Adds hems weather tool

One of the conclusions of the summit was that there was an absence of usable ceiling and visibility data between reporting and forecasting stations. Often, HEMS operators conduct entire HEMS flights in the area between such stations, with reliance on off-course stations and area forecasts to make critical flight planning decisions. One of the outputs of this summit was a commitment to provide the HEMS operating community access to information, which might support better weather decision-making in VFR operations.

The ceiling and visibility data are 'assessments,' meaning they are determinations of the ceiling and visibility that are likely to exist in the grid block based on terrain influences, technical assessments, and observations provided to software forecasting models that automatically generate the graphical product.

The user must understand that this weather product is not a report of an observation or a forecast. It is an assessment of the ceiling and visibility at the time chosen by the user and at the location of the grid block s.

In addition, this product has not completed a rigorous Flight Standards operational suitability assessment. This assessment establishes the product as either a primary weather product that meets all safety and regulatory requirements e.

Until that assessment, the product currently is experimental, but highly informational. The user should be aware that the weather tool derives ceiling and visibility by interpolating the nearest METAR data. This interpolation process, in effect, 'stretches' limited-area METAR observations across a broader area between stations accounting for terrain effects on ceiling height. However, a critical issue is that the reliability of the information generally degrades as distance from a METAR site increases.

Thus, users should apply practical judgment when considering the 'likely' weather conditions that are remote from a METAR site. To aid in this judgment, the product provides confidence fields that integrate a variety of product quality factors. Accordingly, indications of a 'likely' weather condition that indicates a no-go condition should strongly influence the decisions of certificate holders authorized to use this product.

The weather data available includes flight category, ceiling, visibility, radar, convection, icing, temperature, relative humidity, and wind. The limitations of the radar such as blockage by mountains, lack of radar to radar overlap and overprocessing of clutter and AP can cause the image to not show precipitation where there might be some. The image used is the RALA product.

This only uses the reflectivity from the lowest scan of the nearest radar. This is a 1km image for the contiguous United States. Like the satellite images, the radar mosaic is sliced up and put into the tile cache to provide the maximum resolution and optimal transmission bandwidth.

The tile cache is only updated every 10 minutes MRMS data available every 2. The display incorporates the latest radar image plus the previous 4 into a loop of radar data showing progression of precipitation echoes. By moving the time slider into the past, the radar loop will always show the latest 5 images ending in the time shown in the slider box.

The gridded analysis product provides near surface ceiling and visibility information every 15 minutes. It's important to note that the analysis is an interpolation between observation points, and therefore may not represent actual conditions occurring. This set of rules is commonly used throughout the aviation industry. Ceiling grids are color-coded to show ceilings up to ft AGL , and visibility displays color-coded grids for visibility up to 5 miles.

Values above ft AGL for ceilings, or 5 miles visibility are transparent. The forecast products are displayed by advancing the time slider forward. The Time slider is located in the upper right corner of the display, just below the current date and time. The product displayed is valid at that hour. Figure 2: Time display and time slider. This tool provides hourly forecasts of ceiling, visibility, and flight category see table below out to 6 hours.

The forecast is utilizing the same model as the Gridded Ceiling and Visibility Analysis. The icing severity product is a three-dimensional product and provides depictions at specified altitudes above ground level AGL at , , , and feet. In regions of steep terrain, these altitudes may have significant deviations from actual height above terrain given the limiting factor of grid cell size, which is approximately 13 km and the resolution of the topography in the model.

The icing severity product combines a multitude of weather observations temperature, humidity, satellite, observed surface weather and pilot reports, radar data, etc. These products start with data from the RAP which is run hourly. FIP has forecasts at 1, 2, 3, 6, 9, 12, 15 and 18 hours. Temperature, relative humidity and wind speed are presented on ' AGL increments to '.

These grids are available every hour and forecasts run to 6 hours into the future. Data overlays offer not only a display of data but each feature can be clicked on to get more information.

It should be noted that each feature on the display could overlap another feature making it unselectable. To select that underlying feature, a layer or two might have to be turned off.

This is especially true of the wind barb display. The METAR observations are plotted using the standard station model where temperature, dewpoint, winds, altimeter setting, weather, ceiling and visibility are displayed around the station location. The stations displayed follow a progressive priority scheme that will show more stations depending on how far the user zooms in.

This density can be changed through the Options menu. If the time slider is moved into the past, the nearest observation before the listed time is displayed. If the slider is moved into the future, the TAF for that station is shown. The Aviation Weather Center delivers consistent, timely and accurate weather information for the world airspace system.

We are a team of highly skilled people dedicated to working with customers and partners to enhance safe and efficient flight. The link you have selected will take you to a non-U. Government website for additional information. This link is provided solely for your information and convenience, and does not imply any endorsement by NOAA or the U.