# November 1, 2010

## Movement of Features on Upper Air Charts

1. Annotate the NAM 60 hour forecast of 500 mb heights provided. (Troughs, Ridges, Highs and Lows).

2. Label the long wave ridge over the western U.S., and the two short wave troughs over the midsection of the country as follows: Ridge 1-00 UTC 4 Nov 2010; Trough 1-00 UTC 4 Nov 2010; Trough 2-00 UTC 4 Nov 2010. (Note: it doesn't matter which trough is labeled 1 or 2 as long as you are consistent).

3. Now go the Weather Briefing page on the class website. Look at the NAM 48 hour forecast 500 mb pattern for 12 UTC 3 November and find the previous posiiton of all three features. Annotate their positions on the 60 h forecast (with correct notation) and label the date and time of each as in (2) above.

4. Repeat (3) for the 36 h, the 24 h, the 12 h and initializations from the NAM.

5. Now connect each position of the troughs and ridge with arrows to the next successive position (to show motion of features).

(a) Which trough moved the fastest, and which the slowest?

(b) Which trough was embedded in the stronger portion of the current at initialization?

(c) How would you characterize the wavelength of the ridge compared to the wavelengths of the troughs?

(d) Complete the following sentence: "...long waves tend to move _____________ (faster or slower) than short waves..."

(e) Complete the following sentence: "...short waves embedded in swifter currents tend to move ____________________ (faster or slower) than short waves embedded in slower currents.

(f) Circle which statement is more true: (i) Long waves tend to move around short waves; (ii) Short waves tend to move around long waves?