Weather Alert in Hawaii
Flood Watch issued February 20 at 6:02PM HST until February 21 at 6:00AM HST by NWS Honolulu HI
AREAS AFFECTED: Niihau; Kauai Southwest; Kauai Mountains; Kauai North; Kauai East; Kauai South
DESCRIPTION: ...FLOOD WATCH IN EFFECT FOR NIIHAU KAUAI AND OAHU THROUGH SATURDAY MORNING... * WHAT...Flash flooding caused by excessive rainfall continues to be possible. * WHERE...Niihau and Kauai. * WHEN...Through late tonight. * IMPACTS...Flood prone roads and other low lying areas may be closed due to elevated runoff and overflowing streams. Urban areas may receive more significant flooding and property damage due to rapid runoff. * ADDITIONAL DETAILS... - An upper level trough swinging through the northwestern islands tonight will produce periods of heavy showers and isolated thunderstorms. The trough axis should lift north of the area by mid day Saturday, which should diminish the flooding threat.
INSTRUCTION: You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.
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Weather Topic: What is Precipitation?
Home - Education - Precipitation - Precipitation
Next Topic: Rain
Precipitation can refer to many different forms of water that
may fall from clouds. Precipitation occurs after a cloud has become saturated to
the point where its water particles are more dense than the air below the cloud.
In most cases, precipitation will reach the ground, but it is not uncommon for
precipitation to evaporate before it reaches the earth's surface.
When precipitation evaporates before it contacts the ground it is called Virga.
Graupel, hail, sleet, rain, drizzle, and snow are forms of precipitation, but fog
and mist are not considered precipitation because the water vapor which
constitutes them isn't dense enough to fall to the ground.
Next Topic: Rain
Weather Topic: What are Shelf Clouds?
Home - Education - Cloud Types - Shelf Clouds
Next Topic: Sleet
A shelf cloud is similar to a wall cloud, but forms at the front
of a storm cloud, instead of at the rear, where wall clouds form.
A shelf cloud is caused by a series of events set into motion by the advancing
storm; first, cool air settles along the ground where precipitation has just fallen.
As the cool air is brought in, the warmer air is displaced, and rises above it,
because it is less dense. When the warmer air reaches the bottom of the storm cloud,
it begins to cool again, and the resulting condensation is a visible shelf cloud.
Next Topic: Sleet
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