Understanding Local Diurnal
Winds
• Sea Breezes and Land Breezes dependent on the
differences in heating and cooling between land and
water.
• Upslope and downslope winds forced by the
differences in heating and cooling between terrain
and lowlands.
Diurnal Local Winds
Diurnal Winds 101
Why?
Sea and Land Breezes Influence Clouds!
Converging Sea Breezes Can
Force Convection in the Middle
of Peninsulas and Islands
Stepped Art
Fig. 7-6, p. 175
Fig. 7-7, p. 176
Summer
Diurnal
Winds
Over Western
Wa
The Sound Breeze
Viewed Using
Ferry Data
Picture take in Sequim looking N
Strong Regional Sea Breeze
Winds During the Summer
Sea Breeze Winds Along the
Southern Oregon Coast
• Gusts frequently reach 30-35 knots during
the summer during the afternoon.
• Very painful to stay on the beach!
• Strong pressure gradient normal to the coast
between the warm land areas and the cold
upwelling water.
Southern Oregon Coast Near Brookings
Average Summer Wind Speeds
18
16
14
Wind Speed (knots)
12
10
8
6
Hoquiam
4
Newport
North Bend
Gold Beach
2
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Hour (LDT)
2-minute average July-August winds along the Northwest coast.
Land Breezes Tend to Be Weak
in the Northwest
• Why? Because the land rarely cools down
more than the water.
• Local minimum temperatures generally in
the low to mid-50s…similar to the
temperature of the Sound and the Pacific
Ocean.
• But it can happen in winter during
unusually cold periods.
Land Breeze
example during a
cold period.
Slope Winds
Upslope Flow on Heated Slopes
Downslope Flow on Cooled Slopes
Upslope Winds Can Produce Clouds Over the Mountain
Crests During the Day
Fig. 7-11, p. 178
Fig. 7-12, p. 179
You can feel upslope winds on warms days and
hang gliders often take advantage of them!
A Local Example of Upslope and
Downslope Flow: Eastern WA
Low temperatures are generally cooler
in low spots on cold, cloud-free nights
due to downslope flows.
The Columbia River Gorge: A
Regional Local Diurnal
Circulation
Diurnal Local Winds in the
Columbia Gorge
High
Pressure
Hot
Low Pressure
35
Columbia Gorge Winds: August 25, 2002
30
Dales Mean Wind
Dales Gusts
25
Carson M ean Wi nd
Wind Speed (kts)
T routdale
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Hour
14
15
16
17
18
19
20
21
22
23
24
Stateline Wind Farm