National Marine Weather Guide British Columbia Regional Guide Cat. No. En56-240/3-2015E-PDF 978-1-100-25953-6 Terms of Usage Information contained in this publication or product may be reproduced, in part or in whole, and by any means, for personal or public non-commercial purposes, without charge or further permission, unless otherwise specified. You are asked to: • Exercise due diligence in ensuring the accuracy of the materials reproduced; • Indicate both the complete title of the materials reproduced, as well as the author organization; and • Indicate that the reproduction is a copy of an official work that is published by the Government of Canada and that the reproduction has not been produced in affiliation with or with the endorsement of the Government of Canada. Commercial reproduction and distribution is prohibited except with written permission from the author. 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Photo credits Cover Left: Chris Gibbons Cover Center: Chris Gibbons Cover Right: Ed Goski Page I: Ed Goski Page II: top left - Chris Gibbons, top right - Matt MacDonald, bottom - André Besson Page VI: Chris Gibbons Page 1: Chris Gibbons Page 5: Lisa West Page 8: Matt MacDonald Page 13: André Besson Page 15: Chris Gibbons Page 42: Lisa West Page 49: Chris Gibbons Page 119: Lisa West Page 138: Matt MacDonald Page 142: Matt MacDonald Acknowledgments Without the works of Owen Lange, this chapter would not have been possible. A former long-time marine forecaster at the Pacific Storm Prediction Centre in Vancouver, he shared a wealth of knowledge about coastal weather patterns in British Columbia through his books Living with Weather Along the British Columbia Coast and The Wind Came All Ways, both of which are the foundation for this regional guide. Special thanks also go to the following Environment Canada employees for reviewing, editing, and combining his works: Barry Brisebois, Senior Meteorologist, Pacific Storm Prediction Centre, Meteorological Service of Canada Michel Gelinas, Meteorologist, Pacific Storm Prediction Centre, Meteorological Service of Canada Mike Gismondi, Pacific Region Lead, Marine Program Supervisor, Pacific Storm Prediction Centre, Meteorological Service of Canada Shayne Keetley, Meteorologist, Pacific Storm Prediction Centre, Meteorological Service of Canada Eric Mak, Meteorologist, Pacific Storm Prediction Centre, Meteorological Service of Canada Anne McCarthy, Weather Service Specialist, Meteorological Service of Canada Environment Canada – national marinE WEATHER GUIDE – British Columbia Regional Guide I II Environment Canada – natIONAL MARINE WEATHER GUIDE – British Columbia Regional Guide Table of Contents Acknowledgements ...................................................................................................................I 1. Introduction .........................................................................................................................1 1.1 Determining Pressure Slope .........................................................................................2 1.2 Categories of Weather Patterns ....................................................................................3 1.3 Approaching Front: Easterly Pressure-Slope Winds ...................................................4 1.4 Ridge Over the Interior: Northerly Pressure-Slope Winds ........................................10 1.5 Coastal Ridge: Southerly Pressure-Slope Winds .......................................................15 1.6 Offshore Ridge: Westerly Pressure-Slope Winds.......................................................18 1.7 Coastal Low: All Pressure-Slope Wind Directions .....................................................21 2. The South Coast .................................................................................................................25 2.1 The Georgia Basin ......................................................................................................25 2.1.1 The Strait of Georgia .........................................................................................26 2.1.1.1 Northwest Winds .................................................................................27 2.1.1.2 Southeast Winds ..................................................................................32 2.1.1.3 Outflow winds ......................................................................................36 2.1.1.4 Southwest Winds .................................................................................37 2.1.1.5 Local Waves and Currents ...................................................................40 2.1.1.6 Local Weather ......................................................................................41 2.1.2 Desolation Sound .............................................................................................43 2.1.2.1 Northwest Winds .................................................................................44 2.1.2.2 Outflow and Northeast Winds .............................................................45 2.1.2.3 Southeast Winds ..................................................................................47 2.1.2.4 Inflow and Southwest Winds ..............................................................48 2.1.2.5 Local Waves and Currents ...................................................................48 2.1.2.6 Local Weather ......................................................................................49 2.1.3 Juan de Fuca Strait ............................................................................................50 2.1.3.1 Easterly Winds .....................................................................................50 2.1.3.2 Westerly Winds ...................................................................................53 2.1.3.3 Local Waves and Currents ...................................................................57 2.1.3.4 Local Weather ......................................................................................57 2.1.4 Victoria and the Islands ...................................................................................58 2.1.4.1 Northerly Winds ..................................................................................60 2.1.4.2 Easterly Winds .....................................................................................62 2.1.4.3 Southwesterly Winds ...........................................................................65 2.1.4.4 Local Waves and Currents ...................................................................68 2.1.4.5 Local Weather ......................................................................................69 2.1.5 Vancouver Area ................................................................................................70 2.1.5.1 Outflow Winds .....................................................................................71 Environment Canada – national marinE WEATHER GUIDE – British Columbia Regional Guide III 2.1.5.2 East to Southeast Winds......................................................................73 2.1.5.3 South to Southwest Winds ..................................................................75 2.1.5.4 Westerly Winds ...................................................................................76 2.1.5.5 Local Waves and Currents...................................................................79 2.1.5.6 Local Weather ......................................................................................79 2.1.6 Howe Sound ......................................................................................................80 2.1.6.1 Northerly Winds ..................................................................................81 2.1.6.2 Southerly Winds ..................................................................................84 2.1.6.3 Local Waves and Currents...................................................................86 2.1.6.4 Local Weather ......................................................................................86 2.2 Chatham Point to Port Hardy ....................................................................................88 2.2.1 Easterly Pressure-Slope Winds ........................................................................88 2.2.1.1 Queen Charlotte Strait .........................................................................88 2.2.1.2 Broughton Archipelago .......................................................................89 2.2.1.3 Johnstone Strait ...................................................................................90 2.2.2 Northerly Pressure-Slope Winds .....................................................................91 2.2.2.1 Knight Inlet ..........................................................................................91 2.2.3 Southerly Pressure-Slope Winds ......................................................................93 2.2.4 Westerly Pressure-Slope Winds .......................................................................95 2.2.4.1 Post-Frontal Westerlies