Smart Bay Sentinels

Two Smart Bay Sentinel Buoys have been deployed in the Galway Bay Area with one at Mace Head near Carna in Connemara and the other east of the Aran Islands (Mid-Bay). These buoys are equipped with an array of sensors including Weather Stations,Wave monitors,Water Quality Monitors and Current measuring Devices. The latest data from the Weather and Wave Instrumentation can be viewed on the Map and table below. Click on the readings and columns in the table to view a graphical representation of the data.

Please note that the times of the reading is in Universal Co-ordinated Time(UTC) which is one hour behind BST(British Summer Time) so a reading shown at 13:00 is actually 14:00.

Beaufort Wind Scale and Descriptions of the sea


The Beaufort Scale of Wind Force was developed in 1805 by Admiral Sir
Francis Beaufort as a means for sailors to gauge wind speeds through visual
observations of the sea state. Land based equivalent observations were added later on.

The scale runs from Force 0 (calm) to Force 12 (Hurricane)

No.

Knots

(m/sec)

Description

Effects at sea

Effects on land

Probable mean wave height (m)

Probable max wave height (m)

0

0

0- 0.5

Calm

Sea like a mirror.

Smoke rises vertically.

0

0

1

1-3

0.3 - 1.5

Light air.

Ripples, but no foam crests.

Smoke drifts in the wind.

0.1

0.1

2

4-6

1.6-3.3

Light breeze.

Small wavelets.

Leaves rustle. Wind felt on face.

0.1

0.3

3

7-10

3.4-5.4

Gentle breeze.

Large wavelets crests, not breaking.

Small twigs in constant motion. Light flags extended.

0.6

1.0

4

11-16

5.5 - 7.9

Moderate wind.

Numerous whitecaps

Small branches move

1

1.5

5

17-21

8.0 - 10.7

Fresh wind.

Many whitecaps, some spray.

Small trees sway.

2.0

2.5

6

22-27

10.8 - 13.8

Strong wind.

Larger waves form. Whitecaps everywhere. More spray.

Large branches move. Whistling in phone wires.

3.0

4.0

7

28-33

13.9-17.1

Very strong wind.

White foam from breaking waves begins to be blown in streaks.

Whole trees in motion.

4.0

5.5

8

34-40

17.2-20.7

Gale.

Edges of wave crests begin to break into spindrift.

Twigs break off trees. Difficult to walk.

5.5

7.5

9

41-47

20.8-24.4

Severe gale.

High waves. Sea begins to roll. Spray may reduce visibility.

Chimney pots and slates removed.

7.0

10.0

10

48-55

24.5-28.4

Storm.

Very high waves with overhanging crests. Blowing foam gives sea a white appearance.

Trees uprooted. Structural damage.

9.0

12.5

11

56-63

28.5 - 32.6

Severe storm.

Exceptionally high waves.

Widespread damage.

11.5

16.0

12

63

32.7 plus

Hurricane force.

Air filled with foam. Sea completely white. Visibility greatly reduced.

Widespread damage. Very rarely experienced on land.

14

(-)



Storm-Generated Waves: Swell

The most intense wave generating activity is where the winds are strongest, directly under the storm system. As waves radiate out from the center, the winds decrease near the margins of the storm system. The waves soon begin to outpace the wind speeds; waves with the longest wave lengths travel fastest. These large waves travelling away from a storm are called swell.

Swell waves are long-crested, uniformly symmetrical waves that have travelled outside the area of their origin. Swell waves expel little energy and travel vast areas of the ocean, fanning out from approaching storm systems. Wave dispersion begins to take effect and the swell waves becomes grouped by their wavelength. Waves with longer wavelengths travel faster and soon outrun the slower waves with shorter wavelengths. The long-wavelength waves do not have steep wave heights but move out of the generating area first, with wave groups of progressively shorter wavelengths following. This procession is termed a "swell wave train" and can travel long distances, breaking on distant shores.

Length of Swell

  • Short 0 – 100 m
  • Average 100 – 200m
  • Long over 200m

Height of Swell

  • Low 0-2 m
  • Moderate 2-4 m
  • Heavy over 4m

Wave height for a given wind strength depends on the distance travelled (fetch), the length of time for which the wind has been blowing and any currents.

Sea States used in some forecasts are described relative to average wave heights as follows:

  • Calm 0.1 - 0.5 m
  • Slight 0.5 – 1.25m
  • Moderate 1.25 – 2.5m
  • Rough 2.5 – 4m
  • Very Rough 4-6m

 

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