CW3E AR Update: 04 April 2018 Outlook

CW3E AR Update: 04 April Outlook

April 04, 2018

Click here for a pdf of this information.

Atmospheric river forecast to impact California over the next four days

  • Forecast confidence is increasing for a moderate or strong AR to strike the U.S. West Coast between this Thursday and Saturday
  • This will be the strongest AR of the season for this region, with total water vapor transport greater than approximately 25 Mississippi Rivers worth of water
  • Heavy precipitation is predicted over the CA coast and Sierra Nevada, with accumulation up to 7 inches possible
  • High freezing levels during the heaviest precipitation will result in rain at high altitudes over the Sierra Nevada leading to potential flooding

Click IVT or IWV image to see loop of 0-102 hour GFS forecast

Valid 0600 UTC 04 April – 1200 UTC 08 April 2018

 

 

 

 

 

 

 

Summary provided by B. Kawzenuk, F.M. Ralph, and C. Hecht; 10 AM PT Wednesday 04 April 2018

*Outlook products are considered experimental

CW3E AR Update: 03 April 2018 Outlook

CW3E AR Update: 03 April Outlook

April 03, 2018

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Atmospheric river forecast to impact Northern California later this week

  • GFS Ensemble members are currently forecasting a potentially strong to extreme AR over northern and central California later this week
  • Forecast certainty has increased since yesterday but there is still some uncertainty in the onset, duration, and strength of the AR
  • Up to 7 inches of precipitation is forecasted to fall over the Coastal and Sierra Nevada Mtns in CA, OR, and WA
  • The GEFS is currently suggesting high freezing levels for most of this event, which may lead to most of the precipitation falling as rain

Click IVT or IWV image to see loop of 0-126 hour GFS forecast

Valid 0600 UTC 03 April – 1200 UTC 08 April 2018

 

 

 

 

 

 

 

Summary provided by B. Kawzenuk, F.M. Ralph, and C. Hecht; 11 AM PT Tuesday 03 April 2018

*Outlook products are considered experimental

CW3E AR Update: 02 April 2018 Outlook

CW3E AR Update: 02 April Outlook

April 02, 2018

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Atmospheric river forecast to impact Northern California later this week

  • GFS Ensemble members are currently forecasting a potentially strong to extreme AR over Northern California later this week
  • There is currently large uncertainty in the onset, duration, and magnitude of AR conditions, creating uncertainties in the potential impacts of this event
  • >5 inches of precipitation could fall during this event over the high elevations of the Coastal and Sierra Nevada Mountains in Northern California
  • The GFS is currently suggesting freezing levels >8,000 feet for most of this event, which may lead to most precipitation over the high Sierra falling as rain

Click IVT or IWV image to see loop of 0-141 hour GFS forecast

Valid 1200 UTC 02 April – 0900 UTC 08 April 2018

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Monday 02 April 2018

*Outlook products are considered experimental

CW3E AR Update: 23 March 2018 Post Event Summary

CW3E AR Update: 23 March Post Event Summary

March 23, 2018

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A strong AR made landfall over southern California this week

  • The atmospheric river made initial landfall over Big Sur around 1800 UTC Wednesday, 20 March 2018
  • AR conditions were present over southern California about ~1200 UTC Friday, 23 March 2018
  • This was an R-Cat 1 event as over 200 mm of precipitation was observed just south of Big Sur and over the northern Sierra Nevada over 72 hours
  • This event produced nearly 7 percent of normal annual precipitation over all of California and the Northern Sierra 8 Station Index

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 19 March – 1200 UTC 23 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-48 hour GFS forecast

Valid 1200 UTC 22 March – 1200 UTC 24 March 2018

NEXRAD Radar Reflectivity
Valid 00 UTC 20 March – 12 UTC 23 March 2018

  • Precipitation began over central CA early morning on 20 March 2018
  • Moderate to heavy precipitation occurred over central and Southern CA for nearly 72 hours during 20–23 March
  • The highest precipitation amounts occurred over the Coastal Mts. between Santa Barbara and Big Sur and over the southern Sierra Nevada
  • Several thunderstorms also occurred during this event on 22 and 23 March as evident by the highest reflectivity values observed by radar


 

 

 

 

 

 

Summary provided by C. Hecht, B. Kawzenuk, and F.M. Ralph; 3 PM PT Friday 23 March 2018

*Outlook products are considered experimental

CW3E AR Update: 22 March 2018 Outlook

CW3E AR Update: 22 March Outlook

March 22, 2018

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Update on Atmospheric River Currently Impacting California

  • Precipitation continues to fall across portions of California
  • The AR will begin to propagate southward bringing moderate AR conditions to Orange and San Diego Counties
  • As much as 9.5 inches of precipitation has fallen over the Coastal Mountains of California during the last 48 hours
  • ~3.75 inches of precipitation has fallen over the high elevations of Santa Barbara and Ventura Counties and 3.5 more inches could fall during the remainder of the storm
  • AR conditions are expected to end at ~11 pm PDT (+/– 3 hours) tonight over Southern California

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 19 March – 1600 UTC 22 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-48 hour GFS forecast

Valid 1200 UTC 22 March – 1200 UTC 24 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 3 PM PT Thursday 22 March 2018

*Outlook products are considered experimental

CW3E AR Update: 21 March 2018 Outlook

CW3E AR Update: 21 March Outlook

March 21, 2018

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Update on Atmospheric River Currently Impacting California

  • Light to moderate precipitation has begun falling over portions of California
  • GFS Ensemble members have continued to converge on coastal IVT forecast for the remainder of the AR
  • Portions of Southern California are forecast to experience Strong AR conditions between 2 and 5 AM on Thursday 22 March
  • ~1–2 inches of precipitation has fallen over the Santa Ynez Mountains over the past 24 hours
  • An additional 10+ inches of precipitation are forecast to fall over the higher elevations of Santa Barbara and Ventura Counties during the remainder of this AR

National Weather Service Composite Radar Reflectivity

Valid 1748-1858 UTC 21 March 2018

Images from weather.gov

Click IVT or IWV image to see loop of 0-72 hour GFS forecast

Valid 1200 UTC 21 March – 1200 UTC 24 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Wednesday 21 March 2018

*Outlook products are considered experimental

CW3E AR Update: 20 March 2018 Outlook

CW3E AR Update: 20 March Outlook

March 20, 2018

Click here for a pdf of this information.

Update on Atmospheric River Forecast to Impact California This Week

  • The terminus of the atmospheric river plume is approaching coastal CA and precipitation will begin today
  • Models are suggesting potentially strong (IVT >750 kg m-1 s-1) AR conditions over San Luis Obispo and Santa Barbara Counties
  • Locations further south may experience moderate strength AR conditions (IVT >500 kg m-1 s-1)
  • AR conditions are forecast to peak over portions of SoCal between Midnight and 11 AM PDT on Thursday, 22 March 2018
  • As much as 10 inches of precipitation may fall over the higher elevations of Santa Barbara and Ventura Counties
  • The National Weather Service has issued numerous Flash Flood Watches and Winter Weather Warnings in California

SSMI/SSMIS/AMSR2-derived Integrated Water Vapor (IWV)

Valid 0000 UTC 18 March – 1600 UTC 20 March 2018

Images from CIMSS/Univ. of Wisconsin

Click IVT or IWV image to see loop of 0-72 hour GFS forecast

Valid 1200 UTC 20 March – 1200 UTC 23 March 2018

 

 

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, J. Rutz, and B. Kawzenuk; 1 PM PT Tuesday 20 March 2018

*Outlook products are considered experimental

CW3E AR Update: 19 March 2018 Outlook

CW3E AR Update: 19 March Outlook

March 19, 2018

Click here for a pdf of this information.

Update on Atmospheric River Forecast to Impact California Next Week

  • Several changes have occurred in the forecast for the AR that may impact CA this week
  • GFS Ensemble members have continued to converge on Coastal AR conditions
  • While there is more agreement between GFS Ensemble members there are still numerous changes from model run to model run, introducing several uncertainties in the impacts associated with this event

Click IVT or IWV image to see loop of 0-102 hour GFS forecast

Valid 1200 UTC 18 March – 1800 UTC 23 March 2018

 

 

 

 

 

 

 

 

Summary provided by C. Hecht, F.M. Ralph, and B. Kawzenuk; 1 PM PT Monday 19 March 2018

*Outlook products are considered experimental

CW3E AR Update: 7 March 2018 Outlook

CW3E AR Update: 7 March Outlook

March 7, 2018

Click here for a pdf of this information.

Weak Atmospheric River expected to impact the U.S. West Coast this week

  • A weak or potentially moderate AR is expected to make landfall over northern CA and the Pacific Northwest on 8 March 2018
  • This AR will produce precipitation over the Pacific Northwest and northern CA over the next three days
  • Precipitation amounts during this event are not expected to be extreme, with the highest accumulations predicted to be less than 3 inches

Click IVT or IWV image to see loop of 0-78 hour GFS forecast

Valid 0600 UTC 7 March – 1200 UTC 10 March 2018

 

 

 

 

 

A second AR is expected to make landfall this weekend

  • A second weak Atmospheric River is expected to make landfall over southern CA and Baja CA on 10 March 2018
  • This AR is expected to produce precipitation over the southern CA with two day accumulations of less than 1 inch

Click IVT or IWV image to see loop of 60-120 hour GFS forecast

Valid 1800 UTC 9 March – 0600 UTC 12 March 2018

 

 

 

 

 

Summary provided by B. Kawzenuk, J. Kalansky, and F.M. Ralph; 12 PM PT Wednesday 7 March 2018

*Outlook products are considered experimental

CW3E Publication Notice: Genesis, Pathways, and Terminations of Intense Global Water Vapor Transport in Association with Large-Scale Climate Patterns

CW3E Publication Notice

Genesis, Pathways, and Terminations of Intense Global Water Vapor Transport in Association with Large-Scale Climate Patterns

February 13, 2018

CW3E researchers Scott Sellars and Brian Kawzenuk and director Marty Ralph in collaboration with Phu Nguyen (UC Irvine) and Soroosh Sorooshian recently published a paper in Geophysical Research Letters titled Genesis, Pathways, and Terminations of Intense Global Water Vapor Transport in Association with Large-Scale Climate Patterns (http://onlinelibrary.wiley.com/doi/10.1002/2017GL075495/full). The study uses the CONNected objECT (CONNECT) algorithm applied to integrated water vapor transport (IVT) data for the period of 1980 to 2016 calculated from Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) to identify objects associated with extreme moisture transport (Sellars et al., 2013, 2015).

The algorithm generated a global dataset of life-cycle records in time and space of evolving strong water vapor transport events. Each object was associated with distinct physical and climatological features such as object size, location, and intensity, various climatological teleconnection patterns, and many other characteristics. This algorithm identified various weather phenomena associated with strong moisture transport such as atmospheric rivers, hurricanes and tropical cyclones, monsoon transport, and various other systems that produced extreme moisture transport. It was illustrated that these events typically occurred in five distinct regions located in the midlatitudes (off the coast of the southeast United States, eastern China, eastern South America, off the southern tip of South Africa, and in the southeastern Pacific Ocean) (Figure 1a). Additional analysis showed distinct genesis and termination regions and global seasonal peak frequency during Northern Hemisphere late fall/winter and Southern Hemisphere winter (Figure 1c and d). In addition, the frequency and location of these events were shown to be strongly modulated by the Arctic Oscillation, Pacific North American Pattern, and the Quasi-Biennial Oscillation. Moreover, a positive linear trend in the annual number of objects was reported, increasing by 3.58 objects year-over-year. The vast dataset produced in this study will be used for various future research opportunities focused on extreme moisture transport and its connection to large-scale climate dynamics.

Figure 1:(a) Total number of IVT objects from January 1980 to August 2016. (b) Average duration in hours of object at each grid cell. (c) The number of objects at genesis (starting) locations for all IVT objects. (d) The number of objects at termination (ending) locations for all IVT objects. The gray areas represent landmass.