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Illustration of a warm front. The warm air behind the front is slowly overtaking the cold air ahead of the front, which is moving more slowly in the same direction. The warmer air, due to lower density, rises over the colder air as it moves. As a result of its increased altitude, it cools off and its
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also appears, there is greater airmass instability approaching ahead of the front. When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 8 hours away. A thickening and lowering of these high
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can also occur preceding a warm frontal passage. Clearing and warming is usually rapid after frontal passage. If the warm air mass is unstable, thunderstorms may be embedded among the stratiform clouds ahead of the front, and after frontal passage thundershowers may continue. On
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A warm front is also defined as the transition zone where a warmer air mass is replacing a cooler air mass. Warm fronts generally move from southwest to northeast. If the warmer air originates over the ocean, it is not only warmer but also more moist than the air ahead of it.
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is a good sign the warm front or low has moved closer and precipitation may begin within less than six hours. Once the clouds have thickened to 2,500 metres (8,200 ft) from the earth’s surface, precipitation can begin to fall from heavy
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that form over source regions. The warm air mass behind a warm front is not only warmer, but often (but not always) also higher in humidity than the colder air preceding it. Because of a warm air mass’s higher temperature and thus lesser
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Usually none, but in summer or warm temperatures, cumulus congestus may continue to exist under cirrostratus and altostratus creating light to moderate showers.
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Persistent rain, usually moderate with some lighter periods and some heavier bursts. In winter, snow may turn to rain after passing through
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will increase until the front reaches the location, at which time the clouds can extend all the way to the earth’s surface as
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Different air masses that affect North
America, as well as other continents, tend to be separated by frontal boundaries.
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typically forms in precipitation falling from the thick nimbostratus layer. Often in warm temperatures, rain bearing
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a shift from winds blowing from northeast to northwest. Common characteristics associated with warm fronts include:
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As the air mass rises into regions of lower pressure, it expands and cools. As it cools, any
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cover. The first clouds that indicate an approaching warm front tend to be mostly high
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clouds if convection is sufficient. In cold humid conditions, low airmass stratus or
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with or instead of altostratus (particularly if the front is weak), and occasionally
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may precede and follow the front and temperature changes will be larger.
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573:(8th ed.). Belmont, Calif.: Thomson/Brooks/Cole. pp. 298–300.
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Air masses are large bodies of air with similar properties of
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moisture condenses, forming clouds and possibly precipitation.
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clouds can appear under the cirrostratus, and more rarely
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Warm Front: transition zone from cold air to warm air
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244:South to southwest (veering) (northern hemisphere)
234:North to northeast (veering) (southern hemisphere)
231:South to southeast (backing) (northern hemisphere)
44:located at the leading edge of a homogeneous warm
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174:blowing from southeast to southwest, and in the
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631:AIR MASSES AND FRONTS - THE WARM FRONT (1962)
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539:The environment: principles and applications
407:characteristics, this air is susceptive to
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422:A surface weather analysis for the
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542:. Psychology Press. p. 309.
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536:Chris C. Park (2001).
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380:Rise, then steady
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519:. Retrieved
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498:. Retrieved
437:weather maps
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374:Steady rise
338:cumulonimbus
336:, sometimes
334:Nimbostratus
308:cumulonimbus
300:cirrocumulus
292:nimbostratus
284:cirrostratus
198:Temperature
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133:nimbostratus
119:cirrocumulus
115:cirrostratus
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63:weather maps
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625:Warm Fronts
521:21 November
387:Warm sector
355:Visibility
304:altocumulus
288:altostratus
262:ice pellets
128:altocumulus
124:altostratus
99:water vapor
83:temperature
69:Development
50:cold fronts
555:2010-12-17
500:2010-12-17
470:References
449:Cold front
397:cold front
54:stratiform
38:warm front
597:cite book
431:Depiction
370:Dew point
239:Variable
644:Category
589:66911677
443:See also
393:air mass
294:, then
157:air mass
149:rainfall
103:condense
87:humidity
46:air mass
377:Steady
344:stratus
316:fractus
296:stratus
276:Clouds
166:In the
92:density
587:
577:
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364:Sunny
280:Cirrus
226:Winds
111:cirrus
491:(PDF)
405:humid
358:Poor
201:Cool
107:cloud
40:is a
603:link
585:OCLC
575:ISBN
544:ISBN
523:2013
346:and
264:and
172:wind
85:and
435:On
328:fog
153:fog
126:or
58:Fog
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
