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These images are total precipitable water vapor derived from the GOES-East and GOES-West sounders using the physical retrieval method. The product displayed is the total atmospheric precipitable water vapor value. (Precipitable water is the amount of liquid water, in millimeters, if all the atmospheric water vapor in the column is condensed.) The value is color-coded with browns being the driest and reds being the most moist. Clouds are represented as a gray color (see the color bar at the bottom of the image). A time sequence of the images is the best way to monitor drying and moistening trends. In spring, the central US region is frequented with return flow moisture situations; moist air available for later convective storms over the central US often originates from the Gulf of Mexico. During mid to late summer, moisture from the Gulf of California region likewise is frequently available for convection over the southwestern US (the "Southwest Monsoon").
The images are displayed in a Mercator projection and are generated every hour. The images are calculated using radiance measurements from most of the longwave channels (2-8), the water vapor channels (10-12) and most of the shortwave channels (13-14, 16). More detailed information on the sounder is available. The algorithm for Derived Product Imagery (DPI) was originally developed at the CIMSS by the NESDIS/STAR Advanced Satellite Products Branch (ASPB), formerly the NESDIS/ORA Systems Design and Applications Branch (SDAB). The following products are available:
Combined GOES-East/West Coverage
These images cover a wider east/west geographical region and have an effective resolution of 14 km (nominal resolution, which occurs at the sub-satellite point, over the equator, is 10 km).
Entire conterminous US
This DPI display is purposely shown at an effective resolution of 10 km for viewing of smaller scale features.
Precipitable water partitioned into three vertical layers
The vertical distribution of moisture as provided by three water vapor sensitive spectral bands on the Sounder (at 7.5, 7.0, and 6.5 um) is displaying in these images. This is done by comparing the precipitable water content within three layers of the troposphere. These layers, surface to 0.9 sigma ("low"), 0.9 to 0.7 sigma ("mid"), and, 0.7 to 0.3 sigma ("high"), approximately correspond to layer tops at 900 mb (1 km or 3000 ft), 700 mb (3 km or 10,000 ft), and 300 mb (9 km or 30,000 ft). This animation of layered PW allows one to compare the total precipitable water with that from each of the three layers, for the last available 12 hours (with interactive selection of the layers or total). Thus, for two separate areas with equal total precipitable water, one can determine if and how that equal total is distributed differently in the vertical for the two locations. (The PW DPI shown are at SFOV resolution.)
Entire conterminous US with Radiosondes
In this product the most recent 00 and 12 UTC GOES PW DPI, as described above, are shown with their corresponding 00 and 12 UTC radiosonde values of total precipitable water vapor (in mm) and 850 mb wind flags. The winds have been included to provide a sense of the mean lower level flow pattern which strongly impacts the transport of the PW. These comparison displays are typically updated at about 05 and 17 UTC.
Comparison with reported severe weather
Preliminary severe weather reports over the last 24 hours (12 UTC yesterday to 12 UTC today), as available from the Storm Prediction Center, have been plotted over a representative GOES Sounder PW DPI from last evening (00 UTC) in this product. This combination provides a simple, quick look at the level of correlation that exists between the GOES derived atmospheric moisture field and subsequent severe weather.
GOES Sounder precipitable water listings in text format
Simple hourly "ascii" text listings of parameters derived from the GOES vertical sounding profiles, including total and layered precipitable water, are made available on-line to be downloaded. The files available for about the last week are labeled by: date, time (UT), satellite (12-East, 10-West, 9-far Pacific), and data type ("tpw") and region (a-Atlantic; c-CONUS; p-Pacific).
GOES Sounder verification statistics
Daily comparisons are made between the full GOES retrievals and the radiosonde profiles of temperature and dewpoint temperatures. These comparsions are made both at 00 and 12 UTC whenever a retrieval is with 111 km of the radiosonde location. Similar comparisons are made between the National Environmental Prediction Center regional forecast (which serves as the first guess for the retrieval) and the radiosonde. Plots of total precipitable water, and dewpoint temperature statistics are available. In general, the GOES retrievals add information to that of the first guess for both moisture and temperature, though more so for moisture.