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Topic: Extratropical

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	CH2.5
		Compound extratropical transformation occurs when the tropical cyclone merges with a pre-existing extratropical cyclone, which usually intensifies because of the additional diabatic heat and moisture.
		Complex extratropical transformation occurs when a tropical cyclone approaches a frontal zone and induces a new low-pressure wave on the front.
		Extratropical cyclogenesis occurs as low-level ascent associated with warm advection becomes superimposed with upper-level ascent associated with cyclonic vorticity advection.
	www.bom.gov.au /bmrc/pubs/tcguide/ch2/ch2_5.htm (1896 words)

	ALERT - Extratropical Cyclone
		Extratropical cyclones arise through a process called cyclogenesis, in which cold and warm air masses interact in an unstable environment.
		Because extratropical cyclones form where cold and warm air masses come into contact with each other, however, storm formation is most favorable in the mid latitudes (between 35 and 60 degrees latitude) of both the Pacific, near the Asian coast, and the Atlantic, near Greenland and the North American coasts.
		Extratropical storm systems are typically comprised of multiple areas of relatively low and high pressure, the locations of which can change quickly and frequently.
	alert.air-worldwide.com /alert/_public/about_alert/Extratropical.asp (441 words)

	Wintertime Extratropical Cyclones of Siskiyou County
		Extratropical (outside the tropics) cyclones (storms with a low-pressure center) occur in the mid-latitudes where typically cold, dry air from the poles meet the typically warm, moist air from the tropics.
		The stages of the development of an extratropical cyclone are discussed below, but it should be realized that this explanation is a generalization.
		It is a fall or winter evening in Siskiyou County and you have just had a pleasant, clear (although rather chilly) day and you are sitting back listening to the evening news when Jon Galfano or Jeff Heaton comes on with the weather.
	www.siskiyous.edu /shasta/env/clouds/extra.htm (1310 words)

	Secret Tenerife: Experts Say Delta Was an Extratropical Cyclone
		On November 28th, Tropical Storm Delta began its transition to extratropical and lost its symmetry (another of the characteristics of tropical storms).
		Cyclones circulate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
		Extratropical Cyclone: The extratropical, or middle-latitude, cyclone originates as a wave, or perturbation, in the polar front separating the cold polar easterly winds from the warmer prevailing winds farther toward the equator.
	www.secret-tenerife.com /2006/06/experts-say-delta-was-extratropical.shtml (1449 words)

	Nor'easters: Comprehension. Preparation. Survival.
		Extratropical storms form in the middle latitudes and have cold cores (meaning that their strongest winds are NOT near the surface and NOT concentrated near the center of the Low).
		Minimum winds associated with a hurricane are 65 knots, and the winds associated with an extratropical storm seldom exceed 50 knots.
		Bombs (being a type of Nor'easter) are extratropical, and therefore are associated with fronts, higher latitudes, and cold cores.
	www.mcwar.org /articles/noreasters/NorEasters.html (2160 words)

	Winter Storms (Extratropical Cyclones) - Waves, Currents, and Storm Surges - An Overview of Coastal Land Loss: With ...
		In North America, extratropical cyclones are large, mid- to high-latitude, winter storms associated with cold air masses that generally travel from west to east.
		Extratropical winter storms also cause significant land losses around the Great Lakes, an area that is unaffected by hurricanes.
		The Halloween storm began as an extratropical disturbance that was later reinforced when it merged with the remnants of Hurricane Grace.
	pubs.usgs.gov /of/2003/of03-337/winter.html (640 words)

	The impact of tropical cyclones on extratropical predictability
		The impact of the extratropical transition of tropical cyclones (ET) on extratropical predictability has been investigated in this special project through case studies of ET in the ECMWF ensemble prediction system.
		Case studies of 3 typhoons in the western North Pacific and 2 North Atlantic hurricanes have shown that regions of increased uncertainty spread downstream of the ET event.
		The results of the EOF/ cluster analysis are being compared with results of a different method of grouping the ensemble members based on the forecast structure of the tropical cyclone undergoing ET (Arnott et al.
	www.ecmwf.int /about/special_projects/jones_impact_tropical_cyclones/index.html (469 words)

	QBO
		The recent QBO studies tend to take extratropical stratospheric westward Rossby waves into account, because extratropical Rossby waves have been observed at the equator(Hitchman et al, 1987), although most equatorward radiating Rossby waves are absorbed at low latitudes, but the absorption process must not be complete.
		The study assumes that tropical Kelvin wave is the forcing of the QBO westerly winds and tropical mixed Rossby-gravity wave is the forcing of the QBO easterly winds.
		The extratropical planetary waves become one of the QBO forcing is parts of the reasons 3D QBO simulation become important on this topics.
	www.atmos.ucla.edu /~cwhung/qbo.html (2193 words)

	Savage Planet: Storms of the Century - Extratropical Storms
		An extratropical storm is a popular name for two different seasonal events.
		One begins with a clash of warm and cold air and results in the typical winter storm.
		They also tend to lose their cyclonic spinning action, and spread into enormously large storms ranging from 620 to 2,500 miles across, with wind gusts that can reach 50 miles per hour.
	www.pbs.org /wnet/savageplanet/02storms/01extratropical/indexmid.html (697 words)

	Cyclone Phase Analysis and Forecast: Help Page
		The example to the left is a schematic for a conventional tropical cyclone, which has a maximum of thickness in the center of the cyclone that decreases almost uniformly outward in all directions.
		This schematic is for a conventional intensifying or mature extratropical cyclone.
		Cyclones aren't simply tropical or extratropical; there is a great continuum of cyclone types, with a significant fraction of them having characteristics of both tropical and extratropical cyclones.
	moe.met.fsu.edu /cyclonephase/help.html (2077 words)

	A Lagrangian “1-year climatology” of (deep) cross-tropopause exchange in the extratropical Northern ...
		A Lagrangian methodology is applied to operational European Centre for Medium-Range Weather Forecasts analyses to study upward cross-tropopause exchange (troposphere to stratosphere exchange (TSE)) and downward cross-tropopause exchange (stratosphere to troposphere exchange (STE)) in the extratropical Northern Hemisphere for the period from May 1995 to April 1996.
		The adopted approach enables identification of a range of novel aspects of extratropical cross-tropopause transport which are of primary importance when assessing its chemical impact.
		For the considered year the annual cycle of the hemispherically integrated net cross-tropopause mass flux compares well with estimates from previous studies.
	www.agu.org /pubs/crossref/2002/2001JD000812.shtml (387 words)

	[No title]
		Moreover, because extratropical oceanic conditions are very persistent, dynamical forecast skill levels that are superior to persistence forecasts are very difficult to achieve even for short-term forecasting (e.g., Miller et al., 1995).
		This may improve tropical ocean forecasts and potentially improve extratropical forecasts in regions where feedbacks to the atmosphere may be important such as the Kuroshio-Oyashio Extension region (e.g., Schneider et al., 2001).
		In the extratropical ocean, the main feature is a positive growing anomaly off the US west coast and extending to the central North Pacific at around 20N resembling the structure and behavior of westward propagating Rossby waves.
	grads.iges.org /ellfb/Jun01/auad.two.jun01.htm (1642 words)

	NCDC: Satellite Events Art Gallery: Cyclones
		The color-enhanced infrared image of 1200 UTC October 30, 1991 depicts a monster storm off the Eastern Seaboard, which was described by the National Weather Service as the "perfect storm." In this image, the storm was at its peak intensity.
		On October 28, 1991, a extratropical cyclone developed along a cold front which had moved off the Northeast coast of the U.S. By 1800 UTC, this low was located a few hundred miles east of the coast of Nova Scotia.
		At 1800 UTC on the 29th, the vigorous cold front from the extratropical low undercut and quickly destroyed Grace's low level circulation east of Bermuda (Note the red and yellow area east of Charleston, SC in Figure 1).
	www.ncdc.noaa.gov /oa/satellite/satelliteseye/cyclones/pfctstorm91/pfctstorm.html (1631 words)

	Justin Arnott
		My Masters thesis focused on the extratropical transition of tropical cyclones and was entitled "Characterization of Extratropical Transition using Cluster Analysis".
		The next stage of my research will involve using a numerical model to simulate the process of extratropical transition, to gain increased insight into the physical processes involved during transition.
		Arnott, J. M., 2004: A cluster analysis derived synoptic evolution of extratropical transition in the North Atlantic.
	met.psu.edu /~arnottj/myweb/?C=D;O=A (289 words)

	DGT98 Extended Abstract
		Jet streaks, defined as localized wind speed maxima along the jet stream, are a common feature of the extratropical atmosphere, particularly at the level of the tropopause, and have assumed a prominent role in synoptic meteorology, largely in recognition of their association with cyclogenesis and severe weather.
		There is significant observational evidence (e.g., Hakim 1997; Pyle 1997) that in many cases jet streaks result from the superposition of coherent monopolar and dipolar vortices of mesoscale dimensions (vortex radius ~500 km) with the enhanced potential vorticity gradients that constitute the extratropical tropopause.
		Such vortices often are long lived, with documented lifetimes of up to several weeks, and may be associated with multiple jet streaks during their life cycles.
	www.atmos.albany.edu /student/cunning/turbabs.html (462 words)

	Barbara E. Prater: Case Study of Hurricane Irene (1999)
		Despite this proximity to a large population and financial interests, the process of extratropical transition remains poorly forecasted, in terms of both intensity change and the time period of transition.
		Whatever the means of interaction, a TC undergoing extratropical transition experiences a period of transition; during this period, the structure of the storm changes through surface to upper levels from a "pure" TC into a storm of extratropical characteristics.
		The extratropical transition of a TC is not well defined by a point in time because of the nature of the transition process.
	www.angelfire.com /mi/cyndertobey/irene/index.html (912 words)

	Ch1 Figures - Extratropical Transition Thesis - Josh Darr (Site not responding. Last check: )
		(2002) to diagnose mid-latitude and tropical cyclone contributions to the reintensification stage of extratropical transition.
		1.4 Conceptual model of extratropical transition in the southwestern Pacific Ocean basin, proposed by Sinclair (2002).
		1.6 Schematic of extratropical transition and associated weather proposed for transitioning tropical cyclones in the Atlantic Ocean basin (Fogarty 2002).
	mywebpages.comcast.net /jdarr/ch1fig.htm (261 words)

	Influence of Variations in Extratropical Wintertime Teleconnections on Northern Hemisphere Temperature
		Multivariate linear regression is used to show that nearly all of the cooling in the northwest Atlantic and the warming across Europe and downstream over Eurasia since the mid-1970s results from the changes in the NAO, and the NAO accounts for 31% of the hemispheric interannual variance over the past 60 winters.
		Most notable is the reduction of the warm anomalies over the NH extratropical landmasses and the elimination of the strong cooling over the northwest Atlantic.
		The claim of this study is not that the NAO and the SO indices provide the best fit to NH extratropical anomalies; rather, the indices were selected because they relate to well-understood circulation anomalies that have persisted for much of the past two decades.
	www.cgd.ucar.edu /cas/papers/grl96/grl96.html (2507 words)

	Workshop on Extratropical Transition
		Forecasting the extratropical transition of cyclones in the South East Indian Ocean
		Extratropical transitions occurring in the western North Atlantic
		Mechanisms contributing to extratropical transition of tropical tyclones in the western North Pacific: a modeling study
	www.meteo.physik.uni-muenchen.de /~sarah/programme.html (371 words)

	Lagrangian Perspective of Extratropical Cyclogenesis
		The study of the formation and three-dimensional structure of extratropical cyclones constitutes a key element of dynamical meteorology.
		Several aspects of midlatitude cyclogenesis are examined in this dissertation and the focus is on the Lagrangian perspective as a complementary view to the established PV-framework.
		A set of selected examples reveals for instance the importance of diabatic processes for the generation of certain low-level PV anomalies, and illustrates again the complementary character of the Lagrangian approach.
	iacweb.ethz.ch /staff/abstracts/wernli.html (716 words)

	EO Newsroom: New Images - Extratropical Cyclone in the Southern Ocean
		These images from the Multi-angle Imaging SpectroRadiometer (MISR) portray an occluded extratropical cyclone situated in the Southern Ocean, about 650 kilometers south of the Eyre Peninsula, South Australia.
		The stereoscopic algorithms used to generate these results are still being refined, and future versions of these products may show modest changes.
		Extratropical cyclones are the dominant weather system at midlatitudes, and the term is used generically for regional low-pressure systems in the mid- to high-latitudes.
	earthobservatory.nasa.gov /Newsroom/NewImages/images.php3?img_id=5211 (282 words)

	JTWC TN 97/002 Page 2
		The application of this extratropical transition technique begins with the decision that a system is in the process of becoming extratropical.
		The single most important determining factor for deciding if a system is becoming extratropical in nature is the decrease or loss of persistent central convection.
		Observational experience has shown that during the extratropical transition an increase in the subsidence generates an irregular shaped "warm hole" near the low-level circulation center as seen on the IR imagery using the BD enhancement.
	home1.gte.net /anstett/XT_Pg02.htm (511 words)

	Extratropical storms are major weather makers
		From fall through the winter and well into spring, extratropical storms dominate the weather across much of the United States and other parts of the globe outside the tropics.
		"Extratropical" means the storms originate outside the tropics.
		A water vapor satellite image reveals the different air masses in a both types of storms.
	www.usatoday.com /weather/wstorm.htm (223 words)

	2005: Weak simulated extratropical responses to complete tropical deforestation
		There are no significant differences in any hydroclimatic variables (e.g., precipitation, soil moisture, evaporation) in either the northern or the southern extratropics.
		Use of the same statistical tests on two 50-year segments of the control run show that the small but significant extratropical differences between the deforested run and the control run are similar in magnitude and area to the differences between non-overlapping segments of the control run.
		#These results suggest that on the time scale of 50 years, extratropical responses to complete tropical deforestation are unlikely to be distinguishable from natural climate variability.
	www.gfdl.noaa.gov /reference/bibliography/forthcoming/klf0502_man.html (332 words)

	Heini Wernli home page
		Identification and ERA15 climatology of potential vorticity streamers and cut-offs near the extratropical tropopause.
		Cross-tropopause mass exchange and its relation to potential vorticity streamers and cut-offs near the extratropical tropopause.
		A Lagrangian "1-year climatology" of (deep) cross-tropopause exchange in the extratropical northern hemisphere.
	www.uni-mainz.de /FB/Physik/IPA/forschung/ag_wernli/wernli.html (492 words)

	Tropical/Extratropical forcing of the AO/NAO: A corrigendum
		Here, we point out a problem with the way the split between tropical and extratropical forcing was carried out.
		In the corrected model results, we find that extratropical forcing dominates tropical forcing in accounting for interannual variance in both the observed NAO and AO indices.
		We find that the recent upward trend in the NAO index is driven from the tropics, whereas for the AO index, we now find that extratropical forcing also contributes to the upward trend in the model.
	www.agu.org /pubs/crossref/2003/2003GL017406.shtml (277 words)

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