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While the most obvious motion of clouds is toward the center, tropical cyclones also develop an upper-level (high-altitude) outward flow of clouds. These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine. This outflow produces
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change between the cooler air from the downdraft and the warmer environmental air. This density boundary will increase the number of echo returns from the leading edge. Clouds and new thunderstorms also develop along the outflow's leading edge. This makes it possible to locate the outflow boundary
73:. However, outflow aloft is essential for the strengthening of a tropical cyclone. If this outflow is restricted or undercut, the tropical cyclone weakens. If two tropical cyclones are close, the upper-level outflow from the upwind system can limit the development of the other system.
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that spiral away from the center. The clouds are thin enough for the sun to be visible through them. These high cirrus clouds may be the first signs of an approaching tropical cyclone. As air parcels are lifted within the eye of the storm the
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motion. If two tropical cyclones are in proximity to one another, the outflow from the system downstream (normally to the west) can hinder the development of the system upstream (normally to the east).
173:, or arc, cloud. The image to the right depicts a particularly strong outflow boundary ahead of a line of storms. Often, the outflow boundary will bow in the direction it is moving the quickest.
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when using precipitation mode on a weather radar. Also, it makes outflow boundaries findable within visible satellite imagery as a thin line of cumuliform clouds which is known as an
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are swept along by the prevailing winds, making them good indicators of the presence of outflow boundaries. The signature of the leading edge is also influenced by the
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imagery. For observers on the ground, a thunderstorm outflow boundary often approaches in otherwise clear skies as a low, thick cloud that brings with it a
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524:"Frequently Asked Questions: What's it like to go through a hurricane on the ground? What are the early warning signs of an approaching tropical cyclone?"
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typically bow out the most, or bend the most convex outward, at the leading edge of low level outflow due to the formation of a mesoscale
426:
John A. Knaff and John F. Weaver (September 2000). "A Mesoscale Low-Level
Thunderstorm Outflow Boundary Associated with Hurricane Luis".
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can lead to the initial development of the convective complex and surface low similar to the mid-latitudes, but it must relax to allow
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For thunderstorms, outflow tends to indicate the development of a system. Large quantities of outflow at the upper levels of a
54:, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on
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indicate its development. Too much outflow in the lower levels of a thunderstorm, however, can choke off the
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156:. Convergence of dust, aerosols, and bugs at the leading edge will lead to a higher clear air signature.
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is formed due to strong descending motion behind the squall line, and could come in the form of a
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277:, forming a wedge of denser air which spreads out from the base of the parent thunderstorm. If
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31:, Oklahoma. The outflow boundary's weak echo moves left-to-right and passes overhead of the
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behind the leading edge of thunderstorm outflow, or outflow boundary. Moderate vertical
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Low-level outflow boundaries from thunderstorms are cooler and more moist than the
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152:(especially in clear air mode). Convergence occurs along the leading edge of the
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The outflow boundary indicated by the presence of this shelf cloud preceded a
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574:"History of Thunderstorm Forecasting: Part VI: The Thunderstorm (to 1900)"
371:"Birds migrate together at night in dispersed flocks, new study indicates"
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which forms within the stratiform rain area behind the initial line. This
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Structure of a tropical cyclone. The upper level outflow is depicted by
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549:"Preliminary Report: Tropical Storm Iris - 16–21 September 1989"
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289:, reducing visibility. This type of weather event is known as a
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is reduced, causing the outflow from a tropical cyclone to have
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485:"Hurricanes... Unleashing Nature's Fury: A Preparedness Guide"
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Low-level outflow boundaries can disrupt the center of small
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10.1175/1520-0493(2000)128<3352:AMLLTO>2.0.CO;2
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can send out a large enough outflow boundary to weaken the
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as the tropical cyclone center moves into the more stable
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Outflow boundary that preceded a strong thunderstorm in
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the thunderstorm originally formed within due to its
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Desert
Research Institute. Retrieved on 2006-10-22.
301:which would then obscure the sun and reduce solar
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305:around the outermost edge of tropical cyclones.
528:National Oceanic and Atmospheric Administration
492:National Oceanic and Atmospheric Administration
330:National Oceanic and Atmospheric Administration
293:, and is most common in the late spring within
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285:events, dust and sand can be carried into the
522:, Hurricane Research Division (2004-08-13).
348:Peter S. Parke and Norvan J. Larson (2005).
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297:. Upper-level outflow can consist of thick
16:Air that flows outwards from a storm system
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261:, just before nightfall on April 27, 2005.
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281:speeds are high enough, such as during
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605:Western Region Climate Center (2002).
626:Glossary of Meteorology (June 2000).
466:University of Illinois (1999-10-04).
394:Glossary of Meteorology (June 2000).
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189:in the upper part of the schematic
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199:The development of a significant
674:Synoptic meteorology and weather
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632:American Meteorological Society
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438:American Meteorological Society
406:American Meteorological Society
50:flow. In the low levels of the
547:Dr. Harold P. Gerrish (1989).
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1:
669:Severe weather and convection
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572:John F. Weaver (June 1982).
201:mesoscale convective complex
23:Radar image animation of an
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10:
690:
416:. Retrieved on 2009-05-03.
359:. Retrieved on 2008-07-30.
350:Boundary Waters Windstorm.
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58:imagery or a fine line on
553:National Hurricane Center
148:can often be detected by
664:Meteorological phenomena
481:National Weather Service
353:National Weather Service
322:National Weather Service
396:Line echo wave pattern.
27:of a storm approaching
429:Monthly Weather Review
375:University of Illinois
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36:
470:Retrieved 2008-08-17.
377:at Urbana - Champaign
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217:tropical cyclogenesis
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136:
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33:Doppler radar station
22:
369:Diana Yates (2008).
584:(6). Archived from
446:2000MWRv..128.3352K
612:2017-05-21 at the
483:(September 2006).
401:2008-09-24 at the
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144:The "edge" of the
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124:high-pressure area
120:high-pressure area
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357:Duluth, Minnesota
355:Forecast Office,
177:Tropical cyclones
71:tropical cyclones
56:weather satellite
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195:Tropical cyclone
146:outflow boundary
114:which fuels it.
112:low-level inflow
98:Outflow boundary
25:outflow boundary
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249:A sandstorm (
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241:Local effects
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234:anticyclonic
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116:Squall lines
108:thunderstorm
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102:Thunderstorm
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48:anticyclonic
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578:Storm Track
468:Hurricanes.
287:troposphere
271:wet bulbing
223:high, thin
52:troposphere
44:meteorology
658:Categories
642:2010-03-27
592:2010-04-22
558:2010-04-08
533:2006-07-26
505:2010-04-09
381:2009-04-26
335:2010-04-09
309:References
303:insolation
283:microburst
213:wind shear
193:See also:
162:arthropods
96:See also:
64:gust front
230:vorticity
154:downdraft
128:downburst
91:Minnesota
628:"Haboob"
610:Archived
399:Archived
267:air mass
209:air mass
139:Oklahoma
442:Bibcode
255:Al Asad
205:cyclone
166:density
158:Insects
87:derecho
40:Outflow
412:
291:haboob
251:Haboob
499:(PDF)
488:(PDF)
436:(9).
295:Sudan
171:arcus
42:, in
29:Tulsa
410:ISBN
279:wind
275:rain
259:Iraq
160:and
100:and
450:doi
434:128
326:"O"
273:by
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