COVER: Tornado near Salix, Iowa on July 28,1986. Photography by Billie Kermey. Theirhouse was destroyed soon after this picture was taken.

Storm Track is a non-profit publication intended for the scientist and amateur alike whoshare an avid interest in the acquisition and advancement of knowledge concerning severe

or unusual weather phenomena.

Storm Track is printed on a bi-monthly basis.

PUBLICATION STAFF

Timothy P. MarshallEditor-in-Chief

Philip E. ShermanAssistant Editor

Gene D. RhodenDesign Editor

DAVID HOADLEY, FOUNDER, 1977

Subscription price is $9.00 per year.Persons wishing to subscribe should make checks payable to:

Tim Marshall1336 Brazos Blvd.Lewisville, Texas 75067

March 30, 1990Tim Marshall, EditorPhil Sherman, Asst. Ed.1336 Brazos Blvd.Lewisville, Texas 75067

STORMTRACK$9.00/year

Volume 13, No. 3Bi-monthly

Checks payable tothe editor only

TRUE CHASER DEDICATION

I. COMMENTARY

My phone rang at 8 o'clock in the morning on January 19, 1990. It was the Texas TechTornado Chase Team who flew in from Lubbock on the early bird flight. They were readyto chase storms and wanted to know the latest weather information. What?, I said. It'sJanuary! Sure, I realized a low pressure canter was passing through the Dallas areatoday, and there was a chance of severe weather, but it was cold, rainy, and foggy.They said it was a new year, a new spring, and why not be the first to chase storms.And sure enough, a squall line moved through Dallas about mid- morning. Two downburstscaused extensive roof damage in south Dallas and yes, the first TORNADO struck portionsof Garland, just east of Dallas around 11:30 am. The Tech team and mother nature signalthe beginning of a new chase season. Ah, the chance of convection and chaserdedication.

II. CHASER NEWS

STORMTRACK is now accepting classified advertising which will appear on the back coverof the magazine. Sell or swap your wares at only 25c per word (20 word minimum --$5.00, 100 word maximum -- $25.00). Business card size blocks are $15. Send yourrequest within 45 days of the next issue date. You will help defray some of theprinting costs of this publication which have almost doubled since January, 1989.

The 16th Conference on Severe Local Storms will be held on October 22-26, 1990 inKananaskis Provincial Park, Alberta, Canada, about 50 miles west of Calgary, or 40miles east of Banff. Make your travel plans early if you are going and by all meansdress warmly for the arctic chill. For further information contact polar bears Dr.Davies-Jones or Dr. Charles Doswell, at NSSL, 1313 Halley Circle, Norman, OK. 73069.

III. LETTERS TO THE EDITOR

Sam Barricklow conducted a damage survey of the Garland, Texas tornado which struckjust east of Dallas on January 19, 1990. The early season tornado formed in thenorthern portion of a squall line in association with the surface low pressure center.The damage path ranged from 100 to 400 feet wide (only a few houses across) andtraveled northeastward in a well defined path about one mile in length.

Steve Hodanish writes in response to a question raised by Ken Nakamura in the lastissue of ST. "The minimum sea level pressure in Hurricane Gilbert was 888 mb. I wasvery fortunate to be on-board the aircraft when this measurement was taken. The "exact"pressure will never be known for two reasons: 1) the drop-windsondes were accidentallyleft off the plane, and 2) even if they were on-board, the odds of dropping theinstrument exactly in the center of a hurricane, whose eye was only 8 nautical milesacross at the time, would be nearly impossible." For more information refer to theDecember 1989, Monthly Weather Review article on Hurricane Gilbert, pages 2824 to 2828.

Steve also writes about a spectacular sculpted Cb he saw: "On July 1, 1989, I wentchasing on the dryline 'out near Sterling, Colorado. About 6 pm, an impressive stormformed about 5 miles southeast of town. It did not produce any hail or funnels, bit therotation and structure of the storm was nothing like I've ever seen before! The factthat it occurred while the sun was setting made for some beautiful pictures.

Randy Zipser recently discovered a neat little gizmo that no serious storm chasershould be without. "It's a universal camcorder battery pack discharger. It will allow achaser to fully discharge their camcorder battery packs and then recharge them eachnight after the chase, so they can go into the next chase day with MAXIMUM batterypower. There are two kinds of units: the standard unit has a microswitch to set for usewith either 6 volt, 9 volt, or 12 volt battery packs. They are about the size of acigarette pack. I have one and mine works great. It took about 7- 10 days to receiveafter placing the order. For more information, write or call Spontaneous Creations,3813-7 N. Monroe St., 015, Tallahassee, FL 32303, or call 904-385-2886.

Sue Gruning wants to know where's winter?? After a cold December, January did an aboutface as the upper air jet stream shifted to the north across the northern U.S. border.Balmy temperatures broke many wintertime records across the U.S. This pattern continuedwell into February and looked even more springlike as severe weather returned. By the10th, a powerful storm formed along the South and triggered an outbreak of 13 twistersfrom eastern Texas to Georgia along with numerous accounts of hail, heavy rains anddamaging winds. On Valentines' Day an even more potent storm system was taking shapeover the southern Rockies effecting the Midwest and moving to the Eastern Seaboard.

By noon on February 14, a low pressure center over southwestern Colorado formed anintensified as it moved into central Oklahoma the next day. A cold front extended southfrom the low through eastern Texas while a stationary front extended northward to theGreat Lakes. Warm, moist unstable air across the Tennessee Valley created the rightconditions for strong thunderstorms. A slight risk area for severe weather extendedfrom central Texas to southern Indiana with a higher risk centered in the lowerMississippi Valley. As afternoon progressed, tornado watches covered most of Arkansas,Louisiana, Mississippi, Alabama, and western Tennessee and Kentucky. Four tornadoeswere reported.

IV. ROSTER

The ST Roster lists names, addresses, and brief biographies of those persons interestedin or willing to correspond with others about storms and storm chasing.

Rob Wyatt "I'm 33, and a general class ham radio operator 618 Madison Ave.KC4JTA. My 20 meter phone band is 14.30-14.35. Madisonville, KY 42431 My 10 meter mobile is 28.350. I'd like to start phone: 502-825-3938 a storm chasers net on 20 meter side band. If you hear me on the band call for "rag chew".

Patrick Kerrin "I'm a 27 year old, single, Univ. of Western 309-85 Fiddlers Green Rd Ontario student who has a long standing interest London, Ontario, CANADA in severe weather. At present, I only chase N6H-4S9 locally, but eventually hope to venture out to the plains each May. I'd be happy to correspond with other enthusiasts."

V. FUNNEL FUNNY: Chase Simulator

How do chasers cope with the long harsh winter? They prepare for spring using theCHASE SIMULATOR!

A NORTHEAST TORNADO OUTBREAK: JULY 10, 1989 by Boris Konon

On July 10, 1989, one of the most widespread and potent severe weather outbreaksoccurred in the Northeast. At least 13 tornadoes touched down, 2 of which wereconfirmed as F4 intensity with others in the F2-F3 range. This outbreak occurred innorthwesterly flow aloft, which has been historically the best for tornadoes in thispart of the country.

On Friday, July 7, severe thunderstorms rumbled through New England with the passage ofa cold front. Cooler and drier air with brisk northwest winds prevailed over theweekend, but apparently the atmosphere didn't completely stabilize. A few thunderstormspopped up in Connecticut (CT) on Saturday afternoon and some rather strong storms withsmall hail erupted over southeastern Massachusetts (MA) on Sunday. These, however, weremerely a prelude of things to come. The 60 hour AVN from Saturday morning showed astrong short wave with a deep surface low (for July) traversing southern Ontario,headed for northern Maine. Strong, warm advection was depicted over New England duringthe day on the 10th along with excellent directional shear. The exit region of a 300 mbjet (in excess of 100 knots) was juxtaposed over the area. The timing looked good. Thisleft no doubt in my mind that tornadoes were a strong possibility. It was rare to seethis so far in advance.

Monday, July 10 dawned clear and cool across southern New England, but strongthunderstorms had already developed in Ontario ahead of a warm front and were movingrapidly southeast. These storms became severe in Vermont (VT) and eastern NY by 7 am.The storms continued to intensify during the morning and moved into western MA withwinds over 60 mph and hail up to golfball-size. Less intense storms moved througheastern MA, and Rhode Island and quickly moved off the coast by 12:30 pm. The passageof the warm from was very noticeable. Dewpoints rose from the low 60's to the low 70'sin a short time with many people reporting their windows fogging over. Surfacetemperatures rose into the 80's in western sections with skies remaining mostly cloudy.Windsor Locks, CT temperature and dewpoint were 68 and 66 respectively at noon, androse to 86 and 73 degrees by 2 pm. The stage was set.

Severe thunderstorms redeveloped in upstate NY and VT by noon and rapidly moved south-southeast at 50 to 60 mph. The first tornado, rated Fi, touched down at Ames, NY andtracked 24 miles to Schoharie, NY. Path width ranged from 1/2 to 3/4 of a mile.Widespread damage was reported. This was only the beginning for this thunderstorm cellwhich had tops to 60,000 feet. A weak tornado (F0) was spawned farther to the southeastat Surprise, NY! The supercell storm now moved into CT, and a tornado (F4) practicallywiped out the town of Bantam. Another strong tornado struck Waterbury. A tremendousamount of damage occurred in the cities of Hamden and New Haven from yet another F4tornado. This storm was unusual since it continued to intensify as it approached the CTcoast; usually storms weaken markedly. Long Island was hit very hard with anothertornado at East Moriches. Extreme wind damage and large hail was reported along theentire path. The storm turned day into night when it struck. Huge canopies of mammatuswere reported. Oxford, CT received 4.4 inches of rain in just 30 minutes.

In central and eastern MA, a tornado struck cities of Hubbardston, Sterling, WestBoyleston, and Ashland. Farther to the southeast, small tornadoes struck Brockton andHanover. A large hook echo was clearly visible on radar with this cell. Refer to theattached maps.

ROGER JENSEN: A BIOGRAPHYby David Hoadley

Minnesota's Roger Jensen, who's articles and photographs have been published nationallyand internationally, was the first contemporary storm chaser to turn his eyes to theskies and wheels to the road. Roger was riding the highways of North Dakota andMinnesota as early as 1953, photographing the tall towers -before most of us were evenborn. I was just a Sophomore at; Bismarck High, concerned with making new friends (justmoved from Washington, D.C.). The only Dakota storms I cared about were the white ones-and the current wind chill.

Roger's earliest storm memory dates to 1940,as a 7 year old with his parents in Fargo,North Dakota. A late evening Julythunderstorm began forming, and he"remembers the sky growing darker and eerielooking" before it struck. It was especiallyintense and lasted several hours. When hewas 8, he began going out to a flat field onthe family farm near Lake Park, Minnesota towatch the storms build and move toward himfrom the Red River Valley.

The family moved to the Seattle area in1950. There, the young teenager took hisfirst storm slide -with a Kodak "Pony" #828camera- of towering thunderheads over theCascades (July, 1952). However, the climatewas too stable for him, and -luckily- thefamily moved back to the plains and Fargolater that year.

Roger's first actual chase was in the summer of 1953, as his father began driving himto local thunderstorms within 50-60 miles of Fargo/Moorehead. In the fall of 1954, theJensens moved back to the family farm at Lake Park -- east of Fargo. In 1960, he boughthis current camera, a single lens reflex 35 mm Miranda "S" with wide angle andtelephoto lenses. He currently lives in Detroit Lakes, where he moved in 1974.

Over the past 36 years, Roger Jensen has driven thousands of miles across the easternDakotas and Minnesota and is the most experienced chaser of northern plains storms. "Hecan name any cloud in the sky" and "by his own admission, can keep up a conversationwith the best weathermen" (Detroit Lakes Record, Jan. 22, 1979). He has seen andphotographed hundreds of severe storms, roll clouds, golden mammatus (Weatherwisecover, Oct., 1976), the largest (soft- ball) hail ever documented in the state, seventornadoes (Up to a mile wide, northeast of Moorehead, June 28,1975), and some singularlightning encounters (Close enough to smell the ozone after a concussion blast thatnearly knocked him over).

Roger is interested in corresponding with other chasers and in exchanging or purchasing(at a "reasonable price") good quality prints or slide copies (less utility lines) oflarge tornadoes, mammatus, roll clouds (a special favorite), multiple lightningstrikes, and irregular hail stones. I have seen some of his prints, and they areexcellent, high contrast and varied.

One of the longer and more rewarding chases was on June 30, 1967, when he pursuedintensifying thunderstorms -southeast across Minnesota to near Minneapolis/St. Paul. At9PM, that storm bore down hard on the twin cities with "blinding rain," heavy hail andwinds in excess of 150 MPH ("Which moved and shook my car like it was a piece ofcork"). Roger documented one of the most photogenic and dramatic storms ever seen onthe northern plains that day and wrote about it in the Correspondence Section of theJanuary, 1973 "Bulletin of the American Meteorological Society." I saw one print ofthis storm at maximum tilt, as it advanced darkly with a solid wall of fractus "teeth"beneath a mid-level wind-sheared shelf, that hung from above -like the dark brow of anangry giant. It was one of those end-of-the-world scenes that makes one catch hisbreath and then look for cover.

He has been widely published, including three articles and photos in the CorrespondenceSections of the "AMS Bulletin": Vol. 54, No. 1; Vol. 56, No. 7; and Vol. 58, No. 6. Hispictures have also been published by "Weatherwise" and in Clouds of the World byRichard S. Scorer; Stackpole Books, London, 1972; pgs. 33, 47, 51 and 55.

Reflecting on some of his close encounters with danger, this former Minnesota farmerand Swift Company employee is more often filled with "deep respectful awe andadmiration" than fear. "A thunderstorm is the most spectacular natural phenomenon thereis." Interestingly, however, no favorite storm stands out in his mind. All are "veryimpressive in their own different kinds of ways." But if he did have to choose onefeature over another (including tornadoes), it would be to see a magnificent, toweringthunder- head, with the characteristic "cauliflower" sharpness and high base ofnorthern plains storms. Of course, the ideal storm always exists in the mind's eye:

"... a spectacular 60-70,000 foot tall thunderstorm" moving in from the west andoverhead, "with a roll cloud [at] the base and down to 'tree top' level from onehorizon to the other." He would also have two or three "lenticular, laminatedcloud 'plates' just above, where the roll cloud drops out of the parentthunderstorm." After "grape- fruit hail and spectacular mammatus," the stormdrifts off to the southeast through an evening palette of "orange, coral, roseand red."

However, this original Minnesota chaser no longer drives hundreds of miles to see suchstorms. Nor do reporters seek him out for newspaper articles. Roger Jensen is nowconvalescing in a Detroit Lakes nursing home *, making a slow recovery from a lengthyillness. Nonetheless, he still "chases," undaunted, to a nearby hill a few hundredyards away, where he can just see over the trees and watch the far clouds. But he isnot depressed or bitter. His heart and mind are filled with the wonders of the sky andthe memories of a lifetime of chasing -and his vision is permanently on that distanthorizon, ever promising and golden at the end of day -and at its beginning.

* St. Mary's Nursing Home, Room #2201040 Lincoln Avenue, Detroit Lakes, MN 56501

TYPES OF LIGHTNING

by Jack Thunderhead Corso

CG Cloud to GroundCC Cloud to CloudCA Cloud to Air

THE THUNDERSTORM SPECTRUM by Alan Moller and Dr. Charles Doswell III

The National Weather Service began organizing severe local storm spotter networks inthe early 1950's, about the time the severe storm Watch and Warning (WW) system wasinitiated. Although some thought that the advent of the NWS weather radar network atthe end of that decade would eliminate the need for spotters, it became obvious thatradar and spotters arete complimentary; radar detects storms and possible severe stormsignatures while spotters detect storm-generated severe events.

Over the next thirty years, the importance and utilization of spotter networksincreased as local communities began taking a more active role in disaster mitigationplanning. Spotters became a key element of what was becoming aWatch/Warning/Preparedness (WWP) system. The increased reliance on spotter networksresulted in a need for improvements in spotter training programs. Thus, the authorshave developed several slide sets and movies including "A Spotter's Guide forIdentifying and Reporting Severe Local Storms", "Tornado-A Spotter's Guide", "A SlideSeries Supplement to Tornado- A Spotter's Guide", and "A Look at Thunderstorms andTheir Severe Weather Potential". The latest slide series begins with an introduction tothe thunderstorm spectrum, from which four major thunderstorm types (single cell,multicell cluster, multicell line, and supercell) are extracted. A strong caveat ismade that real storms may not fit neatly into one of these four categories. Indeedthere are a number of "hybrid" storms which contain physical traits of more than onestorm classification.

Arrangement of storms within athunderstorm spectrum is dependent onupdraft strength, relative frequencies ofthese updraft strength categories, andrelative threats of the derived stormtypes. Note from Figure 1 that whereas a"strong" intensity updraft is less commonthan a "weak" updraft, the rela- tivethreat to life and especially property isconsiderably greater with the "strong"updraft storms. Similarly, even though"intense" updraft storms (usuallysupercells) are quite rare, they inflict adisproportionate amount of damage andpersonal injury.

The importance of the environment indetermining which storm type willpredominate in a given scenario isillustrated in Figure 2, which positionsstorm types within the framework of avertical shear vs. draft strength. Notethat severe storms occur in a variety ofmodes, from dry microbursts and summerpulse storms, to supercell storms. Thedraft strength axis on this diagram is anindirect way of indicating positivelybuoyant energy available for downburst-intensity downdrafts.

Figure 1. Thunderstorm spectrum.

Figure 2. Shear vs. draft strength.

* Condensed from 15th Conf. on Severe Storms.

OBSERVING STORM TYPES by Tim Marshall

Most thunderstorms contain several cells of updrafts and downdrafts and are calledMULTICELL storms. You can visibly distinguish a multicell storm from single cell stormsby counting the number of visible cloud towers or updraft "puffs". Refer to Photograph1 which shows five updraft puffs. Note, the weakest updraft is furthest downstream (tothe right) as upper winds tilt the towers to the right. The most actively growingtowers are furthest upstream (on the left). Typically, the heaviest precipitation in amulticell storm falls beneath the highest cloud top. This multicell storm is ISOLATEDin that there are no other storms around it. Thus, it can last an hour or two, longenough until the storms outflow undercuts the updraft. However, such a storm canstrengthen if the wind structure is right and evolve into a SUPERCELL. Note the line oftowers extending into the upwind from this storm is frequently referred to as aFLANKING LINE.

Photograph 1. A multicell stormwith five updraft puffs. Towersare tilted over to the rightwith height due to increasingwinds aloft. This stormproduced brief heavy rains andstrong bursts of outflow winds.Photograph by Alan Moller.

Occasionally, isolated multicell storms grow into a line of storms called a SQUALL-LINE. Small hail, and strong gusty outflow winds accompany the passage of a squall-line. The isolated or line multicells can either be severe or non-severe. A severestorm by definition is one that has 3/4 inch diameter hail or larger, 50 knot winds,funnel cloud, or a tornado. A severe storm can have one or all these parameters. Strongstraight-line winds can be produced by multicell storms as the storm's outflow spreadsoutward along the ground. Sometimes the downdrafts pulse with collapse of each stormcell resulting in DOWNBURSTS or MICROBURSTS. Chasers should watch for plumes of dustblowing out from areas of falling precipitation or virga and take necessary evasiveaction. A bulge in the edge of the rain area in contact with the ground or RAIN FOOT isalso dangerous and likely indicates very strong winds ahead.

Severe multicell storms sometimes produce tornadoes. However, tornadoes associated withmulticell storms are usually brief in duration and occur in single events. I have yetto see a tornado from a multicell storm. However, I have seen a number of multicellstorms evolve into supercells that eventually produce tornadoes. I have not been ableto determine when or if such a multicell storm will evolve into a supercell.

The most intense thunderstorm is the SUPERCELL. These storms are rare but they aresought by most storm chasers as they produce more tornadoes than any other storm type.Supercell storms are usually isolated and contain a large, single, rotating updraft.The supercell storm usually forms in a wind shear environment that allows the storm tocoexist at a quasi-steady state for several hours. This enables the storm to build-upgreat energies pulling in moist inflow air from miles around. Thus, a supercell canproduce several tornadoes in a row throughout it's life.

There are three types of supercells currently recognized in the field: the CLASSIC,DRYLINE or low precipitation (LP) storm, and COLLAPSED or high precipitation (HP)storm. Some storms have a combination of these features as mother nature continues toresist having us put storms into nice neat categories.

The CLASSIC supercell is identified by a dominant precipitation area to the northeastof the main cloud tower (Photograph 2). High altitude winds aloft (the JET STREAM) isresponsible for shifting the bulk of the descending rain and hail well to thenortheast. This must be done to insure that the cloud base continues to draw in morewarm, moist air. The rain cooled air northeast of the main cloud tower is called aFORWARD FLANK DOWNDRAFT (FFD). The intensity of the FFD must be just right if the stormis to sustain itself. If the FFD is too strong, cool air can undercut the storm'supdraft causing the demise of the storm. If the FFD is too weak, not enough warm, moistair will be channeled toward the cloud base. You can think of the main precipitationarea as a wall or barrier where the moist inflow air runs up against it and is lifted.The presence of the FFD alone does not mean the storm will produce a tornado. Anotherimportant downdraft in back of the main cloud tower is needed to help direct andconstrict the inflow air. This downdraft is called the REAR FLANK DOWNDRAFT (RFD).Sometimes the RFD appears as a cloud free zone which wraps around the main cloud tower.

The DRYLINE or LP supercell is a hybrid storm usually found in drier areas of the highplains. It differs from the classic supercell in that it usually has a smallerprecipitation area (FFD) and rain free RFD (Photograph 3). However, this does not meanthe actual precipitation is small. "All of a sudden there was fist-size hail smashingmy car" is a common statement made by chasers who get on the wrong side of a drylinetype storm! The main cloud tower appears skeletal having spiral cloud bands orstriations frequently appearing like bands on a barber shop pole. Frequently, theflanking line is smeared to a point at the southwest edge of the storm indicating highinflow winds.

The COLLAPSED or HP supercell is another hybrid and usually occurs where there is anabundant supply of low-level moisture. This storm has two large precipitation areas,each being the RFD and FFD. Sometimes these precipitation areas combine. Heavy rain andhail accompany each downdraft. This storm is not a good multiple tornado producer asthe heavy precipitation interferes with the storm's updraft. Refer to Photograph 4. Itis a difficult storm to chase as dense precipitation and low stratocumulus cloudsrestrict visibility.

As on any storm, the key is to watch the rain free portion of the cloud base for wallcloud formation, a precursor to most tornadoes. Ask yourself whether the wall cloud ispersistent? Watch the wall cloud for signs of rotation, and most importantly, identifywhether there is inflow into the cloud base?

Schematic plan view diagrams of keyfeatures in the Classic, LP, and HPsupercell storms. Diagrams from Mollerand Doswell (1988). Shaded areasindicate downdrafts. Outlined areas areanvil and updraft edges.

Photograph 2. A CLASSIC SUPERCELL near Canadian, Texas on March 22, 1987. Note thebarrel-type, single updraft standing erect in a 120 kt jet stream, cumuliform rocksolid anvil, and stratocu inflow at lower right. The storm produced several tornadoes.Photograph by Tim Marshall.

Photograph 3. A dryline type or LP SUPERCELL near Wayside, Texas on May 25, 1987. Notethe striated cloud banding like that of a barbershop pole, the inflow tail on right,tapered point on left, and small funnel beneath the cloud base. Photograph by TimMarshall.

Photograph 4. Tornadic HP SUPERCELL over Windthorst, Texas on May 14, 1986. Note theheavy precipitation area along the backside of this storm, the large "beaver tail"inflow band on the north side, and cloud "vault" on the north side of the updraft.Photograph by Phil Sherman.