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.
Sea and Land Breezes
Return Flow
Return Flow
Sea Breeze Front: leading edge
of cooler air
Can See the Influence of Sea and
Land Breezes on Clouds
Washington Coast Sea Breeze
Front
Colliding Sea Breezes Can Produce Strong Upward Motion
Fig. 7-7, p. 176
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.
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.
Southern Oregon Coast Near Brookings
Summer
Diurnal
Winds
The Sound Breeze
Viewed Using
Ferry Data
Picture take in Sequim looking N
Strong Regional Sea Breeze
Winds During the Summer
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
Slope Winds
Upslope Flow on Heated Slopes
Downslope Flow on Cooled Slopes
Low temperatures are generally cooler
in low spots on cold, cloud-free nights.
Eastern Washington Slope flows
Fig. 7-11, p. 178
L
L
Valley breeze
H
H
Mountain breeze
Editable Text
Fig. 7-11, p. 178
Fig. 7-12, p. 179