SCAN The System for Convection Analysis and Nowcasting
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SCAN 2.0

AWIPS 5.0 - Expected delivery to field in January/February 2001



RPS List Needs
Interpreting the SCTI values
Editing the SCAN Site List and Use of Spotter Maps
Using the "purgetime.txt" file
SCAN 2.0 User's Guide
SCAN 2.0 Screen Captures




RPS List Needs

The following WSR-88D Products must be included in the AWIPS RPS List of each dedicated radar in order to run the full suite of SCAN 2.0 functionality on each of those radars:
  1. Composite Reflectivity (CZ), 16-level, 1-km resolution, product #37 (Vital)
  2. Vertically Integrated Liquid (VIL), product #57 (Vital)
  3. Base Reflectivity (Z), 16-level, 1-km resolution, product #19 (Vital)
  4. Storm Track and Identification (STI), product #58 (Suggested)
  5. Mesocyclone (M), product #60 (Strongly suggested)
  6. Tornado Vortex Signature (TVS), product #61 (Strongly suggested)

Interpreting the SCTI values

The SCAN Convective Threat Index (SCTI) is a numerical representation of the severe weather occurring within a CWA. The SCTI button is located directly below the WarnGen button on the D2D. The SCTI button has a severe weather symbol on it. The button will be colored according to the following criteria:

WhiteLittle or no activity in the CWA
GreenGeneral thunderstorms with low severe weather probabilities in the CWA
YellowThunderstorms with moderate severe weather probabilities or a mesocyclone or TVS detected in the CWA
RedThunderstorms with high severe weather probabilities and a mesocyclone and/or TVS detected in the CWA
GreyInvalid index number, which means the SCAN processor is not behaving properly.

If the mouse cursor is focused over this colored button, a small text tip widget will appear, providing the maximum SCTI value over the CWA and what it represents.

In addition to the SCTI button, the actual grid of SCTI values over the CWA can be viewed via a D2D depictable, selectable from the SCAN section of the radar menus. The following table can be used to interpret the SCTI values:

100Cell SWP >=70, MESO & TVS
90Cell SWP >=70, MESO or TVS
80Cell SWP >=70
7030 <= Cell SWP < 70, MESO & TVS
6030 <= Cell SWP < 70, MESO or TVS
5030 <= Cell SWP < 70
40Cell SWP < 30, MESO & TVS
30Cell SWP < 30, MESO or TVS
10CG LTG, High VIL, CZ

To make the SCTI values, we see which of the following "ingredients" are present in a radar-centric field of 4x4 km grid boxes - VIL, 4-km CZ, NLDN lightning, TVSs, MESOs, and our cell-based Severe Weather Probabilities (SWPs). The non-gridded data - lightning, MESOs, TVSs, and SWPs - are assigned to the nearest grid box. Depending on how many severe weather indicators are present in each grid box (and in what combinations), the box is assigned a SCTI value.

It is important to keep in mind that these numbers are not percentages; they are assigned threat values that model the gamut between a garden variety thunderstorm and a rotating, tornadic supercell. The numbers are not cumulative -- a grid box with CG lightning and high VIL (for a SCTI value of 10) that also has a MESO, TVS, and high SWP (a SCTI value of 100) will not be assigned a a value of 110; instead, the maximum threat found is the one that is used.

See the SCAN 2.0 User's Guide for information on the SCTI.

Editing the SCAN Site List and Use of Spotter Maps

Below are instructions on how to edit the site list for the SCAN thunderstorm site detection function in AWIPS 4.1, i.e., the function that monitors for the presence of a thunderstorm threat at a fixed geographic (point) location.

It might be useful to add the locations of fixed spotters to this list in order to automatically monitor for the occurrence of thunderstorms at these locations. The spotter map depictable could be used in conjunction with the SCAN site threat depictable.

This information is also being included in the 4.2 D2D User's Guide.

To add a local site of interest (such as a local landmark or a spotter location, for example) to the SCAN site field, perform the following steps:
  1. If the SCAN site threat depictable is loaded in the IGC screen, unload the depictable.
  2. Use an editor to open the file: /data/fxa/radar/XXXX/tstorm/sites.dat, where "XXXX" is the four-letter identifier of the dedicated radar.
  3. At the bottom of the file add a new line. At the beginning of the line, type a character string (with a maximum size of 5 characters) as an identifier. Note that any new sites should be placed at the bottom of the file -- not in alphabetical order in the list -- so as not to disrupt the site ordering of previous SCAN runs in the inventory.
  4. Skip at least 1 space and, on the same line as the identifier, add the latitude of the new site in decimal degrees format.
  5. Skip at least 1 space and , on the same line as the identifier and latitude, add the longitude of the new site in decimal degrees format, using a negative value to represent a point west of the prime meridian.
  6. Save the file.
  7. To test the addition, wait at least 1 volume scan before displaying the SCAN site threat depictable. When the depictable is loaded, the new site should be displayed in the site field. If the site threat popup window is invoked, the text message inside will describe the conditions at the site.
Sites can also be removed from the "sites.dat" file by deleting the appropriate line of site information. The file should contain no blank lines. Note that this action may cause site threat data mismatches in the previously inventoried site threat message files. It is therefore recommended that this action only be taken in fair-weather conditions, when the inventoried files are less likely to be displayed.

Using the "purgetime.txt" file

The editable "purgetime.txt" file in the $FXA_DATA/tstorm directory allows the user to change the number of hours beyond which the purge function will delete records in the SCAN Storm Cell database tables. For example, if the file contains "5.0", when the purge function is called, it would delete all records older than 5.0 hours for all tables (cells, mesos, tvs's, and sites) in the "scandata" database.

Click on the link below to bring up a new window with the latest version of the SCAN User's Guide.
SCAN 2.0 User's Guide

SCAN 2.0 Screen Captures

Click on an image to see the full size image:


This figure includes the D2D, SCAN Storm Cell Table, single trend, trend set, the Attribute Color Threshold window, and the Alarm Information window. It also shows the SCTI button turned yellow (more info on the SCTI button).
The Storm Cell Identification Display (SCID) window.

This figure includes the D2D, SCAN Storm Cell Table, Configurations menu, Trend Set cascading menu, Edit/Create Trend Set window, and a trend set example.
SCAN Data Monitoring System

This figure shows the Mesocyclone Table, the Storm Cell Table with Vert and Tips options on, and one pop-up tip.



National Weather Service
Last Modified: 15 Dec 2000, RLS.