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Topic: Mesocyclone

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	Mesocyclone - Wikipedia, the free encyclopedia
		Mesocyclones are most often identified in the right-rear flank of supercell thunderstorms and squall lines, and may be distinguished by a hook echo or gate-to-gate rotation signature on Doppler weather radar.
		Mesocyclones are believed to form when strong changes of wind speed and/or direction with height ("wind shear") sets parts of the lower part of the atmosphere spinning horizontally in invisible tube like rolls.
		The presence of a mesocyclone is believed to be a key factor in the formation of the strong tornados associated with severe thunderstorms.
	en.wikipedia.org /wiki/Mesocyclone (319 words)

	NWS Norman, Oklahoma - Weather Glossary for Storm Spotters
		Therefore, a mesocyclone should not be considered a visually-observable phenomenon (although visual evidence of rotation, such as curved inflow bands, may imply the presence of a mesocyclone).
		It extends outward from the mesocyclone center, usually toward the south or southwest (but occasionally bows outward to the east or southeast in the case of an occluded mesocyclone), and is characterized by advancing of the downdraft air toward the inflow region.
		It extends outward from at or near the mesocyclone center, usually toward the east or southeast, and normally is either nearly stationary or moves northward or northeastward ahead of the mesocyclone.
	www.srh.noaa.gov /oun/severewx/glossary3.php (4037 words)

	Supercell - Wikipedia, the free encyclopedia
		A supercell is a severe thunderstorm with a deep rotating updraft (a mesocyclone) [1].
		The first storm to be identified as such was the Wokingham storm over England, which was studied by Keith Browning and Frank Ludlam in 1962.
		These are especially dangerous storms, since the mesocyclone is wrapped with rain and can hide the tornado from view.
	en.wikipedia.org /wiki/Supercell (1597 words)

	Correspondence Between Tornado Strength and NSSL Mesocyclone Detection Algorithm Numerical Output
		The MDA derived mesocyclone attributes were then used as predictors in linear regression models that attempted to predict the strength of a future tornado using the Fujita scale as the response variable.
		A mesocyclone is often approximated by a rotating column of air in the vertical where the velocity in a horizontal plane increases linearly outward from a point to a ring of maximum velocity and then decreases exponentially outward from that ring (Desrochers and Donaldson 1992).
		Given all the problems inherent in even detecting mesocyclones and their associated attributes by the algorithms, the ability of the models to predict to impending strength of a tornado using the MDA derived mesocyclone attributes must be seem as a sign that radar algorithms in general can be useful in tornado forecasting (Stumpf et al.
	students.ou.edu /J/Thomas.A.Jones-1/netAMS.htm (8324 words)

	TC mesocyclone tornadoes (Site not responding. Last check: 2007-11-03)
		The skill of the algorithm in identifying many mesocyclones is limited by the need for rotation within two vertically linked elevation slices rather than through a specific depth, by adaptable parameter settings defaulted for average dimension supercells, and by the inability to account for aspect ratio sampling limitations.
		As with the first tornado, a manually identified mesocyclone was present, but remained weak prior to and during the time of damage, with rotational velocities of 7-11 m s-1 at 0.5 and 1.5 (Fig.
		For example, at a range of 160-km, the strength of a given mesocyclone with a rotational velocity of 15 m s-1 and diameter of 6.5 km would be classified as minimal, while the same feature with a contracted diameter of 1.85 km would be classified as strong (suggestive of a tornado warning).
	www.srh.noaa.gov /mlb/waf2.html (10473 words)

	THE MESOCYCLONE EVOLUTION OF THE WARREN, OKLAHOMA TORNADOES
		After the storm organized, it was observed that as the parent mesocyclone moved northeastward, it occluded into the rain area and a new mesocyclone began to develop further southeastward.
		The paths of the mesocyclones and their evolution are shown in Figure 2 along with the meso-gamma scale observations.
		A generalized schematic of the mesocyclone evolution of the Warren storm is presented in Figure 5.
	www.stormtrack.org /library/1981/warren.htm (1860 words)

	tornadogenesisi (Site not responding. Last check: 2007-11-03)
		This vorticity is again tilted into the vertical, and then lifted into the mesocyclone where it is intensified and stretched or elongated and where the increased vorticity induced by the stretching, produces the extreme wind speeds associated with a tornado.
		The tornado then builds down from the mesocyclone toward the ground, pulling surrounding moist air into the lowered pressure in the center of the now vertical vortex, and becoming visible as the moisture in the rising air is condensed.
		One of the early puzzles in the development of the idea of super cell thunderstorms and mesocyclones, and their association with tornadoes, was the observation that not only do all mesocyclones not produce tornadoes, but that not all tornadoes occurred in conjunction with rotating thunderstorms.
	www.ux1.eiu.edu /~cfrlw/T2k/Unit4/tgenesis.html (1810 words)

	TORNADOES
		A mesocyclone is a vertical rotating column of air in a supercell.
		The mesocyclone is born as slow, south winds close to the ground and fast, westerly winds aloft start a tube of air to spin horizontally.
		The counterclockwise half is stretched by the updraft connecting the newly formed column of air with the mesocyclone, hence a tornado is formed (Williams, 129).
	www.phys.ufl.edu /~peterson/tornado/micktornado.html (2273 words)

	Tornadic wall cloud formation
		The events leading up to the development of the mesocyclone present a good case for beginning storm chasers to recognize one set of precursors to wall cloud development.
		A small inflow tail is beginning to form on the south side of the mesocyclone but never became more organized.
		The mesocyclone continues to tighten it's spin and become smaller.
	www.chaseday.com /mesoformation.htm (1038 words)

	[No title]
		The mesocyclones appear to have lesser rotational velocities, smaller diameters, and shallower depths when compared to the often studied mesocyclones in the Plains region.
		It is important to note that the average diameter at lowest levels of mini supercell mesocyclones was smaller (by 1.5 nm) than the assumed 3.5 nm diameter for the OSF mesoscale recognition guideline nomogram.
		Mesocyclone depth was also not considered to have much operational utility as a precursor to tornado initiation.
	www.wdtb.noaa.gov /modules/MINIMESO/minimeso.htm (2038 words)

	Mesocyclone - (Site not responding. Last check: 2007-11-03)
		The presence of a mesocyclone can only be truly verified by radar, although visual clues such as curved inflow bands may be present.
		Mesocyclones form when strong changes of wind speed and/or direction with height ("wind shear") sets the lower part of the atmosphere spinning horizontally.
		Mesocyclones, being a intense area of turbulent rotating air, can even be a sign to an impending tornado.
	psychcentral.com /psypsych/Mesocyclone (233 words)

	Radar Project
		Away from the center of the mesocyclone the toward and away wind vectors are naturally less as velocity decreases as the distance from the center of the mesocyclone detection increases.
		Since the number of verifiable mesocyclone detections was so small for this case certain parameters such as the percentage of true anticyclonic vs. cyclonic detections were not calculated.
		It does not appear to be a mesocyclone in the traditional sense as it is partially associated with the outflow boundary and only detectable at a few elevations.
	students.ou.edu /J/Thomas.A.Jones-1/radar.html (5144 words)

	A REVIEW OF RESEARCH AND DEVELOPMENT ACTIVITY RELATED TO WSR-88D ALGORITHMS
		A departure from the traditional mesocyclone model is that the inner core is modeled as an ellipse with prescribed vorticity and divergence.
		Because mesocyclones often undergo radical changes in their flow structure as they evolve, it is not clear how important the details of mesocyclone flows are to the warning function.
		Mesocyclone detections from the previous volume scan are associated with two-dimensional detections from the lowest elevation in the current volume scan, and the old position is updated.
	www.osf.noaa.gov /app/sta/algorithm98.htm (17534 words)

	Tornado thoughts (Site not responding. Last check: 2007-11-03)
		Assuming that a supercell is a storm with a mesocyclone, the generally accepted mechanism for mesocyclogenesis at mid-levels in supercells is the tilting of streamwise environmental vorticity into the vertical by the updraft of the convective storm.
		In the conceptual model, long-lived, low-level mesocyclones are the result of a vertical alignment of the mid-level and low-level mesocyclones, leading to a deep vortex from the surface to well up into the convective storm.
		In this vein, it appears that a critical issue about the tornadic potential of a storm with a mid-level mesocyclone may be whether or not that mesocyclone is "undercut" by cold air, either from storm-induced outflow or from tapping the cold air north of a frontal boundary.
	webserv.chatsystems.com /~doswell/Tornadostuff_m.html (4273 words)

	Hurricane Opal (1995) Severe Weather (Site not responding. Last check: 2007-11-03)
		This storm's mesocyclone exhibited particularly significant tilt in the vertical orientation of the mesocyclone, leaning nearly 45 degrees from the vertical in the direction of storm motion.
		Since the vertical orientation of the mesocyclones was sharply tilted in the direction of motion, the dynamic pressure gradient that drives supercells to the right of the mean shear vector was likely ineffective at deviating the direction of motion, yet McCaul found that dynamic pressure dominated vertical forcing over buoyancy.
		However, mesocyclone depths did not appear to be correlated with intensity or duration of tornado events, with an inverse correlation suggested by this set of storms.
	redrock.ncsa.uiuc.edu /CMG/People/romine/op_severe.html (2006 words)

	12B
		The second mesocyclone paradigm is that of the ETC analog (Lemon and Doswell, 1979, hereafter, LandD).
		Thus, in the mesocyclone and analogues to the ETC, two airstreams (that from the warm and cold conveyer belt analogs) combine to rise within the cumulonimbus updraft (which is the analog to the ETC cloud head).
		Apparently descending from high-levels and on the storm rear flank, is the RFD.
	www.stormchasers.au.com /lemon7.htm (2452 words)

	WESTERN REGION TECHNICAL ATTACHMENT NO. 98-12
		From the algorithm results several variables are determined including the diameter of mesocyclone rotation (nm), mesocyclone distance from the RDA sight or range (nm), and mesocyclonic rotational velocity (kts).
		Using these variables, the mesocyclonic rotational velocities are plotted on the nomogram to determine potential mesocyclone strength.
		No mesocyclones were defined by the mesocyclone algorithm, but rotational velocity values analyzed by hand were 12kts and 16kts.
	www.wrh.noaa.gov /wrh/98TAs/9812 (829 words)

	Tornadoes in Non-mesocyclone Environments with Pre-existing Vertical Vorticity along Convergence Boundaries
		Even with no prior mesocyclone on radar, the boundary intersection and low-level thermodynamic setting were features that could be noted and assessed in advance of the tornado.
		However, radar evidence of a pre-existing midlevel mesocyclone was located several kilometers to the northeast of the reported tornado.
		Because nonmesocyclone tornadoes are not preceded by midlevel or low-level mesocyclones, WSR-88D velocity data is usually of limited use in the traditional mode of tornado warning by radar for most tornadoes in nonmesocyclone environments.
	www.nwas.org /ej/cardav (3880 words)

	MSN Encarta - Tornado
		This interaction causes the updraft to rotate at the middle levels of the atmosphere.
		The rotating updraft, known as a mesocyclone, stabilizes the thunderstorm and gives it its long-lived supercell characteristics.
		The next stage is the development of a strong downdraft (a current of cooler air that moves in a downward direction) on the backside of the storm, known as a rear-flank downdraft.
	encarta.msn.com /encyclopedia_761554892/Tornado.html (1426 words)

	1
		The process that leads to this periodicity in tornado formation is referred to as “cyclic mesocyclogenesis” and is defined as “a periodic succession of low and/or mid-level mesocyclones” (Adlerman et al.
		(1982) suggested that the tilting and stretching of pre-existing vorticity in the low-levels might be sufficient for low-level mesocyclone generation.
		Low-level mesocyclones in parallel mode will rotate around the center of the larger scale circulation, producing tornadoes when tilting and stretching are at their maximum (outside of the main precipitation core) and dissipate when precipitation loading overwhelms the low-level circulation (Agee et al.
	weather.ou.edu /~garfield/gg_meso_2.htm (2474 words)

	The dynamic pipe (from tornado) -- Britannica Concise Encyclopedia - The online encyclopedia you can trust! (Site not responding. Last check: 2007-11-03)
		In this state, the pressure-gradient force, which acts to move air inward in response to the lower pressure in the centre of the rotating column, is equaled by the outward-directed centrifugal force.
		Almost all the air flowing along the mesocyclone's axis is drawn in through the bottom of the pipe.
		Frequently, the maturation of the mesocyclone is heralded at the bottom of the cloud by a lowering of a portion of the thunderstorm's base in the area of the updraft.
	www.britannica.com /ebc/article-218380 (1179 words)

	The Tornado
		Although not all tornadoes form from mesocyclones, most of the larger and stronger tornadoes are spawned from supercell storms with mesocyclones.
		The tornado circulation develops at mid levels (about 20,000 feet) in the storm where the storm's updraft and mesocyclone are strongest.
		Multiple-vortex tornadoes have two or more circulations (vortices) of the storm and do not originate in mesocyclones, so in some ways they are not "legitimate" tornadoes.
	www.tsgc.utexas.edu /stars/tornado.html (714 words)

	Search Results for mesocyclone - Encyclopædia Britannica
		Essential conditions for such storms are the presence of cool, dry air at middle levels in the troposphere,...
		As spin-up of the mesocyclone continues, its rotating action begins to reorganize airflow in the updraft.
		The extension of a concentrated swirling core to the surface—in other words, the actual formation of a tornado—can occur once the mesocyclone is established.
	www.britannica.com /search?query=mesocyclone&submit=Find&source=MWTEXT (186 words)

	april6 (Site not responding. Last check: 2007-11-03)
		The wind damage path was several miles in length with estimated winds of 45-55 mph (based on tree damage).
		Shown is the northern portion of the mesocyclone with scud feeding in from the north.
		The mesocyclone can be seen here although no tornadic activity developed with this storm.
	www.ladeltaweather.com /stormchase2003/april6.html (375 words)

	The System for Convection Analysis and Nowcasting (SCAN)
		Closes the mesocyclone table until it is activated again from the SCAN Storm Cell Table.
		These value ranges are intended to reflect the degree of strength of the mesocyclone, from white (weak) to yellow (moderate) to red (strong).
		Allows the user to choose the mesocyclone attribute by which the data in the table body will be sorted.
	www.nws.noaa.gov /mdl/scan/scanusersGuide.htm (6105 words)

	WSR-88D TVS Parameter Study
		This shear value is difficult to reach because the TVS algorithm uses the maximum inbound and outbound radial velocities within the mesocyclone.
		5 and 6) indicates that the mesocyclone detection is northwest of a stronger circulation that is accompanied by a hook-shaped echo.
		However, within the "detected" mesocyclone, the strongest shear anywhere in the volume is at this tilt.
	www.wrh.noaa.gov /wrh/LITETAs/TALITE9611/talite9611.html (1215 words)

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