Odds of Reaching 100% of Normal Precipitation for Water Year 2018 (December Update)
December 8, 2017
Contribution from Dr. M.D. Dettinger, USGS
The odds shown here are the odds of precipitation in the rest of the water year (after November 2017) totaling a large enough amount to bring the water-year total to equal or exceed the percentage of normal listed. “All Yrs” odds based on monthly divisional precipitation totals from water year 1896-2015. Numbers in parenthesis are the corresponding odds if precipitation through March had been precisely normal (1981-2010 baseline).
Click here for a pdf file of this information.
How these probabilities were estimated:
At the end of a given month, if we know how much precipitation has fallen to date (in the water year), the amount of precipitation that will be required to close out the water year (on Sept 30) with a water-year total equal to the long-term normal is just that normal amount minus the amount received to date. Thus the odds of reaching normal by the end of the water year are just the odds of precipitation during the remaining of the year equaling or exceeding that remaining amount.
To arrive at the probabilities shown, the precipitation totals for the remaining months of the water year were tabulated in the long-term historical record and the number of years in which that precipitation total equaled or exceeded the amount still needed to reach normal were counted. The fraction of years that at least reached that threshold is the probability estimate. This simple calculation was performed for a full range of possible starting months (from November thru September) and for a wide range of initial (year-to-date) precipitation conditions. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, and 150%, to ensure that the resulting tables of probabilities cover almost the full range of situations that will come up in the future.
[One key simplifying assumption goes into estimating the probabilities this way: The assumption that the amount of precipitation that will fall in the remainder of a water year does not depend on the amount that has already fallen in that water year to date. This assumption was tested for each month of the year by correlating historical year-to-date amounts with the remainder-of-the-year amounts, and the resulting correlations were never statistically significantly different from zero, except possibly when the beginning month is March, for which there is a small positive correlation between Oct-Mar and Apr-Sept precipitation historically.]
Contact: Michael Dettinger (USGS)
Lake Mendocino Forecast Informed Reservoir Operations Steering Committee Submit Major Deviation Request
November 15, 2017
On November 2nd members of the Lake Mendocino Forecast Informed Reservoir Operations (FIRO) Steering Committee1 submitted a major deviation request to Lt. Colonel Travis Rayfield, Commander of the San Francisco District, US Army Corps of Engineers. The purpose of the request is to improve water supply reliability and environmental conditions while maintaining flood management capacity of Lake Mendocino.
The deviation request, based on the Lake Mendocino FIRO Preliminary Viability Assessment, represents the culmination of a three-year collaborative effort by the FIRO Steering Committee to produce a significant body of technical and scientific work including watershed and atmospheric observations, atmospheric and hydrologic forecast analyses, and parallel modeling applications. If approved, this deviation would result in a maximum additional storage of 11,650 acre-feet between November 1 and February 28. The figure below shows the existing guide curve for the Coyote Valley Dam Lake Mendocino Water Control Manual and the proposed guide curve with the requested changes.
Existing Lake Mendocino guide curve (red dashed line) and the proposed guide curve with requested changes (blue solid line).
1 The Lake Mendocino FIRO Steering Committee consists of representatives from the Sonoma County Water Agency (SCWA), Scripps Institute of Oceanography (Scripps), U.S. Army Corps of Engineers (USACE), National Oceanic and Atmospheric Administration (NOAA), U.S. Geologic Survey (USGS), U.S. Bureau of Reclamation and the California Department of Water Resources. This deviation request is being submitted on behalf of steering committee members representing the following organizations: Sonoma County Water Agency, Scripps Institution of Oceanography, US Army Corps of Engineers, National Oceanic and Atmospheric Administration, and California Department of Water Resources.
CW3E Hosts California DWR Winter Outlook Workshop
November 6, 2017
CW3E hosted the annual California Department of Water Resources Winter Outlook Workshop (WOW) from Nov. 1-3, at Scripps Institution of Oceanography. The purpose of the workshop is to highlight the latest science in seasonal to subseasonal (S2S), 1-month to 3-month, atmospheric forecasting. This timescale bridges the gap between weather and climate prediction. The meeting was organized by Jeanine Jones, Interstate Resources Manager, and covered a variety of topics including paleoclimate, week three predictions, atmospheric rivers (ARs), summer North American monsoon, new forecasting tools, and drought.
During the first day, Dave Meko, from University of Arizona, discussed paleodrought in Southern California and how this compared to paleodrought in Northern California and in the Colorado River Basin. The second day of the workshop highlighted recent accomplishments in subseasonal to seasonal forecasting. Dr. David DeWitt, NCEP CPC Director, presented on the S2S activities on-going at the National Weather Service (NWS) Climate Prediction Center (CPC). Dr. Marty Ralph, Director of CW3E, gave an overview of the activities at CW3E related to observations, modeling and S2S prediction ARs. This was followed by a session chaired by Dr. Duane Waliser and Dr. Aneesh Subramanian on current S2S activities at CW3E and an experimental CW3E week-3 AR outlook product. The session had three talks presented by Dr. Alexander Gershunov, Dr. Michael DeFlorio, and Dr. Aneesh Subramanian on the experimental CW3E week-3 AR outlooks and the multi-pronged effort to design and evaluate the product. The day ended with presentation by Yolande Serra, from the University of Washington, on the dynamics and predictability of the summer monsoon. The third and final day began with a presentation on the influence of ARs in the Colorado River Basin as well an historical perspective on atmospheric river maps by Jon Rutz, National Weather Service. The last presentation of the day was by Dan Cayan on how various atmospheric patterns can lead to drought in the western U.S. WOW provided an opportunity for CW3E researchers and collaborators to share their latest advancements in subseasonal to seasonal forecasting and discuss future research collaboration and needs.
CW3E Director, Marty Ralph, discusses the research and activities at CW3E during the DWR WOW.
During the workshop Jeanine Jones also presented Department of Water Resources Climate Service Awards to Dr. Jason Cordeira, Plymouth State University, Dr. Duane Waliser, NASA JPL and Dr. Dave Meko, University of Arizona. The awards highlight the three individuals’ contribution to climate science as it applies to DWR operations. Jason Cordiera, a close collaborator of CW3E spoke of the honor, “My collaboration with CW3E has led to the synergistic development of many weather forecast tools that have benefited and informed water resource management and related impact-based decision support. Receipt of the CA DWR Climate Science Service Award reflects the dedication of many individuals at CW3E and Plymouth State who support and provide invaluable resources to maintain a productive research and application environment. Thank you to the CA DWR for the honor and I look forward to continued collaboration in pursuit of improving our ability to understand and forecast hydrological extremes”.
Recipients of the Department of Water Resources Climate Service Awards, presented at the WOW. From left, Dr. Duane Waliser, NASA JPL, Dr. Dave Meko, University of Arizona, and Dr. Jason Cordeira, Plymouth State University.
FIRO Steering Committee Co-Chairs Provide In-depth Briefing to USACE
November 2, 2017
FIRO Steering Committee Co-chairs, Marty Ralph and Jay Jasperse, as well as Steering Committee member Cary Talbot (USACE Engineer Research and Development Center), provided an in-depth briefing to the US Army Corps of Engineers (USACE), South Pacific Division Commanders, at the Regional Management Board meeting on October 24 in Sacramento, CA. The presentation included findings from the Lake Mendocino Preliminary Viability Assessment and the scientific research that is informing the Viability Assessment. The group discussed transferability of FIRO and next steps for completion of the Final Viability Assessment.
Photo from a briefing on FIRO for the US Army Corps of Engineers (USACE), South Pacific Division Commanders, at the Regional Management Board meeting on October 24 in Sacramento. .
CW3E, UCAR, and NCAR Meet to Discuss West-WRF Regional Model Development
October 9, 2017
On 4-5 October 2017, CW3E had the privilege of hosting visitors from NCAR and UCAR to discuss the development and implementation of West-WRF, the regional forecast model that CW3E is developing focusing on extreme precipitation. The team from UCAR and NCAR included Bill Kuo, the director of UCAR Community Programs, who also helped lead the development of WRF. Chris Davis, NCAR associate director and leader of the Mesoscale and Microscale Meteorology (MMM) Laboratory also attended, along with, David Gill, Jake Liu, and Wei Wang, WRF experts in computation, data assimilation, and modeling, respectively.
The first day of the two day visit began with CW3E director, Marty Ralph, briefing the NCAR/UCAR visitors on CW3E, and how West-WRF supports the mission and goals of the center. After this introduction, CW3E researchers and staff had the opportunity to learn about best practices with respect to WRF computation, modeling, and data assimilation, as well as the new MPAS modeling system. The entire CW3E group had lunch with the NCAR/UCAR visitors and had a chance to hear all the CW3E updates including on AR reconnaissance, publications, and instrument deployments.
After lunch, the CW3E West-WRF team shared the current applications and status of the West-WRF development with the UCAR/NCAR team. The afternoon ended with Bill Kuo giving the CASPO seminar on assessment of the impacts of assimilation of COSMIC radio occultation measurements in typhoon forecasts. The second day of the visit, allowed for detailed discussions on many of the technical aspects of West-WRF development and applications. The UCAR/NCAR team provided recommendations to the CW3E researches and staff on ways to improve the implantation of West-WRF as well as design experiments. In addition the groups discussed ways for the CW3E team to provide feedback in the WRF development at NCAR/UCAR through sharing new code for verification metrics and scientific and technical advancements made through recent experiments. The meeting was a very productive initial collaboration between CW3E and UCAR/NCAR and we are looking forward to many more. The engagement of UCAR and NCAR in supporting one of its member institutions technical development efforts is greatly appreciated.
CW3E Publication Notice
The Chiricahua Gap and the Role of Easterly Water Vapor Transport in Southeastern Arizona Monsoon Precipitation
Spetember 13, 2017
Click here for personal use pdf file
This study is a collaborative effort between CW3E and University of Arizona that identifies a terrain feature along the Arizona-New Mexico border just north of Mexico that is potentially important to the weather and climate of the southeast Arizona summer monsoon. The terrain feature is a “gap” that is approximately 250 km across and 1 km deep and represents the lowest terrain elevation along the 3000-km length the Continental Divide from 16-45°N. The name “Chiricahua Gap” is introduced to identify this key terrain feature, which reflects the name of a nearby mountain range in southeast Arizona and the region’s Native American history. The importance of the Chiricahua Gap is that it represents the primary pathway in which low altitude atmospheric water vapor is transported across the Continental Divide.
Motivated by identification of the Chiricahua Gap, upper-air observations from a wind profiling radar in Tucson, model reanalyses (Climate Forecast System Reanalysis), and gridded daily precipitation data (NCEP Stage-IV) are used to construct a case study and 15-year climatology to link summer monsoon rainfall events in southeast Arizona to low-altitude water vapor transport within the Chiricahua Gap. The results show that 76% of the wettest summer monsoon days in southeast Arizona during 2002-2016 occurred in conditions of low-altitude easterly water vapor transport in the Chiricahua Gap on the previous day. This result highlights how low-altitude water vapor associated with the wettest summer monsoon days in southeast Arizona originates from the east side of the Continental Divide, which differs from previous studies published since the 1970s. Much of the recent scientific literature points to southwesterly surges of low-altitude water vapor from over the Gulf of California as the primary driver of rainfall over southern Arizona during the summer monsoon. The current study by F. M. Ralph and T. J. Galarneau shows that the source region of low-altitude water vapor in southeast Arizona during the summer monsoon is potentially more complex, and is significantly influenced by source regions east of the Divide.
The paper is an example of CW3E expanding its research to examine the dynamics of the North American monsoon. Because monsoon is an important source or water for the US southwest and can cause flooding events, particularly flash floods, better understanding and improving forecasts of the North American monsoon is and important component of CW3E achieving its goal of revolutionizing the physical understanding, observations, weather predictions, of extreme events in Western North America and their impacts on floods, droughts, hydropower, ecosystems and the economy.
Figure 1: Terrain height (shaded in m) over Arizona, New Mexico, western Texas, and northern Mexico. Key terrain features are labeled in black. The location of Tucson, Arizona, is labeled by the black-filled circle. Low-altitude easterly water vapor transport through the Chiricahua Gap is shown by the blue arrows. This figure is modified from Fig. 1b in Ralph and Galarneau (2017).
CW3E Field Team Beats the Heat, Installs Meteorology and Hydrology Instruments in Russian River Watershed
September 6, 2017
A group of CW3E graduate students, postdocs, and staff worked to install soil moisture, meteorology, and streamflow instruments in the Lake Mendocino watershed August 28 – September 1. Taking extra precautions and shifting work schedules due to California’s triple-digit heat wave, the team installed three soil moisture and surface meteorology arrays and a stream gauge on ranchlands representative of the hilly topography draining into Lake Mendocino. CW3E thanks the landowners who have volunteered to have instruments installed on their properties, as well as Steve Turnbull of the U.S. Army Corps of Engineers for participating in the installations. Two more soil moisture and meteorology arrays and three more stream gauges are planned to be installed in the watershed prior to the 2017-18 AR season for a total of six soil moisture and meteorology arrays and six stream gauges. The data from these sites will be used to better understand AR meteorological and hydrologic impacts in this region and improve streamflow forecasts on the Russian River.
The field team after completion of the Potter Valley North site: Lindsey Jasperse, Steve Turnbull, Will Chapman, Maryam Asgari-Lamjiri, Douglas Alden, Anna Wilson and Xin Zhang. Not pictured: Julie Kalansky and Brian Henn
Sonoma County Water Agency Board of Directors Chairwoman, Zane, testifies on FIRO before Senate Committee
August 2, 2017
CW3E works closely with Sonoma County Water Agency (SCWA) on the application of atmospheric river science to inform water management practices in the Russian River. SCWA and CW3E are leaders on the Forecast Informed Reservoir Operations (FIRO) project. FIRO is a proposed management strategy that uses data from watershed monitoring and modern weather and water forecasting to help water managers selectively retain or release water from reservoirs in a manner that reflects current and forecasted conditions. FIRO is being developed and tested as a collaborative effort focused on Lake Mendocino that engages experts in civil engineering, hydrology, meteorology, biology, economics and climate from several federal, state and local agencies, universities and others.
Shirlee Zane, SCWA Board of Directors Chairwoman, today testified before the Senate Committee on Energy and Natural Resources’ Subcommittee on Water and Power to discuss the many innovative water supply and drought resilience initiatives the Water Agency is currently implementing, including FIRO. The purpose of the hearing was to examine increasing water security and drought preparedness through infrastructure, management and innovation.
“I was honored to testify and share with the committee the innovative water supply management tools the Sonoma County Water Agency is developing and implementing,” said Sonoma County Water Agency Chairwoman Shirlee Zane. “Securing our water future means thinking outside of the box and not being afraid to lead by example. That is exactly what the Water Agency continues to do as we develop first-class initiatives with our partners. Our investment in water innovation can be replicated across the nation. I am excited to share our experiences to help build innovation in the water industry.” Zane highlighted FIRO, amongst the many innovative water management programs the Water Agency is currently implementing.
For more information on FIRO: Click here
For video of the briefing click here.
CW3E welcomes Dr. Liza Díaz-Issac
June 19, 2017
Dr. Liza Díaz-Issac has joined CW3E at the Scripps Institution of Oceanography as a Postdoctoral Scholar in April 2017. Liza earned her Ph.D. in Meteorology at The Pennsylvania State University under the direction of Dr. Kenneth J. Davis and Dr. Thomas Lauvaux. Her dissertation was focused on evaluating the impact of atmospheric transport errors on both CO2 concentrations and meteorological variables over the Midwestern United States, using an ensemble of different simulations developed with the Weather Research and Forecasting (WRF) model. Her work helped to identify the different physical processes, such as land-surface, planetary boundary layer and convection, that are responsible for the transport errors on CO2 . In addition, she was able to generate an ensemble that efficiently represented transport errors using a smaller number of member models. Her research will help to improve transport model error estimates to support more accurate estimates of greenhouse gas emissions. She is excited to work with her colleagues at CW3E in the Megacities Project in collaboration with Dr. Ralph Keeling and other partner organizations to improve the estimates of carbon emissions over the city of Los Angeles (LA). In her new position, she will evaluate the atmospheric transport errors over the city of LA and how these errors may influence the estimates of the greenhouse gases emissions over LA; especially, under challenging weather scenarios (e.g., Catalina Eddy, Santa Ana winds).
CW3E AR Update: 05 June 2017 Outlook
June 05, 2017
Click here for a pdf of this information.
Late Season AR Forecast to Impact West Coast
- An unseasonably strong AR is forecast to impact the Pacific Northwest and Northern CA over the next couple of days
- As much as 4.1 inches of precipitation is forecast to fall over the higher elevations of the Coastal Mountains in CA and OR over the next week
- With higher freezing levels forecast during landfall, there is a potential for rain on snow and increased runoff
- Due to the combination of snowmelt and the landfalling AR, several rivers in the Pacific Northwest are forecast to rise above flood stage
Click IVT or IWV image to see loop of 0-114 hour GFS forecast
Valid 1200 UTC 05 June – 0600 UTC 10 June 2017
Summary provided by C. Hecht and F.M. Ralph; 1 PM PT Monday 05 June 2017