surge

/serrj/, n., v., surged, surging.

n.

1. a strong, wavelike, forward movement, rush, or sweep: the onward surge of an angry mob.

2. a strong, swelling, wavelike volume or body of something: a billowing surge of smoke.

3. the rolling swell of the sea.

4. the swelling and rolling sea: The surge crashed against the rocky coast.

5. a swelling wave; billow.

6. Meteorol.

a. a widespread change in atmospheric pressure that is in addition to cyclonic and normal diurnal changes.

b. See storm surge.

7. Elect.

a. a sudden rush or burst of current or voltage.

b. a violent oscillatory disturbance.

8. Naut. a slackening or slipping back, as of a rope or cable.

9. Mach.

a. an uneven flow and strong momentum given to a fluid, as water in a tank, resulting in a rapid, temporary rise in pressure.

b. pulsating unevenness of motion in an engine or gas turbine.

v.i.

10. (of a ship) to rise and fall, toss about, or move along on the waves: to surge at anchor.

11. to rise, roll, move, or swell forward in or like waves: The sea surged against the shore. The crowd surged back and forth.

12. to rise as if by a heaving or swelling force: Blood surged to his face.

13. Elect.

a. to increase suddenly, as current or voltage.

b. to oscillate violently.

14. Naut.

a. to slack off or loosen a rope or cable around a capstan or windlass.

b. to slip back, as a rope.

15. Mach. to move with pulsating unevenness, as something driven by an engine or gas turbine.

v.t.

16. to cause to surge or roll in or as in waves.

17. Naut. to slacken (a rope).

[1480-90; perh. < L surgere to spring up, arise, stand up]

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▪ weather

      in meteorology, an atmospheric process that operates on oceans and inland waters whereby a change in atmospheric pressure or a high-velocity wind works in conjunction with normal gravitational tides to produce dramatic changes in oceanic circulation, and, oftentimes, flooding in coastal areas. Though surges usually occur over vast areas, they can also be generated by local storms over inland seas and lakes.

      Changes in atmospheric pressure are commonly noted in regions close to the large, semipermanent pressure centres of the Earth, such as the high-pressure area associated with the southern North Atlantic Ocean. Passage of a high-pressure centre causes a fall in the water level, and passage of a low-pressure centre causes a rise. In areas where such occurrences have often been noted, a rise or fall of 2 millibars in 24 hours over an area of about 8,000,000 square km (about 3,090,000 square miles) is common.

      The sudden increase in the speed of a large wind stream, especially in the tropics, can also cause surges. The progress of this type of surge can be followed on weather maps as it expands. During a “surge of the trades (trade wind)” in the trade-wind belts, wind speed often increases by about 40 km/h (25 mile/h) throughout the region between the surface and the 4,500-metre (15,000-foot) level. A surge in the monsoon currents is called a burst, or surge, of the monsoon.

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