Assignment 1, part c: Final weather maps and discussion Map: 20 points Discussion: 15 points Grading elements Front types/positions, highs, lows: 10 points CAA, WAA areas, air mass types: 5 points Precipitation areas: 5 points Key points for Weather discussion There is a well-developed mid-latitude cyclone with the surface low pressure located in northwest Iowa, with a sea level pressure of 999 mb. The highest sea level pressure is located in North Dakota. A cold front extends from the center of low southward through western Iowa, western Missouri, and eastern Oklahoma. The main identifying features of this cold front are: 1. Location of well-defined pressure trough 2. Wind shift, from southeasterly winds ahead of the front (in warm sector) to generally northwesterly winds behind the front 3. Narrow bands of scattered showers and thunderstorms at or ahead of the pressure trough (e.g. Missouri, Arkansas) 4. Some decrease in moisture, clearing skies behind the southern part of the front (e.g. Kansas, Oklahoma) 5. Changes in temperature and moisture are more profound in the northern part of the front, near the low center (e.g. Iowa, Nebraska) Key points for Weather discussion (continued) A warm front extends from the center of low eastward through northern Iowa and northern Illinois. The main identifying features of this warm front are: 1. Weak pressure trough in the vicinity of the front, though not as clear as cold front! 2. Wind shift from southeasterly behind the front (in warm sector, e.g. eastern Missouri, central and southern Illinois) to easterly, northeasterly ahead of the front (e.g. Wisconsin, Minnesota) 3. Widespread overcast skies and broad area of precipitation ahead of the front, with snow occurring well north and west of the front where cold air is deep enough (e.g. northern Wisconsin, central Minnesota) Also further back behind the warm front and to the north and west of the surface low in the coldest air, there are relatively strong surface winds (20 kts or more) and snow being reported (southwestern Minnesota, eastern South Dakota, eastern Nebraska). Where surface pressures are highest is generally in the cold area (e.g. North Dakota) where temperatures fall to teens and single digits. Key points for Weather discussion (continued) Stage of development per Norwegian cyclone model: The mid-latitude cyclone appears to be in the mature stage, with well developed cold, warm fronts and the pattern of precipitation in the northern Plains and upper Midwest characteristic of strong winter storm. The pattern of precipitation on your map should be indicative of the characteristic ‘comma’ shape, similar to what is shown on satellite or radar imagery. Also know this cyclone has not substantially occluded yet because there is relatively strong cold advection behind the cold front and warm advection in the vicinity of the warm front, as indicated by crossing of surface isotherms, isobars. Where would weather watches or warnings likely be warranted? • Winter storm watches/warnings: in northern Wisconsin, central and southern Minnesota, eastern south Dakota, eastern Nebraska. • Possible blizzard warnings: southwest Minnesota, eastern south Dakota, eastern Nebraska (where some surface wind reports are 20 kts or more). • Cold/wind chill advisories in areas generally north and west of the surface low. • Severe thunderstorm watches/warnings: eastern Missouri and Arkansas (ahead of cold front) .