a. Case #1. Periodic Event: Buoys #46027, #46022, #46030, and #46014 (12-23 June 2001).

(1) Event description: Figures 3a(1) through 3a(4) show the wind speed and wave height trends for buoys 46027, 46022, 46030, and 46014, respectively, and Figures 3a(5) through 3a(8) show the corresponding wind direction and wind speed trends. This event was characterized by strong diurnal variations in both wind speed and wave height over an extended period (12 consecutive days).

Winds were typically moderate to strong from the north to northwest at favored times of day, depending on each buoy. Diurnal tendencies were most pronounced during this period at buoy 46027, where wind speeds typically varied from near calm in the early morning, to moderate or strong in the early evening. Wind speed increases occurred rapidly on most days, especially at buoys 46027 and 46014, where hourly increases up to 14 knots occurred. For the 12 days as a whole, winds were strongest at buoy 46027, with 9 of the 12 days peaking at or above 25 knots (maximum 31 knots with gusts to 39 knots). Conversely, winds were weakest overall at buoy 46022, where daily wind peaks were typically only about 12-15 knots. Diurnal trends were more difficult to assess at buoy 46022 due to frequent missing data.

Wave heights also tended to follow diurnal patterns, generally following the wind trends. Wave heights were highest overall at buoy 46014, which is not surprising, since its location was near the downwind end of the fetch for most of this period.

(2) General Weather Situation: Figures 3a(9) through 3a(20) show the surface and upper air analyses for this event. A strong surface pressure gradient prevailed along the northern California and southern Oregon coasts, due to interaction between the thermal trough and high pressure off the coast. The upper air pattern was characterized by a series of weak upper level lows moving through the Pacific Northwest, with a generally zonal flow over northern California. This pattern persisted until a stronger upper trough moved southeast from the Gulf of Alaska near the end of the event. The surface pressure gradients then weakened, as a pair of weak cold fronts moved into northwest California in association with the upper trough.

(3) Harmonic Analysis of wind speed and wave height. Harmonic analysis was conducted on wind speeds and wave heights, with a fundamental period of 24 hours to assess the diurnal trends in a more detailed fashion. Analysis was not conducted for buoy 46022 due to frequent missing data. Table 3a and Figures 3a(21) through 3a(24) summarize the results of the analysis for buoys 46027 and 46014, where diurnal trends were strongest. Overall, buoy 46027 showed 47 percent of the total variance to be explained by the first harmonic (period = 24 hours), with each day individually exceeding 60 percent, and seven days exceeding 80 percent. Concerning wave heights for this case, buoy 46027 also displayed the highest percent-variance (23.6%) explained by the first harmonic.

(4) Pressure Gradients. Figures 3a(25) through 3a(27) show wind speeds for buoys #46027, 46030, and 46014, along with absolute values of the pressure gradients (46027-46022, 46022-46014, and 46027-46014) for this event. The actual numerical pressure values appeared to be somewhat suspect, based on comparison with the surface pressure analyses in Figures 3a(9)-(20), especially for buoys #46027 and/or #46022. In most cases, the 46027-46014 pressure difference should have been larger than the 46022-46014 difference (given the observed pressure patterns and larger distance between buoys), but for this period the opposite was generally true. It is possible that there could have been a pressure sensor calibration problem at one or both of the buoys. However, the actual pressure values are much less important than the trends, which do appear to be reasonable. Wind speed data for 46022 was not included here, due to frequent periods of missing data.

Harmonic analysis was also conducted on wind speeds and pressure gradients for this event (Figures 3a(28) thorugh 3a(30)), to better illustrate the timing differences of each cycle, as well as the overall strength of relationships. Similar to the wind speeds, each set of pressure gradients displayed definite diurnal tendencies for the duration of the event, with the first harmonic of the 46027-46022 pressure gradients explaining 63.5 percent of the observed variance over the 12 days of the event (highest of the three sets of pressure gradients for this event).


Figure 3a(1). Wind speed and wave height, buoy #46027 (12-23 June 2001).

Figure 3a(2). Same as Figure 3a(1), but for buoy #46022. Zero-values denote missing data.

Figure 3a(3). Same as Figure 3a(1), but for buoy #46030.

Figure 3a(4). Same as Figure 3a(1), but for buoy #46014.

Figure 3a(5). Wind speed and direction, buoy #46027 (June 12-23, 2001).

Figure 3a(6). Same as Figure 3a(5), but for buoy #46022. Zero-values (speed) denote missing data.

Figure 3a(7). Same as Figure 3a(5), but for buoy #46030.

Figure 3a(8). Same as Figure 3a(5), but for buoy #46014.

Figure 3a(9). Surface analysis (left) and 500 mb analysis (right) : 1200Z, 12 June 2001.

Figure 3a(10). Same as Figure 3a(9), but for 13 June 2001.

Figure 3a(11). Same as Figure 3a(9), but for 14 June 2001.

Figure 3a(12). Same as Figure 3a(9), but for 15 June 2001.

Figure 3a(13). Same as Figure 3a(9), but for 16 June 2001.

Figure 3a(14). Same as Figure 3a(9), but for 17 June 2001.

Figure 3a(15). Same as Figure 3a(9), but for 18 June 2001.

Figure 3a(16). Same as Figure 3a(9), but for 19 June 2001.

Figure 3a(17). Same as Figure 3a(9), but for 20 June 2001.

Figure 3a(18). Same as Figure 3a(9), but for 21 June 2001.

Figure 3a(19). Same as Figure 3a(9), but for 22 June 2001.

Figure 3a(20). Same as Figure 3a(9), but for 23 June 2001.

Table 3a. Time of peak amplitude and percent-variance explained by the first harmonics of wind speed and wave height (period = 24 hours) at buoys #46027 and #46014 (12-23 June 2001).

Figure 3a(21). Harmonic analysis of wind speed data, Buoy #46027, 12-23 June 2001.
Figure 3a(22). Harmonic analysis of wave height data, buoy #46027, 12-23 June 2001.


Figure 3a(23). Harmonic analysis of wind speed data, buoy #46014, 12-23 June 2001.

Figure 3a(24). Harmonic analysis of wave height data, buoy #46014, 12-23 June 2001.

Figure 3a(25). Wind speed (#46027) and pressure gradients (between buoys) , 12-23 June 2001.


Figure 3a(26). Wind speed (#46030) and pressure gradients (between buoys) , 12-23 June 2001.

Figure 3a(27). Wind speed (#46014) and pressure gradients (between buoys) , 12-23 June 2001.

Figure 3a(28). First harmonics of wind speed (#46027) and pressure gradient magnitudes (#46027-46022), 12-23 June 2001.

Figure 3a(29). First harmonics of wind speed (#46030) and pressure gradient magnitudes (#46027-46014 and #46022-46014), 12-23 June 2001.

Figure 3a(30). First harmonics of wind speed (#46014) and pressure gradient magnitudes (#46022-46014 and #46027-46014), 12-23 June 2001.