Atmospheric River Forecast Products

The products are provided “as is” and are intended for research purposes only (disclaimer).

This page contains graphics designed to forecast the presence and strength of Atmospheric Rivers using data from the NCEP Global Forecast System (GFS), North American Mesoscale Forecast System (NAM), Global Ensemble Forecast System (GEFS – v12) and the European Centre for Medium-Range Weather Forecasts (ECMWF) models. The Ensemble based products are produced by Dr. Jason Cordeira at Plymouth State University as a cooperative effort with CW3E. For more information on ARs visit the AR FAQs or watch this informational video about ARs.

Deterministic Model Forecasts

IWV, IVT, and Time-Integrated IVT Click on an image to see forecasts out to 180 hours from the GFS, ECMWF, and NAM

North Pacific
Northeast Pacific
U.S. West Coast
North America
North Atlantic
IWV
North Pacific GFS IWV Northeast Pacific GFS IWV U.S. West Coast GFS IWV North America GFS IWV North Atlantic GFS IWV
IVT
North Pacific GFS IVT Northeast Pacific GFS IVT U.S. West Coast GFS IVT North America GFS IVT North Atlantic GFS IVT
TIVT
North Pacific GFS TIVT Northeast Pacific GFS TIVT U.S. West Coast GFS TIVT

Integrated Water Vapor Transport (IVT) and Relative Humidity GFS Meteograms

These meteograms illustrate the forecasted conditions over a given locations for the 3 or 7-day forecast period from the GFS. The top panel includes water vapor flux (kg m-2s-1) or relative humidity (%) shaded with the 0°C isotherm contour and wind barbs(m/s), gray shading indicates location elevation. The middle plot illustrates the 3-hour precipitation represented by the bars, total 72-hour precipitation, height of the 0oC isotherm, and location elevation. When the freezing level is below the location elevation, line and bars are blue representing the likelihood of snow and when the freezing level is above the location elevation line and bars are green representing the likelihood of rain. The bottom plot illustrates the IWV and IVT, as well as the presence of AR conditions shaded in gray. The yellow dot on the map indicates the location of the current plot. Click here to view Alaskan domain

Select type of meteogram, latitude and longitude to generate plot. Click image to open in new tab.

Type

Model

Latitude

Longitude




Integrated Water Vapor Transport (IVT) GFS Cross Sections

These cross sections illustrate the forecasted conditions along a longitudinal line from 25-65°N for the given forecast time from the GFS or ECMWF deterministic model. The top panel shows water vapor flux (kg m-2s-1, shaded), the 0°C isotherm (contour), and wind barbs (m/s) and the bottom panel illustrates the IWV and IVT. Black shading in the top panel represents terrain. The dashed lines on the bottom panel illustrate thresholds for AR conditions. The map on the left shows the location of the cross section as well as the IVT (kg m-1s-1) at the forecast time. Gray shading indicates the presence of AR conditions (IVT >250 kg m-1s-1 and IWV >20 mm). Select the model, longitude, and forecast lead time from the menus to see the cross section and click the image to open in a new window.

Select Longitude and Forecast Hour to generate plot

Model:  

Longitude:  

Forecast Hour:  



West Weather Research and Forecasting (West-WRF) Model

Integrated Water Vapor (IWV) Click on an image to see forecasts out to 180 hours from the GFS and NAM

Northeast Pacific (9 km)
California (3 km)
Northeast Pacific WWRF IWV
California WWRF IWV

Integrated Water Vapor Transport (IVT) Click on an image to see forecasts out to 180 hours from the GFS and NAM

Northeast Pacific (9 km)
California (3 km)
Northeast Pacific WWRF IVT
California WWRF IVT

Ensemble Forecast Systems

CW3E AR Landfall Tool
Developed in collaboration with Dr. Jay Cordeira, Plymouth State University

The CW3E AR Landfall Tool displays the likelihood and timing of AR conditions at each point on the map in a line along the West Coast of North America or inland derived from either the NCEP Global Ensemble Forecast System or the ECMWF Ensemble Prediction System. The probability of AR conditions represents the fraction of the 30 or 50 ensemble members that predict IVT to be greater than the chosen threshold at the given location and time. To see how each forecast type has changed over the previous seven days click on dProg/dT. These plots are maintained by Jay Cordeira, Plymouth State University.

Select variable or threshold to be displayed, location, and forecast length to generate plot, click image to open in a new tab.

Model

Type

Location

dProg/dT



West Coast IVT Magnitude Plume Diagrams
Developed in collaboration with Dr. Jay Cordeira, Plymouth State University

The IVT magnitude plume diagrams represent the integrated water vapor transport (IVT) magnitude forecast from either the NCEP Global Ensemble Forecast System (GEFS) or the ECMWF Ensemble Prediction System (EPS). The images illustrate each of the 30 GEFS ensemble members or 50 EPS members (thin gray lines), the unperturbed GEFS/EPS control forecast (black line), the GEFS/EPS ensemble mean (green line), and plus or minus one standard deviation from the ensemble mean (red line (+), blue line (-), and gray shading). The dot on the map indicates the location of the current plot.

Select model, forecast length of plot, and location to generate plot. Click image to open in new tab.

Model:  

Forecast Length:  

Location:  



IVT Ensemble Probability Plots
Developed in collaboration with Dr. Jay Cordeira, Plymouth State University

Select forecast hour, threshold, and domain to generate plot. Click image to open in new tab.

Threshold:

Forecast Hour:

Domain:

The above images display the probability of IVT exceeding 250 kg m-1 s-1 based on the 30 members of the NCEP Global Ensemble Forecast System (GEFS) and the IVT vectors from the ensemble mean forecast.

The above images display the probability of IVT exceeding 250 kg m-1 s-1 based on the 30 members of the NCEP Global Ensemble Forecast System (GEFS) (gray shading), the IVT vectors from the ensemble mean forecast, and the 250 kg m-1 s-1 contours from each ensemble member.


IVT Thumbnail Ensemble Plots
Developed in collaboration with Dr. Jay Cordeira, Plymouth State University

Select forecast hour and domain to generate plot. Click image to open in new tab.

Forecast Hour:  

Domain:  

The above images display the 30 members of the NCEP Global Ensemble Forecast System (GEFS); each thumbnail shows IVT (kg m-1 s-1) magnitude shaded according to scale and IVT vectors.


Subseasonal Outlooks (Weeks 1-3)

A multi-model experimental forecast for AR occurrence (defined as the # of AR days per week) at week-1, 2, and 3 lead time is shown below for the NCEP dynamical model.

This product was developed in collaboration with NASA’s Jet Propulsion Laboratory.

Weeks 1-2: Shading indicates the odds of AR occurrence for each day. ARs are defined using the Guan and Waliser (2015) algorithm and probability is calculated by the number of ensemble members predicting an AR at each grid point at 00 UTC on the given forecast day. Click on a panel to open in a new tab, click on title to open seven day panel plot.

Week 3: The top row shows the forecast number of AR days during week-3; the middle row shows the climatological values of AR occurrence in each model’s hindcast record for the week-3 verification period; the bottom row shows the departure of the AR occurrence forecast for that same verification period (top panel forecast minus middle panel climatology). For this row, blue values represent higher than average AR activity predicted during week-3; red values represent lower than average AR activity predicted during week-3. Grey rectangles surround grid cells where >75% of forecast ensemble members agree on the sign of the AR occurrence anomaly with respect to climatology. These regions can be interpreted as having higher confidence in their prediction of week-3 AR occurrence. The hindcast skill assessment associated with the NCEP, ECMWF, and ECCC hindcast systems is described in DeFlorio et al. 2019b.

Week 1
Week 2
Week 3