TORNADO FORECASTERS WORKBOOK (#1) PREFACE Whether you are a chaser, spotter, or just interested in tornadoes, this workbook has been designed for you to have fun in trying to forecast tornadoes. You will find that mother nature does not follow many rules, especially when it comes to tornado forecasting. Trying to figure out where tornadoes will form is difficult especially when the situations are not the “textbook” variety. Thus, we have selected several non-traditional weather situations for you to analyze and determine: 1) Is this a day when tornadoes are likely? and 2) If so, then which town or towns will be the closest to the tornadoes? If you said yes to the first answer, then pick your target town(s). If you said no, then leave the target town(s) blank. Your answer to the second question will be correct if you pick a town that is within a sixty mile radius of the reported tornadoes. Please fill in the blanks below. Use the outline of a quarter (coin) on the surface map provided to draw your target area. Please note that some exercises have up to three areas/ answers where tornadoes occurred. The answers along with a discussion of each case is presented in back of the workbook. (Please don’t read the answers first.) There are 10 exercises presented. Each potential tornado day has a surface map, 12z upper air maps, a few soundings, and/or miscellaneous statements from either the Storms Prediction Center (SPC) or the local National Weather Service (NWS). Not all of these days produced tornadoes. You may choose to analyze the weather maps or not. Incorrect data HAS NOT been edited. The surface maps herein have temperatures and dewpoints in degrees Fahrenheit. Winds are blowing from the direction indicated. A full barb represents 10 knots and half barbs indicate 5 knots. Surface barometric pressures are indicated in millibars. Upper air maps are constant pressure surfaces and the heights of these surfaces above sea level are already contoured for your convenience. Both surface and upper air maps were plotted on the Weather Graphics software program developed by Tim Vasquez. Soundings are plotted using the RAOB software program developed by John D. Skewchuk of Environmental Research Services. Additional references are provided in the back of this booklet. WRITE DOWN YOUR ANSWERS HERE EXERCISE TORNADO DAY? (example) Yes

(ANSWERS ARE ON PAGES 46-50) FORECASTED TOWN OR TOWNS Lincoln, NE, Pueblo, CO, Midland, TX

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INTRODUCTION “Many proponents of new technology believe that it is important to relieve forecasters from the “burden” of weather map analysis. From the author’s perspective, this is terribly wrong! Performing map analysis is an essential component in diagnosis-it allows one to compare models of atmospheric behavior to the data. This is the way a forecaster forms an understanding of what is happening in the atmosphere. Rather than freeing time to do science, taking map analysis away from forecasters minimizes their opportunity to function as practitioners of meteorological science”. - storm researcher Dr. Chuck Doswell, 1986 It is the late 1990’s and the art of severe weather forecasting seems to be crumbling into a push-button-type approach. It is especially easy to find this attitude in weather-related discussion groups on the Internet. “When the storms are being forecast, look at super-computer model forecasts, and when they’re now occurring, look at the Doppler radar.” Part of this philosophy has been perpetuated by the widespread availability of model data on the Internet, which in turn has been influenced by the overwhelming emphasis placed on numerical theory by university meteorology programs. It has also been caused by the rapid advances in computing power, which make powerful model forecasts easily available to the masses and leads many forecasters into thinking that there is no longer any need to subjectively interpret the atmosphere. There even seems to be an attitude nowadays that there’s isn’t any time to analyze, especially when you have all those great models and Doppler radar data. This is unfortunate, because weather analysis is not simply drawing lines-it is the basic process of understanding what is happening right now. Weather analysis is taking the current observations and plotting them on a map (whether by hand or by computer). It’s looking at the regional radar. Looking at visible satellite imagery. Reading the remarks in weather observations. Checking soundings and profiler observations. Analysis is not looking at the zero-hour panel of a model run. Forecasting without analysis is analogous to taking a literature quiz on Ivanhoe, having studied it using only Cliff Notes. The Cliff Notes do provide all of the important answers, but give a poor understanding of the subtleties and evolution of events in the novel. Furthermore, numerical weather predictions are never correct, and always contain some degree of error. It is impossible to adequately represent the real atmosphere in a computer and precisely simulate all of the physical processes that may occur. Sometimes the errors are indiscernible, and sometimes they are grave (especially in unusual weather situations). Only through analysis can a forecaster challenge the models, adjust their output, or know when to ignore them. The sharpest chasers rely mostly on analysis with observed data, satellite, and soundings, using models only as guidance. Models are a great tool, but they aren’t needed to successfully forecast a tornado outbreak. That’s part of the purpose of this workbook. So, get out your colored pencils. This workbook is targeted at intermediate and advanced spotters and chasers, and assumes you have a basic understanding of fronts, air masses, and weather symbols. If not, consider reading up on meteorology topics in weather textbooks and articles before continuing so that you get all the benefits of what this workbook has to offer. Advanced chasers may wish to skip ahead to the case scenarios, but for the intermediate chasers we’ll now delve into a quick discussion of analysis topics to help you find what to look for. The forecast hints presented on the next few pages are general and are not all inclusive. As certain weather situations arise, the forecaster must select which analyses will work best. For example, a sounding may be important BEHIND the dry line or front in order to look at how cold the air is aloft and how fast the winds are blowing. Forecasting is a trial and error process. There may be times when you’ll make some great forecasts but also you will be reminded of some great errors. Dr. Chuck Doswell has said it best: “The first rule you will learn in forecasting, is that there are no rules.”

THE SURFACE CHART The surface chart has much greater time and space resolution than upper-level charts, so it is quite important that the storm forecaster monitor the ever changing conditions. In many instances, surface features reflect changes that are happening aloft. Analysis of the surface chart can reveal the presence of boundaries, mesolows, the dry line, or moisture convergence which are just a few of the features frequently associated with severe weather. However, if you just analyze the surface chart and forget about the upper air or soundings, you will find that your forecasts are less accurate. The upper air data can provide you with information on the capping inversion and winds aloft which play a role in severe storm forecasting. Do the following: 1.

Draw isobars at intervals of every 2 millibars (although 4 mb is the standard, we are doing a mesoanalysis and need to resolve small details). This will help you identify lows, highs, mesolows, and mesohighs. Look for rapid pressure falls. Severe weather has been associated in regions of sharply falling pressures, and within 200 miles northeast of meso-lows.

2.

Locate all frontal boundaries, outflow boundaries, dry lines, and wind shift lines. Identify those stations where rain, fog, dust, or thunderstorms are occurring. Fronts are always located on the warm (usually south) side of thermal gradients. Use wind shifts and dewpoint differences to find fronts or bound aries only if the line corresponds to the warm side of a thermal gradient. Storms often prefer to fire along the dryline, which is often in closest proximity to upper-level disturbances and destabilization coming from the west.

3

Draw temperature and dew point contours every 3 degrees when values are greater than 55 degrees. This will help identify the warm, moist sector. Locate the axes of maximum temperatures and dew points. Storms normally develop where temperature and dewpoint are highest (highest equivalent potential temperature, or theta-e). Of course, they are affected by the strength of the lid, too, which is why storms often don’t form in the juicy temperatures and dewpoints in far south Texas. Severe weather is most likely from the intersection southward. Monitor hourly changes in temperature and dewpoint. Areas which are warming and moistening indicate destabilization.

4.

Note the wind direction and speed especially any changes of the wind vectors from hour to hour. Backing winds over a period of time may indicate increasing confluence and possible mesolow formation. Areas where winds have a strong easterly component tend to encourage tornado development if storms form, due to the greater low-level shear. Areas with southwesterly surface winds are not normally conducive to tornadic development with southwesterly flow aloft.

5.

Identify the extent of cloud cover. Dense cloud cover can deter solar heating and thus, convection.

UPPER LEVEL CHARTS Upper level charts reflect conditions and processes that will have an impact on thunderstorm development. Severe weather forecasters are usually concerned with two things: processes that will directly cause instability (cooling aloft or warming at the surface), and processes that will enhance vertical motion (upward motion tends to enhance severe weather activity; downward motion tends to have a suppressing effect).

300 MB CHART A good way to start is from the top down. Begin analyzing using the 300 mb chart. Located at about 30,000 feet above mean sea level (MSL), this chart shows the “big thermodynamic picture”. The 300 mb chart can reveal the locations of troughs, the upper-level jet stream, jet streaks, cold air pools, and diffluent areas.

Do the following on the 300 mb map: 1.

Draw height lines (contours) at intervals of 60 meters. The height contours already have been plotted for you by the computer but you may want to reanalyze the maps. Station plot heights are tens of meters, so the contours will be every 6 when using these digits. Use a pencil.

2.

Locate the high and low height areas on the map. Lower heights are found where there is colder air. Why? Colder air is denser and hugs the surface, leaving lower pressure aloft and forcing the 300 mb height closer to the ground. So, you will find lower heights over cold air masses. Lower heights con tours extending southward in a U-shaped configuration are called troughs; upside-down U’s are ridges. Troughs destabilize the air by transporting colder air south and eastward. Severe weather is most likely in advance of a trough. What are the axes of the troughs: positive, neutral or negative? Troughs that have a neutral or negative tilt (northwest-to-southeast) have more energy than positive tilt troughs.

3.

Identify the greatest height falls and coldest temperatures. Troughs with the greatest height falls on their east sides (in the northern hemisphere) and height rises on their west sides will give you a relative indication of how fast the trough will move or deepen. Monitor the position of the trough during the next 12 to 24 hours. Does the low or trough deepen? Digging, intensifying troughs or lows are more ener getic especially if they track eastward across the four-corners area. In contrast, filling troughs or lows are less apt to produce extensive severe weather especially if they eject quickly northward.

4.

Locate jet streams with thick purple arrows. Severe storms love a strong jet stream.

5.

Find jet streaks, which are definite “blobs” of significantly higher winds embedded within the jet stream. Shade these in purple. Areas downwind and to the left of jet streaks (i.e. usually northeast of a jet streak) are associated with upward motion, and are called the “left front quad”. Areas upwind and to the right of jet streaks are also associated with upward motion, and are called the “right rear quad”. Likewise, downward motion is associated with the right front and left rear quadrants. When the jet streak is embedded in cyclonic curvature (height lines bent in the shape of a “U”), the left quadrants are enhanced and the right quadrants are dampened. When the jet streak is in anticyclonic curvature (height lines bent in the shape of an upside-down “U”), the left quadrants are dampened and the right quadrants are enhanced. Strong winds in upper levels (30 kts or greater) help separate the updraft from the downdraft and enables new storms to persist or strengthen. According to Miller (1972), 300 mb westerly winds greater than 40 knots are moderate and greater than 65 knots are strong for tornado potential.

6.

Find areas of diffluent flow, where the height contours spread apart as you move downstream. Diffluent flow, where contours spread apart as you move downstream without any significant decrease in wind speed, is an indicator of upper-level divergence and favors upward vertical motion. Rising motion causes mid-level cooling, increasing instability. In contrast, sinking motions causes mid-level warming and strengthens any capping inversions at lower altitudes.

500 MB CHART The 500 mb chart is located at about 18,000 ft MSL. This level is frequently referred to as the “steering level” which moves storm systems generally from west-to-east. The 500 mb chart can reveal the locations of troughs, the mid-level jet stream, jet streaks, cold air pools, and diffluent areas.

Do the following on the 500 MB map. 1.

Draw height lines at intervals of 60 meters (station plot heights are tens of meters, so this will be every 6 when using them). Use a pencil. (The height contours already have been plotted for you.) Look for a trough moving inland into California. This feature can enhance moisture convergence into the western high plains. Identify negative tilt troughs (these have the main trough axis tilted southeast to northwest). As mentioned previously, negative-tilt troughs transport a great deal of energy and rapidly lift larger amounts of air. Open troughs moving eastward are preferred over slow moving closed lows. The former overturns the atmosphere quickly resulting in explosive convection.

2.

Locate jet streams, drawn parallel to the height lines along axes of strongest winds as thick blue arrows. According to Miller (1972), 500 mb wind speeds greater than 30 knots are moderate and greater than 50 knots are strong for tornado potential.

3.

Find jet streaks, which are definite “blobs” of significantly higher winds embedded within the jet stream. Shade these in blue.

4.

Locate short waves, which are drawn in black perpendicular to contours. Short waves represent areas of marked wind shifts and/or sharp bends in the contours and can be only a few hundred miles long. Rising motion usually occurs east of short waves; sinking motion occurs west of them. The sharper the wind shift or curvature, the stronger the short wave. In general, the short waves move faster than the larger amplitude long waves.

5.

Locate temperatures less than -9 Celsius. The colder temperatures the better. Look for the possibility of cold air advection upstream (i.e. -9C at Oklahoma City and -15C at Albuquerque). Each Celsius degree of cooling moving into the region decreases the lifted index by 1 degree and increases severe weather potential.

6.

Note height fall trends. This will give an indication of trough movement or deepening. Negative numbers indicate a trough that is moving eastward and/or is intensifying. According to Miller (1972) height falls of 30 to 60 meters in the past 12 hours are moderate and greater than 60 meters are strong for tornado potential.

700 MB CHART The 700 mb level, located about 10,000 ft MSL, is often within the mid-level capping inversion or “lid”, which often suppresses thunderstorms until solar heating has increased to significant levels. Crucial information is presented on temperature, moisture, and winds. Do the following on the 700 mb map: 1.

Draw height lines at intervals of 30 meters (station plot heights are tens of meters, so this will be every 3 when using them). Use a pencil. (The height contours already have been done for you.)

2.

Locate jet streams, which are drawn parallel to the height lines along axes of strongest winds. Use a brown pencil.

3.

Draw temperature and dewpoint depression contours, between 2 and 4 degrees Celsius. Very warm 700 mb conditions indicate a strong lid, which may suppress all activity. Cool 700 mb conditions indicate no lid, favoring widespread, weak, or disorganized storm activity. The most violent weather usually happens somewhere in between. Also, large dewpoint depressions indicate dry air intrusions and can be associated with a strong capping inversion.

850 MB CHART The 850 mb level is located at about 5,000 ft MSL. This level can reveal the presence of low-level jets, moisture, and the capping inversion. Do the following on the 850 mb map: 1.

Draw height lines at intervals of 30 meters (station plot heights are meters, so no conversion is needed). Use a pencil. (The height contours already have been done for you.) A favorable situation for tornadoes in West Texas and Oklahoma occurs when an 850mb low is positioned in eastern Colorado during the morning.

2.

Locate the low-level jet. If it is present, it will appear as a tongue of strong winds extending north from south Texas or the Gulf of Mexico. Draw an arrow along the low-level jet using a red pencil. Find where the low level jet intersects a surface boundary. The region from the intersection west is a prime area for severe weather. South winds with speeds greater than 20 knots are moderate and greater than 35 knots are strong for tornado potential. Also note the difference in wind speed and direction between 850 mb and 700 mb. Strong shear can contribute to high helicity, rotating storms, and tornadoes.

3.

Define regions where dew point depressions are within four degrees of the temperature. This will usually give you an indication of the presence of deep moisture. Caution: The top of the moist layer may actually lie below the 850mb level. So, check the soundings for more information.

4..

Define regions where the temperature is between 9 and 16 degrees Celsius. The chances for convection decrease with higher temperatures and may indicate a strong capping inversion. Temperatures greater than about 20 degrees Celsius usually indicate a strong capping inversion.

SOUNDINGS Soundings are plotted for you so all you need to do is interpret them. Plotting soundings can reveal the strength of the capping inversion, the instability of the atmosphere (or lack thereof), and provide a profile the wind speed and velocity. It is important to anticipate changes in the sounding profile throughout the day (i.e. temperature increase in low levels, cooling aloft). Do the following: 1.

Locate the height and extent of the capping inversion. Storms will not develop if the inversion is too strong. If the inversion is weak, the atmosphere may overturn early in the day and squall lines may dominate. The best possibility for tornadoes exist in “explosive” thunderstorms which tend to be isolated. This is most likely to occur when the inversion is strong enough to hold until around 4 p.m.

2.

Determine the convective temperature.- Continue downward dry adiabatically from the mixing ratiotemperature intersection to the ground (surface pressure). Convective instability theoretically can’t be released until the forecasted afternoon temperature reaches the convective temperature.

3.

Look at the stability parameters such as the Lifted Index (LI), CAPE+, and CAPE- to name a few. High instabilities can result in explosive storms if the capping inversion is broken. LI’s greater than -10 are moderate and -12 are strong for tornado potential.

4.

Note the change in wind direction between the ground and around 700 mb. Strong veering winds (south to west) provide an environment for rotating storms.

5.

Determine the depth of the moist layer near the surface. If the moisture is too shallow, say less than 75 mb, there is usually insufficient moisture to support strong convection.

DISCUSSION OF EACH CASE ALONG WITH ANSWERS CASE #1 - SURFACE: Lots of cool, overcast skies over much of the area. Looks like an early spring situation with the big question being moisture return. Negatives features are the low dewpoints and temperatures as well as the extensive low overcast. Positive features are the westerly winds and drying in New Mexico with warmer temperatures and breaking higher overcast. A dry line is located along the Texas-New Mexico border and a warm front is positioned south of the Red River (Note the 48 degree surface temperature at Childress compared to 61 degrees at Lubbock). The surface low in southeast Colorado has helped bring a southeasterly component to the winds across Kansas, Oklahoma, and Texas. 12Z SOUNDINGS: The Norman sounding shows a nice bell-shaped profile with good low level turning of the winds and stronger winds aloft though temperatures and dewpoints are relatively low. There is quite a strong capping inversion, and convective temperatures are approaching 90 degrees F. Midland has a dry sounding which is typical for being right on the dry line. Amarillo has quite a temperature inversion but it is at a lower elevation and with a convective temperature of about 23C (76F), this should be broken by mid-afternoon. 12Z UPPER AIR: At 300 mb, a long wave trough is approaching the four-corners area with a narrow speed max of 50+ knots extending from Amarillo through Oklahoma City and Little Rock. At 500mb, the trough is still open with plenty of cold air (-21C at Albuquerque,NM with -24C at Winslow, AZ). The speed max is less defined thanks to the missing observation at Dodge City. At 700mb, there is a closed low over central Colorado with moderate southwest winds of 20 knots, and a ten degree drop in temperature between Amarillo and Winslow. At 850 mb, the westerly winds at Midland will help drive the dry line eastward. Don’t see much in the way of deep moisture here. MY FORECAST: A marginal chase day, agree with SPC outlook. TARGET: Childress, TX.

CASE #1 ANSWER- No tornadoes occurred. The big minus was the lack of surface moisture. Isolated severe storms did develop along the dry line in western Oklahoma and the eastern Texas panhandle. A tornado watch was issued from 50 NW of GAG to 50 SSW of CDS. Date: 4-6-93. CASE #2 - SURFACE: There is a strong warm front across southern Nebraska with upslope flow in northeast Colorado. A surface low is in the southeast portion of Colorado. I don’t like the southwest winds ahead of the dry line in western Kansas extending down to the Texas panhandle. The moist axis extends through central Kansas and intersects the warm front near Grand Island, NE. 12Z SOUNDINGS: The Amarillo, TX sounding has little lowlevel moisture and the winds all are tending southwesterly. The strong capping inversion sends the convective temperature over the century mark. North Platte, NE and Dodge City, KS are much more interesting with deeper moisture, and better low-level turning. 12Z UPPER AIR: At 300 mb, a large closed low is situated over western Nevada. A fairly strong ridge extends over Texas shunting the higher speed winds northward from Denver to North Platte. The 500 mb map shows the same situation as the 300 mb map. Look at the -5C at Midland; too warm for me. At 700 mb, the low is still far to the northwest and the strongest winds are kept over the mountains. At 850 mb, there is a broad low-level jet extending northward from Texas to Nebraska. MY FORECAST: A definite chase day. However, the cap is too strong in Texas. I booked a flight to Denver. TARGET: McCook, NE.

CASE #2 ANSWER- South-central Nebraska. Numerous tornadoes occurred along the warm front just north of I-80 between Overton and Kearney. An F-3 occurred at Overton, F-2 at Elm Creek, and F-2 at Riverdale. A tornado watch was issued from 30 NW of IMP to 45 S of Columbus, NE. The atmosphere remained capped over the Texas and Oklahoma panhandles. Date: 6-6-93. CASE #3 - SURFACE: Looks like a classic tornado outbreak day for Oklahoma. The dry line extends across the Texas panhandle a surface low in southeast Colorado. I like the southwest winds at Amarillo with south winds at Childress, lower clouds and deeper moisture. The moist axis extends through central Oklahoma. 12 Z SOUNDINGS: Moisture is too shallow at Dodge City, KS, so I expect the dry line to roar through there. The

Longview, TX sounding has deep moisture but little capping inversion. The best sounding to me is Norman, OK. It has adequate moisture and a not so strong capping inversion. 12Z UPPER AIR: At 250 mb, Holy Cow!, there is a negative tilt trough extending from Oregon to New Mexico. Look at the 90 degree change in wind direction from El Paso to Amarillo. The diffluence axis extends from Midland right across Oklahoma. The negative-tilt trough is still evident at 500 mb with a nice speed max rounding the base of the trough and heading out across west Texas. The flow is too unidirectional across Kansas for tornadic activity but some tornadoes could occur in Nebraska if they had easterly winds along the warm front (surface not shown). At 700 mb, the exit region of the speed max still is over west Texas but this will move east throughout the day. At 850 mb, look at the 50 knot low-level jet at Amarillo! MY FORECAST: Agree with SPC on a tornado outbreak in Oklahoma. 10 AM TARGET: Oklahoma City, OK. At 3 PM my target was revised to Dallas, TX as a squall line formed and in the Texas panhandle and roared through Oklahoma. Headed home just in time to see a tornado at Cedar Hill.

CASE #3 ANSWER- There are two answers: Central Colorado and North Texas. A cluster of F-0 tornadoes occurred in central Colorado, 3 miles and 10 miles east of Ft. Carson (near Colorado Springs) in El Paso County as well as near Limon in association with the surface low. By far the most intense tornadoes occurred along the tail end of a squall line which broke up into isolated cells at dusk over Dallas, Texas. F-3 and F-4 tornadoes struck DeSoto and Lancaster, respectively. Date: 4-25-94. CASE #4 - SURFACE: Another classic set up for severe weather with surface low in southeast Colorado and a warm front extending across southern Kansas. There is a strong dry line heading out into west Texas (62 degree F dewpoint at Lubbock and 26 F at Hobbs). The southwest winds in west Texas indicate that convection will probably fire off the caprock. The moist axis runs from Dallas through Oklahoma City and to Wichita where it intersects the warm front. Overnight convection is still going on from Enid to Abilene but that shouldn’t hurt convection in west Texas today, but will east/northeast of there. 12 Z SOUNDINGS- To me, Topeka, KS has the best looking sounding. Great low-level turning here. With major levels only, it’s tough to gauge the extent of the capping inversion. Temperatures are quite cool at the surface though. The Norman, OK profile has major levels only so the extent of the capping inversion is not really known. I would like to see more westerly components in the winds at 700 mb. The Dodge City, KS profile looks contaminated. 12Z UPPER AIR- At 300 and 500mb, we have a deep trough with closed low over central Arizona. Thus, we can expect unidirectional winds over west Texas which means squallline to me. The best low-level turning would actually be in eastern Kansas down through eastern Texas. The 300 mb jet stream core runs from Midland, TX to Oklahoma City, OK to Monett, MO. There is some diffluence north of this axis that will shift east throughout the day. At 700 mb, note the dry air intrusion at Midland. At 850 mb, the 50 knot southeast wind at Norman is pretty stout. MY FORECAST TODAY: Expect a squall-line today due to unidirectional flow . The upper low is too far south for me. Maybe a few tornadoes early as the squall-line develops. TARGET: Childress, TX.

CASE #4 ANSWER- There are three answers: The central-Texas panhandle, south-central Texas, and north-Texas/south-central Oklahoma. F-2 tornadoes occurred near Canyon and Amarillo in the Texas panhandle early in the day. Then, a squall line formed and moved east. Isolated supercells developed ahead of the squall line and became tornadic. One lone supercell (ahead of the line) produced F-2 tornadoes in south-central Texas, 16 miles north of Leakey in Real County and 4 miles northeast of Mountain Home in Kerr Co. Another supercell formed ahead of the line west of Fort Worth and produced F-3 tornadoes that traveled from Sunset, Texas in Montague County to Ardmore, Oklahoma in Carter, County. The latter tornado caused severe damage to a tire manufacturing plant on the west side of Ardmore. Date: 5-7-95.CASE #5 - SURFACE: Cold upslope flow in northeast Colorado with overcast skies. Surface low appears to be southwest of Goodland, KS. Warm front boundary appears to extend diagonally across Kansas. I don’t like the relatively low dewpoints in Kansas and northern Oklahoma, however, the deeper moisture should make it to northern Oklahoma by evening. Another negative is that there is no real pronounced dry line until you get near the foothills in eastern New Mexico and Colorado. 12 Z SOUNDINGS:

At North Platte, there is nice low-level turning in the wind field, but no significant temperature inversion since it’s so cold there. Dodge City, KS appears to have the best sounding to me with nice low-level turning and a capping inversion. At Norman, OK there is decent directional and speed shear between the surface and 400 mb. The temperature and dewpoint profiles are too smooth due to the partial data. 12 Z UPPER AIR: At 300 mb, we have a weak negative tilt trough extending from Oregon to Salt Lake City. The main diffluence axis extends across northern Kansas, say from Goodland to Lincoln, NE. At 500 mb, the mid-level jet is much farther south extending from Winslow, AZ to Amarillo, TX. There is a nice 4 C temperature drop from Amarillo to Albuquerque. At 700 mb, the best winds are across west Texas and they are much weaker in northern Kansas and Nebraska. There is plenty of dry air to enhance the capping inversion from Dodge City southward. At 850mb, a broad low-level jet extends across the high plains. Westerly winds at Midland will insure the dry line will punch east there. MY FORECAST TODAY: There is a lack of focus today; I am only luke warm about chasing. I rule out Kansas due to the low temperatures and dewpoints as well as weaker mid-level winds. TARGET: Enid, OK.

CASE #5 ANSWER- Western or northwestern Kansas. An isolated supercell formed along the warm front near the surface low in northwest Kansas. The storm produced numerous tornadoes from Colby, Kansas in Thomas County to Plainville in Rooks County. Another tornadic storm developed near Tribune, Kansas in western Kansas. Date: 5-12-95. CASE #6: SURFACE: Cold front is roaring south through Oklahoma and west Texas. Meanwhile, ahead of the front 70+ dewpoints cover most of the warm sector in Texas, Louisiana, Arkansas and extreme southeastern Oklahoma. The main negatives are 1) line lifting along the cold front, and 2) winds are tending southwesterly across northeast Texas. There is not enough residual moisture in place for upslope in eastern New Mexico. 12Z SOUNDINGS: The Del Rio sounding has fantastic low-level turning, but the wind speeds are weak. There is also a “nuclear cap” there with a convective temperature well over 100 degrees F. All that CAPE going to waste. I like the temperature and dewpoint profile at Little Rock, AR the best, but there is still a strong cap and southwesterly winds at the surface. The same is true with the Lake Charles, LA sounding. 12Z UPPER AIR: At 300 mb and 500 mb, there is a flattened ridge over Texas with strong zonal flow across Kansas. No diffluence axis is noted. At 700 mb, a high is parked over Midland, the strongest winds are still in Kansas. At 850 mb, the northerly winds in the Texas panhandle indicates the cold air is deep. MY FORECAST TODAY: Stay home. No chasing.

CASE #6 ANSWER- Southwest Texas. An isolated supercell developed at the tail end of the front and produced numerous tornadoes in eastern Tom Green County (east of San Angelo) and western Concho County including one that was an F-3. A squall line developed along the cold front producing severe, non-tornadic storms across northeast Texas, southeast Oklahoma and Arkansas. Date: 5-14-95. CASE #7: SURFACE: Strong upslope flow is occurring into west Texas and southeastern New Mexico. A stationary front extends from Mineral Wells to south of Lubbock, TX. and the dry line is backed up against the New Mexico foothills. The big negative today is the lack of surface moisture. A surface low is trying to form near Roswell. 12Z SOUNDINGS: The Del Rio and Midland soundings look similar except that Del Rio is slightly warmer. There is ample speed and directional shear on both soundings. Amarillo appears to have a contaminated sounding. 12Z UPPER AIR: At 300 mb, there is a sharp neutral axis trough over Utah with a phenomenal speed max working around the west side of the trough. Look at the diffluence over west Texas. I like the 50 knots atMidland increasing to 85 knots at El Paso. Similar observations are made at 500 mb with respect to the winds. The cold pool is small, not extending southward into southern Arizona. At 700 mb, there is a 90 degree change in the wind direction between Amarillo and Midland. Not much dry air can be found. At 850 mb, there is a low-level jet extending from Del Rio to Midland. Note the wind direction changes from south at Midland to west at El Paso. MY FORECAST: If only the dewpoints were 10 degrees higher, I would love this situation. I hope the moisture makes it back in time. TARGET: Play the dry line front intersection at Morton, TX.

CASE #7 ANSWER- No tornadoes occurred. Isolated severe storms developed along the east-west cold front boundary from southeast New Mexico into west Texas. Strongest storms were near Tatum, NM in Lea County and Lamesa, TX in Dawson County. Date: 4-24-97. CASE #8: 15Z SURFACE: A weak cold front (actually enhanced by storms last night) is moving through north Texas. High dewpoints are pooling along the front. A mesolow has formed on the front north of Waco. There is plenty of surface moisture for storms, however, there are weak surface winds. The best convergence appears to be east of Dallas. There is some residual moisture behind the front out at Midland and San Angelo which could interesting later this afternoon. 12Z SOUNDINGS: The Fort Worth sounding is quite unstable with a small capping inversion at low elevation and there is adequate surface moisture, about 100 mb. Mid- and upper-level winds are not impressive but could sustain a few storms. Weak low-level flow is typical along the front. The Lake Charles, LA and Corpus Christi, TX soundings are quite unstable. Note the weak wind fields aloft and a stronger cap than at Fort Worth. 12Z UPPER AIR: Nice negative-tilt trough over the Midwest with apparent secondary short wave extending through west Texas. Strongest upper winds are right around the low. At 500 mb, there is broad westerly flow over the Ark-La-Tex. I like the -12 C temps at Fort Worth and El Paso. With warm, moist low levels, this makes for very unstable atmosphere. The 700 mb and 850 mb winds are weak. MY FORECAST: No tornadoes forecasted. Storms will likely be severe though given the instability so I’ll head out east since it’s close to home. Any storms that do develop along the front should move east toward me. TARGET: Longview, TX.

CASE #8 ANSWER- North-Central Texas. A tornadic storm formed south of Waco, Texas and moved/backbuilt southwestward along the boundary producing numerous tornadoes near I-35. An F-5 tornado struck Jarrell, Texas (northwest of Austin). Date: 5-27-97. CASE #9: There are three areas which show promise today. First, a cold front has stalled out along the Red River with a surface low north of Wichita Falls, TX near Lawton, OK. High dewpoints and high temperatures make for a very unstable air mass in the warm sector especially around the Dallas area. Second, there is nice upslope flow behind the front extending into eastern Colorado down into New Mexico and some residual moisture. If skies break there, it could get interesting. Third, there is the warm front across central Illinois extending to a surface low northwest of St. Louis. 12Z SOUNDINGS: The Amarillo, TX sounding is not very unstable and has a formidable capping inversion with a convective temperature over 90 F. Wind fields aren’t too bad especially higher up. The Fort Worth, TX wind profile looks promising. It will take some time to get rid of the capping inversion but this is possible since 15Z surface temperatures are already at 86 degrees. There is not much instability at Denver, CO, however, the weak capping inversion appears that it can be overcome around 70 degrees F. MY FORECAST: Looks like a marginal upslope event for Colorado and I don’t like all that convection around Illinois so I’ll stay with the Dallas area. TARGET: Sherman, TX.

CASE #9 ANSWER- This was an upslope tornadic event in central Colorado. Tornadoes were reported 29 miles north-northeast of Colorado Springs in Elbert County and 24 miles west-southwest of Limon in Matheson County. Date: 6-13-97.

CASE #10: SUMMARY- Cold front extends from Minneapolis, MN through northwest Iowa into Nebraska. I don’t believe the observation at McCook, NE. There is a hint of a surface low trying to form along the tail end of the front in Colorado. I don’t like the southwest winds extending across Iowa into Oklahoma. Ample moisture is moving northward with low clouds up to the Kansas border. I like the westerly winds at Childress, TX with southeasterly winds at Oklahoma City and McAlester. 12 Z SOUNDINGS: The Dodge City and Topeka, KS profiles look pretty good with plenty of moisture and a breakable capping inversion. I don’t like the weak mid-level winds though. Omaha, NE has the best sounding with a bit stronger mid-level winds. I just don’t like the southwest surface winds across Iowa. 12 Z UPPER AIR: Not a bad looking 300 mb map with a closed low near Las Vegas, NV. Broad area of strong winds centered on Kansas. At 500 mb, there is a 5 degree C temperature difference between Amarillo, TX and Albuquerque, NM. Winds are surprisingly weak from Kansas southward and are even more pathetic at 700 mb. The 850 mb winds aren’t too bad in the Texas and Oklahoma panhandles. MY FORECAST: Marginal chase day. TARGET: Woodward, OK.

CASE #10 ANSWER- There are two answers for this case. A tornadic storm formed along the outflow boundary of an old mesoscale convective complex (MCC) in north-central Iowa. Tornadoes occurred northeast of Fort Dodge to southwest of Mason City. Also, landspouts were reported about 20 miles north of Denver, Colorado. Date: 6-15-97. BOOKS AND PUBLICATIONS you should read. Chaston, Peter R., 1995: Weather Maps: How to Read and Interpret All the Basic Weather Charts. (Available from him at P.O. Box 758, Kearney, MO 64060, phone: 816-628-4770; fax: 816-628-9975. ) Crisp, Charlie A., 1979: Training Guide for Severe Weather Forecasters, United States Air Weather Service, Offutt AFB, NE 68113. 74 pp. Doswell, C.A. III, 1982: The Operational Meteorology of Convective Weather, Volume I: Operational Mesoanalysis NOAA Technical Memorandum, NWS-NSSFC-5. 100 pp. (Available from NTIS, 5285 Port Royal Road, Springfield, VA 22161) Doswell, C.A. III, 1985: The Operational Meteorology of Convective Weather, Volume II: Storm Scale Analysis, NOAA Technical Memorandum, ERL-ESG-15. 240 pp. (Also available from NTIS). Djuric, Dusan, 1994: Weather Analysis. Prentice-Hall, Englewood Cliffs, NJ 07632, 304 pp. Miller, R.C., 1972: Notes on Analysis and Severe Storm Forecasting Procedures of the Air Force Global Weather Central, Air Weather Service. (Also available from NTIS). Ray, Peter S., 1986: Mesoscale Meteorology and Forecasting, American Meteorological Society, 793 pp. (Available from the AMS, 45 Beacon St., Boston, MA 02108.) Siebers, J.O., F. Hidalgo, S.A. Tegtmeier, and M. Young, 1975: Guide for using GOES/SMS Imagery in Severe Weather Forecasting, USAF, AWS, unnumbered technical guide, 56 pp. Serious storm spotters and chasers should also get STORM TALK and the STORM CHASE MANUAL. Write to: Tim Marshall, 4041 Bordeaux Circle, Flower Mound, TX 75022-7050 for more information or check out our STORMTRACK on-line web site. For software to analyze surface and upper air data as well as soundings and hodographs contact: Tim Vasquez, 900 Red Rock Road, Norman, OK 73026.

TORNADO FORECASTERS WORKBOOK #1 Surface Analysis Suggested Solutions prepared by Tim Vasquez

Cases #1-7 Solutions for cases #8-10 not available