About the Tracking of Heavy Precipitation Objects (THePrO) Prototype Page
***This is an experimental product from WPC-DTB***

Overview

    Because precipitation frequently takes the form of "blobs" or objects, displaying an ensemble mean can smooth precipitation fields. On the other hand, looking at precipitation forecasts from every existing Convection Allowing Model (CAM) can be cumbersome for forecasters. Instead, we want to simplify the process by tracking the forecast precipitation "objects" through time, and then display several object attributes such as object centroid location, intensity, and size. We define an object as a region of moderate to heavy preciptation that covers an area of at least ~2000 km^2. 


Ensemble Details

    The WPC Ensemble QPF Tracking site is run for three different CAM ensembles shown below:


  • The HREF consists of 5 current and 5 time-lagged members and updates at 00 and 12 UTC. The models that make up the HREF are the current HRRR, the 6-hour time-lagged HRRR, the current ARW, the 12-hour time-lagged ARW, the currrent ARW2, the 12-hour time-lagged ARW2, the current FV3, and the 12-hour time-lagged FV3. Note that the ARW2 is designed to mimic the NSSL model.
  • The HRRR is a Time Lagged Ensemble (TLE), but consists of only the extended runs (i.e. the runs that go out to forecast hour 48), which are performed every 6th hour. 
  • The FV3 LAMs* consist of three experimental models run at EMC (FV3LAM, FV3LAMx, and FV3LAMda), and are run out to hour 60 two times a day at 00 and 12 UTC. 
                * -  The FV3 LAMs are experimental products and may not always be available.

Experimental Website Layout

Ensemble Type:

    By default the displayed Tracking of Heavy Precipitation Objects (THePrO) product shown is from the most recent run of the HREF for the CONUS.  Use the scrollbar to move through each forecast hour. Along the top of the webpage are toolbar options to change the ensemble type, domain, precipitation exceedance threshold, and model run.  If a chosen configuration is not available, a notice will pop up. Please pick another configuration if this occurs.  An example of the THePrO toolbar can be seen below.


Domain:
 

    There are seven domain choices; ALL (full CONUS) and 6 smaller domains consisting of the North East, South East, North Central, South Central, North West, and South West.


Threshold:
            ***currently there is only one threshold that is calculated***

Initialization Model Time (Init):

        A drop down menu exists with all potential model initialization times.
d[model]/dt:

        This feature shows any model trends fixed on the valid time the user has selected from the scroll bar. Clicking on "d[model]/dt" will load a new page that displays these model trends. Simply click the back arrow to return to the previous page.


Description of Product Layout

This tracking image simultaneously conveys information about QPF track location, size, timing, and intensity.

Referring to the image shown below:

    -- The QPF object centroid and the model are identified by a marker symbol for some ensembles (right legend). 
    -- The marker color indicates the 90th percentile of hourly accumulated precipitation (left legend).
    -- The color scale on the right side of the product is the ensemble probability of being in a heavy precipitation object. When looking at the >= 0.1" per hour threshold, this blue shading represents the probability of  >= 0.1" per hour for organized rainfall events.