updated 3 July 2009
Pacific Ocean
North America
Atlantic Ocean
 |
 |
 |
| Archive | Forecast | Archive + Forecast |
| Archive | Forecast | Archive + Forecast |
| Archive | Forecast | Archive + Forecast |
For the remainder of the "summer" the DT potential temperature shading has been modified to provide a larger range of values (accomplished by using a 5-degree interval, rather than four) and to accomodate warmer potential temperatures. - implemented with the 1200 UTC run on 3 July 2009.
As described by Ron McTaggert Cowan in association with the Mesoscale Research Group, McGill/UAlbany/UQAM, "...The DT has become commonly used as a dynamically based representation of the top of the troposphere. The distribution of potential temperature on the DT is indicative of the topography of this surface and therefore of the potential vorticity (PV) structure of the upper troposphere and lower stratosphere. Cooler potential temperatures suggest regions of depressed tropopause height and warmer potential temperatures suggest regions of elevated tropopause height. Because both potential temperature and PV are conserved for adiabatic, inviscid flows, the potential temperature distribution shown in these analyses should - barring diabatic influences - essentially be simply advected by the DT winds. Active regions for cyclogenesis are generally found near tropopause folds (manifested as large gradients in potential temperature on the DT). Areas where the nonconservation of potential temperature on the DT is significant are commonly associated with upper-level diabatic heating and ridging on the DT produced by enhanced convection downstream of tropical and extratropical cyclones."
The DT imagery uses the Global Forecast System (GFS) gridded forecast data. The 0 to 84-hour forecast plots utilize the half-degree (latitude by longitude) data, while the 90 to 180-hour forecast plots utilize the one-degree data. Plots are made in GEMPAK using a c-shell script that was programmed in UNIX and called 4xdaily using cron. The cron scheduler begins generating plots at 0530, 1130, 1730, and 2330 UTC from the 0000, 0600, 1200, and 1800 UTC datasets, respectively. Each image takes approximately 90 seconds to generate and is 400 Kb in size. The last plot is typically generated at 56 minutes past the hour mentioned above.
DT imagery (both forecast and analysis data) can be
found from the websites listed below:
*Jim Steenburgh at the University of Utah
*Greg Hakim at the University of Washington
*Ron McTaggert-Cowan in associated with
the Mesoscale Research Group, McGill/UAlbany/UQAM
*Ryan Maue at Florida State University