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In this section we describe two experimental web displays that were developed at NCAR to display the Convective Hazard forecasts produced by NCWF2. The displays that will be described are the AJAX-based Experimental ADDS Display and the Java-based Flight Path Tool. Both displays receive the detection and forecast data generated by NCWF2 running at the Aviation Weather Center. The data are obtained from NOAAport. The two displays use the same color tables to display the convective hazard field and the probabilistic forecasts of convection that maybe hazardous to aviation.
Experimental ADDS NCWF2 Display
The new AJAX-based Display of NCWF-2 was developed at NCAR/RAL. AJAX, which stands for Asynchronous JavaScript and XML, is a term used to describe a new approach to using a number of existing technologies for developing web-based applications. The result is an application that is faster and more responsive to user interactions, making it an ideal display for those with limited band-width or limited access to the internet.
Startup page for Experimental ADDS NCWF2 display.
Components of the Display
1) Data Display Window – Appears as CONUS map with Base Interest field just below the time bar.
2) Legend – Located in lower left corner of the display.
3) Time Bar – located above the data display window. The displayed time is highlighted in orange. Dwell over tick marks with cursor to see corresponding time. The small left/right arrows just above the time bar on the left hand side of the display may be used for changing the length of viewable history.
4) Movie Controls – located just above time bar, backward looping, boomerang looping, forward looping along with movie speed control.
5) Field List – select different backgrounds and overlays fields for display. Only one background field may be viewed at a time.
Display Variables
Several NCWF2 fields depicting the current convective weather, the probabilistic forecasts of convection and the forecast accuracy are available for display and are listed below.
1) Base Interest – a blend of radar and lightning data that gives an indication of the location and intensity of precipitation.
2) Convective Diagnosis – this field depicts the current location of storms based on storm intensity and structure and also is a mix of radar and lightning data.
3) 1 hr Past Performance Polygons - Outline of previous 1 hour probabilistic forecast of convection which is valid at the user selected time before present. The contour depicts the area spanned by forecasted probabilities of 40% or greater.
4) Storm Motion Vectors – Indicates the most recent observed motion of the area of storms and used in forecasts out to 2 hours. The speed of the storm is proportional to the length of the vector.
5) Probability Forecasts - The predicted likelihood that storms posing an aviation hazard will impact a location at a given time. The forecasted likely storm positions are given at discrete leadtimes of 30, 60, 90, and 120 min.
Display Variable Details
The Base Interest and Convective Diagnosis fields are displayed using VIP levels with level 3 and greater indicating the presence of convection that is hazardous to aviation.
Past performance of the forecasts can be determined by selecting the 1 hr Past Performance Polygons. The past performance polygons are created by contouring the 1-hr forecast generated 1 hour ago at the 40% probability level. The amount of overlap between this contour and the corresponding Convective Diagnosis indicates how well the system is performing. Very close alignment of the contour and the Convective Diagnosis indicates that the system is performing very well and the user can have confidence in the forecasts.
The Storm Motion Vectors may be overlaid on any of the available fields. The length of the vector indicates the speed of the area of storms (see Motion Vector Legend). The storm motion vectors are available in both BUFR (motion vectors linked to individual storms) and GRIB (grid of storm motions) format. Currently the display uses the gridded motion vector data (i.e., a motion vector is available every 4 km). This results in multiple identical motion vectors being displayed for each tracked area of storms. Currently the gridded field is subsampled so that a motion vector is given at every third grid point.
Zoomed in view of Convective Diagnosis field with Motion Vectors overlaid.
The forecasted locations of the Convective Hazards are given in terms of probability. The probability indicates the likelihood that a storm will be present at a given location at that time. The probability forecasts are displayed in shades of pink with the darker shades of pink corresponding with the higher probabilities. The display allows the user to view the forecasts by either clicking a major tick mark in the future labeled +30, +60, +90, +120 min or by executing the movie loop. The movie loop shows the past history of storms (given in VIP levels) followed by the probabilistic forecast of convection (pink shades denoting probabilities). At the forecast times, the current weather, which may be given by either the Base Interest or the Convective Diagnosis, remains beneath the forecast layer.
Zoomed in view of 120 min Probabilistic Forecast with Base Interest field underlaid. Image obtained by left-clicking on major tick mark 2 hours in the future.
Controls
Time Bar Features - By clicking on the major tick marks on the Time Bar, the user can select a specific time in the past or future (i.e., forecasts) for display. The current time is always labelled now just above the Time Bar. The current time displayed is outlined in orange. Missing images are depicted with a missing major tick mark.
Flexible Past History – The small arrows at the left-hand side of the display, above the time bar can be used to reduce or increase the viewable time history to view of Base Interest or Convective Diagnosis. Left arrow increases past history, right arrow decreases past viewable history. The maximum viewable past history is set at 6 hours.
Movie Looping – The movie looping capability allows the user to examine how storms have evolved and where they are likely to be in the next 2 hours. The forward animation is started by clicking the arrow pointing to the right. By default, the past 120 min of weather are available for display at 10 min resolution followed by 4 forecast images that are 30, 60, 90 and 120 min into the future. The amount of past history included in the movie loop can be adjusted by left clicking on the arrows just above the time bar on the left had side of the display. The user increase the past history by up to 6 hours. The forecast length (2 hrs) and forecast interval (30 min) are fixed. The images may be animated forward (right-pointing arrow) or backward (left-pointing arrow) or in boomerang (back and forth) mode (center button). The looping speed can also be adjusted.
Overlays – The motion vectors and/or the past performance polygon fields may be overlaid on either the Base Interest or Convective Diagnosis / Probabilistic Forecasts. Note: past perfomance is not displayed on the forecast images.
Zooming – Left click on a point in the CONUS to zoom in on a predefined ‘zoom’ region. To unzoom, click button with plus sign on it in the upper left corner of the display.
Panning – First zoom in on a region of interest, then pan by left clicking and dragging.
Experimental ADDS Flight Path Tool
The flight path tool is a java-based viewer written in Jade by developers at NCAR. The java tool grabs data from disparate sources to provide up-to-the-minute analyses and forecasts of atmospheric conditions including temperature, moisture, wind speed, icing conditions, turbulence and convection in space and time.
Figure 1. Startup page for the convective weather flight path tool depicting the current significant weather across the US (VIP levels) and the terrain above 10kft (brown).
Please see the Flight Path Tool User’s Guide (http://www.weather.aero/tutorials/fptAppTutorial/step1.php) for detailed instructions on how to use the Flight Path Tool. A description of the convective weather products available for display with the flight path tool is given below. By default the CONUS is displayed along with terrain features and states (Figure 1). The default settings can be changed and saved on your machine (see User’s Guide for details).
The flight path tool can be used to see the current position of thunderstorms and their most likely position in the next two hours. Both the Convective SIGMETS and products produced by Version 2 of the National Convective Weather Forecast (NCWF2) system running at the AWC can be displayed with the Flight Path Tool. Both are meant to serve as graphical tools for depicting the current and 0 to 2 hour forecast positions of thunderstorms. The C-SIGMET is specifically defined as areas where severe thunderstorm activity is expected over the next 2 hours. The NCWF2 data distribution includes the Base Interest field, the National Convective Hazard Detection (NCHD) field, and the NCWF2 Probabilistic 30,60,90 and 120 min forecasts. In addition, previous 1-hr forecasts produced with NCWF2 are available for overlay on the NCHD field for users to graphically estimate the recent performance trends in the system. A detailed description of each field in the NCWF2 data distribution is given under Hazard Detection
Tutorial
Start up the Flight Path Tool. This will bring up the most recent observation of convection (NCWF – Significant Weather – Figure 1 *labeled NCWD/F in viewer*). Note that the cross section tool and the altitude bar at the right of the display are not functional for convective weather products.
Figure 2. Magnified Significant Weather field (labeled NCWD/F) depicting convective SIGMET given by red polygon and 1-hr performance shapes given by magenta contours. Note the 1-hr performance shape is obtained by contouring at 0.4 the 1-hr forecast probability field valid at the current time. The variable list below the display indicates data availability (dots), which fields are selected (cyan dots), and which fields are displayed (circled cyan dots).
Zoom in on an area of convection. Your display should look something like Figure 2. This significant weather field depicts areas of convection and stratiform precipitation of VIP level 1 and greater. The gray dots next to each field name indicate the times when observations or forecasts are available (Figure 2). These dots become cyan when the data field is selected. The data point that is currently displayed is highlighted with a black circle. While higher temporal resolution in the observations is available in the observations, the observed fields can only be displayed in 30 min intervals relative to the current time.
Figure 3. Magnified view of the most recent Convective Hazard Detection field valid at 1747 UTC on 30 May 2006.
Weather is considered an aviation hazard when the VIP level exceeds 3. Select NCWD/F Low Filter. This field depicts the areas of convection that are hazardous to aviation (Figure 3). This is what we now call the National Convective Hazard Detection (NCHD). The NCHD field is used to derive the storm motion vectors and determine trends in storm area coverage. The probability forecasts are based on a trended version of this field.
Figure 4. One and two hour forecasts produced by NCWF2 valid at 1852 UTC and 1952 UTC, respectively. The convective SIGMETS (red dashed) and AIRMETS (blue dashed) are also displayed.
The AIRMETS and SIGMETS are valid until 1955 UTC. Note that the 30 and 90 min forecasts are also available for display.
As you step forward in time, the background field (either Significant Weather or NCHD) will change to a convective weather hazard forecast. The forecasts are intended to indicate where the observed convective hazards are likely to be in the next 2 hours. Advancing forward in time (either by using the movie loop or clicking on the time bar) will show successive hazard detections (given in 30 min increments) up to present, followed by the 30,60,90 and 120 min probability forecasts (Figure 4 - 60 and 120 min forecasts). The display automatically updates to the latest observation (Significant weather or hazard detection depending on which field has been selected) whenever a new observation becomes available.
There are several data overlays which may be plotted simultaneously over the background grid. If convective SIGMETS is selected, they are displayed as red dashed polygons with thunderstorm symbol in its center. You may mouse over the thunderstorm icon within the convective SIGMET to see the text associated with the C-SIGMET. Additional text information from TAFS (black squares), PIREPS and METARS (colored squares, circles and Ms’, respectively) may also be displayed by selecting each field and mousing over the corresponding symbols. Figure 2 gives an example of overlaying the convective SIGMET on top of the Significant Weather. The 1 hour performance polygon (magenta contours) is obtained by contour the 1 hour probability forecast at the 0.4 probability level.