Lemon technique

{{Short description|Meteorological method to determine relative strength of thunderstorm cells}}

The Lemon technique is a method used by meteorologists using weather radar 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. |author-link=Leslie R. Lemon |author2=Charles A. Doswell III |title=Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis |journal=Mon. Wea. Rev. |volume=107 |issue=9 |pages=1184–97 |date=September 1979 |doi=10.1175/1520-0493(1979)107<1184:STEAMS>2.0.CO;2 |bibcode=1979MWRv..107.1184L |doi-access=free }} 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. |author-link=Keith A. Browning |author2=Frank H. Ludlam |title=Airflow in convective storms |journal= Quarterly Journal of the Royal Meteorological Society|volume=88 |issue=376 |pages=117–35 |date=April 1962 |url=http://www.rmets.org/pdf/qj62browning.pdf |bibcode=1962QJRMS..88..117B |doi=10.1002/qj.49708837602 |url-status=dead |archive-url=https://web.archive.org/web/20120307213602/http://www.rmets.org/pdf/qj62browning.pdf |archive-date=2012-03-07 }}; {{cite journal | doi = 10.1002/qj.49708837819 | title = Airflow in convective storms |year = 1962 |last1 = Browning |first1 = K. A. |last2 = Ludlam |first2 = F. H. |journal = Quarterly Journal of the Royal Meteorological Society| volume = 88 | issue = 378 | pages = 555 |bibcode = 1962QJRMS..88..555B }}{{cite journal |last=Browning |first=Keith A. |author-link=Keith A. Browning |title=Airflow and Precipitation Trajectories Within Severe Local Storms Which Travel to the Right of the Winds |journal=J. Atmos. Sci. |volume=21 |issue=6 |pages=634–9 |date=November 1964 |doi=10.1175/1520-0469(1964)021<0634:AAPTWS>2.0.CO;2 |bibcode = 1964JAtS...21..634B |hdl=2027/mdp.39015095125533 |hdl-access=free }}{{cite journal |last=Browning |first=Keith |author-link=Keith A. Browning |title=Some Inferences About the Updraft Within a Severe Local Storm |journal=J. Atmos. Sci. |volume=22 |issue=6 |pages=669–77 |date=November 1965 |doi=10.1175/1520-0469(1965)022<0669:SIATUW>2.0.CO;2 |type=abstract |bibcode = 1965JAtS...22..669B |hdl=2027/mdp.39015095128867 |hdl-access=free }}

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. |author-link=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=July 1977 |location=Kansas City, MO }}{{cite book |last=Lemon |first=Leslie R. |author-link=Leslie R. Lemon |title=New Severe Thunderstorm Radar Identification Techniques and Warning Criteria |publisher=Techniques Development Unit, National Severe Storms Forecast Center |date=April 1980 |location=Kansas City, MO }} These features include:

Image:BWER on radar data.PNG exhibiting a BWER.]]

• Updraft tilt - The tilted updraft (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 weak echo region and on the low-level inflow inside side of the storm.{{Cite web |url=http://amsglossary.allenpress.com/glossary/search?p=1&query=echo+overhang |title=AMS Glossary |access-date=2007-12-16 |archive-url=https://web.archive.org/web/20110606101250/http://amsglossary.allenpress.com/glossary/search?p=1&query=echo+overhang |archive-date=2011-06-06 |url-status=dead }}
• Weak echo region (WER) - An area of markedly lower reflectivity, resulting from an increase in updraft strength.{{Cite web |url=http://amsglossary.allenpress.com/glossary/search?id=weak-echo-region1 |title=AMS Glossary |access-date=2007-12-16 |archive-url=https://web.archive.org/web/20070816163236/http://amsglossary.allenpress.com/glossary/search?id=weak-echo-region1 |archive-date=2007-08-16 |url-status=dead }}
• 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. A mesocyclone is not strictly necessary for BWER development. Storm rotation can be reliably detected by the Doppler velocities of a weather radar.{{Cite web |url=http://amsglossary.allenpress.com/glossary/search?p=1&query=bounded+weak+echo+region |title=AMS Glossary |access-date=2007-12-16 |archive-url=https://web.archive.org/web/20110606101311/http://amsglossary.allenpress.com/glossary/search?p=1&query=bounded+weak+echo+region |archive-date=2011-06-06 |url-status=dead }}
• Descending reflectivity core