DataStreme Activity 10B:

CYCLONE TRACK WEATHER

Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1, Image 2 and Image 3 Files.
  3. Print (when available) the Thursday, 15 November 2001, Daily Summary File.

To Do Activity:

  1. Read Chapter 10 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 10B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 10B Now


WELCOME BACK: Procedure continued from STUDY GUIDE.

  1. Recent weather patterns across the "lower 48", particularly the central and eastern states, have been relatively mild and tranquil. Storm systems have generally followed a track across southern portions of Canada. This type of pattern is somewhat unusual for this time of year. For this portion of the activity we will consider a vigorous spring storm from last April. Associated with this storm were severe thunderstorms that stretched from Virginia to north Texas, some spawning tornadoes. There were also heavy rains, some occurring atop melting snows, that caused extensive flooding. And this storm system was just getting started!

    Image 1 is the surface map of 00Z 11 APR 2001. At map time the center of the storm circulation, as marked by the innermost closed isobar, was located [(in the TX-NM-CO-OK border region) (along the Arkansas-Mississippi border)]. The circulation around the low-pressure center was [(clockwise and outward) (counterclockwise and inward)].

  2. Winds in the warm sector, between the warm/stationary and the cold fronts, were predominantly from the [(south or southeast) (west or northwest)]. Winds at stations ahead of the warm/stationary front were generally from the [(east or northeast) (south or southwest)]. Winds at the stations in New Mexico behind the cold front were from the [(west) (north)].

  3. Comparing temperatures and dewpoints at stations ahead of and behind the warm/stationary front, stations behind the front were [(warmer) (cooler)] and had [(higher) (lower)] water vapor contents. Compared to stations ahead of and behind the cold front, stations behind the front were [(warmer) (cooler)] and had [(higher) (lower)] water vapor contents.

  4. The threat of severe weather, as indicated by the tornado watch box (parallelogram labelled T119) was located in the warm air ahead of the cold front. Another threat of severe thunderstorms existed along the warm/stationary front combination as shown by a tornado and severe thunderstorm watch boxes. In both instances, the lifting mechanism of the warm, humid air to produce thunderstorms was [(frontal) (orographic)].

  5. While not shown, the upper air flow as depicted on 500-mb and 300-mb maps at 00Z 11 APR 2001 throughout the region from the Southwest to the Great Lakes, was towards the northeast. Based on this upper-air flow, the 11 APR storm system would have been predicted to move toward the [(southeast) (northeast)].

  6. Image 2 is a DataStreme forecast map. It is a sample of the kinds of maps available in the "Forecasts" section of the DataStreme Homepage. These forecast conditions at stations across the country are produced by a computer model of the atmosphere using mathematical equations of the physical laws applying to fluid motions, starting from the observed conditions at a given time. This particular numerical weather prediction model producing the forecast shown is the Nested Grid Model (NGM), so named for the mathematical scheme used in the calculations.

    This forecast map was delivered on the DataStreme homepage as a "24 Hour" map, meaning it was a projection of weather conditions 24 hours into the future. The "Valid" time, shown on the printed map's upper left corner, is when these conditions are expected to exist. The Valid time of the map is 00Z 12 APR 2001, consequently, the forecast would have been based on actual observations at [(00) (12)] Z on 11 APR 2001.

  7. The forecast data for each station are presented in a "forecast station model" that is explained in the Homepage User's Guide, found in the Extras section on the DataStreme Homepage. The forecast conditions for the valid time of 00Z 12 APR 2001 at Springfield, Missouri (in southwest MO) were:


  8. Although weather systems are not shown on forecast maps, by utilizing the hand-twist model and observing the wind directions, weather features may be approximately located. Winds having a general direction from the south and southeast were predicted across the Great Lakes at 00Z 12 APR. Winds having directions from the north were predicted across the Dakotas. Based on this circulation pattern, the low-pressure center was forecast to be located near [(northern Michigan) (southeastern South Dakota)]. The weather symbols show that there was a good chance of [(freezing rain) (thunderstorms)] across Minnesota.

  9. The wind directions can also be used to anticipate the location of the cold front. Southerly winds and warm air advection were expected ahead of the cold front while northerly or westerly winds and cold air advection were expected behind the cold front. Based on these wind directions and their change across a narrow zone, the cold front was expected to stretch from eastern Nebraska to [(Wyoming) (central Oklahoma)].

  10. Wind speeds at several stations in the north-central portion of the country were predicted to be 30 to 35 knots, relatively strong and probably gusty. Even without the depiction of isobars, these wind speeds would suggest a [(strong) (weak)] pressure gradient to have existed in that region.

  11. Image 3 is the actual surface map of 00Z 12 APR 2001. This [(is) (is not)] the same time as the forecast weather conditions of the Image 2 map. Lay the forecast map on the actual map. Hold up to the light and draw the locations of the low-pressure center (L) and fronts on the forecast map. The storm system location and the high wind speeds shown were generally [(consistent with) (very different from)] the data appearing on the forecast map.

  12. Compare the weather conditions forecast with those actually reported at 00Z 12 April for the following stations under the influence of the storm system: (a) Minneapolis, Minnesota, (b) Huron, South Dakota, (c) Des Moines, Iowa, (d) Chicago, Illinois, (e) Dallas, Texas, and (f) Lake Charles, Louisiana. Specifically for the values of temperature, wind direction, and cloud cover, the forecast conditions would have been [(a useful guide) (very misleading)] to residents of those cities.

DataStreme forecast maps can be used to anticipate weather conditions in your area. Actual forecasts issued by the National Weather Service are produced by meteorologists beginning with this computer guidance material. Have students compare the forecast weather conditions for your location with those that actually occur at the forecast "valid time". You might also compare the DataStreme forecasts to those delivered by your NOAA Weather Radio station and local radio and television stations or newspapers. (Weather forecasts appearing in newspapers may be the least accurate due to the long lead time needed to meet their publication deadlines.)


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday, 19 November 2001, or as coordinated with your mentor for Break Week:

  1. Chapter 10 Progress Response Form,
  2. 10A and 10B Activity Response Form,
  3. STUDY GUIDE, Part B: Applications, page 10B-3.

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URL: datastreme/learn/b_act.html
©Copyright, 2001, American Meteorological Society