67 Atmospheric River Research in Alaska

Monday, 7 January 2019
Hall 4 (Phoenix Convention Center - West and North Buildings)
Aaron Jacobs, NOAA/NWS, Juneau, AK; and E. Holloway and A. Dixon

Atmospheric River (AR) events have been well documented and monitored for years, especially in the
West Coast of the continental United States. ARs impact the entire west coast of North America
including British Columbia, the Alaska Panhandle, the southern mainland of Alaska including Prince
William Sound and the Cook Inlet region, as well as the west coast and interior Alaska. There were a few
impactful AR events over western and interior Alaska in June and July of 2016. Depending on the time
of year a significant amount of precipitation can be generated from these systems across the state of
Alaska. These systems can impact communities with flooding, large debris flows, disruption to
transportation, significant snowfall in winter events and in rare cases casualties.
From a forecasting perspective, discerning significant AR events from a more typical strong synoptic
storm is very difficult. Steep and complex coastal terrain, proximity to arctic air masses, and significant
data sparsity can cause numerical models to struggle considerably with unexpected results in the short
term, which affects the ability of the forecaster to provide accurate and timely impact-based decision
support to communities and other core partners. Research to help in the decision making process has
commenced in the following methods:
● Southern coast including Southwest mainland: Will first look at impactful events, relate that to
precipitation information, and then correlate that back to the historical AR detection schemes
● Southeast Panhandle: Will look at all historical precipitation data and relate it back to AR
detected dates from reanalysis IVT database (ERA,MERRA,NCEP), SSMI IWV AR detected
algorithm and IVT algorithm for CFSR.
The expected outcomes include:
● Climatology of specific fields( Integrated water transport(IVT), Precipitable water values(IWV),
time integrated IWV with statistics(mean and standard deviation) from precipitation data
and/or impact base analysis
● Derive a regional and seasonal classification scheme: non-AR, weak AR, moderate AR and Strong
● Assign different types of impacts (none, minor, moderate, major) to AR classification.
● Compute AR event analogs for pattern and strength of moisture transport
● Verification of reanalysis data to AR detection algorithms
● A tool for forecasters to provide increased situational awareness and impact-based decision
support services to emergency management.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner