Chapter 4: Team Descriptions: Missions and Personnel

This is the unofficial, WWW version of the VORTEX-95 Operations Plan. It may differ from the published operations plan which is available by 15 March from the National Severe Storms Laboratory.

This chapter describes the missions of each field team, and the personnel on the team. Descriptions of the specific operations of each team, based on the announced field activities, can be found on the " activity cards" contained in the companion publication " VORTEX-95 Team Activity Cards." (published by 15 March 1995 and available to VORTEX participants). Field activities will be chosen based on storm type and motion, as well as stage of development, as discussed in Ch. 3.

Every team, at a minimum, will have a driver and a leader. The driver is responsible for the safe and lawful operation of the vehicle ( See " Storm Intercept: Safety and Personal Considerations" ). When other team members are outside the vehicle, the driver will be responsible for monitoring communications. The team leader will be responsible for all decisions concerning the team's operations, strategies, and safety. In VORTEX, the Field Coordinator will provide a large amount of information for planning routes and stops, and will determine overall experiment activities ( See " Field Experiments" ). However, mainly because of safety considerations, the team leader must have the final authority and responsibility for the team. If the team leader deems a particular mission to be too dangerous to perform, the mission should be abandoned and the FC notified. Keep this in mind: there will be other opportunities to perform the mission. No VORTEX mission is so vital that the safety of a team should be risked.

The team leader will also be in charge of communications. Each vehicle will be equipped with a VHF transceiver for voice communications. A very strict protocol will be enforced during field operations ( See " Communications" ). Whenever requested by the FC, the teams should promptly transmit their position or weather information as explained in the chapter on Communications.

Unless the team leader designates a third team member to be in charge of navigation and documentation, these responsibilities will also belong to the leader. Detailed atlases will be provided for each vehicle. However, the FC will typically recommend routes based on the maps displayed on the Field Coordination Computer (which include all dirt roads, trails, landmarks, and terrain). The vehicle location and time are self-documented on the notebook system using GPS position systems. However, the leader must make sure a certain amount of additional documentation is obtained and recorded ( See " Documentation Requirements and Forms" ).

It must be stressed that the primary responsibility of the team leader is safety. The leader should keep a close eye on the sky and near environment, monitor the nowcasts from the FC closely, and if there are concerns about safety that must be discussed with the FC, do not hesitate to contact him via VHF radio.

The following table lists the teams in VORTEX, their broad missions, and the team leader(s).

Field Coordinator

In VORTEX, all field operations are coordinated from a mobile coordination vehicle. This vehicle is equipped with redundant cellular phones, redundant VHF radios, an aircraft radio, and a satellite messaging system. The FC team will be the communications hub of VORTEX ( See " Communications" ).

A portable computer will be used to access real-time radar and weather information. The field coordination computer is a workstation ( link to image of computer display ) that displays high-resolution maps derived from USGS Digital Line Graph data for the central U.S. This display system zooms from a 4-degree to 0.1 degree display region. All field teams are displayed as icons on the map. Map data include terrain (shaded), all roads, trails, railroads, towns, and landmark geographic and man-made features. The software allows triangulation of field team reports for tracking and extrapolation of important storm features, and automatically generates reports useful for nowcasting. Communications are monitored so that no teams will be " forgotten" if their communications fail. The system automatically reminds the FC when it is time to broadcast an updated " nowcast" via VHF radio; it also logs all events and vehicle position reports. The power supply for this vehicle is a one kilowatt gasoline-powered generator attached to an uninterruptable power supply.

In VORTEX-95, field team positions and limited weather information will be telemetered to the FC vehicle using tone encoding over the VHF radio. This telemetry will be activated from the field team vehcile by pressing key combinations on the laptop computer. When a position packet is received, the FC computer will automatically reposition the team's icon on the display. Weather packets will be decoded and cause the plotting of conventional weather map symbols on the display.

The FC vehicle will also carry spare forms, atlases, Ops Plans, etc.

The FC team will consist of a driver, the Field Coordinator (FC), and the Assistant Field Coordinator. The driver will be given route instructions by the FC; if unsure of the route plans, the driver should discuss them with the FC. Whenever the vehicle is stopped for storm operations, the driver is responsible to park on unobstructed high ground to facilitate communications. The vehicle is outfitted with an antenna mast that can be raised which the driver will raise upon stopping (if lightning has not been observed in the vicinity!). The driver must also check the generator at regular intervals and refuel if necessary (it can be stopped for short times and equipment operated off of the UPS). Until it is time to move again, the driver is free to photograph and enjoy the storm, but must remain within earshot of the FC. When it is time to resume travel, the antenna mast must be stowed if it has been raised.

In some situations, the FC will request the driver to get out of the vehicle and set up a compass for tracking various storm features. Then, whenever requested, the driver will read the azimuth of the storm feature and communicate it to the FC. These azimuths will be used for triangulation and are vital for team safety.

The assistant field coordinator is primarily responsible for communicating with the NOC and obtaining real-time weather data. The assistant must inform the NOC whenever the strategy of the field armada changes, and whenever we change activities.

The field coordinator will direct the field experiment, and be responsible for all logistics and strategy decisions that apply to the entire experiment. Specific guidance will be provided to all teams concerning route and site selection, operational modes and strategies, etc. During the TRAVEL activity ( See " TRAVEL" in Ch. 3 ), the FC will broadcast weather briefings whenever updated information is received. During the PRESTORM and TCU activities, nowcasts will be broadcast about every 10 minutes. During other activities, nowcasts will be made at 5 minute intervals.

Although limited real-time radar and weather information will be available to the FC, visual observations will be of primary importance in coordinating the experiment. This is based on many years experience in comparing visual and radar observations; cyclonic shear and rotation is usually recognizable to the eye before it is conveyed through radar data, simply because radar data ages a few minutes before it can be displayed and interpreted. Reliance on radar data can be a serious handicap; on several occasions, intercept teams have missed tornadoes by relying on aging or incorrect radar information that did not agree with their visual observations. In VORTEX, the FC will track important storm features through automated triangulation of azimuths reported by the field teams.

Photography

The goal of movie photography in VORTEX is to obtain imagery, of the tornado and mesocyclone region, suitable for stereo photogrammetry. It should be stressed that the photography is for scientific analysis, not for artistic value. Given two images shot at approximately the same time from separate angles, the location of objects in three-dimensional space can be derived from the image pairs. Given a series of these images (as captured by movie cameras), a set of positions can be obtained yielding the three-dimensional velocity vectors. Several photogrammetric studies have been performed using single camera movie segments, but these studies only provide a velocity vector in the image plane, which can then be rescaled to a corresponding vector in a parallel plane at the distance of the tornado from the camera. No stereo movie pairs have been studied using stereo photogrammetry, although a few suitable segments may have been obtained in the past. If suitable stereo imagery is gathered in VORTEX it will be digitized and analyzed on workstations which will be developed in collaboration between NSSL and Texas A&M University.

VORTEX will use 16 mm movie film for close-in documentation of tornadoes. This decision was made because current movie films have at least four times the resolution of the best high-end consumer video technology, and commercial video gear is far too expensive to acquire and maintain under storm intercept conditions. The higher resolution of movie film was an important consideration in that photography teams can operate at safer distances from the tornado when using film compared to video. A comparison between the usable filming areas of the two media is shown in the accompanying figure . In this figure, the shaded regions are areas in which uncertainty in 3-D positions of simultaneously photographed objects are less than 2 m. This assumes cameras zoomed to field of view of 4.5 degrees (close to full zoom for a Canon Scoopic movie camera), 1000 line resolution for movie film and 350 line resolution for video (equivalent to 1000 pixel image width), and that four film grains or pixels are required to resolve an object (a somewhat conservative estimate). It is further assumed that optics and survey/scaling work are perfect and the images are perfectly synchronized. It can be seen that with video, teams would need to operate within 1500 m of the tornado, and errors would be minimized over comparatively very short path lengths. Because safety and the ability to resolve small objects are less of a concern in wide-angle stereo photography, we will use high-end consumer video equipment.

The ability to obtain footage suitable for stereo photogrammetry is a function of the movie camera baseline and the tornado location. This is illustrated in the accompanying figure . As the camera separation increases, the usable region for stereo photogrammetry grows in size, and is maximized somewhere around 8 km separation. Note that as separation increases, an unusable region between the cameras and very near the baseline also grows in size. At separations of 10 km, this unusable region grows to engulf the entire area between the cameras and off of the baseline, implying that camera separations of more than 8 km are too large. As shown by the broken rectangle, the goal of the photography teams (and the FC) should be to position the cameras about 1.5 to 3.5 km off of the projected tornado path. Fortunately, being too close to the tornado path is a disadvantage. This is because as the tornado comes between the cameras, " triangulation" suffers and errors grow.

An example of camera positions relative to two tornado paths is shown in the accompanying figure . In some circumstances, it may be possible to obtain photogrammetry-optimized footage for 11 km of tornado path length! The FC will use this " template" of suitable camera positions, combined with tornado path projections and terrain data, when advising the camera teams of optimum locations.

There are several other important considerations that must be made when deciding on camera separation. If visibility is low due to blowing dust, precip, or haze, it will be necessary to position the teams somewhat closer to the tornado. If the tornado is opaque, it will be necessary to position the teams further from the tornado so that the same tracers will be visible to both cameras (consider the limiting case in which the tornado is between the cameras: no common tracers will be visible). Finally, unless the tornado is very large, teams will have to be positioned on a baseline with a length of about 5-6 km so that the tornado fills a significant part of the image when fully zoomed.

In order to perform stereo photogrammetry, it is necessary to know the time that each image was exposed in order to match stereo pairs. We will be using Canon Scoopic 16 mm cameras because of their proven capabilities for storm intercept work and their availability at NSSL. These cameras do not have data backs, so any time encoding must be done in the photographed image. Cameras will be synchronized using the following procedure: The stereo teams will both begin filming; both vehicles will tune their VHF radios to VHF CH3. The CAM1 team leader will request a break in communications on VHF CH3, and announce that camera synchronization is going to be performed. At that time, both teams should point their cameras at the LED's on the VHF radio (it is OK to remain focused at infinity through this exercise; the flash of light from the colored LED is all that needs to be recorded on film). The CAM1 leader will then announce on the VHF that synchronization will take place in n seconds (e.g., " Camera synch in 5 seconds." ). At the end of n seconds, the CAM1 leader will key his microphone 3 times within about 1 second. The CAM1 VHF LED will flash as the transmitter is keyed, and the RAD1 VHF LED will light as squelch is broken on his receiver. In order to encode the imagery with a time stamp, the team's stopwatches, which should be synched at the start of the mission, should be filmed.

There will be one dedicated photography team (CAM1) in VORTEX-95. The other movie photography team will be RAD1 because the OU Radar team is typically in ideal position for movie photography work, and it is possible that the radar and movie data can be combined to aid in 3-D velocity estimation. A third 16 mm movie camera will be carried by PROBE8 for target-of-opportunity filming under the direction of FC. If a tornado develops, the FC will direct the CAM1 team to a position within about 2 km of RAD1. When RAD1 chooses a site, they must notify FC with a very short message that they have stopped, followed by a position telemetry report. At that time, FC will provide final position guidance to the CAM1 team so that an adequate baseline can be formed. Also at that time, team PROBE8, which will have the third 16 mm movie camera, may be directed to a position which will form a second baseline with team RAD1.

The following considerations will be uppermost for siting the photography teams:

At least three fixed landmarks, and the ground horizon, must be available in the field of view of the camera, even when it is fully zoomed on the tornado. The white lines in the view finder are a good indication of the actual field of view of the images. Sites should be chosen that offer more than three landmarks if possible.
Intervening terrain between the team and the tornado should be reduced; i.e. a hilltop is preferred over a valley (but lightning safety must be considered).
Reduce intervening obstructions. The camera must be sited so the tornado will not pass out of view behind buildings, tree rows, etc. Set up on the side of the road that the tornado is on, so that vehicles will not be passing through the image.

The following photography techniques must be used to ensure the imagery is usable for photogrammetry:

Panning must be done in steps, allowing the tornado to move from one side of the image to the other. Continuous panning is not allowed. Try not to pan more than (say) once every ten seconds if possible.
Three fixed landmarks must appear in the image, and if three are not available, the zoom setting must remain constant at the same setting as the last image in which three landmarks appeared. In other words, if you are zoomed in on a tornado and can see sufficient landmarks, but then you pan and can no longer count three landmarks, don't change the zoom setting. The scaling from the last pan position may be useful for the new position.
Zooming must be kept to a minimum. The camera should be zoomed so that the tornado debris cloud is completely contained in the image but no more (see this example ). That is, do not zoom in on subfeatures in the tornado. Less zooming (wider view; see the third panel in the figure) is allowable if it is necessary to obtain the landmarks. This is an important standard to adhere to; if closer zooming were allowed, it is possible that both photographers would be zoomed on different tornado features and the imagery would be rendered useless for stereo photogrammetry. The zoom setting should be changed quickly, not smoothly.

There is an exception to the comments made above concerning zooming. Even when operating close to the tornado, PROBE8 should use the camcorder to document the entire wall cloud, attendant features, and tornado area, just as they do when positioned at greater distances. So PROBE8 will be zoomed as described above with their 16 mm camera, and covering the wider-angle view with the camcorder. If short-handed, the PROBE8 crew should concentrate on obtaining movie footage.

It should be noted that PROBE8 will not be moved in for close footage very often. The " leapfrog" filming strategy will only work with dense road networks, and relatively slowly moving tornadoes. It may also be used in situations of cyclic tornadogenesis, when a new baseline is urgently needed for a cyclic tornado, but either CAM1 or RAD1 is too far out of position.

Movie camera training will be provided for participants. Photographers should remember some of the following rules (which are included in " Checklists" ). The leader of CAM1 will determine, and announce, the camera framing rate prior to filming. In general, movies should be exposed at 16 frames per second in order to maintain the largest possible reserve of film. The exception is that for tornadoes that appear to be strong or violent, or very close to the camera, the framing rate should be set to 24 frames per second to avoid blurring in each frame while the shutter is open. Focus should be on infinity. If the tornado is backlit, put the camera in auto-exposure mode, check the aperture setting, then switch to manual exposure and open the aperture by 1.5 stops. If you are in low-light conditions, and the light meter is pegged at the underexposed end of the scale, double the film ASA setting. If you do this, you MUST note this change on the film label so the film processing lab can accommodate the change.

Remember to keep the film cool, with magazines kept out of the sun. It is also a good idea to keep the spray paint can in a cool location so that it won't burst inside the car.

Another function of each photography team is to provide the field coordinator with azimuths (from a compass) as requested. Using azimuths from several teams, the field coordinator can then use automated triangulation techniques to determine locations and paths of storm features with good accuracy. Thus, the field coordinator can provide good motion estimates and position forecasts to aid intercept team decisions.

The third function of the photography teams is to document carefully the locations of the video equipment. This will be done by noting odometer readings, landmarks, etc. in field logs. Small spray-painted marks will be made below the camera tripod to locate the camera exactly; be careful not to let the spray paint go airborne and be deposited on the camera optics. Teams should use their camcorders to document the filming site so it will be easy to find the next day.

The fourth function is post-intercept field survey work, which is described in " Pre-photogrammetry Surveys" .

Each photography team will consist of a driver, a team leader, and the photographer. On some occasions, an assistant photographer may be in the field. It is up to the leader to choose routes and filming sites, with guidance and terrain information provided by the field coordinator. Upon arrival at a site, the team leader should commence video documentation of the site and the weather, and assist with movie camera setup if needed. The driver should leave the vehicle running, get out, and assist the photographer with setup. One participant, designated by the team leader, must have the photography checklist in hand and ensure that all procedures are being followed; there is just too much to remember in camera setup and use (esp. photographing the clock!) to be the sole responsibility of the photographer.

The camera should be set up on high ground (i.e. to avoid preventable obstruction like roadside or railroad embankments, etc.). However, teams should be cognizant of lightning danger. If lightning or precip is occurring, it may be necessary to set the camera just outside a car door and film from inside the car. Keep the camera protected from rain.

If it appears that a significant, long-lasting film segment is about to be obtained, be sure the camera has a lot of film available. If it is near the end of a roll, shoot the roll and reload, or change magazines, so that a full roll is available. Teams should always take the time to correctly store exposed film and label the containers using one of the gummed labels provided. On a past storm intercept, an intercept team actually reloaded an exposed roll, starting with the trailing end, and reshot it, giving a spectacular time-lapse exposure of two wall clouds... one hanging upside down. Similar " special effects" are not useful in VORTEX.

Mobile Ballooning Laboratories

VORTEX will have a significant ballooning component whose foundation will be the use of four NSSL and one NCAR M-CLASS (Mobile Cross-chain Loran Atmospheric Sounding Systems). Provided in the following sections are general information for all teams and specifics for launch of additional instruments for electric field and precipitation particle measurements.

Rawinsondes

All sondes flown will be Vaisala RS80-15H. There may be differences in configuration of their Loran receiving antenna. We plan on using preassigned frequencies to reduce the likelihood of overlapping frequencies and data loss. For " official" frequency allocations valid in VORTEX-95, see " Communications Frequencies and Phone Numbers"

Since we are planning for flights as often as every 60 min, we will use a sonde cutoff device in order to reduce possible interference. Specific procedures are covered in the NSSL M-CLASS Training Manual. The cutoff device is placed in the battery connection line. The appropriate tab is broken off to set the timer for 15, 30, 45, or 60 min. At the end of the time, a switch turns off power to the transmitter, thus terminating data transmission. We will not use the cutoff on the last flight of the sequence if we know that in advance. All teams should assume that the cutoff switch should be set to 60 minutes unless notified otherwise by the FC.

Safety and general information for all teams

The crews will be positioned in coordination with the FC as described in the companion publication " VORTEX-95 Team Activity Cards" for individual experiments. Safety must be the paramount concern. The team leader is responsible for the safety of crew at all times. Crew members should be encouraged to participate in being alert for hazards, but for crews to function smoothly under the sometimes difficult launch conditions near severe storms, the crew leader or designee must be in charge and make the decisions. Crew leaders are expected to assign tasks for all procedures to specific crew members prior to arrival at the first launch site. This will help speed the launch process and minimize risks to crew members. Note that the biggest hazard once on site and while out of the mobile labs will be lightning. Even when lightning is not very close, do not lean or touch vehicle while outside it. You can receive a painful and possibly dangerous electrical shock from electromagnetic coupling of the lightning. The team leader should be prepared to abort a launch in the event that lightning strikes too close. This is a judgement call. At times the fastest way to \qabort\q a launch is to launch the balloon, get everyone in the vehicle, and then try to acquire data from the sonde as soon as possible. If this not viable because of your being too early in the prelaunch preparation, cut the sonde off the balloon and puncture the balloon. (Note balloon crew members should carry easily accessible and sharp knives for such emergencies.) Then get inside the vehicle. The overall recommended procedure is to minimize exposure to lightning by remaining inside vehicles as much of the time as possible. When your task allows it, you can reduce your risk of injury from lightning by squatting down on the balls of your feet. Remember the published small probability of being struck by lightning grossly understate your risk when you are standing beneath a thunderstorm. Finally, the decision whether to move or remain stationary after launch will be made by the team leader, based on the required time and location of the next launch. The team should move whenever necessitated by safety considerations; e.g., approaching wall cloud, deteriorating road conditions, etc. Be cognizant of escape routes in case they are needed.

Training for all M-CLASS operators who have no experience in mobile ballooning or need a refresher will be done upon arrival at VORTEX. Training will be under the supervision of Les Showell and will be from the NSSL M-CLASS Training Manual; contact him to arrange for training.

Note that soundings into storm clouds likely will suffer significant loss of wind and position data unless the sonde has a modified LORAN-C receiving antenna. There are two different antenna options; details may be obtained from Tom Shepherd or Dave Rust. Both improve performance, but the more complicated to build " Rhue Antenna" (patent pending) is the better. The simpler one is easy to construct and does not require making solder connections to the sonde. A large supply of sondes with this simple modification will be available to NSSL2 and NSSL4. If needed, instructions and training will be provided.

If it becomes necessary to travel to a new site while a balloon is in there, teams should avoid doing so until the balloon reaches about 3 km. The low-level data is the most critical for VORTEX, and it may be compromised as the vehicle moves through towns.

In case of a burst balloon during storm intercept operations, contact the FC. If a balloon bursts during the INIT activities ( " Field Experiments" ), inflate a new balloon and launch as soon as possible.

Soundings in the updraft region (NSSL1)-n

The objective is to obtain thermodynamic and wind profiles by launching the balloons in the updraft region of storms. When it will not cause a detrimental delay, this team may also launch electric field meters and occasionally a particle- charge-and-size-measuring instrument. When an electric field meter is flown, the team will use larger, 1200-g balloons using tested launch procedures developed previously. In the absence of precipitation loading, the free lift of these instrument trains is the same as for the smaller balloons carrying just sondes (approximately 5 ms-1). Crew assignments and launch strategies will be given by the team leader. Once launched, the team leader will make the decision as to whether to inflate another balloon to be carried in the launch tube in the balloon truck. If not, inflation will be part of the preparation for the next updraft sounding. (The time to inflate the large balloons is about the same as for the smaller ones since a high-flow rate procedure is used.)

Mobile ballooning strategy #1 " storm mode" )

In both mobile ballooning strategies, NSSL1 will be obtaining updraft soundings. On each operations day, one strategy (#1 or #2) will be designated after consultation between NCAR and the FC. In strategy #1, NSSL2 and NSSL4 will be utilized to assess the degree of low-level baroclinity, and the consequent magnitude of horizontal vorticity, across the forward-flank region 10-20 km ahead of the updraft. This strategy may be modified based on preliminary findings. If the storm motion is rapid, or is expected to be, the teams will remain stationary and let the storm pass by. It is possible that only one sounding may be obtained. However, if the storm motion is slow, the teams will reposition after each launch to maintain (approximately) fixed storm-relative positions. NCAR and NSSL3 will be positioned in the storm environment to evaluate the evolution of the storm environment (See the diagram of strategy #1 ).

Mobile ballooning strategy #2 " environment mode" )

In strategy #2, NSSL2 (if available), NSSL3, NSSL4, and NCAR will be utilized for experiments designed to evaluate the degree of homogeneity in the storm environment, and, more specifically, at what range from the storm the environment is " undisturbed" yielding proximity soundings. This strategy will be used if NSSL2 is unavailable due to staffing problems, and will sometimes be considered if rapid storm motion is expected or is occurring making forward flank coordinated launches difficult. In it, the teams will remain stationary and obtain as many soundings as possible. NSSL1, NSSL2 (if available), NSSL4, and NCAR will form a line extending from near the storm updraft in the inflow region (NSSL1) to several tens of kilometers away from the storm in the inflow sector (NCAR; See the diagram of strategy #2 ).

Mobile Mesonets

In VORTEX, each vehicle will be equipped with systems that continuously measure temperature, humidity, pressure, wind direction and speed, position, vehicle velocity and heading; this effectively creates a " mobile mesonet." The purpose of the mobile mesonet is to provide very detailed mappings of meteorological variables in the vitally important near-ground region of tornadic and potentially tornadic storms. The temperature, humidity, and pressure sensors are manufactured by Vaisala, propeller-vane anemometers by R.M. Young, flux gate compasses by KVH, Global Positioning System receivers (GPS) by Motorola, data loggers by Campbell Scientific, and an Intel 386-based notebook for archive and display. (Mention of a commercial product does not constitute endorsement by the U. S. Government.) Reduced (to a common height) pressure mappings will be produced in post-analysis (if required) by using GPS position information and post-analysis differential GPS techniques. However, derived quantities (mixing ratio, dewpoint, and equivalent potential temperature) will be computed, displayed, and recorded in real time using the measured quantities. Actual wind direction and speed will be computed in real time by vector addition of the vehicle motion vector (derived from GPS vehicle speed estimates and flux gate compass heading) and the vehicle-relative wind vector.

Each VORTEX vehicle will have at least two people. One person will have the sole responsibility of driving. The second person (usually the team leader) will be responsible for navigation, and communication with the field coordinator. The route and strategy decisions always will be made in consultation with the field coordinator, except when communications fail or when safety demands quicker decisions. The " activity cards" for the mobile mesonet teams (called " PROBEs" ) cover all foreseeable scenarios and can be found in the companion document " VORTEX-95 Team Activity Cards" . The third person (second person in two person crews), called the scribe hereafter, will be responsible for observations and documentation, and will assist with navigation. The crews are listed in " Team Assignments" .

A checklist-driven procedure for \qspot\q calibration of each mobile mesonet will be used immediately before each field mission. The results of these checks (i.e., differences from the benchmark instrument) must be written in the field log of each VORTEX vehicle. The team leader of each VORTEX vehicle will be responsible for the making the pre-intercept calibration checks. All instrument peculiarities and failures that occur during a mission also must be logged on a TROUBLE REPORT form which will be turned in to the Field Data Manager. The FDM will in turn forward them to Dennis Nealson (and also notify the mobile mesonet coordinator [Jerry Straka]) so that instruments can be repaired or replaced in a timely fashion. It is imperative that malfunctions be reported immediately as some repairs and replacements can be made in the field.

After each mission, each vehicle's mobile mesonet data should be stored on a separate diskette and turned in to the FDM. The next morning, the Quality Assurance Manager (QAM) will download the data to the NSSL VAX computer, plot time series, and evaluate them for gross errors or malfunctions. These time series will be made available on hard copy to the mobile mesonet coordinator. The diskettes will then be returned to the FDM for permanent storage.

In VORTEX-95, the team leaders will be responsible for logging sky condition, precipitation, lightning at 5 or 10 minute intervals as requested by the field coordinator. This will be done by setting the laptop to prompt for a weather log at the specified interval. Team leaders should make a weather log any time they observe any changes in sky condition, lightning, or precipitation. If one of these impromptu observations is made within two minutes of the mandatory observation, the mandatory observation won't be required.

It is imperative that each VORTEX vehicle log when precipitation (rain and hail) starts, changes (intensity, hydrometeor size), and stops. Approximate rain intensity (light, moderate, heavy, extreme) should be logged (occurrence, location, time) as best as can be estimated. Qualitative information of gross rain drop size (e.g., sparse, very large rain drops) should also be logged (occurrence, location, time). The occurrence of hail, and change in intensity of hail and size of hail should be recorded. In cases of hail larger than 2 cm, attempts should be made to periodically stop to video hailstones on the ground with a ruler in place for reference. Measurements of the largest hail sizes should be made and logged if they can be made safely.

" PROBES"

Described below are the team missions of vehicles called " PROBEs" which have the sole mission of collecting mobile mesonet data. Each of the PROBEs will work in pre-determined locations of a storm, and will be guided by the field coordinator. Some of the probes may work in potentially dangerous locations of a storm. Therefore it is of utmost importance that all safety precautions, as described in " Storm Intercept: Safety and Personal Considerations" , be followed. While the field coordinator may request a PROBE to move into a particular position or location in a storm, the team leader of each PROBE has the ultimate responsibility in determining whether his or her crew can proceed safely. (If you are the pilot of an aircraft and the control tower instructs you to land on a runway with a plane waiting for takeoff, you are responsible if you hit the aircraft while attempting to land. You should have aborted the landing and notified the tower.).

In VORTEX, we are especially interested in the low-level gradients of qe. It is important that teams thoroughly document these low-level gradients. qe reads out directly on the notebook computer in each mobile mesonet vehicle. However, in order to adequately sample strong gradients of qe, it probably will be necessary for the team scribe to keep careful notes of when and where rapid changes were encountered, what larger-scale " ambient" values are, and where they were last located.

Whenever mobile mesonet teams encounter gust fronts, or large gradients in qe, they should report the locations of these features to the FC. This will enable him to track the storm evolution and advise teams of important safety considerations.

It is not acceptable to have two PROBEs operating in close proximity to one another. Vehicles must maintain a separation of at least 0.1 miles; preferably more. Vehicles should never stop and park at the same location, no matter how good the view is. Team leaders are encouraged to take it upon themselves to make sure these rules are observed. When vehicles fail to maintain separation, one vehicle's data is effectively lost, which is a serious waste of human and financial resources, and may cost us the knowledge we're seeking to gain.

PROBE1

The objective of the crew of PROBE 1 is to make observations of state variables in and near the region of tornadogenesis. PROBE1 will attempt to stay near the tip of the precipitation area, if possible, especially as precipitation wraps around the mesocyclone. As tornadogenesis proceeds, PROBE1 should be positioned, in order of preference, just to the right, behind, or left of the anticipated storm path. Once the tornado is on the ground, PROBE1 should attempt to maintain a safe position in the baroclinic zone near the main storm circulation (possibly just behind or to the left of the tornado path).

The crew of PROBE1 must document wall cloud development, and the formation of storm and tornado-scale circulations. In addition, the formation of the rear flank downdraft must be anticipated and documented if possible. Examples of the positioning of PROBE1 can be seen in the figures and discussions throughout the chapter " Field Experiments" . The crew of PROBE1 will be located in one of the most dangerous locations of a storms. Therefore it is imperative for the crew to take extreme precautions. Because of the dangers in this region of the storm, the field coordinator will provide rapid updates to PROBE 1 of weather conditions, storm movement, and tornadogenesis. If conditions exceed those necessary for safety, experience has shown that escaping behind the tornadogenesis region or to the left of the storm path into the precipitation core is the safest. Escapes to the right of the storm path can be complicated by extreme straight line winds (often in excess of 80 kt) associated with the rear flank downdraft. Escapes along and ahead of the storm path are not advised unless there is no alternative. PROBE1's progress may be impeded by debris or downed power lines on the roads. If this happens, PROBE1 should leave the storm on the inflow side, attempt to catch up to the storm, and recontact the FC. If necessary, PROBE1 can contact the NOC for guidance while attempting to return to the storm.

PROBE2

The objective of the crew of PROBE2 is to make observations of state variables near the region of tornadogenesis, along the forward flank gust front, and beneath the main updraft. In the pre-tornadic phase, PROBE2 should move back and forth across the forward flank gust front. As tornadogenesis begins and proceeds, PROBE2 should be positioned, in order of preference, directly ahead of the storm path, ahead of and to the left of the storm path, or ahead of and to the right of the storm path, maintaining about 3-8 km separation from the tornado. Examples of the positioning of PROBE2 can be seen in the figures and discussions throughout the chapter " Field Experiments" . As with PROBE1, PROBE2 often will be in regions of the storm that can be very dangerous. PROBE2 should attempt to avoid very large hail and blinding rain as necessary for safety when traversing the forward flank gust front into the storm core; the team should U-turn if possible and retreat toward the inflow sector before entering damaging hail. It is important that PROBE2 maintain a safe distance ahead of the tornado. As PROBE2 will usually be ahead of the tornado, preferred escape routes often are to the right of the tornado path. Escapes into the storm core ahead of the tornado can be dangerous, and should be avoided. The field coordinator is available to give advice for route planning and escape routes should such become necessary.

PROBE3

The objective of the crew of PROBE3 is to make observations of state variables in and near forward flank gust front, well ahead of the main updraft. In the pre-tornadic phase, PROBE3 should move back and forth across the forward flank gust front. As tornadogenesis begins and proceeds PROBE3 should attempt to continue traverses of the forward flank gust front as roads and safety considerations permit. Examples of the positioning of PROBE3 can be seen in the figures and discussions throughout the chapter " Field Experiments" . As with PROBEs 1 and 2, PROBE3 often will be in regions of the storm that can be very dangerous. PROBE3 should attempt to avoid blinding rain as necessary when traversing the forward flank gust front into the storm core. It is important that PROBE3 maintain a safe distance well ahead of the tornado. As PROBE3 is to work in the far regions of the forward flank this should not be an issue. Nevertheless, preferred escape routes for PROBE3 often are to the right of the tornado path. Escapes into the storm core ahead of the tornado can be dangerous, and should be avoided. The field coordinator is available to give advice for route planning and escape routes should such become necessary.

PROBE 4

The objective of the crew of PROBE4 is to make observations of state variables in and near the region of tornadogenesis and in the rear flank downdraft. PROBE4 will attempt to stay to the right of the upshear tip of the precipitation area, if possible, especially as precipitation wraps around the mesocyclone. As tornadogenesis proceeds, PROBE4 should be positioned close in to the mesocyclone to the right of the anticipated storm path. Once the tornado is on the ground, PROBE4 should attempt to maintain a safe position in the baroclinic zone near the main storm circulation (possibly just to the right of the tornado path). At this point, PROBE4 should start out behind the rear flank gust front, then will drive ahead of the gust front (as indicated by a wind shift), then will stop to let the gust front pass overhead (all the while keeping an eye on the tornado and watching for possible tornadogenesis near the gust front), then drive ahead of the gust front, and so on. This stop-and-go procedure should be continued as long as safety and roads permit.

The crew of PROBE4 must document (on a log sheet or minicassette) wall cloud development, and the formation of storm and tornado scale circulations. In addition, the formation of the rear flank downdraft must be anticipated and documented if possible. If strong winds indicative of the RFD do develop, this event should be reported to the Field Coordinator since it often precedes tornadogenesis. As with PROBEs 1 and 2, PROBE4 often will be in regions of the storm that can be very dangerous. The crew of PROBE4 will be located in one of the more dangerous locations of a storms. Therefore it is imperative for the driver and team leader to take extreme precautions. Because of the dangers in this region of the storm the field coordinator will provide rapid updates to PROBE4 of weather conditions, storm movement, and tornadogenesis. If conditions exceed those necessary for safety, experience has shown that escaping behind the tornadogenesis region or to the right of the storm path is the safest. Note that escapes to the right of the storm path can be complicated by extreme straight line winds (often in excess of 80 kt) associated with the rear flank downdraft. The field coordinator is available to give advice for route planning and escape routes should such become necessary.

PROBE5

The objective of PROBE5 is to observe regions of the storm, in heavy precipitation, well to the left (on the order of 3-10 km) of the forward flank gust front. Observation here should provide valuable information about state variables in the precipitation core, as well as enhance the surface analysis data base for regions beneath the storm. PROBE5 will work in the core precipitation region of the storm. Examples of the positioning of PROBE5 can be seen in the figures and discussions throughout the chapter " Field Experiments" . PROBE5 should take extreme precaution in flash flooding and blinding rain situations. If crew of PROBE5 becomes fatigued they will switch duties with PROBE3.

PROBE6

The objective of PROBE6 is to observe that part of the storm immediately to the left and rear of the mesocyclone back into the trailing cold pool region. Observation here should provide valuable information about state variables in the rear-flank downdraft region, as well as enhance the surface analysis data base for regions beneath the storm. PROBE6 will usually be making transects from the clear air behind the storm to just into the edge of the precipitation associated with the supercell hook or appendage echo. This mission does not call for penetration of the hook echo! PROBE6 should drive into the storm only to the point at which precipitation commences, and then turn around and exit the storm. PROBE6 must be especially cautious in driving due to the likelihood of hail accumulation on the road, and the possibility of debris on the road. Examples of the positioning of PROBE6 can be seen in the figures and discussions throughout the chapter " Field Experiments" .

PROBE7

The objective of PROBE7 is to document the state variable across the inflow region ahead of the storm updraft. What PROBE7 should document is the structure of the wind and pressure field, and the amount of baroclinity in this region (caused by, for example, the cooling due to anvil shading). Examples of the positioning of PROBE7 can be seen in the figures and discussions throughout the chapter " Field Experiments" . The addition of PROBE7 in VORTEX-95 is required due to the " decommissioning" of two photography vehicles which were positioned in the inflow region in VORTEX-94.

PROBE8

The objective of PROBE8 is to collect data in whatever region the FC deems necessary based on realtime displays of team positions and storm character. The crew of PROBE8 should be familiar with the missions of all of the other PROBEs. The FC will provide specific routing instructions and requests to observe particular phenomena. Once the orders of the FC have been carried out, PROBE8 should initiate communications with the FC, and inform him that they are available for another mission. PROBE8 will not be used in the near-tornado environment, but is much more likely to be used to gather data wherever other PROBEs are finding significant windshifts or baroclinity in the forward-flank environment.

Turtles

Turtles are portable, low-profile, deployable instrumentation packages that sit on the ground and are designed to withstand tornadic wind speeds while measuring pressure, temperature, and humidity. A new system has been developed for VORTEX-95, and 15 of these instruments will be available for deployment. An additional 5 to 10 turtles with electrification measurement capabilities also will be available for deployment. In VORTEX-95, we will have two turtle teams in order to speed deployment, and so that at least two good deployment opportunities can be had on each storm.

The objective of the crew of the turtle vehicle is to make observations of state variables in and near the region of tornadogenesis with the mobile mesonet and by deploying the turtle instrument packages. Like PROBEs 1 and 2, TUR1 and TUR2 will attempt to stay near the tip of the precipitation area or along the front flank gust front. The field coordinator will project the mesocyclone track using triangulation and extrapolation of available information. The turtle teams will be dispatched well ahead of the mesocyclone. As tornadogenesis begins and proceeds, TUR1 will be positioned to deploy the turtles. At this point, the turtle teams will coordinate their efforts with each other via VHF radio. Efforts will be made to have the turtle crews deploy their instruments while moving to the right of the anticipated storm path to allow for a safe escape. If significant time does not permit, but it is decided that a safe deployment can be made moving to the left of the storm path, escape will be into the storm core as described below. The turtles should be deployed with a spacing of 100 to 250 m. With any luck, we should get detailed measurements from front to rear through the mesocyclone, and we might get a tornado strike on one of the turtles. Examples of the positioning of TUR1 and TUR2 can be seen in the figures and discussions throughout the chapter " Field Experiments" . On most storms, the FC will suggest that the TUR team with the best position should deploy, while the other TUR team should hold their turtles for a later deployment opportunity. The crews of TURs will be located in the most dangerous parts of a storms. Therefore it is imperative for the crew to take extreme precautions. Because of the dangers in this region of the storm the field coordinator will provide rapid updates of weather conditions, storm movement, and tornadogenesis. If conditions exceed those necessary for safety, experience has shown that escaping to the left of the storm path into the precipitation core is the safest for the turtle crews if they are close to and to the left of the mesocyclone path. Escapes to the right of this path can be complicated by tornadoes and extreme straight line winds (often in excess of 80 kt) associated with the rear flank downdraft . Escapes along and ahead of the storm path are not advised unless there is no alternative. Escapes and repositioning after an escape will be directed through collaboration between the team leader and the field coordinator. Prior to tornadogenesis, and after escape or deployment, TURs will act as a PROBEs and will be instructed by the field coordinator to follow procedures similar to one of the other PROBES or to retrieve the deployed turtles.

Portable/Mobile Doppler Radars

The radar teams will make ground-based, portable Doppler measurements of the tornadic flow structure. RAD1, led by Dr. Howie Bluestein, will utilize both a portable CW Doppler radar and a mobile pulsed 3 mm wavelength Doppler during VORTEX-95. When two radars are available, two vehicles will be deployed, with one in radio contact with the FC. The second van will convoy with the first and communicate with it via a second radio channel. RAD2, led by Dr. Jerry Straka, will operate a mobile, scanning, pulsed 3-cm Doppler radar.

The general team objectives are the following.

To determine the maximum horizontal wind velocities in a tornado from Doppler spectra.
To determine the vertical variation of the maximum horizontal wind velocities in a tornado from Doppler spectra.
To locate the region within a wall cloud of the formation of a tornado vortex; to map out the incipient circulation.
To map out the Doppler wind field in a developing, mature, and dissipating tornado.
To map out the reflectivity structure of a developing, mature, and dissipating tornado.
To map out the reflectivity structure and the vertical velocity profile of a convective updraft in a supercell, LP supercell, LP tower, and ordinary cumulus congestus.
To map out the reflectivity field in a hook echo.
To map out the reflectivity field in a wall cloud.

The RAD1 radars will be operated at ranges of approximately 1-5 km from the tornado, and from within the intercept vans if possible. This range allows for the simultaneous collection of photographic and video documentation in most cases. RAD1 will also obtain 16 mm movie footage of all tornadoes. Furthermore, deployment at such close ranges allows data to be obtained with the maximum possible azimuthal resolution.

In order to minimize the possibility of range-folding contamination when using pulse or FM-CW mode, the team will be positioned so that there is as little precipitation evident on the other side of the tornado as possible. The optimum position is generally to the right of the tornado path (looking along the path) with the rear flank downdraft behind the tornado, and with the radar team out of the precipitation. In case the team cannot be positioned so that there is little precipitation beyond the tornado (such as in an HP supercell), range-folding contamination may be reduced by using a lower PRF or sweep-repetition frequency, which will reduce the maximum unambiguous velocity.

The system operated by RAD2 is an experimental prototype radar being developed under the direction of Dr. Josh Wurman (OU) in collaboration with NSSL. At this time, we anticipate operating it immediately to the rear of the hook echo or mesocyclone. This radar should be able to easily obtain data throughout the target storm, and positioning it to the rear will minimize hazards associated with the storm overtaking the radar truck. This radar will be used to obtain volume scans of the mesocyclone region on an update cycle of roughly 30 seconds to 1 minute.

The methods of operation will be determined by the team leader, with logistics consultation and advice from the FC. The FC will be capable of providing tornado location, path, and projected path information. In addition, the coordinator can suggest optimal intercept locations based on terrain and range considerations. For additional information, contact Dr. Howie Bluestein and/or Dr. Josh Wurman at OU ( See " Principal Investigators" . ).

Aircraft

For a complete description, see " Aircraft Operations" .

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