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.[1] The Lemon technique is largely a continuation of work by Keith A. Browning, who first identified and named the supercell.[2][3][4]
The method focuses on updrafts and uses weather radar to measure quantities such as height (echo tops), reflectivity, and location and to show features and trends described by Lemon.[5][6] 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.[7]
- Weak echo region (WER) - An area of markedly lower reflectivity, resulting from an increase in updraft strength.[8]
- 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.[9]
References
- ^ Lemon, Leslie R. (Sep 1979). "Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis". Monthly Weather Review. 107 (9). American Meteorological Society: 1184–97.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Browning, Keith A. (Apr & Oct 1962). "Airflow in convective storms" (PDF). Quarterly Journal of the Royal Meteorological Society. 88 & 88 (376 & 378). Royal Meteorological Society: 117-35 & 555.
{{cite journal}}: Check date values in:|date=(help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Browning, Keith A. (Nov 1964). "Airflow and Precipitation Trajectories Within Severe Local Storms Which Travel to the Right of the Winds". Journal of the Atmospheric Sciences. 21 (6). American Meteorological Society: 634–9.
- ^ Browning, Keith (Nov 1965). "Some Inferences About the Updraft Within a Severe Local Storm". Journal of the Atmospheric Sciences. 22 (6). American Meteorological Society: 669–77.
- ^ Lemon, Leslie R. (Jul 1977). New severe thunderstorm radar identification techniques and warning criteria: a preliminary report. Kansas City, MO: Techniques Development Unit, National Severe Storms Forecast Center.
- ^ Lemon, Leslie R. (Apr 1980). New Severe Thunderstorm Radar Identification Techniques and Warning Criteria. Kansas City, MO: Techniques Development Unit, National Severe Storms Forecast Center.
- ^ AMS Glossary
- ^ AMS Glossary
- ^ AMS Glossary
See also
External links
- Paul Sirvatka and Les Lemon The Lemon Technique – College of DuPage Meteorology (PDF)
- The Lemon Technique (LT) to determine updraft strength (University of Illinois)
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