Precipitation Enhancement Studies Model Visualization
Realtime Four Dimensional Data Assimilation (RT-FDDA)
The RT-FDDA system was developed to provide high-resolution short-term analyses/forecasts (0-12 [hours]). (click on image at left for realtime display, from ral.ucar.edu)
However, recent advances in computing power have allowed for a much longer forecast cycle; up to 36 [hours] at current operational sites given the present grid and model physics configuration.
In contrast, the twice-daily MM5 runs were specifically designed to provide long term forecasts (24-48 [hours]).
RT-FDDA employs a time-continuous assimilation of a variety of synoptic and asynoptic (meaning they are not measured at [specific] observing times but may be measured at variable times, from "An Introduction to Atmospheric and Oceanographic data", PDF) observation data including:
* METAR observations (includes "Specials")
* Ship/buoy observations
* Local surface observations
* WMO rawinsonde observations
* NESDIS satellite-derived winds
* ACARS aircraft observations
[T]he RT-FDDA forecasts contain realistic and detailed mesoscale atmospheric structures, including cloud and precipitation systems, and local thermally-forced circulations. (image at right example of thermal forcing, click image for detail, from wrh.noaa.gov)
It should be noted that RT-FDDA does not assimilate cloud/precipitation data.
The diagnosed cloud and precipitation systems in the analysis cycles result from the vertical motion and humidity assimilated from the available data.
This means that they start with no cloud and precipitation systems, or local thermally-driven circulations.
Therefore, a certain amount of model 'spin up' time is required for the atmosphere, as it is represented by the MM5, to begin responding to the mesoscale forcing resulting from variations in the local complex physiography. (image at left of a particle model using MM5 technology, click for detail, from dri.edi)
Special Thanks go to the 4DWX team
(image below of MM5 realtime precipitation forecast, click for detail, from mmm.ucar.edu)