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)
