Storm Spotting – Solidifying the Basics PROFESSOR PAUL SIRVATKA COLLEGE OF DUPAGE METEOROLOGY HTTP://WEATHER.COD.EDU Focus on Anticipating and Spotting • What do you look for? • What will you actually see? • Can you identify what is going on with the storm? Is Gilbert married? Hmmmmm….rumor has it….. Its all about the updraft! Not that easy! • Various types of storms and storm structures. • A tornado is a “big sucky • Obscuration of important thing” and underneath the features make spotting updraft is where it forms. difficult. • So find the updraft! • The closer you are to a storm the more difficult it becomes to make these identifications. Conceptual models Reality is much harder. Basic Conceptual Model Sometimes its easy! North Central Illinois, 2-28-17 (Courtesy of Matt Piechota) Other times, not so much. Reality usually is far more complicated than our perfect pictures Rain Free Base Dusty Outflow More like reality SCUD Scattered Cumulus Under Deck Sigh...wall clouds! • Wall clouds help spotters identify where the updraft of a storm is • Wall clouds may or may not be present with tornadic storms • Wall clouds may be seen with any storm with an updraft • Wall clouds may or may not be rotating • Wall clouds may or may not result in tornadoes • Wall clouds should not be reported unless there is strong and easily observable rotation noted • When a clear slot is observed, a well written or transmitted report should say as much Characteristics of a Tornadic Wall Cloud • Surface-based inflow • Rapid vertical motion (scud-sucking) • Persistent • Persistent rotation Clear Slot • The key, however, is the development of a clear slot Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather Storm Type Matters: Tornado Types • Supercell tornado • Non-supercell tornado • QLCS tornado • Land (water) spout • A gustnado is not a tornado but can and should be reported for what it is More traditional supercell - Classic You are not going to have problems identifying this tornado. But neither will Doppler Radar. More traditional supercell - HP More traditional supercell tornado Tail Cloud Clear Slot A Reasonable Look for a Clear Slot Photo by Jeff Duda No (readily) apparent clear slot Possible landspout-type beginning? Photos by Matt Piechota Occlusion (wrapping of cold air around the low-level mesocyclone) taking place - clear slot Rear Flank Gust Front Rear Flank Downdraft Clear slot beginning Washburn IL tornado 2-28-17 (Courtesy Matt Piechota) Washburn IL tornado 2-28-17 (Courtesy Matt Piechota) Multicells and supercells Multicell storms will pose a different problem Tornado embedded within line A Whole Spectrum of Rotation QLCS – Quasi Linear Convective System LEWP – Line Echo Wave Pattern QLCS Tornado LEWP-T Misovortex 2. Warm sector (AR/MO/IL): 28/00z sounding from OUN exhibited a steep-lapse-rate environment with substantial low-level moisture. Strong capping and neutral-weak subsidence will allow this air mass to Convective Outlook from 2-28-17 6Z “Forecast soundings suggest very large hail could accompany this activity and a few strong tornadoes are possible, especially if discrete structures evolve… “Damaging winds should be noted with this [cold] frontal convection and tornadoes may also be embedded along the line.” QLCS Tornado? “[R]ecently, Atkins and Laurent developed more than one theory for mesovortex formation because they saw different evolutions within the QLCS. This one requires a locally intense updraft along the gust front to tilt and stretch streamwise vorticity running down the boundary. The resulting vortex would be of a single sign and not a couplet.” Summary • Find the updraft • Think about what kind of storm it is • What are the hazards associated with your spotting • Get a good radar image (e.g. GRLevel3 or Radarscope) and know where the greatest rotation is • Report what you actually see, not what you hope to see NEXLAB Weather http://weather.cod.edu Storm Chasing http://weather.cod.edu/chasing Paul Sirvatka [email protected].