An Introduction to Forecast Models Outline Important Considerations: Atmospheric Science, Physical Processes. Weather Forecasting and Creating a Forecast Model. Model Construction and Resolution. Initialization and Model Run. Verification. Basics to Model Viewing, Time and Types of Data.
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(From Holton’s An Introduction to Dynamic Meteorology)
This image will be referred to again later in the presentation.
"Richardson's Forecast Factory"
Richardson knew that the amount of data that would need to be processed would be enormous, to create forecasts with accuracy and practical value.
Today, computers are used to handle all of the information needed.
Networks of upper-air observation were introduced in the 1940s, allowing for tracking atmospheric data.
Equations of atmospheric motion were studied and simplified, and by 1950, the first NWP experiments began.
The first forecast computer model was created and it used the Barotropic Equation of Atmospheric motion to create 500hPa height forecasts. (hPa = millibar(mb))
Those forecasts out to 24 hours were significantly more accurate than any previous forecasts, but aside from the scientists, were not very practical or easy to understand.
MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1230 PM EST MON FEB 04 2008
VALID FEB 04/1200 UTC THRU FEB 08/0000 UTC
...SEE NOUS42 KWNO ADMNFD FOR STATUS OF UPPER AIR INGEST...
MODEL INITIALIZATION ERRORS DO NOT APPEAR TO HAVE A SIGNIFICANT IMPACT ON THE FCST.
...TROF PUSHING INTO THE W D1-2 AND THRU THE CNTRL CONUS D3... THE NAM IS TOO COLD WITH H85 TEMPS OVER WRN TX AND THE ADJACENT RIO GRANDE VLY BY UP TO 6 C. THE GFS HAD SIMILAR ISSUES...BUT NOT TO THE DEGREE OF THE NAM...WITH TEMPS OFF BY APPROX 2-3 C IN THE SAME LCNS. THE NAM AND GFS MAY BE TOO COLD WITH THE H85 TEMPS AHEAD OF THE TROF OVER THE SRN PLAINS/LWR MS VLY INTO THE FORECAST PD AS A RESULT. TO THE N...THE NAM...AND TO A LESSER EXTENT THE GFS...DID NOT DO A GOOD JOB INITIALIZING THE STRENGTH OF THE H85 TEMP GRADIENT OVER NERN CAN/ERN AK...WITH THE NAM AND GFS UP TO 3-4 C TOO WARM WITH THE COLD POOL OVER THE YUKON AND UP TO 4 C TOO COLD OVER NRN B.C./ALBERTA. SOME OF THIS AIRMASS IS XPCTD TO PHASE WITH THE TROF OVER CONUS LATER IN THE PD. THE NAM AND GFS MAY NOT BE ACCURATELY DEPICTING THESE AIRMASSES AND THE TEMP GRADIENT IN THE FORECAST PD.
Models have various schemes of evaluating and forecasting these processes.
This site is commonly used and has several American models.
This site has a lot of various models, from SR to MR, American to Foreign and is a personal favorite of mine!
Radiation – The transfer of energy. cooling, heating, etc
Advection – Transport from one location to another.
Conduction – Heat transfer through physical objects.
Turbulence – Irregular fluctuation in (atmospheric) flow.
Drag – Frictional force between the air and the ground.
Latent heat – Heat transfer through change of state.
Saturation – Deals with moisture content.
Stability – Deals with resistance to vertical movement.
Buoyancy – The ability of an object to rise or sink.
Precipitation – Formation, size, intensity, velocity; type.
Gradient – The rate of change of a quantity. (P, T, etc)
Development and dissipation. (fronto- and cyclo-genesis)
Divergence – Outflow/separation of a physical quantity.
Convergence – Inflow/coming together of a quantity.
Tendency - Trend. (pressure, temperature, etc)
Orographics – How land and water affect weather.
Vorticity – A measure of rotation. (ie. Air parcel)
Condensation – The change from vapor to a liquid.
Evaporation – The change from liquid to a vapor.
Random probability – Must be considered, since it is impossible to create perfectly precise forecasts.
Data Assimilation these processes.