Lemon technique

The Lemon technique is a method used by weather radar operators to determine the relative strength of thunderstorm cells in a vertically sheared environment. It is named for Leslie R. Lemon, the co-creator of the current conceptual model of a supercell.cite journal |last=Lemon |first =Leslie R. |authorlink=Leslie R. Lemon |coauthors=Charles A. Doswell III |title=Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis |journal=Monthly Weather Review |volume=107 |issue=9 |pages=1184–97 |publisher=American Meteorological Society |date=Sep 1979 |url=http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0493%281979%29107%3C1184%3ASTEAMS%3E2.0.CO%3B2 |doi=10.1175/1520-0493(1979)107<1184:STEAMS>2.0.CO;2 |format=abstract |year=1979 ] The Lemon technique is largely a continuation of work by Keith A. Browning, who first identified and named the supercell.cite journal |last=Browning |first=Keith A. |authorlink=Keith A. Browning |coauthors=Frank H. Ludlam |title=Airflow in convective storms |journal=Quarterly Journal of the Royal Meteorological Society |volume=88 & 88 |issue=376 & 378 |pages=117–35 & 555 |publisher=Royal Meteorological Society |date=Apr & Oct 1962 |url=http://www.rmets.org/pdf/qj62browning.pdf ] cite journal |last=Browning |first=Keith A. |authorlink=Keith A. Browning |title=Airflow and Precipitation Trajectories Within Severe Local Storms Which Travel to the Right of the Winds |journal=Journal of the Atmospheric Sciences |volume=21 |issue=6 |pages=634–9 |publisher=American Meteorological Society |date=Nov 1964 |url=http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0469%281964%29021%3C0634%3AAAPTWS%3E2.0.CO%3B2 |doi=10.1175/1520-0469(1964)021<0634:AAPTWS>2.0.CO;2 |format=abstract |year=1964 ] cite journal |last=Browning |first=Keith |authorlink=Keith A. Browning |title=Some Inferences About the Updraft Within a Severe Local Storm |journal=Journal of the Atmospheric Sciences |volume=22 |issue=6 |pages=669–77 |publisher=American Meteorological Society |date=Nov 1965 |url=http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0469%281965%29022%3C0669%3ASIATUW%3E2.0.CO%3B2 |doi=10.1175/1520-0469(1965)022<0669:SIATUW>2.0.CO;2 |format=abstract |year=1965 ]

The method focuses on updrafts and uses weather radar to measure quantities such as height ("echo tops"), reflectivity (such as morphology and gradient), and location to show features and trends described by Lemon.cite book |last=Lemon |first=Leslie R. |authorlink=Leslie R. Lemon |title=New severe thunderstorm radar identification techniques and warning criteria: a preliminary report |publisher=Techniques Development Unit, National Severe Storms Forecast Center |date=Jul 1977 |location=Kansas City, MO |url = ] cite book |last=Lemon |first=Leslie R. |authorlink=Leslie R. Lemon |title=New Severe Thunderstorm Radar Identification Techniques and Warning Criteria |publisher=Techniques Development Unit, National Severe Storms Forecast Center |date=Apr 1980 |location=Kansas City, MO |url= ] These features include:

* "Updraft tilt" - The tilt (vertical orientation) of the main updraft is an indication of the strength of the updraft, with nearly vertical tilts indicating stronger updrafts.

* "Echo overhang" - In intense thunderstorms, an area of very strong reflectivity atop the the weak echo region and on the low-level inflow inside side of the storm. [ [http://amsglossary.allenpress.com/glossary/search?p=1&query=echo+overhang AMS Glossary ] ]

* "Weak echo region" (WER) - An area of markedly lower reflectivity, resulting from an increase in updraft strength. [ [http://amsglossary.allenpress.com/glossary/search?id=weak-echo-region1 AMS Glossary ] ]

* "Bounded weak echo region" (BWER) - Another area of markedly lower reflectivity, now bounded by an area of high reflectivity. This is observed as a "hole" in reflectivity, and is caused by an updraft powerful enough to prevent ice and liquid from reaching the ground. This powerful updraft is often an indication of, or is facilitated by, a mesocyclone. It should be noted, however, that a mesocyclone is not strictly necessary for BWER development. Storm rotation can be reliably detected by the Doppler velocities of a weather radar. [ [http://amsglossary.allenpress.com/glossary/search?p=1&query=bounded+weak+echo+region AMS Glossary ] ]

References

See also

* Convective storm detection

External links

* [http://weather.cod.edu/sirvatka/es115/unit1/lemontechnique.pdf Paul Sirvatka and Les Lemon "The Lemon Technique" – College of DuPage Meteorology] (PDF)
* [http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/comp/up/lt.rxml The Lemon Technique (LT) to determine updraft strength] (University of Illinois)