20 



^15 - 



East Matagorda 



244 246 248 250 252 254 256 258 260 262 264 266 268 270 272 



Year Day 1 997 



Figure 22. Time series of wind speed measured at the East Matagorda station 



Conversely, minimum wind speeds are experienced at approximately 0800 GMT, or 

 0200 CST. From YD 245 through 250, the maximum wind speeds are associated chiefly 

 with northerly winds (Figure 23). (Wind direction is defined by the standard 

 meteorological convention so that an angle of "0" defines a wind blowing from north to 

 south, and that angles increase in the clockwise direction to a maximum of 360 deg, 

 which again is north) The near-vertical discontinuities seen in this figure result from the 

 wind shifting from the north-northwest to north-northeast (e.g., wind direction from 

 350 deg to 10 deg) or vice versa. 



Measured water-surface elevation at the Galveston Pleasure Pier (Figure 24) shows a 

 distinct set down for this period, which should be expected given the east-west 

 orientation of the gulf coastline in the vicinity of the pier, together with the northerly 

 peak daily winds experienced in the region. This same phenomenon was experienced at 

 Lavaca Bay (Figure 25) where the tidal range was reduced to approximately 0.15 m for 

 the period of YD 247 at 1200 GMT to YD 248 at 1200 GMT. (The tidal range is 

 typically about 0.30 m at this station.) 



For YD 251 through 253, wind direction at the time of peak measured wind speed 

 correspond to an east-southeasterly wind. Water level in Lavaca Bay during this period 

 show a moderate rise with peak maximum and minimum of 0.35 and 0.20 m, 

 respectively. Water level at the Galveston station also appears elevated with a peak water 

 level of 0.45 m. 



From YD 254 through 261, it appears the tide is the dominating force, as opposed to 

 wind, governing water level in the bay. Water elevation measured over this time span at 

 the Galveston station varied from -0.30 to 0.40 m. The measured water level at he Port 

 Lavaca station varied from -0.02 to 0.40 m. 



' All water elevations specified for the model are referenced to mean sea level. 



28 



Chapter 3 Circulation Modeling 



