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Topic: Trough (meteorology)

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	Trough (meteorology) - Wikipedia, the free encyclopedia
		A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.
		If a trough forms in the mid-latitudes, a temperature difference between two sides of the trough usually exists in the form of a weather front.
		A weather front is usually less convective than a trough in the tropics or subtropics (such as a tropical wave).
	en.wikipedia.org /wiki/Trough_(meteorology) (257 words)

	Mauna Kea Weather Center Glossary/Dictionary
		To the west of the trough line in an easterly wave over the ocean, there is generally found divergence, a shallow moist layer, and exceptionally fine weather.
		The moist layer rises rapidly near the trough line; in and to the east of the trough line intense convergence, much cloudiness, and heavy rain showers prevail.
		In meteorology, the mixing of environmental air into a preexisting organized air current so that the environmental air becomes part of the current; the opposite of detrainment.
	mkwc.ifa.hawaii.edu /glossary/index.cgi?letter=e (1307 words)

	Fiji Weather Jan-Feb 1999
		A trough moving across the group from the east brought with it widespread rainfall at the start of the month, with some notable falls during the first two days.
		As the trough moved to the southwest of Fiji on the 5th, heavy rain was experienced in Kadavu and parts of the Southern Lau.
		The trough moved to the west of Fiji on the 21st with rain and floods easing.
	www.hawaii.edu /oceanic/rotuma/os/NewsArchive/Archive1999/weather9902.htm (1402 words)

	Troughs: upper level lows
		Strong troughs are typically preceded by stormy weather and colder air at the surface.
		A trough is located over the eastern United States and is indicated by the dip in the geopotential height field.
		This is the upper level extension of a surface low pressure center, which is why troughs are also called upper level lows.
	ww2010.atmos.uiuc.edu /(Gl)/guides/mtr/cyc/upa/trgh.rxml (204 words)

	Horizontal Pressure Variation - Meteorology Self Instructions - [Meteorological Service of Canada - The Green Lane]
		Once you have identified that a trough or ridge is present by a bulge in the isobars, you can locate the actual trough or ridge easily.
		a) a trough or ridge may be represented by a line extending from the centre of the pressure area outwards to the sharpest point in the bulge, and that
		You have also learned that trough and ridge lines, which indicate the ACTUAL troughs or ridges, are drawn so that they extend from the CENTRE of the pressure area OUTWARDS to the sharpest part of the bulge.
	www.msc-smc.ec.gc.ca /education/msi/m3/3B032_e.cfm (3688 words)

	Abbott, D
		At 200 mb, high pressure dominates the land area, large-scale troughs are found over the Atlantic and Pacific oceans, the easterly jet forms south of Asia, and subtropical jets develop in the westerlies.
		In particular, both of the simulated versions and the observed version all involve periodic deepening and filling of the monsoon trough resulting from northward propagation of troughs and ridges from the equatorial region.
		The forecast errors in the positions of the northward propagating monsoon troughs and ridges at Day 20 are generally within the range of 1 similar to 2 days behind the observed, except in some extreme cases.
	www.soest.hawaii.edu /MET/Faculty/bwang/msnbook/references/ch13_ref.html (16015 words)

	untitled (Site not responding. Last check: 2007-10-12)
		The purpose of this project was to use a case study approach to analyze winter storms involving inverted troughs which had a major impact on the Northern Plains.
		Specifically, two cases with precipitation primarily ahead of the trough were to be compared with two cases with precipitation behind the trough (ahead and behind cases are defined in Weisman, R. McGregor, and P. Schumacher, 1998: Precipitation regimes during cold-season inverted trough cases in the Central U.S. Preprints 16th Conf.
		When inverted troughs are noted in the forecast models, forecasters are examining low-level warm advection and frontogenesis in order to determine the location of the precipitation.
	www.comet.ucar.edu /outreach/9890782.htm (1426 words)

	Meteorology and Satellite images
		The high pressure area of the wave (the ridge) is warm and dry while the low pressure area (the trough) is cool and moist.
		Middle and upper tropospheric clouds can typically be found along the leading edge of the ridge and trough in association with surface warm and cold fronts.
		Trough and ridge development, which is usually slight over the Southeastern Pacific, may add a meridional component to the cloud cover and water vapour advection patterns.
	eso.org /gen-fac/pubs/astclim/forecast/workshop/summarymess/node3.html (350 words)

	Planetary scale tropospheric systems
		Over the Pacific the trough does not shift very far from that average position, but due to differential heating it moves considerably further north and south over continental land masses.
		The low level air moving towards the trough from the sub-tropical high belts at about 30°S and 30°N is deflected by Coriolis and forming the south-east and north-east trade winds.
		The air in the trade wind belts is forced to rise in the ITCZ and large quantities of latent heat are released as the warm, moist maritime air cools to its condensation temperature.
	www.auf.asn.au /meteorology/section4.html (2200 words)

	NWS Norman, Oklahoma - Weather Glossary for Storm Spotters
		Shortwave (or Shortwave Trough) - A disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.
		Trough - An elongated area of relatively low atmospheric pressure, usually not associated with a closed circulation, and thus used to distinguish from a closed low.
		"Wall cloud" also is used occasionally in tropical meteorology to describe the inner cloud wall surrounding the eye of a tropical cyclone, but the proper term for this feature is eyewall.
	www.srh.noaa.gov /oun/severewx/glossary4.php (4121 words)

	Upper Air Meteorology (Site not responding. Last check: 2007-10-12)
		In meteorology, we don't take a fixed height, and measure the pressure of that height (though in the early days of upper air meteorology, that was in fact done), but instead define a pressure level (850 hPa, 700 hPa, 500 hPa etc.), and find the height (amsl) at which that pressure value is found.
		Broadly speaking, msl low pressure is found in and forward of a marked upper trough, and msl high pressure is found in and forward of a marked upper ridge.
		The trough may be a slight hesitation in the upper flow, but combined with adequate moisture, and perhaps enhanced by land heating, can lead to notably more intensive shower activity, and operational forecasters are always on the look-out for such irritations at such levels as 500 hPa or 300 hPa.
	homepage.ntlworld.com /booty.weather/metinfo/uppair.htm (1988 words)

	Federation and Meteorology, Meteorological Work in Australia, page 1562
		These are frequently productive of good general rains; the winds on the east side of the trough are northerly, and southerly on the west side—strong if the valley is narrow and nipped up between two "highs" with steep gradients on either side.
		The maps for the previous day or two show that the formation of the valley of low barometers was preceded by a general taking off of pleasure over the interior of Western Australia on the 3rd.
		Subsequent maps show that as the isobars moved eastward the low pressure valley or trough underwent considerable modification, though the valley-like depression was clearly.
	www.austehc.unimelb.edu.au /fam/1562.html (296 words)

	Federation and Meteorology, Antarctic Operational Meteorology, page 1588
		The solution of these equations at various time and space scales is the principal end product of operational meteorology and provides the basis for modern analysis and prognosis of the various atmospheric variables and hence of weather and climate.
		It is to these computers (as well as to the expansion of observational techniques) that the remarkable improvement in short term weather forecasting which has occurred over the past 25 years is largely due.
		Thus, FGGE as with the IGY was to provide a catalyst and impulse to global observing and numerical analysis and prediction.
	www.austehc.unimelb.edu.au /fam/1588.html (702 words)

	Sadler, UHMET-75-05
		It is commonly called the Mid-Pacific Trough (MPT) in the central Pacific and the Mid-Atlantic Trough (MAT) in the central Atlantic.
		The term "Tropical Upper-Tropospheric Trough" is preferred since similar troughs exist during summer in the Southern Hemisphere, eastern North Pacific, Central America, and the Gulf of Mexico.
		In the Northern Hemisphere it crosses near where the eastern end of the TUTT merges with the mean trough in the midlatitude westerlies; therefore, the subtropical ridge, which normally lies poleward of the TUTT, does not show at this longitude.
	www.soest.hawaii.edu /Library/Sadler.html (6771 words)

	Anticyclones, Lee Troughs and Inverted Troughs: and their roles in the development of freezing rain
		One type of pressure trough, called a "lee trough", is commonly observed in the central United States.
		West of the trough, surface winds are usually from the northwest while ahead of the trough, winds are southerly.
		Surface winds west of the inverted trough are north or northwesterly while winds east of the trough are east to northeasterly.
	ww2010.atmos.uiuc.edu /(Gl)/guides/mtr/cld/prcp/zr/cond/prs.rxml (264 words)

	New Book - Glossary (Site not responding. Last check: 2007-10-12)
		For dead fuels, moisture content is governed primarily by exposure to precipitation or soil moisture and by the tendency of the dead fuels to approach equilibrium with the relative humidity of the surrounding air.
		Looping: a pattern of plume dispersion in an unstable atmosphere in which the plume undergoes marked vertical oscillations as it is alternately affected by rising convective plumes and the subsiding motions between the plumes.
		Short-wave trough: a relatively small-scale trough that is superimposed on and propagates through the longer wavelength Rossby waves.
	www.pnl.gov /atmos_sciences/Cdw/Glossary.html (11111 words)

	MM5 Community Model Homepage
		Meteorology and Atmospheric Physics, Vienna, Austria, 63(3-4), 131-148.
		Agricultural and Forest Meteorology, Amsterdam, The Netherlands, 106(1): 1-21.
		Meteorology and Atmospheric Physics, Vienna, Austria, 49(1-4): 93-106.
	www.mmm.ucar.edu /mm5/Publications/mm5-papers.html (12684 words)

	IEI \| meteorology - Google News
		The cold snap is expected to stay at Hotham, with the Australian Bureau of Meteorology predicting snow showers to continue.
		Naval Meteorology and Oceanography Center Preps for Hurricane...
		The cold snap is expected to stay at Hotham throughout Monday, with the Bureau of Meteorology predicting snow showers to continue today.
	www.inmtn.com /html/news/googlemeteorology.php (373 words)

	Mauna Kea Weather Center Glossary/Dictionary
		This term is sometimes restricted to those troughs that are much more pronounced aloft than near the earth's surface.
		These troughs are often described as either short-wave or long-wave features.
		upper air - In synoptic meteorology and in weather observing, that portion of the atmosphere that is above the lower troposphere.
	weather.hawaii.edu /glossary/index.cgi?letter=u (402 words)

	paper-obs
		The majority of the events (72%) fall into three main patterns that include a well-defined upstream trough (40%), a ridge (20%), and a zonal, low-amplitude flow (12%), which is identified as an additional warm-season pattern.
		The mean pattern displays a short-wave trough in the process of breaking down the northern extent of the strong ridge.
		Despite the lack of an identifiable mid-level trough in the mean flow, a trough axis is evident at 850-mb, which extends southwest to northeast upstream of the DCS location (Fig.
	www.nssl.noaa.gov /users/mcon/public_html/paper-obs.htm (8875 words)

	THE KATHMANDU POST - LOCAL NEWS
		The meteorologists at the Department of Hydrology and Meteorology (DoHM) say that the cited regions usually witness deficient rainfall every year in July, expecting the situation to improve in August because the monsoon usually becomes active in these regions during this period.
		The monsoon is weakening gradually as its trough is moving slightly southward of the country.
		As the monsoon trough, which lies at a distance of 350 km from our country in normal condition, comes closer to Nepal, precipitation becomes more active in the country, according to the meteorologists at the DoHM.
	www.nepalnews.com /contents/englishdaily/ktmpost/2003/aug/aug04/local1.htm (646 words)

	uk.sci.weather FAQ: GLOSSARY
		:in operational/synoptic meteorology this is usually taken to be the layer at the bottom of the atmosphere wherein surface friction is important.
		This latter measure is often used in operational meteorology in NW Europe: At the 850hPa level, it is used as a 'tracer' for air masses, and is much used for defining frontal boundaries, and for defining the axes of warm 'plumes' of air.
		To cope with all this, the concept of 'conveyor belts' was adapted for use in synoptic and mesoscale meteorology as a means of explaining the movement of heat, moisture and momentum around such systems.
	www.weather.org.uk /resource/ukswxglo.htm (8818 words)

	Connections between the summer east African and Indian rainfall regimes
		Variations in the monsoon trough, which is located over east Africa extending eastward to southeastern Asia, regulate the connection between east Africa and India and mediate the precipitation covariability in the model.
		When the monsoon trough is weak, northern Ethiopia and western India are dry, in association with a weaker Somali jet, but rainfall is enhanced over southern Ethiopia.
		The atmospheric response when the monsoon trough is strong is not the opposite of the weak trough simulation as conditions are wetter over West India, but drier over all of Ethiopia.
	www.agu.org /pubs/crossref/2003/2003JD003452.shtml (318 words)

	Trough and Ridge Amplification: in response to lower level temperature advection
		Trough and Ridge Amplification: in response to lower level temperature advection
		Warm advection beneath an upper level ridge causes it to build (increase in amplitude), while cold advection beneath an upper level trough will contribute to its deepening.
		Observe how the ridge over the east gradually builds (raises northward) while the trough over the northern plains gradually deepens (sinks southward).
	ww2010.atmos.uiuc.edu /(Gl)/guides/mtr/cyc/upa/amp.rxml (145 words)

	Area Forecast Discussion Common Terminology Decoder
		Many of these definitions have been simplified somewhat, but this glossary may help users who have little or no meteorology background to better interpret the reasoning behind the current forecast as expressed by the forecaster in his/her Area Forecast Discussion.
		The base of the trough moves out ahead of the rest of the trough.
		Cooler air masses are generally found under an upper level trough.
	www.wrh.noaa.gov /boi/AFD_Common_terms.php (1169 words)

	Satellite Meteorology Glossary
		Amplitude: Half the height from the crest to the trough of the wave.
		In meteorology, convection infers vertical movement or upward motions due to differential heating.
		Meteorology: The study of the atmosphere and the ways weather is affected by interactions with the Earth’s land and water surfaces and living things.
	cimss.ssec.wisc.edu /satmet/glossary/glossary.html (3664 words)

	Lance Bosart
		He works on a variety of multiscale (time and space) research problems that relate to the weather and climate of the middle latitudes and tropics.
		Lai, C.-C., and L. Bosart, 1988: A case study of trough merger in split westerly flow.
		Dean, D. B., and L. Bosart, 1996: Northern Hemisphere trough merger and fracture characteristics: A climatology and case studies.
	www.atmos.albany.edu /facstaff/bosart.html_3_19_99 (1313 words)

	Clustering of synoptic activity by Indian summer monsoon intraseasonal oscillations
		Using genesis data of monsoon low pressure systems (LPS) and circulation data for the period 1954 to 1993, it is shown that the frequency of occurrence of LPS is nearly 3.5 times higher in the active phase of monsoon as compared to the break phase.
		In addition, the tracks of these synoptic systems are also strongly spatially clustered along the monsoon trough during the active phase of the monsoon.
		The enhanced (decreased) frequency of occurrence of LPS during active (break) phases is due to modulation of meridional shear of zonal winds and cyclonic vorticity along the monsoon trough by the intraseasonal oscillations (ISO).
	www.agu.org /pubs/crossref/2003/2002GL016734.shtml (257 words)

	National Weather Digest: Meteorological aspects of south-central and southwestern New Mexico and far western Texas ...
		There were four distinct large-scale patterns that were associated with flash flood events, but a common feature was the presence of a surface thermal trough or "heat low" covering western Arizona, southeastern California and northwestern Mexico.
		The thermal trough supports a low-level easterly or southeasterly surface flow favorable for the advection of abundant moisture from the Gulf of Mexico into the region.
		While there was more variability in the large-scale middle and upper-tropospheric patterns, deep convection frequently developed near an advancing upper-level short-wave trough and/or in the left front or right rear quadrants of upper tropospheric jet streaks.
	www.findarticles.com /p/articles/mi_m0QRG/is_27/ai_n11836127 (419 words)

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