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
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.
GPS Integrated Water Vapor: 1515 UTC 3 March 2016 IWV values greater than 2 cm throughout central California -Current AR conditions |
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CNRFC River Forecasts 2000 UTC 3 March 2016
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7-day Precipitation Forecasts: Ending 4:00 am PST 10 March 2016
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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)
Reconnaissance Flights Into Atmospheric Rivers Aim To Improve West Coast Storm Predictions
February 13, 2016
Scripps Oceanography, NOAA, U.S. Air Force team up on flights through atmospheric rivers this month, starting with flights on Saturday 13 February into a moderate strength AR between Hawaii, Alaska and the Pacific Northwest. Although of only moderate strength, this AR is likely to stall somewhere in the WA-OR area, creating a long-duration AR landfall. The long duration of landfall is key to determining whether the AR produces extreme rainfall and possibly flooding, or is more of a benefit to water supply and snow pack. Details in the AR conditions offshore, that are not represented accurately in the “initial conditions” needed for weather prediction limit the skill of forecasts of AR landfall duration and intensity. The flights today, one from Hawaii, and one from Tacoma WA, are aimed at reducing that uncertainty.
Researchers at Scripps Institution of Oceanography, UC San Diego have developed a new method for improving atmospheric river (AR) forecasts that is being used for the first time in National Weather Service-directed flights over the Pacific Ocean.
Scientist F. Martin Ralph, director of the Center for Western Weather and Water Extremes at Scripps, said the observations made aboard two U.S. Air Force C-130 aircraft later this month are aimed at improving forecasters’ ability to say exactly where storms will make landfall. Current forecasts of landfall location of ARs made one to three days in advance are typically off by 300 kilometers (200 miles).
Contact: F. Martin Ralph (CW3E Director, and PI of the C-130 AR Recon Mission)
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 – cw3e.ucsd.edu). 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.
Setting the Stage for a Global Science of Atmospheric Rivers
January 25, 2016
The above image, from the EOS article, is a depiction of an atmospheric river, interacting with West Coast mountains and a midlatitude cyclone over the northeast Pacific on 5 February 2015. This image provides an example of approximate locations of associated tropical moisture exports and a warm conveyor belt (WCB). Credit: Adapted from NOAA/ESRL Physical Sciences Division
An EOS article from CW3E scientists Dettinger, Ralph and Lavers summarizes key outcomes from a unique workshop held at Scripps Institution of Oceanography in June 2015. The Workshop brought together leading scientists and users of scientific outputs to discuss emerging advances in Atmospheric River (AR) science and applications. A “Meeting Report” about the workshop appeared in print in the EOS issue published on 1 January 2016: Click here to acccess the report.
Points of contact: F.M. Ralph (mralph@ucsd.edu), M.D. Dettinger (mddettin@usgs.gov), and D. Lavers (dlavers@ucsd.edu) at the Scripps Institution of Oceanography, UCSD.
AR storms impact northern California: January 12-15
January 15, 2016
DRI/CW3E researcher Nina Oakley, CW3E researcher Scott Sellars and other CW3E team members evaluate two storms that had an impact on northern California as well as the Pacific Northwest from 12-15 January 2016. Fresh Sierra snow can be seen in the cover satellite image from Friday, January 15 (courtesy NWS Sacramento). The approaching clouds from the next series of storms can be seen approaching the coast as well as valley fog in the Sacramento region. The first storm event leading to this fresh snow was a moderate atmospheric river (AR) storm with 1 to over 4 inches of precipitation from northern California to the Canadian border. The second storm event was weaker and ahead of a larger scale AR that will impact the same region from 15-18 January 2016. The weaker event spun off the Aleutian Low and produced some areas of heavy snowfall in the Sierra Nevada. An outlook for the upcoming AR event for 15-18 January is also briefly examined.
Click here for a pdf file of this information.
Above is a sequence of SSMI water vapor imagery from 10-13 January 2016 which shows the AR propagating towards northern California and making landfall.
Above is a sequence of SSMI water vapor imagery from 12-15 January 2016 which shows the first AR making landfall and the dissipation of the second AR as it approaches land.
Recent Rainy Week in San Diego County
January 8, 2016
El Nino-fueled storms over the last few days, including a land-falling atmospheric river on 5 January (see cw3e.ucsd.edu for more details), have brought San Diego county’s accumulated winter precipitation to well above normal for this time of year. These numbers are tracked by the California-Nevada Applications program (cnap.ucsd.edu) and the Center for Western Weather and Water Extremes (cw3e.ucsd.edu) at UCSD’s Scripps Institution of Oceanography, in association with KPBS. The precipitation tracking tool shows the impact of the recent storms on the accumulated winter precipitation:
In the last three days, San Diego county has received almost 17% of the amount of precipitation it receives in an entire year, on average.
Precipitation gauge records compiled by the California Nevada River Forecast Center show accumulations of 3-5″ over much of the Los Angeles basin in the 72 hour period, reaching 7″ in some locations in the surrounding mountains. San Diego county accumulations are 1-3″ over much of the city, and 4-5″ in the North County interior:
These storms bring San Diego county’s running total accumulated precipitation so far this winter to 42% of the total typically received over an entire average year. This is an above-average value for the first time since the winter started; typically, by this point in the winter, San Diego will have accumulated 32% of the average year-end total precipitation.
Before the recent storms hit, the accumulated precipitation in the Los Angeles region since the winter started was only 11% of the typical end-of-winter total, far below the average value of 29%. In three days the accumulation has jumped to 27%. This rapid increase is more than is experienced in 95 out of 100 wet periods of 3-day duration in the region, leading to strong flows in the normally quiescent Los Angeles river and localized flooding in Southern California coastal areas.
Precipitation during the week was widespread, with rain and snow delivered from Washington to Northern Mexico. California statewide totals also were boosted during the Jan 4-7 period (cnap.ucsd.edu), although amounts were not as heavy in Northern California as they were in Southern California.
These accumulated precipitation totals can be tracked in real time from the California-Nevada Applications Project (CNAP) and Center for Western Weather and Water Extremes (CW3E)’s “San Diego Precipitation Page”. This includes monitoring of how current winter precipitation compares to that during the last 5 strongest El Nino winters (1982-83, 1997-98, 1957-58, 1972-73, and 1965-66), shown as the colored lines in the upper panels:
The current El Nino event is is one of the three strongest in records that go back to 1950, with a broad area of unusually warm ocean surface waters in the tropical Pacific ocean and highly anomalous winds and other atmospheric conditions in the region. El Nino events can alter the North Pacific winter storm track, producing unusually wet winters in Southern California about 60% of the time, compared to about 11% of the time during years when no El Nino or its opposite, La Nina, is present. Forecasts indicate that El Nino conditions are likely to persist through the spring of 2016, before fading in the early summer of 2016.
Points of contact: David Pierce (dpierce@ucsd.edu), Dan Cayan (dcayan@ucsd.edu), and Marty Ralph (mralph@ucsd.edu) at the Scripps Institution of Oceanography, UCSD.
For a PDF version of this information click here.
California Storm of 5 January 2016: A Preliminary Synopsis of a Marginal Landfalling Atmospheric River
January 5, 2016
CW3E researchers Brian Kawzenuk and Scott Sellars and DRI researcher Nina Oakley provide a preliminary analysis and synopsis of a weak Atmospheric River that made landfall over southern California on 5 January 2016. The AR was the first event in what will be an active week over the North Pacific and brought significant precipitation throughout central and southern California. The AR initially developed near Japan and propagated across the entire North Pacific Ocean before making landfall. A brief forecast for the rest of the week is also provided by the San Diego National Weather Service Forecast Office, courtesy Roger Pierce.
Click here for a pdf file of this information.
Above is a sequence of SSMI water vapor imagery from 01-05 January 2016 which shows the Atmospheric River propagating towards California and making landfall.
-Atmospheric River intially developed over the northwestern Pacific Ocean
-AR propagated eastward and strengthened
-AR became disconnected with its parent low and began to dissipate prior to landfall
-Secondary cyclogenesis occurred just off the California/Oregon coast north of the AR shortly before landfall
-AR made landfall over southern California at ~0600 UTC 5 January 2016
Above is a sequence of integrated vapor transport (IVT) from the GFS analysis during 31 December 2015 to 5 January 2016 which shows the Atmospheric River propagating towards California and making landfall.
Above is a sequence of Jason Cordeira’s AR Landfall tool initialized between 0600 UTC 29 Dec 2015 and 0600 UTC 5 Jan 2016. The sequence shows how the forecast developed over the previous eight days and shows the skill this tool had in forecasting the AR. For more information on this product visit the AR Forecast page.
– Greater than 50% of ensemble members predicted the landfall of the AR ~8 days in advance
– Greater than 85% of ensemble members predicted the landfall of the AR ~3 days in advance
– AR conditions were not forecasted over southern CA until ~5 days in – advance
– Between days 8 and 3 duration of AR conditions forecasted ranged from ~18–48 hours
– Duration and location of AR conditions remained constant and accurate during days 0–3 forecasts
The following forecast is from the San Diego National Weather Service Forecast Office
The weather pattern in SoCal will be very active this week with several storm systems moving through the region. This afternoon through Wednesday morning will bring moderate to heavy rainfall over the coast, valleys, foothills and deserts, with heavy snowfall occurring in the mountains above 5,500 ft. Total snowfall for the through Wednesday morning will be around a foot for elevations above 5,500 ft, with lesser amounts between 4,500 and 5,500 ft. Rainfall totals through Wednesday morning will be 1 to 1.5 inches west of the mountains with local amounts near 2 inches in the foothills. If you have travel plans at anytime during the week, especially in the mountains, check local conditions and be prepared for inclement weather. Another storm with moderate to high impacts will affect the region Wednesday afternoon through Wednesday night. A third system on Thursday will bring additional rain and mountains snow, but it appears to be less intense than the first two.
Pacific Northwest Storm of 13-15 November 2015: A Synopsis of Landfalling Atmospheric River Conditions
November 25, 2015
CW3E researcher Brian Kawzenuk provides an analysis and synopsis of an Atmospheric River that made landfall along the U.S. Pacific Northwest over the 13-15 November 2015 period. The AR made initial landfall along the Washington coast and lead to significant precipitation for nearly three days throughout western Oregon, Washington, and British Columbia. The AR initially developed near Japan and propagated across the entire North Pacific Ocean before making landfall.
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The above loop shows SSMI Integrated Water Vapor during 10-15 November 2015. |
