July 21, 2009 — We were lucky last weekend. Although this weekend may seem like deja vu with another serious fire burning dangerously close to Kelowna.
The massive fire in Kelowna of July 19 & 20 can only serve to highlight the potential danger that the weather presents in British Columbia this summer.
This summer has been hot and dry for most of the province; the day by day observations, so far this summer, are eerily similar to those of 2003 - the year of The Okanagan Mountain Park fire in Kelowna.
|Kelowna 2003||Kelowna 2009|
|June Avg Temp - 27||June Avg Temp - 26|
|June Avg Rain - 38mm||June Avg Rain - 15mm|
|July Avg Temp - 32||July Avg Temp - 30|
|July Avg Rain - 2mm||July Avg Rain - 8mm|
The usual temperature for Kelowna in June is 24 and 41 mm of rain; for July - 27 is the usual temperature and about 37mm of rain will fall.
Clearly itís hot and dry.
The topography and summer weather pattern generally conspire in favour of these great fires. The north-south oriented valleys trap heat, and in a manner similar to a convection oven that heat is radiated back and forth by the valley walls.
High pressure that typically sits over southern BC in the summer holds the heat in place, that same high pressure also keeps rain confined to northern BC.
Meanwhile, in Kelowna, this hot dry air is filled with the energy created by hot air molecules rapidly moving about. This hot air rises and the shape of the valley as well as the downward force imposed by the overlying high pressure results in very strong winds racing through the valleys.
As this heated air mass rises into the somewhat cooler air aloft dry thunderstorms will often form.
We call them dry thunderstorms simply because any moisture produced in this instance evaporates before reaching the surface due to the hot and dry nature of the atmosphere.
It is these dry thunderstorms and their associated lightening that lead to so many fires in this region.
Of course human carelessness leads to fires as well. We urge caution and vigilance through the coming weeks. The forecast is for little change in the present pattern.
In short, the coming days and weeks will be hotter and drier than average in southern British Columbia.
Chris St. Clair
No one knows the importance of accurate weather forecasts more than Chris St. Clair. The weather savvy St. Clair joined The Weather Network in 1996 and currently reports fair or foul skies every Saturday and Sunday from 6 a.m. to 3:00 p.m. on This Weekend. A self-confessed weather, climate and geography enthusiast, St. Clair is well-known by viewers for his thorough weather reports.
Viewer Image: 'Valley under fire' - posted by Clayton Kelowna on July 21, 2009 taken in Kelowna, BC on July 19, 2009