SatMet
Home PageOVERVIEW OF CASE (15 min presentation by exercise leader)
MORNING OVERVIEW
In most years, upper flow over the central U.S. becomes relatively weak by the beginning of summer. In fact, by late June the jet stream has typically migrated far to the north, and is found situated over the northern U.S., or southern Canada. The morning of 04 July 1995 found an unusually intense synoptic trough over the central and south central U.S. - - potentially strong upper support at a time of year when daytime temperatures were nearing their yearly peak, and moisture across the central and southern plains was abundant.
You will be playing the part of a forecaster at Pleasant Hill, Missouri (40S of MKC), with an area of forecast responsibility as shown in figure 1. You will be simulating the entire forecast process, from morning outlooks to afternoon nicest updates, as well as weather warnings -- when and if appropriate.
Throughout the exercise, various teams will be selected at random to present required briefings. Also, one team will be selected at the beginning to play the part of the Storm Prediction Center for issuance of Outlooks and Watches (separate from what is done by teams playing local forecasters).
SYNOPTIC SITUATION
Start GARP for the case study of 04 July 1995
Task I. (15 min lab ; 15 min discussion) : The time is 1600 UTC.
Using upper air analyses, together with the WV (6.7) and IR4 (10.7 micron) infrared satellite loops, and gridded data sets, create a brief written summary of the synoptic weather situation over the previous sixteen hours as it affects/will affect your station. Prepare an updated Zone forecast for any zone in which you expect significant weather. Finally, prepare the morning severe weather outlook for the region shown in fig. 1. This outlook is due by 1700 UTC at your station.
Class Discussion: Using all available data, one team (to be selected at random 10 min before briefing time) will present a weather briefing including 1) a review of overnight activity, 2) a synopsis of the current situation, and 3) details of the convective outlook. Input is expected from all teams, particularly on the convective outlook.
What effects did the Mesoscale Convective System (MCS) have on the observed conditions and the 12Z model forecast? Was there more than one MCS of interest in the area? Which model data did you use?
AFTERNOON UPDATES
(This section will be carried out in modified real-time which will pass at about twice normal clock time. The instructor will keep the group apprised of the simulated times.)
Task II. (30 min lab ; 15 min discussion) : The time is 2000 UTC.
Following a class discussion of the write-ups generated in Task 1, you will then begin the process of making the morning convective outlook for the forecast area. This outlook is due by 2000 UTC at your station. Use the 4 km VIS, WV and IR satellite data prior to 19:30 UTC. Look at the Surface RUC and RUC fields up to 18 UTC. (Note: theta-e is available only in RUC.)Evaluate the spatial distribution in the equivalent potential temperature field at 1800 UTC. Are any significant features observable ? Using a new GARP, compare the topography image (under Options, Topographic Maps, Midwest; use the 'roygbv' color enhancement option) with the satellite image animation. Do you think any topographic features could have influenced the propagation of the outflow boundaries over Missouri?
Use the available 1 km VIS satellite imagery prior to 2000 UTC, and other satellite and EAX radar data available before this time. You can use the GARP Options to overlay the NEXRAD sites and radar range rings on the first frame of your satellite loop. You may also wish to use the GARP cursor zoom with the 1km VIS imagery to focus in on the area of interest.
1) Prepare an update to the severe weather outlook at 2000 UTC.
2) If appropriate issue Watches and/or Warnings as they come up.
Class discussion: Using all available data, a randomly selected team will conduct a class discussion on the Zone Forecasts and present a 6-hr Convective Update valid at 2130 UTC.
Task III. (30 min lab; 15 min discussion) : The time is 2300 UTC.
As in TASK 2, but due by 2300 UTC. The Convective Update is valid at 2330 UTC.
Utilize the RUC/Surface RUC analyses and evaluate the
NIDS radar data for EAX and LSX prior to 2200 UTC.
Load an animation sequence of 15-minute interval, 1 km VIS
satellite imagery; for example the rapid scan sequences 2035-2045
and 2135-2145 UTC.
Issue severe weather warnings in the EAX County Warning Area as appropriate. Evaluate which thunderstorms within this Area warrant the issuance of a severe or tornado warning, and be prepared to justify this issuance. Look for storm scale features similar to what was presented in the lecture by John Weaver. Do these features represent the threat of severe weather ? If so, how do you incorporate this information into your warning ?
(Note: A report of a brief tornado touchdown was called in at 2035 UTC. The tornado touched down in Doniphan County, Kansas. Otherwise, the only severe reports have been hail (3/4") in eastern Kansas.)
(Additional notes: After 2315 UTC, new severe reports include 1" hail in Buchanan County, MO, with wind gusts to 60 mph. A tornado has been reported near St. Joseph in Buchanan County within the past 20 minutes, but there are no other details avail able as yet. First look at the Rapid Scan satellite time sequence ending just prior to 2315 UTC, as well as radar data prior to 2315 UTC. Which storm do you think produced the tornado and what is your reasoning? Use the surface RUC and RUC data. Use the cursor zoom function to examine details of the satellite imagery. On the base map, sketch the location of convective features which threaten your Warning Area. What are their formation mechanisms? Will these features intensify, remain the same or weaken?)
FOLLOW-UP DISCUSSION (15 min) : Summary of case and discussion of verification.
