CW3E, UCAR, and NCAR Meet to Discuss West-WRF Regional Model Development

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

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

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

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 Diaz-Issac

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

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

Atmospheric Rivers: Recent Developments and Applications in California

Atmospheric Rivers: Recent Developments and Applications in California

May 19, 2017

In Sacramento on Tuesday, May 23rd, CW3E director, F. Martin Ralph will be presenting a seminar about atmospheric rivers and their impacts to California legislative and agency staff. The seminar, Atmospheric Rivers: Recent Developments and Applications in California, will provide updates on the impacts of ARs on the current water year and the ongoing research to better understand and better forecast ARs. Dr. Ralph is looking forward to sharing all of the exciting research being done at CW3E with the group.

May 31 – June 2 Big Data and The Earth Sciences: Grand Challenges Workshop

May 31 – June 2 Big Data and The Earth Sciences: Grand Challenges Workshop

April 17, 2017

Abstract deadline extended to April 21st

The Center for Western Weather and Water Extremes (CW3E) of UC San Diego’s Scripps Institution of Oceanography and the Pacific Research Platform (PRP) is excited to announce the organization of a workshop focused on earth sciences and information technology at the University of California San Diego. The workshop is a three-day Grand Challenges workshop May 31 to June 2 in La Jolla, Calif., on the topic of “Big Data and the Earth Sciences”.

CW3E is focused on advancing science and technology to support the unique information needs related to western U.S. extreme weather and water events, such as California’s recent flooding and multi-year drought and associated potential for subseasonal-to-seasonal forecasting. PRP is a consortium of universities in the western U.S. that is building a “science-driven, high-capacity data-centric freeway system on a large regional scale.” Funded by the National Science Foundation, PRP is based in the California Institute for Telecommunications and Information Technology (Calit2), a partnership of UC San Diego and UC Irvine. The workshop will take place in UC San Diego’s Atkinson Hall, headquarters of the Qualcomm Institute (the UCSD division of Calit2).

The goal of the The Big Data and Earth Sciences: Grand Challenges Workshop is to bring thought leaders in Big Data and Earth Sciences together for a three day, intensive workshop to discuss what is needed to advance our understanding and predictability of the Earth systems and to highlight key technological advances and methods that are readily available or in the final stages of development.

Sessions will include:

  • Big data collaborations;
  • Big data research platforms, networks, technologies and visualization;
  • Big data and predictability challenges in earth science data;
  • Pattern detection, segmentation and object recognition for earth sciences;
  • Structuring unstructured data in the earth sciences; as well as
  • Data mining and discovery, machine learning and predictive modeling.

For more information please visit:


Official workshop website:

Please send abstracts to

Abstracts are restricted to one page. Please include the abstract title, authors’ names and affiliations. A word document or .pdf is preferred.

CW3E Publication Notice: High-Impact Hydrologic Events and Atmospheric Rivers in California: An Investigation using the NCEI Storm Events Database

CW3E Publication Notice

High-Impact Hydrologic Events and Atmospheric Rivers in California: An Investigation using the NCEI Storm Events Database

April 12, 2017

Two 2016 graduates of the M.S. Applied Meteorology program at Plymouth State University, Klint Skelly (May 2016) and Allison Young (December 2016) advised by CW3E Affiliate Dr. Jason Cordeira, worked collectively on understanding the fraction of floods, flash floods, and debris flows (termed high-impact hydrologic events, or HIHEs) that are associated with landfalling ARs in California.

The HIHE–AR relationship was studied over a 10-water year period from Oct 2004 through Sep 2014 with HIHE reports obtained from the National Centers for Environmental Information (NCEI) Storm Events Database and AR dates obtained from a catalog of landfalling ARs from Rutz et al. (2013). Some detailed results are provided below. More information is contained in a manuscript that was recently published in the AGU Geophysical Research Letters: Young, A. M., K. T Skelly, and J. M. Cordeira, 2017: High-Impact Hydrologic Events and Atmospheric Rivers in California: An Investigation using the NCEI Storm Events Database. Geophys. Res. Lett., 44, doi:10.1002/2017GL073077. click here for personal use pdf file

Key Results: A total of 1,415 HIHE reports in California during the 10-year period of study reduced to 580 HIHE days across the different National Weather Service County Warning Areas (CWAs). A large majority (82.9%) of HIHE days occur over southern California; however, a larger fraction of HIHEs are associated with landfalling ARs across northern California (80.8%) as compared to southern California (41.8%). The 580 HIHE days across the different CWAs, when combined, reduced to 364 unique HIHE days for the state of California. A larger number of HIHE days statewide occur during summer (57.1%) as compared to winter (42.9%). Conversely, a larger fraction of HIHE days associated with ARs occur in winter (78.2%) as compared to summer (25.0%), which corresponds to similar values obtained by Neiman et al., (2008) and Ralph and Dettinger (2012).

Figure caption: Total number of HIHE days per (a) CWA and (b–d) month for (b) all of California, (c) northern California, and (d) southern California. The blue bars and denominator represent the total number of HIHE days, whereas the white hatched bars and numerator represent the total number of HIHE days associated with ARs.

The 580 HIHE days across different CWAs, when combined by region, reduced to 88 unique HIHE days for northern California and 301 unique HIHE days for southern California. A larger number of HIHE days across northern California occur during winter (62.5%) as compared to summer (37.5%), whereas a larger number of HIHE days across southern California occur during summer (60.8%) as compared to winter (39.2%). The fraction of these HIHE days that are associated with ARs is higher over northern California (63.6%) as compared to southern California (39.2%).

This study illustrated that HIHE days contained within the NCEI Storm Events Database for CWAs across California can be attributed to landfalling ARs and their associated precipitation extremes. This attribution is largely valid for HIHE days across northern California in the cold season and not necessarily valid for HIHE days across southern California during the warm season. Approximately 57% of all HIHE days in California occurred during the warm-season, mostly in conjunction with flash floods, and 75% of these HIHE days were not associated with ARs. The composite analysis of flash flood days across California illustrated the climatological warm-season flow pattern for precipitation across southern California and closely resembled the type-IV monsoon synoptic pattern as defined by Maddox et al. (1980). This result motivates additional future work that could focus on the role of the North American monsoon and other non-AR processes that produce HIHEs across California.

Support for this project was provided by the State of California-Department of Water Resources and the U.S. Army Corps of Engineers, both as part of broader projects led by CW3E. Dr. Cordeira and his graduate students at Plymouth State University actively collaborate with CW3E on topics related to atmospheric rivers, such as analyzing, understanding, and forecasting their impacts along the U.S. West Coast.

Odds of Reaching 100% Water Year Precipitation – Apr Update

Odds of Reaching 100% of Normal Precipitation for Water Year 2017 (April Update)

April 6, 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 March 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)