also looking at how atmospheric rivers may serve as “drought busters” and how climate change may affect atmospheric rivers in future decades.

    Scripps researchers said that the February storms provided some relief, but would likely not reverse the dangerous drought conditions throughout California and the West that have built up over the last three years.

    “Part of the reason for the drought has been the absence of atmospheric river storms hitting the region over the last year,” said Scripps climate researcher Marty Ralph. “From Feb. 7-10, a series of modest strength ARs hit Northern California, including near San Francisco and the northern Sierra where AR conditions stalled for up to 48 hours. These conditions created up to 12-15 inches of rain in three days, including in areas hit by the drought. This was more than double the precipitation in Northern California that had fallen in the first four months of the normal wet season. Nonetheless, the extreme drought has produced such a deficit in water that the soils absorbed much of the precipitation and rivers quickly receded to levels that are again well below normal, even though they reached fairly high levels during the storm.”

    Ralph heads the Center for Western Water and Weather Extremes (CW3E), a new center established at Scripps Oceanography that is devoted to California’s special precipitation characteristics. At the core of the center will be a unique advanced network of monitoring stations throughout the state to help industries and 38 million California residents understand phenomena that affect the economy and everyday life in myriad ways.

    The network, built over the last five years by NOAA and Scripps through support from California’s Department of Water Resources, will initially contain four atmospheric river observatories, monitoring stations located in Northern and central California that measure amounts of water vapor in the atmosphere and other climate variables.

    “NOAA is very interested in improving our forecasts of extreme weather events, and atmospheric rivers rank with hurricanes as a major issue,” said Chris Fairall, chief of the Weather and Climate Physics branch of NOAA’s Earth System Research Laboratory in Boulder, Colo. “The West Coast relies on them for water, but it really is like trying to drink from the proverbial firehose. This new research collaboration on atmospheric rivers with Scripps and UC San Diego is a big step in attacking the problem.”

    For this event, Ralph, Fairall, and colleagues gathered data aboard a NOAA Gulfstream IV aircraft that began flying over the Pacific Ocean off the U.S. West Coast on Feb. 7. During the flights, researchers measured several atmospheric properties at several locations along and across the atmospheric river corridor to better understand key processes, such as where the water vapor sources are and how they are sustained by storm dynamics.

    Aboard the aircraft, researchers released small parachuted devices, called dropsondes, across the atmospheric river over the Pacific Ocean. As they descend, the dropsondes measure atmospheric conditions, such as pressure, temperature, humidity, wind speed and direction, and transmit the information back to the aircraft where a flight scientist uses it to guide the mission. After the dropsonde data are analyzed and processed, the information will be put into a standard format established by the World Meteorological Organization and provided to NOAA’s National Hurricane Center for inclusion in global and local-scale weather prediction models.

    Mike Dettinger, a CW3E team member and research hydrologist with Scripps and the U.S. Geological Survey, noted that atmospheric rivers provide 30 to 50 percent of the precipitation in California and are behind 80 percent of the floodplain inundations along parts of the Central Valley where those inundations are a necessary part of ecosystem food webs and fish nurseries. They figure prominently in the ending of California droughts but also in taxing Northern California levees and other components of the state’s water delivery infrastructure.

    “Thus, better understanding of how atmospheric rivers work and how they may change in the future is critical to better water, floods, and ecosystem management and to plans for adapting to future climate changes,” Dettinger said.

    Jay Jasperse, chief engineer for the Sonoma County Water Agency, which provides water to 600,000 people and many agricultural users, said of the February storms, “although this AR may not be the strongest ever, it is certainly the most welcome.”

    Results from this study will help guide atmospheric river research for the upcoming CalWater 2 experiment, which begins in 2015 and will use land-based stations and a research ship as well as multiple aircraft.