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  Deep Thunder Forecast for Philadelphia

Current Deep Thunder Forecast for the Philadelphia Metropolitan Area

Clouds and Total Precipitation at 2 km between Data Points



Description

This page contains an animation that is a visualization of the Deep Thunder forecast focused on the Philadelphia area.   It uses data from the high-resolution nest at 2 km resolution.   Each time step corresponds to 30 minutes of forecast time.   The specific data and representation shown are for potential use for short-term weather-sensitive operations and planning.   They show the local terrain as a shaded surface that is colored by contour bands of total precipitation (as rain in inches), following the scale to the upper right, where brown implies no rain (dry) and heavier rainfall is in darker shades of blue.  If the model predicts no precipitation then a similar visualization of humidity will be shown instead.  If areas where precipitation is forecasted are sufficiently cold, then they may be marked with large or small Xs for snow.  The smaller markers imply light snow or flurries.  In animation, area of precipitation will appear to "paint" the surface blue.  However, the model calculations require some time to "spin-up" the microphysics to enable precipitation.  Therefore, there will typically be no precipitation in the first couple of hours of model results.  Since the precipitation is accumulated through the model run, regions which stop showing changes in color imply that the precipitation has ended.  In some cases when that happens and the temperature is sufficiently cold, snow markers may appear. This implies that wet surfaces may be beginning to freeze. 

The terrain is overlaid with maps of coastlines and state boundaries in black, rivers in blue and county boundaries in dark gray, and cities or other locations in black.   On colder days, a thick light blue line will mark the location of the freezing point of water. The terrain map is in a three-dimensional scene with predicted clouds.  The clouds are shown as a translucent white (boundary) surface derived from a threshold of total cloud water density (liquid and ice) where the ratio of that total to the contents of the atmosphere is 0.0001 kg of water per kg of air.  If the model predicts severe weather, such as convective activity that could lead to the formation of thunderstorms, then a translucent cyan surface may be visible within the clouds.  The region within this cyan surface corresponds to where precipitation is forming within the clouds (e.g., rain shafts) and where any storm activity would be the most severe.  





Instructions

The animation on this page is composed of a set of individual JPEG images with 30 minutes of forecast time between each frame.   Depending on your connection speed and that of your computer, the animation may take a few minutes to load and decompress in your browser.   When it is completed, the animation will play.   There are VCR-like controls under the animation to enable you to stop playback, play forward or backward, or step through the frames one at a time, control the speed of playback, etc.   The mode of playback is controlled via the bottom set of buttons.  Click on the button once, corresponding to the mode of choice (Once: play once in the cuirrent direction; Repeat: play repeatedly in the current direction; Swing: play forward and backward).  The top buttons are used to single step or animate or pause in a forward or backward direction.  The speed of playback can be controlled with the buttons marked Slower and Faster.   If you are having problems viewing or interacting with this animation, make sure your browser has Javascript enabled.

If the forecast information presented on this page does not seem to be current and you have visited this site recently, the results of the previous visit may have been saved in your web browser's cache. If so, you should change your cache settings (e.g., File->Preferences->Advanced->Cache in Netscape and set the document comparison to "Every time"). When you restart your browser, the problem should be solved. For your current session, you should manually clear the cache and reload the page.


The current model forecast indicates that snow, sleet or snow mixed with rain is predicted.   Click on the image below to see and interact with this forecast information.   If there are discrepancies between the values shown for precipitation below and those above, these are due to differences between how the different information is calculated.   For liquid precipitation (equivalent to rain), use the results above.   For frozen precipitation (equivalent to snow), use the results below.  



 

Learn More about Deep Thunder
 

Learn More about how Deep Thunder Visualizes the Data Generated by the Weather Model
 

Current Weather Information and Predictions for Philadelphia (from the National Weather Service)
 

  
 
  

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