MET4300_SWX_LEC6

MET4300_SWX_LEC6 - MET 4300 Lecture 6 Models and...

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MET 4300 Lecture 6 Models and Forecasting 20 January 2012
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Forecasting …expected future occurrence of one or more weather elements ---temperature, humidity, wind, precipitation,… NOT the same as the state variables represented within a numerical model Also NOT the same as measurements of the atmosphere. Example: Density ( ρ )
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Model-Simulated Supercell Thunderstorm
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Model Domains Physical part of the atmosphere being simulated Boundary Conditions around the edges and at top & bottom communicate information from outside to the inside BCs Can come from another model or (for retrospective calculations) from observations, or they might be idealized If not handled properly BCs can cause problems Not needed (apart from top and bottom) if the model covers the globe
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FORECAST HUMAN FORECASTER: Experience, Extrapolation Climatology, Guesswork Surface Observations Soundings Radar Satellite Images …and so forth Numerical Forecast Objective Analysis & Initialization Numerical Model(s) Numerical Forecast for NOW FUTURE Forecast Process
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Model Forecast Cycle Observations 1 h before to ½ h after 00Z & 12Z Modify “first guess”— 12h forecast from previous cycle Calculations can take up to 3 h. Graphical and numerical output Disseminated as soon as available
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Surface Obs
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Model Analysis
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How Do Numerical Models Work? Know prognostic equations that govern the weather Always idealizations Always partial differential equations (non-linear) Represent the “state variables” on a (more -or-less) square grid Convert the rates of change with respect to time and space into finite differences
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This note was uploaded on 02/18/2012 for the course MET 4300 taught by Professor Staff during the Spring '08 term at FIU.

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MET4300_SWX_LEC6 - MET 4300 Lecture 6 Models and...

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