OAR Forecast Discussion 34
11:00PM PDT SAT APR 28 2012
0600 UTC, 29 APR 2012
…Winds expected to shift again around dark on Sunday…
Short term forecast:
A weak low pressure center has moved inland over British Columbia, and a weak low to mid-level shortwave ridge has moved into the area, resulting in light northwest winds. The forecast for the next day concerns the approach of yet another shortwave trough and associated weak surface low. Model guidance agrees that the shortwave will cause winds to shift to southerly late on Sunday–probably between 8PM and midnight Monday.
A bit more uncertainty remains concerning the exact track of the low on Monday. The spread of potential tracks of the low range from the central Washington coast to southern Vancouver Island. If the low tracks farther to the south, then waters offshore BC will experience a gradual transition from southerlies to easterlies and eventually northwesterlies by Monday afternoon. Should the low track farther north, then offshore waters will experience southerlies for a longer period of time, followed by a rapid shift in winds to northwesterlies Monday afternoon. In either event, winds should shift to the west or west-northwest after the low passes. A tight pressure gradient between the subtropical Pacific ridge and a low pressure forecast to stall over the Gulf of Alaska will cause winds to pick up again late Monday, and some sort of wind advisory may be again necessary. Locally, winds near the entrance to the Strait of Juan de Fuca may be higher, so I have allowed for the potential of 35kt gusts by Monday night.
Another stronger storm appears as if it will enter the picture late Wednesday or Thursday. The evolution of this storm will become more clear during the next couple of days, but for now, it looks like sustained winds in excess of 25 to 30kts are not out of the question.
Zone Forecast for offshore waters from Tofino to Panchena Beach out 100 nautical miles
+03HR: Winds WNW @ 5-10kts, Seas 5-7ft., Waves 1-2ft.
+06HR: Winds WNW @ 5-10kts, Seas 5-7ft., Waves 1-2ft.
+09HR: Winds WNW @ 5-10kts, Seas 5-7ft., Waves 1-2ft.
+12HR: Winds WNW, shifting to W @ 5-10kts, Seas 4-6ft., Waves 1-2ft.
+15HR: Winds: Light W winds, Seas 4-6ft., Waves 1-2ft.
+18HR: Winds: Light W winds shifting to SW, Seas 4-6ft., Waves 1-2ft.
+21HR: Winds: SW to S @ 5-10kts, Seas 4-6ft., Waves 1-2ft.
+24HR: Winds: S @ 5-10kts, Seas 5-7ft., Waves 1-2ft.
Extended forecast (Errors may be large)
+30HR: Winds: SE shifting to E @ 10-20kts, Seas 5-7ft., Waves 2-4ft.
+36HR: Winds: N @ 10-20kts G25kts, Seas 5-7ft., Waves 2-4ft.
+42HR: Winds: N shifting to WNW @ 10-20kts G25kts, Seas 6-8ft., Waves 3-5ft.
+48HR: Winds: WNW or W wind @ 15-25kts G35kts, Seas 7-9ft., Waves 4-6ft.
Weather forecasts are provided twice daily by the American Meteorological Society Student Chapter at the University of Washington, a group of undergrad and graduate students interested in weather and climate. Learn more about them at http://www.atmos.washington.edu/uw_ams/.