Enhanced_Wx

Introduction

The Enhanced_WxTool is a significant enhancement to the original Wx_SmartTool, which was written. Both tools assign Wx based on the corresponding PoP grids; however the Enhanced_WxTool offers the following additional functionality:
  1. The forecaster is allowed considerable freedom in choosing individual weather types (RW, R, SW, S, IP, ZR, L, ZL, and F are all supported).
  2. Up to three weather types may be mixed together and a different intensity (very light [--], light [-], moderate [m], or heavy [+]) may be assigned to each. So for example, it is possible to assign weather such as RmSmIP- with this tool.
  3. The forecaster can also choose whether to include thunder (T) with any other supported weather type; if thunder is included, he or she also has the option of specifying whether the thunder is severe in nature (T+).
  4. The forecaster can assign either probability qualifiers or areal coverage qualifiers (where allowed) to the chosen weather types. If a forecaster attempts to use an invalid qualifier for a weather type, the tool will generate an error message appears indicating that this is not allowed.
  5. For each individual weather type, the forecaster can override the default probability/coverage obtained from the PoP grid if desired. The same is also true for thunder (T). This makes it possible to: create weather combinations such as “Lkly RW:Chc SW” or “Def RW:Chc T”; and assign weather types of F, L, or ZL, which aren’t necessarily derived from the PoP grids.
  6. For categorical PoPs, the forecaster can use alternate probability/coverage terms (other than "Def" or "Wide") if desired. The following options are available: "Ocnl", "Frq", "Brf", "Pds", and "Inter". When used, this setting applies to all categorical precip coverages that are derived from the PoP grid.
  7. If thunder is included with the precipitation, the forecaster also has the additional option of specifying the following thunderstorm attributes, if desired:

The tool is designed so that the last three attributes (LgA, DmgW, and TOR) can only be assigned when severe thunderstorms (T+) are forecast. Similarly, the tool will also only allow SmA and GW to be used with non-severe thunderstorms (T). If the forecaster tries to assign a thunderstorm attribute that is invalid, the tool will display a message indicating this, and will automatically ignore such attributes and run to completion.

It should be noted that the tool does not apply any scientific principle to derive the final Wx type; the Wx type assigned is solely decided upon by the forecaster. The forecaster chooses the Wx type through the use of a GUI interface that appears when the tool is executed.


How the Procedure Works

The floating PoP grids for the time period in question must exist before running the tool. After creating all of the necessary floating PoP grids, to run the tool the forecaster needs only to select the BUF_WxTool from the list of available smart tools in GFE; this action brings up the following GUI:

Enhanced_Wx

Here is a brief overview of each section:

Qualifier Type: Allows you to toggle between the use of Probability and Areal Coverage terms. The default setting is “Prob”.

Alter Terms Cat PoPs (new): Allows you to use alternate probability/coverage terms ("Ocnl", "Frq", "Brf", "Pds", and "Inter") when categorical PoPs are used. When used, this setting will apply to all categorical precipitation probabilities/coverages that are derived from the PoP grid. The default setting is “None”.

1st/2nd/3rd Type: Allows you to select/combine up to 3 different weather types. In version 2.0, the lists of available weather types have been expanded to include L, ZL, and F.

1st/2nd/3rd Inten: Allows you to specify the intensity of each weather type (--, -, m, or +). In the case of fog (F), only + (dense) is a valid intensity. If F is selected with any other intensity, the tool will automatically remove the intensity to prevent any errors. The default setting is “-“ (light).

1st/2nd/3rd Type Alternate Prob/Cov (new): Allows you to override the default probability/coverage obtained from the corresponding PoP grid for each individual weather type. This allows the easy creation of weather types such as "Lkly RW:Chc SW". This approach also allows for the use of other weather types (for example, F, L, and ZL) which aren't necessarily PoP-dependent. The default setting is “None” - meaning the probability/coverage terms for each weather type are derived from the PoP grid by default.
Thunder?: Allows you to specify whether you want thunder included with the other weather type(s) selected. Options are “No”, “Yes (T)”, and “Yes (T+)” (severe T). The default setting is “No”.

Thunder Alternate Prob/Cov (new): Allows you to specify an alternate probability/coverage for T if desired. This setting will override the default probability/coverage obtained from the corresponding PoP grid, and makes it possible to create precip types such as "Def RW:Chc T". The default setting is “None” - meaning the probability/coverage term for T is derived from the PoP grid by default.

Tstm Attributes?: Allows you to specify Thunderstorm Attributes if you choose to include Thunder in the Wx grid.

Once the forecaster has made their selections from the above GUI, he/she then assigns the desired weather by clicking either of the Run or Run/Dismiss buttons within the GUI. When this is done, a single weather type is created based on the forecaster input. Unless specifically overridden by the forecaster, probability or areal coverage qualifiers will be determined from the PoP grid in accordance with the following table:

PoP Value (rounded to the nearest %) Probability Qualifier Areal Coverage Qualifier
0 - SChc_min_PoP_threshold* None; is assigned None; is assigned
SChc_min_PoP_threshold* - 24 Slight Chance (SChc) Isolated (Iso)
25 - 54 Chance (Chc) Scattered (Sct)
55 - 74 Likely (Lkly) Numerous (Num)
75 - 100 Definite (Def) Widespread (Wide)


* - SChc_min_PoP_threshold is the minimum PoP needed for a SChc (slight chance) of weather to be included in the Wx grid. This value is site-customizable; the default value is 14.5%. Please see the Installation/Configuration section below if you would like to change this setting at your site.