Author: cw3e-web

CW3E AR Update: 4-9 November 2016 Outlook

CW3E AR Update: 4-9 November 2016 Post Event Summary

November 4, 2016

Two consecutive ARs are expected to make landfall over the Northwest U.S. and Southwest British Columbia. Current forecasts show both ARs with moderate strength, although there is high uncertainty in the forecast of the second AR. Despite high values of integrated vapor transport (IVT) forecasted precipitation values of the Northwest U.S. are modest due to the southwesterly orientation of the ARs. However, this orientation is favorable for precipitation production over Vancouver Island, where 5-day precipitation forecasts are >12 inches. For up to date AR forecasts visit the CW3E AR Portal.

Click here for a pdf file of this information.


 

 

Summary provided by C. Hecht, B. Kawzenuk, and F.M. Ralph; 3 PM PT Fri 05 Nov. 2016

CW3E AR Update: Post-Event Summary: 14-17 October 2016

CW3E AR Update: 14-17 October 2016 Post-Event Summary

October 20, 2016

CW3E gives a post-event storm summary about two Atmospheric Rivers that made landfall over the Pacific Northwest during 14-17 October 2016. This event was an R-Cat 3 event and produced over 15 inches of 72-hour precipitation.

Click here for a pdf file of this information.

NCEP GFS Analysis – Valid: 0000 UTC 12 Oct 2016 – 0600 UTC 17 Oct 2016

 

NEXRAD Radar: 0000 UTC 14-17 Oct 2016

  • Radar imagery shows widespread precipitation over the Pacific Northwest during 14-17 Oct 2016
  • Severe convection on 14 Oct produced multiple tornadoes in OR and high winds across the region
  • Throughout the period the PNW was impacted by several alternating periods of stratiform and convective precipiation


 

 

 

 

 

 

 

 

 

CW3E AR Update: 13-15 October 2016 Outlook

CW3E AR Update: 13-15 October 2016 Outlook

October 12, 2016

A series of ARs are expected to make landfall over the Northwest U.S., including Northern CA. The first AR is expected to make landfall on 13 October 2016 followed by a second AR on 15 October 2016. These systems have R-Cat 2 rainfall potential as some areas could see >12 inches of precipitation in 72 hours. For up to date AR forecasts visit the CW3E AR Portal.

Click here for a pdf file of this information.


 

 

CW3E Represented at NWS San Diego’s WeatherFest 2016

CW3E Represented at NWS San Diego’s WeatherFest 2016

September 22, 2016

Dr. Anna Wilson explaining how weather looks from a satellite’s point of view at WeatherFest 2016

CW3E’s Rachel Weihs and Anna Wilson were on hand at the annual WeatherFest event hosted by the local National Weather Service office in San Diego, CA on September 17th, 2016. WeatherFest is presented by the Young Meteorologist Program and serves as an outreach event informing the general public on weather preparedness, safety, research, and education.

Over 600 local weather enthusiasts attended this year’s WeatherFest where they were able to interact with representatives of the National Weather Service, first responders, research institutions, and local newscasters while enjoying games, viewing demonstrations, and gathering information.

Dr. Rachel Weihs (left) and Dr. Anna Wilson (right) discussing CW3E’s Research with the publc.

The CW3E booth showcased the ongoing research into atmospheric river (AR) events with emphasis on the major contribution of ARs to California’s annual precipitation and their associated impacts on the management of water resources, reservoir flood risk, and drought. Attendees learned about the term “Atmospheric River” by viewing satellite animations of the associated clouds and precipitation during an AR event in December 2014 and referencing the narrow river-like transport of moisture from the tropics using SSMI visualizations. The CW3E booth featured a fully-functioning weather station with state-of-the-art research quality instruments feeding live data into a computer for viewing. They also provided interactive demonstrations and graphical information highlighting the importance of California’s topography and the influence of orographic lift on the spatial distribution of precipitation. Adult attendees enjoyed comparing the weather instruments on display to those they had at home, talking about storms they had experienced during their lifetimes, and viewing the satellite animations. Kids enjoyed the diorama of the California coastline and simulating rainfall with the tipping bucket rain gauge on the weather station. Through these activities, attendees were able to gain a better understanding of ARs and their impact on daily life.

Dr. Rachel Weihs and James Taeger, General Forecaster at the San Diego NWS office, at the CW3E booth

Contact: Anna Wilson (anna-m-wilson@ucsd.edu) and Rachel Weihs (rweihs@ucsd.edu)

CW3E Welcomes Dr. Rachel Weihs

CW3E welcomes Dr. Rachel Weihs

August 8, 2016

Dr. Rachel Weihs started at CW3E in August 2016 as a Postdoctoral Scholar. Rachel earned her Ph.D. in Meteorology at Florida State University in Tallahassee, Florida under the direction of Dr. Mark Bourassa. Her dissertation focused on understanding the role of high frequency variability of sea surface temperatures on the near-surface winds and atmospheric boundary layer as produced by the Weather Research and Forecasting model. In addition, she was able to quantify the relative impact of the local diurnal variability of sea surface temperatures on regional weather and deduce the importance of two-way air-sea feedback processes on the magnitude of diurnal heating in the upper ocean in the extratropical Atlantic. She is excited to have joined the CW3E team in August 2016 to study the influences of the Pacific Ocean on the forecasting of atmospheric rivers as well as examining the role of air-sea interaction on the boundary layer and the low level jet associated with these important weather phenomena.

CW3E Welcomes Dr. Brian Henn

CW3E welcomes Dr. Brian Henn

August 8, 2016

Dr. Brian Henn started at CW3E in August 2016 as a Postdoctoral Scholar. He is a native of Northern California and received undergraduate and master’s degrees from Princeton and Stanford in civil and environmental engineering. With interests in hydrology, water resources and infrastructure, he worked as an engineer on urban stormwater and sustainability projects at Hazen and Sawyer in New York City. Brian pursued doctoral studies at the University of Washington in the research group of Dr. Jessica Lundquist, receiving his Ph.D. in 2015. His dissertation used streamflow observations and novel modeling techniques to better understand orographic precipitation patterns over the Sierra Nevada mountain range. He is also a licensed civil engineer in California.
He is interested in better representing the heavy precipitation associated with Atmospheric Rivers making landfall over mountainous terrain. He looks forward to working with CW3E colleagues on understanding and predicting these events, which are crucial to the water supplies of the Western United States. He is also looking forward to sampling the best of San Diego’s many breweries and exploring Southern California’s mountains and trails.

IARC 2016

The First International Conference on Atmospheric Rivers (IARC) is Being Hosted by the Center for Wester Weather and Water Extremes (CW3E) at the Scripps Seaside Forum from 8-11 August 2016

August 8, 2016

IARC is part of a multi-year effort led by CW3E’s Director F. Martin Ralph, Mike Dettinger of USGS and David Lavers of ECMWF to foster collaboration and exchange of ideas on atmospheric rivers (AR).

  • The first event was held in June 2015 and brought together about 30 key individuals in a workshop, with a special emphasis on identifying the relationships between ARs, warm conveyor belts, and tropical moisture exports, all phenomena involving horizontal water vapor transport. A brief workshop synopsis is available in EOS (Dettinger et al. 2015) and here. Two main directions emerged:
    • 1) agreement that it was time to develop a comprehensive monograph on ARs, and
    • 2) an atmospheric river focused conference should be organized.
  • The second event in this 3-year effort is the 2016 IARC conference held from 8-11 August (described below; agenda).
  • The third event is a summer colloquium intended for summer 2017 at Scripps. It is intended to bring together at Scripps authors of the AR Monograph Book Chapters and graduate students from around the world for roughly 3 weeks of lectures and mentored mini-research efforts.

Woven through this series of events over 3 years is the development of the AR Monograph, which has been funded by a grant, including publication by University of California Press. IARC brings together most of the Chapter authors, at a point in the writing where new ideas garnered during the conference can be incorporated into the Monograph. The goal is then to have the Monograph finalized and in print for the AR Summer Colloquium. A technical editor, Lauren Muscatine (and her experienced team from UC Davis), is supporting preparation of the Monograph.

IARC received 75 abstracts from people around the world studying ARs, their impacts and applications of AR information to decision making. Submissions represent work on 6 continents plus Greenland. It has been planned by an international steering committee of experts on the subject. 90 people have registered for the conference, which will include several invited presentations, oral sessions, a poster session, panels on “applications to decision making,” “converging on a definition of atmospheric rivers” and on “future directions.” Breakout sessions will be held on “AR Forecasting,” “AR Book Chapters” and on “ARs in future climates and subseasonal to seasonal prediction.”

Sessions are organized around the following themes, which represent sections in the AR Monograph:

  • AR Applications
  • Global and Regional Perspectives
  • Observing and detecting ARs
  • Impacts of ARs
  • Theory, Structure and Processes
  • Modeling methodologies

Contact: F. Martin Ralph (mralph@ucsd.edu)

Publication Notice: Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet

CW3E Publication Notice

Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet

July 18, 2016

Ralph, F.M., J.M. Cordeira, P.J. Neiman and M. Hughes, 2016: Extreme Daily Precipitation in the Northern California Upper Sacramento River Watershed Requires a Combination of a Landfalling Atmospheric River and a Sierra Barrier Jet. J. Hydrometeor., 17, 1904-1915.

The top 0.3% most extreme daily precipitation events in the key Sacramento River watershed all involved both a landfalling atmospheric river and a Sierra Barrier Jet. Thus, forecasts of extreme precipitation are related to the skill of forecasts of each of these key phenomena, and can be enhanced by evaluation of, and enhancement of, skill in predicting each of these key processes. This study was led by the CW3E Director, was supported by the California Department of Water Resources, used data from NOAA’s Hydrometeorology Testbed collected over a decade, and epitomizes the focus of the “Center for Western Weather and Water Extremes,” and its partnership with NOAA Research’s Physical Sciences Division and Plymouth State University.

Contact: F. Martin Ralph (mralph@ucsd.edu)

Abstract

The upper Sacramento River watershed is vital to California’s water supply and is susceptible to major floods. Orographic precipitation in this complex terrain involves both atmospheric rivers (ARs) and the Sierra barrier jet (SBJ). The south-southeasterly SBJ induces orographic precipitation along south-facing slopes in the Mt. Shasta–Trinity Alps, whereas landfalling ARs ascend up and over the statically stable SBJ and induce orographic precipitation along west-facing slopes in the northern Sierra Nevada. This paper explores the occurrence of extreme daily precipitation (EDP) in this region in association with landfalling ARs and the SBJ. The 50 wettest days (i.e., days with EDP) for water years (WYs) 2002–11 based on the average of daily precipitation from eight rain gauges known as the Northern Sierra 8-Station Index (NS8I) are compared to dates from an SSM/I satellite-based landfalling AR-detection method and dates with SBJ events identified from nearby wind profiler data. These 50 days with EDP accounted for 20% of all precipitation during the 10-WY period, or 5 days with EDP per year on average account for one-fifth of WY precipitation. In summary, 46 of 50 (92%) days with EDP are associated with landfalling ARs on either the day before or the day of precipitation, whereas 45 of 50 (90%) days with EDP are associated with SBJ conditions on the day of EDP. Forty-one of 50 (82%) days with EDP are associated with both a landfalling AR and an SBJ. The top 10 days with EDP were all associated with both a landfalling AR and an SBJ.

Lake Mendocino Forecast-Informed Reservoir Operations (FIRO) Workshop Summary

Lake Mendocino Forecast-Informed Reservoir Operations (FIRO) Workshop Summary

July 5, 2016

Experts from multiple disciplines and organizations came together for the third annual FIRO workshop, which was held at UC San Diego/Scripps Institution of Oceanography (SIO) from 27-29 June 2016. This workshop was hosted jointly by the Sonoma County Water Agency (SCWA) and SIO’s Center for Western Weather and Water Extremes (CW3E). It was organized by the FIRO Steering Committee, co-chaired by CW3E’s Marty Ralph and SCWA’s Jay Jasperse. There were a total of 52 attendees from organizations including the US Army Corps of Engineers (USACE), California Department of Water Resources (CA DWR), National Oceanic and Atmospheric Administration (NOAA), US Geological Survey (USGS), US Bureau of Reclamation (USBR), SCWA and CW3E.

During the workshop, participants shared recent updates on FIRO activities, discussed reservoir conditions during water year 2016, summarized progress toward goals identified in the FIRO Workplan and identified issues to address regarding development of the Lake Mendocino FIRO “Preliminary Viability Assessment.” Progress was summarized on defining FIRO information requirements (e.g., forecast parameters and lead times), assessing current forecast skill, exploring the origins of forecast errors, advances in atmospheric river science, results of preliminary estimates of FIRO implications on Lake Mendocino water supply, and discussion of potential additional reservoirs for which FIRO may hold promise. Individual task groups (Preliminary Viability Assessment, Science, and Communications/Outreach) conducted break-out sessions in order to discuss progress and next steps towards meeting project goals (see photos below). In addition, the 11-member Lake Mendocino FIRO Steering Committee met afterward to review the workshop outcomes and plans. In short, the initial goals of year-1 of the 5-year FIRO Workplan are on track to be met, including development of the Preliminary Viability Assessment. Longer-term actions supporting the Full Viability Assessment are beginning and transferability is being discussed.

Lake Mendocino FIRO is summarized at /firo/.

Contacts: F. Martin Ralph (CW3E Director; mralph@ucsd.edu) and J. Jasperse (SCWA Chief Engineer; Jay.Jasperse@scwa.ca.gov)