Author: cw3e-web

CW3E Welcomes Dr. Suma Bhanu Battula

CW3E Welcomes Dr. Suma Bhanu Battula

March 6, 2023

Suma joined CW3E as a research associate on Feb 1, 2023. She has an Integrated M.S in Physics from Indian Institute of Technology Roorkee (2016). She earned a joint-degree Ph.D. from Department of Civil Engineering in Indian Institute of Technology Bombay and School of Earth, Atmosphere and Environment in Monash University, Australia (2023). Her PhD is on investigation of multiscale processes of orographic precipitation in the Western Himalayas (WH) in India. She developed a framework to obtain distinct precipitation regimes for the WH using atmospheric variables from reanalysis products. She obtained aerosol-heavy precipitation relationships in monsoonal regimes over the WH. She evaluated fine-resolution WRF simulations of extreme precipitation in WH. She received student travel grants from AGU and AMS during her Ph.D. to present her work in international conferences.

At CW3E, she is interested in looking at different types of Atmospheric Rivers (ARs) causing extreme precipitation in Colorado Front Range and Upper Great Plains of the U.S. under the supervision of Dr. Jason Cordeira.

CW3E Event Summary: 19-26 February 2023

CW3E Event Summary: 19-26 February 2023

3 March 2023

Click here for a pdf of this information.

Active Weather Pattern Brings Heavy Rain and Low-Elevation Snow to Western US

  • An atmospheric river (AR) made landfall over the Pacific Northwest on 19 February
  • AR 1/AR 2 conditions (based on the Ralph et al. 2019 AR Scale) were observed across much of coastal Washington
  • The storm produced more than 6 inches of storm-total precipitation in Western Washington and up to 2 feet of snow in the Washington Cascades
  • As the AR propagated south along the US West Coast and dissipated, an upper-level shortwave trough and associated area of low pressure formed over British Columbia
  • As this trough deepened along the US West Coast, unsettled weather with low-elevation snow continued
  • A second AR formed in association with the trough and made landfall over Central California on 24 February
  • This storm featured strong upper-level dynamics and a favorable moisture flux direction for heavy orographic precipitation along the Transverse Ranges of Southern California
  • The heaviest storm-total precipitation, >10 inches, fell in the western Transverse Range with accumulations >6 inches elsewhere in the Transverse Ranges and the southern Sierra Nevada.
  • More than 36 inches of snow fell throughout the Transverse Ranges with >72 inches in parts of the southern Sierra Nevada
  • Very low freezing levels and ample moisture allowed for snow in locations that rarely see snow accumulations
  • The combination of heavy rainfall and high antecedent soil moisture and streamflow conditions led to riverine and urban flooding

Click images to see loops of NAM IVT/IWV analyses

Valid 0000 UTC 18 February – 1800 UTC 27 February 2023


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary provided by Shawn Roj, Samuel Bartlett, Chris Castellano, J. Kalansky, F.M. Ralph; 3 Mar 2023

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*Outlook products are considered experimental

CW3E Winter Storm and AR Update: 2 March 2023 Outlook

CW3E Winter Storm and AR Update: 2 March 2023 Outlook

March 2, 2023

Click here for a pdf of this information.

Winter Storms Bury California in Heavy Snow

  • A series of upper-level shortwaves brought widespread precipitation to the western US during 26 Feb – 1 Mar
  • More than 4 feet of snow fell across the Sierra Nevada, with nearly 8 feet reported near Lake Tahoe
  • Significant snowfall also occurred in the Klamath Mountains and the higher terrain of the Colorado Basin

Cold Storm to Bring More Snow to California this Weekend

  • Another upper-level trough is forecast to impact Washington, Oregon, and California beginning on Friday
  • More than 3 feet of snow are forecast over the Sierra Nevada, and 1–3 feet of snow are forecast in the Klamath Mountains and southern Cascades
  • Low freezing levels will once again allow for significant snowfall accumulations below 3,000 feet
  • Major winter storm impacts are expected over the Northern California Coast Ranges and Northern/Central Sierra Nevada Saturday into Sunday

Potential for Atmospheric River Activity in California Late Next Week

  • Another upper-level trough is forecast to impact Washington, Oregon, and California beginning on Friday
  • NCEP GEFS and ECMWF EPS are both showing the possibility of landfalling AR activity over California during 9–12 March, but there is a considerable amount of forecast uncertainty given the long lead time
  • Overall, GEFS is showing a higher likelihood of landfalling atmospheric river (AR) activity than EPS
  • More than 30% of all GEFS + EPS ensemble members are forecasting maximum IVT > 500 kg m−1 s−1 over the next 10 days near Bodega Bay, CA
  • Forecast uncertainty in storm track and AR activity is evident in the large spread of ensemble precipitation forecasts in Northern California

Click images to see loops of GFS 500-hPa Vorticity and IVT forecasts

Valid 1200 UTC 2 March – 1200 UTC 8 March 2023


 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, and S. Roj; 2 March 2023

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*Outlook products are considered experimental

CW3E Welcomes Dr. Sagar Parajuli

CW3E Welcomes Dr. Sagar Parajuli

March 1, 2023

Sagar Parajuli joined CW3E on February 21, 2023, and experienced the historical winter storm of late February in California with a lot of rain and cold winds. Sagar is a researcher with expertise in regional and global climate modeling as well as climate data analysis. He has extensively worked on identifying the various sources of natural and anthropogenic aerosols and in understanding their impact on air quality and climate including rainfall processes. Besides, he is also interested in climate and environmental policies, public health, and sustainable development.

Sagar originally comes from the Himalayan country of Nepal but has lived and worked in diverse work environments – from UAE and Saudi Arabia to USA. He brings a unique inter-disciplinary expertise to the CW3E team. Before joining CW3E, Sagar worked at King Abdullah University of Science and Technology (KAUST), Saudi Arabia for more than 5 years, where he looked at the vertical distribution of aerosols and their interaction with sea breezes and quantified the direct and indirect effects of dust on coastal rainfall. Before joining KAUST Sagar worked at The University of California, Irvine as a postdoctoral researcher after his PhD in Geosciences (2016) from The University of Texas at Austin, Austin, TX, USA. He did his master’s degree in Water and Environmental Engineering from Masdar Institute of Science and Technology, Abu Dhabi, UAE, and completed his bachelor’s degree in civil engineering from Institute of Engineering, Lalitpur, Nepal.

At CW3E, Sagar will be working on improving the rainfall simulations over the western coast of the US using WRF/WRF-Chem. With his diverse experience in aerosol modeling, land surface processes and satellite/ground-based data analysis, he will also be working on understanding the various physical processes that contribute to the spatiotemporal variability of atmospheric rivers and associated rainfall patterns over this region.

CW3E Publication Notice: Drought Attribution Studies and Water Resources Management

CW3E Publication Notice

Drought Attribution Studies and Water Resources Management

February 28, 2023

Drs. Rolf Olsen (recently retired from the US Army Corps of Engineers, Institute for Water Resources), Mike Dettinger (CW3E) and Jason Giovannettone (Sisters of Mercy of the Americas Inc.) have published an essay titled “Drought Attribution Studies and Water Resources Management” in the 2021-and-2022 issue of the American Meteorological Society’s special report series Explaining Extreme Events from a Climate Perspective (EEE). This report series annually (in normal times) presents detailed assessments of whether, and how, human-caused climate change has affected the strength and likelihood of specific extreme events in the previous year(s). These assessments generally are highly technical statistical analyses of observations of the particular extreme weather events studied in the context of climate-model simulations of climate conditions under current atmospheric greenhouse-gas concentrations. Typically, their aim is to determine “Has this extreme event (storm, heat wave, drought, or whatever) during the past year been made more likely or extreme by climate changes to date? If so, by how much?” The new essay shares information about how droughts are managed by water managers with climate-change attribution scientists in an attempt to help scientists to focus—when possible—on aspects of droughts and drought management that matter most to resource managers. Like the old story of the man looking for his keys under the street light because it’s easier to see there, it is easy for analysts to end up focusing on aspects of drought (and other extremes) that are the most readily evaluated or attributed to climate change; this essay amounts to a request, with some background information, for attribution analysts to focus the questions they address on the most actionable aspects of drought, both recent and future.

Specifically, well-focused attribution studies can provide insights into changing drought processes in ways that help inform plans and responses in the form of improved future water-supply estimates, reservoir-management decisions (like FIRO), and triggers used to initiate immediate drought responses in various state to local drought-management plans. The essay discusses each of these management challenges, and then surveys several recent droughts around the US, each of which illustrates a relevant drought mechanism that is likely to be worsened in future droughts by ongoing climate changes. Specifically, the recent droughts discussed include the mechanisms and responses to long-term precipitation deficits in recent California droughts; the various forms (and impacts) that snow droughts now take, e.g., in Washington State; and the high-temperature-driven 2017 drought in the northern Great Plains. In each case, knowing (a) what it was about those droughts and mechanisms that made them more impactful on water supplies and stores, and (b) how water managers go about addressing those conditions, can help researchers to design future attribution studies to be most action-able by resource managers. The essay’s authors are members of the American Meteorological Society’s Water Resources Committee, and this drought-focused essay is a “sequel” to a similar EEE essay by committee members that addressed flood-management issues and information needs for attribution studies (Vano et al. 2018).

Olsen, J. R., Dettinger, M. D., & Giovannettone, J. P. (2023). Drought Attribution Studies and Water Resources Management, Bulletin of the American Meteorological Society, 104(2), E435-E441. doi: https://doi.org/10.1175/BAMS-D-22-0214.1

Vano, J. A., Miller, K., Dettinger, M. D., Cifelli, R., Curtis, D., Dufour, A., Olsen, J. R., & Wilson, A. M. (2019). Hydroclimatic Extremes as Challenges for the Water Management Community: Lessons from Oroville Dam and Hurricane Harvey, Bulletin of the American Meteorological Society, 100(1), S9-S14. doi: https://doi.org/10.1175/BAMS-D-18-0219.1

CW3E Publication Notice: Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in Southern California

CW3E Publication Notice

Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in Southern California

February 27, 2023

A new paper entitled “Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in southern California” was recently published in the International Journal of Wildland Fire by authors Daniel Cayan, Laurel DeHaan, Alexander Gershunov, and Joshua Mumford (SIO), as well as Janin Guzman-Morales (UC Santa Barbara), Jon Keeley (USGS/UCLA), and Alexandra Syphard (Conservation Biology Institute). These researchers investigate fire outcomes in California’s South Coast for the period 1948-2018, with respect to the opposing effects of two weather drivers: autumn precipitation and Santa Ana winds (SAWs). This study contributes to the goals of CW3E’s 2019-2024 Strategic Plan to advance monitoring and projections of climate variability and change by quantifying the odds that these weather drivers lead to fire outcomes.

Following typically dry, warm summers, the onset of autumn precipitation for California’s South Coast happens earlier in some years and later in others. For autumn precipitation onset, as defined in this study by the first 3 days when precipitation reaches or exceeds 8.5mm, the mean onset date is 7 November and the standard deviation is approximately 1 month. The onset date has had a negligible trend and there is considerable variation from year-to-year.

The results of this study indicate that the risk of large fires is reduced greatly after autumn precipitation onset. Focusing on fires that burned 100ha or greater, of all that occurred within autumn through winter, 79% started before the autumn precipitation onset. Most (37 of 40) of the South Coast’s very large (＞10,000 ha) fires occur before autumn precipitation onset. Years with early onset autumn precipitation experienced considerably fewer fires and smaller burn areas (just 61% as many 100ha or larger fires and half as much area burns) than years with late onset, as shown below in Table 3 copied from the paper.

Additionally, the results obtained underscore the impact of SAWs in producing large fires. 34 of 40 of the South Coast’s largest fires started and spread during SAW events. Indeed, even after autumn precipitation onset, the risk of large fires resurges when SAWs are present. SAWs were involved with 47% of fires >100ha that started before onset, but they were involved in 75% of those fewer number of fires that started after onset.

The results of this study demonstrate the need for high levels of preparation and vigilance to avoid great fire impacts during the period of autumn before precipitation onset, and particularly during years with late autumn precipitation onset.

This research was funded by the U.S. Geological Survey through the Southwest Climate Adaptation Science Center, the California Department of Water Resources, Congressional Disaster Relief Supplemental Funding, and by San Diego Gas and Electric, however none of these sources were involved in the preparation of the data or the manuscript.

Cayan Daniel R., DeHaan Laurel L., Gershunov Alexander, Guzman-Morales Janin, Keeley Jon E., Mumford Joshua, Syphard Alexandra D. (2022) Autumn precipitation: the competition with Santa Ana winds in determining fire outcomes in southern California. International Journal of Wildland Fire , 31, 1056-1067. https://doi.org/10.1071/WF22065

CW3E Winter Storm Update: 24 February 2023 Outlook

CW3E Winter Storm Update: 24 February 2023 Outlook

February 24, 2023

Click here for a pdf of this information.

Winter Storm to Bring Additional Precipitation to the Pacific Northwest and California

  • A period of unsettled weather will continue for the US West Coast, with a winter storm forecast to bring precipitation to Washington, Oregon, and California starting Sunday
  • A mid-level trough is forecast to move quickly through the Pacific Northwest on Sunday, bringing precipitation primarily to the Olympic Peninsula and Cascades
  • A second, stronger mid-level trough is forecast to develop over the Gulf of Alaska and shift towards the US West Coast late Sunday, bringing precipitation to locations along the Coast Ranges of Washington and Oregon, Northern California, and the Sierra Nevada early next week
  • The National Weather Service (NWS) Weather Prediction Center (WPC) 5-day QPF totals are > 1.5 inch in the Olympic Peninsula and Northern Cascades, > 3 inches along the Coast Ranges of Oregon and Northern California, and > 5 inches for the Sierra Nevada through Wednesday
  • Significant snowfall accumulation is expected in the Cascades and Sierra Nevada as a result of this cold winter storm, with freezing levels dropping below 1,500 meters in the Sierra Nevada during this event
  • This storm will provide an additional boost to the snowpack in the Sierra Nevada, which is already well above normal for the season as a result of a prolonged period of active weather along the US West Coast
  • The 00Z ECMWF is forecasting higher watershed precipitation totals (3-4inches) along the Coast Ranges of Washington and Oregon and in the northern Cascades than the GFS, while the GFS is forecasting higher watershed precipitation totals (4-6 inches) along the Sierra Nevada as compared to the ECMWF

Click images to see loops of GFS Precip and 500 hPa Vorticity forecasts

Valid 0000 UTC 26 February – 0000 UTC 3 March 2023


 

 

 

 

 

 

Summary provided by S. Bartlett, C. Castellano, S. Roj, and F. M. Ralph; 24 February 2023

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*Outlook products are considered experimental

CW3E AR Update: 21 February 2023 Outlook

CW3E AR Update: 21 February 2023 Outlook

February 21, 2023

Click here for a pdf of this information.

Winter Storm and Atmospheric River Forecast to Bring Heavy Rain and Snow to Southern California

  • An amplifying upper-level shortwave trough will continue to produce unsettled weather over much of the western US during the next few days
  • As time progresses, a cutoff low and a weak atmospheric river (AR) are forecast to develop near the California coast and bring a period of heavy precipitation to Southern California
  • The 00Z ECMWF EPS control is predicting AR 1 conditions (based on the Ralph et al. 2019 AR Scale) over coastal San Diego County and AR 2 conditions near the California–Mexico border
  • The NWS CNRFC is forecasting at least 2–5 inches of total precipitation in the Sierra Nevada and coastal Southern California, with higher amounts expected in the eastern Transverse Ranges and Peninsular Ranges
  • The NWS Weather Prediction Center has issued a marginal risk of rainfall exceeding flash flood guidance in coastal Southern California Friday into Sunday
  • Major winter storm impacts are expected over portions of the Sierra Nevada and Transverse Ranges from Thursday through Saturday
  • Low freezing levels will support significant snowfall accumulations in the higher terrain in Southern California
  • Damaging wind gusts are also possible over much of the southwestern US today into Thursday
  • As part of CW3E’s Atmospheric River Reconnaissance Program (AR Recon), the 53rd Weather Reconnaissance Squadron will continue to provide additional weather observations over the North Pacific, sampling the atmosphere upstream of this storm

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 21 February – 0000 UTC 27 February 2023


 

 

 

 

 

 

 

 

 

 

Summary provided by C. Castellano, S. Bartlett, and J. Cordeira; 21 February 2023

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*Outlook products are considered experimental

CW3E AR Update: 17 February 2023 Outlook

CW3E AR Update: 17 February 2023 Outlook

February 17, 2023

Click here for a pdf of this information.

Atmospheric River Forecast to Bring Precipitation to the Pacific Northwest and Northern California

  • An atmospheric river (AR) is forecast to make landfall in the Pacific Northwest on Sunday and bring precipitation to Washington, Oregon, and Northern California through mid-day on Wednesday
  • IVT > 600 kg m-1 s-1 is forecast during landfall along the coast of Washington, bringing AR 2 conditions (based on the Ralph et al. 2019 AR Scale) to coastal locations of the Pacific Northwest
  • This AR is forecast propagate over the ridge positioned in the eastern North Pacific, bringing primarily northwesterly/westerly IVT to the US West Coast, eventually dissipating along the coast of California by late Wednesday
  • A weak mesoscale frontal wave is forecast to occur during the mid-stage of this AR over the Gulf of Alaska, which will have weak secondary cyclogenesis in association with a mid-level shortwave trough
  • The 00Z GFS is forecasting a stronger and longer duration period of AR conditions for points along the coast as compared to the ECWMF, with the GFS bringing AR conditions south to coastal locations in Northern California
  • The 00Z GFS is forecasting greater 7-day watershed precipitation totals throughout northern California, Oregon, and Washington than the 00Z ECMWF, especially within coastal watersheds along the CA/OR border and the Oregon Cascades
  • The 12Z GEFS ensemble is forecasting snow levels to fall dramatically from > 3,000 m to near sea level by 12Z 22 Feb for much of Northern California and the Sierra Nevada Mountains, resulting in the potential for snowfall accumulation at lower elevations than usual elevations

Click images to see loops of GFS IVT and IWV forecasts

Valid 1200 UTC 18 February – 1800 UTC 22 February 2023


 

 

 

 

 

 

Summary provided by S. Bartlett, S. Roj, C. Castellano, and F. M. Ralph; 17 February 2023

To sign up for email alerts when CW3E post new AR updates click here.

*Outlook products are considered experimental