SatMet Home PageCase Synopsis : A developing weather system over the Oklahoma panhandle region threatens the Midwest for the next 36 hours. The analysis period runs from 00 UTC / 18 January through 12 UTC / 19 January, 1996.
Challenge : Forecast the snow amounts for Madison, Wisconsin.
The focus of this exercise is to employ available GOES-8 WV (6.7 micron channel) loops as an analysis and forecast aid. Utilize the WV loops to characterize meteorological features of interest to the forecast challenge, follow the evolution of these features over the forecast period, and verify model prognoses. Key in on 300-500 mb model parameters in pattern matching with the WV imagery. Also consider the rain/snow issue in this case.
Part I : Initial outlook (25 min exercise ; 5 min discussion)
The time is 11 UTC (5 a.m. local time in Madison) on 18 January. Integrate conventional surface reports, radar loops, and satellite loops prior to 1100 UTC. Also use the 00 UTC / 18 Jan raob data and model guidance (00 UTC ETA model forecast).
Task : Develop a point forecast for QPF and snow amounts for Madison valid over the next 25 hours (through 12 UTC / 19 Jan).
Points to ponder :
1. Do the ETA initial upper-level fields appear well-analyzed? Integrate the 00 UTC WV image with overlays (300 mb wind and vorticity). Use the WV loop to hindcast if necessary.
2. Does the 12-hour ETA forecast look reasonable (is the model "on track")? Employ WV interpretation principles to match evolution of features in the imagery through 11 UTC, with the 12-hour upper level prognostic fields.
3. Will the bulk of the precipitation in Madison be rain or snow?
Part II : First forecast update (15 min exercise)
We are now at 23 UTC (5 p.m. local time) on 18 January. It is time to update the forecast based on the 12 UTC upper air data, conventional surface reports, radar images and WV imagery. However, power outages at a primary data processing facility have caused the loss of some of the datasets. The 12 UTC model output is not available. Note also that the radar mosaic data is not available after 19 UTC.
Use the available data to update your Madison precipitation forecast. Load the GOES WV loop prior to 23 UTC. Focus on the information suggested by the WV imagery. Relative to Madison, consider :
Overlay the ETA 24-hour forecast fields from 00 UTC / 18 Jan onto the available WV image which is closest in time to the model valid time, to assess the model forecast accuracy in terms of the positioning of features mentioned above. Examine the model fields of relative humidity at the 700 and 300 mb levels. Update your forecast based on your interpretation of the WV loop and model assessment.
Task : Update the point forecast for Madison (QPF and snow amount).
Points to ponder :
1. What features in the WV loop are revealing the atmospheric structure? In particular, note the evolution of the features, their orientation and juxtaposition relative to Madison.
2. Do the features depicted at the end of the WV loop match the 24-hour ETA forecast position (vorticity center, dry slot)?
3. Do you expect significant "back side" precipitation in Madison based on the vorticity center trajectory and structure depicted in the WV imagery?
Part III : Second forecast update (15 min exercise)
The time is 05 UTC / 19 January. Utilize the 00 UTC upper air data, surface observations and the WV imagery prior to 05 UTC to update your forecast. Additional model and radar products are not available. The valid period for your forecast still extends to 12 UTC (the next seven hours).
Task : Update the point forecast for Madison (QPF and snow amount).
Points to ponder :
1. Does the event appear to be over, based on the WV imagery? Is significant "back side" precipitation occurring or developing?
2. What does the WV imagery tell you about the ETA model forecast of upper-level forcing in this case?
Part IV : Verification and discussion (15 min exercise ; 15 min summary discussion)
1. Forecast teams will provide their QPF and snowfall forecasts.
2. The official NWS operational forecasts will be presented and discussed.
3. Verification data will be distributed and analyzed, with summary on the key points from the satellite data evaluation.
