Mesoscale Observations of
Convective Initiation and Supercell Experiment -'00 & '01
(MOCISE)
 

Albert Pietrycha
NSSL & Texas Tech University
albert.pietrycha@noaa.gov

Revised 3/16/01

Update: MOCISE will collaborate with pre-IHOP and COMPASS in 2001. I'll update this page as information becomes available over the next few months. Information pertaining to the '01 effort is preceded by a *.

Motivation

A plethora of questions pertaining to convective initiation have been generated from ongoing analysis of VORTEX, MOCISE and STEPS data. Additionally, recent publications using data collected during VORTEX have documented various interactions of tornadic supercells with boundaries. It has become increasingly clear that an investigation of the environmental mesoscale thermodynamics and kinematics along and near various boundaries is required in order to understand the underlying dynamics relevant to thunderstorm convective initiation.

Until a more complete characterization of boundaries in general, and the boundaries associated with tornadic supercells in particular, is acheived our knowledge will remain limited. This observational study will add comprehensive information for detailed boundary characterizations and will test applicable hypotheses. Emphasis will be placed on a variety of mesoscale boundaries, including the dryline, outflow boundaries, and quasi-stationary fronts as well as supercells.

 

MOCISE objectives

1.  *Obtain data documenting surface and boundary layer thermodynamics inconjuntion with dual Doppler radar data during the evolution of mesoscale boundaries.
2.  Obtain data documenting coherent kilometer-scale kinematic flow structures and moisture gradients along boundaries.
3.  * Obtain data documenting atmospheric surface variables in conjunction with dual Doppler radar data within deep moist convection.
 
Support for Experiment:

 

 

Field Operations Plan:
 
* The mobile mesonets and mobile laboratory will be located at Texas Tech University. Field operations will focus primarily to the right of line from LBB-AMA-LAA-TRB-HUT-ICT-OKC-SPS-ABI-LBB.
 
2000 operating domain (schematic):
The operations center will be run at Texas Tech University. Field operations will focus primarily in the Texas and Oklahoma Panhandles, West Texas and Western Oklahoma.

Operating window:

* June 1 - June 30, 2001
April 1 - May 15, 2000
 

Observational Platforms:

 

Observational Studies:

Convective Initiation Studies

The Great Plains dryline will be the focus for a majority of the experiment. In order to achieve the project's objectives, quiescent and/or slow ( < 6 m/s) transient dryline events will be targeted. This will enable a detailed sampling of the surface gradients and coherent flow structures embedded within the dryline. Examples are online of Mobile Mesonet (MM) observations of drylines and the Denver Convergence and Vorticity Zone (DCVZ). Convectively active and/or fast-moving drylines will not be considered for operations. Similarly, outflow boundaries and quasi-stationary fronts moving over 6 m/s will not be targeted.

Previous MM operations during VORTEX and HAL have determined that a variety of vehicle speeds are necessary for proper observations along surface boundaries. The MM vehicles will perform opposing transects of the boundary in pairs. One pair will perform transect legs normal to the boundary, proceeding at about 40 mph and ending each leg from 1.0 to 2.0 miles on either side of the boundary. This vehicle speed is ideal to resolve the larger flow structures, i.e., embedded eddies. A second pair of MMs will sample the boundary using the same road at 5 mph (see schematic). These slower sampling speeds will permit a fine-scale quantification of gradients in moisture and temperature across the boundary. The transect legs will cease 0.5 to 1.0 mile either side of the boundary. * The third pair of MMs will operate similarly on a parallel road 1 mile up or downstream of the first two pairs. The additional sampling along the second parallel road will provide essential data to resolve and document the temporal evolution of the boundary. *Additionally, the third pair will operate along the dryline sampling the along-line moisture and thermal variability.

The M-CLASS unit will launch soundings from 2.0 to 4.0 miles on either side of the boundary. Depending on the mission, soundings will generally be deployed once every 1.0 to 1.5 hours. These soundings will provide additional data for temporal characterizations. Resolutions should be adequate for observing the evolution of boundary layer thermodynamics and kinematics. Soundings will be launched directly within the moisture transition zone on the dryline and should enable the detection of moisture plumes emanating from the boundary (assuming plumes are present and thus sampled within the sounding trajectory path as it rises through the boundary layer). When the M-CLASS unit is not preparing for a launch, the vehicle will join one MM team and conduct 40 mph transects of the boundary.

*If operations are conducted in west Texas, target preference will be given to the region bounded within the West Texas Mesonet array.

Supercell Studies

The forward flank (FF) of supercells (see schematic) will be targeted for investigation. The common conceptual model of a supercell (Lemon and Doswell, 1979, Mon. Wea. Rev.) shows a storm-scale front extending along the forward-flank precipitation region, presumably produced by evaporative cooling of forward flank air. However, work by Markowski et al. (1998, Mon. Wea. Rev.) has shown that for VORTEX storms, the forward-flank front was often absent, particularly when the supercell was on the cool side of a mesoscale boundary. This is easily understood in light of the fact that the air on the cool side of these boundaries is typically cool and quite humid, greatly reducing the potential for evaporation from the forward flank. We wish to resume observations of forward flank baroclinity during MOCISE in order to determine if any supercells exhibit significant baroclinity there, and if so, how these supercells might be structurally different than storms that do not have this baroclinity. Low precipitation (LP) and Classic (CL) supercells should provide the best opportunities for achieving project goals. High precipitation (HP), line segments, and squall lines will not be targeted. If a LP of CL should evolve and/or grow upscale into either a HP or squall line, operations on that storm will be terminated.

MMs will be grouped in teams of two performing opposing transects normal to the FF. The individual pairs of MMs will travel separated on parallel roads spaced ~1 mile part and the teams will leap-frog one another, each beginning a new transect further downstream as they keep pace with the storm. This will allow for prolonged sampling of the FF and documentation of the FF temporal evolution. The M-CLASS unit will not launch soundings while engaged on a supercell. The vehicle will be used as a MM working in unison with one of the MM pairs.

 

Team Personnel:

Field Coordinator: The field coordinator (FC) is responsible for all activities pertaining to MOCISE field operations. These responsibilities include but are not limited to the following: monitoring status and availability of vehicles; procuring personnel and equipment; directing experiments; road network density and navigation; logging travel time; communications status; determining next-day target region potential; communicating with Nowcaster, M-CLASS; and the deployment and orchestration of the mobile and stationary mesonets on a mission.

Nowcaster: The Nowcaster will provide meteorological support to the FC once the teams are in the field. Based on mesoscale analysis, profilers, satellite and radar, the Nowcaster will provide support during actual missions. Nowcasting will usually be provided by Dr. Erik Rasmussen in Boulder (BNC). When BNC is unavailable, Jim Johnson with the Dodge City National Weather Service Forecast Office (DNC) will assist with nowcasting and short term forecasting. Communications between the Nowcaster and the FC will occur once an hour. Either individual, depending on environmental changes, will initiate the communiqué. Once a target is chosen, the frequency of contact may or may not increase depending on the pace of environmental changes and the objectives of the mission. A quiescent dryline needs little nowcast support as compared to a supercell mission.

Mobile mesonets will be assigned two persons per car: the driver and the captain. The driver’s sole responsibility is the safe operation of the vehicle. The captain is responsible for communications with the field coordinator (FC), maintaining the operation of the mesonet, data sampling and logging, and will assist the driver with road directions and navigation.

M-CLASS unit will be operated by three people: a driver, captain, and an assistant to the captain. The driver’s sole responsibility is the safe operation of the vehicle. The captain is responsible for conducting and operating the sounding launches, sounding and mobile mesonet data collection, monitoring the M-CLASS electronics and equipment, and communicating with the FC. The assistant captain will aid in sounding launches and data collection, and mobile mesonet sampling, as well as aid the driver with navigation.

 
Safety:-link to VORTEX guide lines.
Participants should be thoroughly familiar with the safety standards established within the document linked above. These same rules apply for all MOCISE participants and will be strictly adhered to.
 

Communications:

In MOCISE, the standard VORTEX radio protocol will be used. It's quite simple

We will utilize two VHF simplex channels, depending on the situation. This will be channels X.XX and Y.YY on the MM VHF radios. Cell phone coverage is rather sparse in some of the MOCISE region; the FC, . unit team, and the M-CLASS team will have project cell phones in the vehicles.

National Weather Service:

The National Weather Service Forecast Office (WFO) in Lubbock (LBB), TX will aid in the operational efforts of MOCISE. The LBB WFO will also provide both resources (also see data archival) and personnel to the project. The WFO will monitor the Spur, TX (KSPR) Campbell unit observations and also increase the temporal resolution of the observations from one-hour, to fifteen minutes. The LBB WFO will closely monitor the Lubbock WSR-88D Archive II data collection system when the project is operating in their warning area. Additionally, when regional precipitation and bordering WSR-88D operations permit, the LBB WFO will prolong the use of VCP 32 volume scans before switching to VCP 11. The lengthen VCP 32 window will aid the MOCISE forecasters and researchers in better resolving and monitoring radar "fine Lines". Please note that during severe weather operations, the primary mission of the NWS - protection of life and property - must take precedent over MOCISE activities in the event that resources are insufficient to accommodate both. Data and observations from the MOCISE data collection will be relayed to the Lubbock WFO in real-time through the Nowcaster, to assist in warning operations. Post-event verification operations will be relayed directly to the LBB WFO by the FC. When possible MOCISE participants will assist the LBB WFO in damage surveys. This may also include the participation of Wind Engineers from TTU.

The Dodge City, KS WFO will help assist with nowcasting. Jim Johnson will head this effort for the office (see Nowcaster).

 

Forecasting:

Several individuals and the FC will conduct daily forecasting. The forecasting will commence the evening before a possible mission. For logistical reasons, the forecast information will be shared via a very informal email exchange between the forecasters and the FC. The email discussion is intended to aid the FC in determining a mission target area. Forecasting emphasis will be placed on the relevant data and guidance pertinent to synoptic and mesoscale features for the following day. Ongoing overnight convection will be closely monitored with regard to outflow boundary development. Given only the evening sounding and numerical model runs will be available, compounded by a 18-hr mesoscale forecast, any target areas chosen should be considered preliminary until the updated morning forecast is distributed. Once the FC has decided upon a preliminary target, he will write a status message and forecast discussion. This will be emailed directly to MOCISE participants. The forecast will consist of a detailed discussion over the synoptic and mesoscale environment. A "GO”, “NO-GO”, or “STAND-BY" status will be issued in the email. The time the email is sent out will vary; therefore, participants are encouraged to read the SPC Day-2 forecast discussion before the receipt of the evening forecast. This will provide the participant with a possible "heads up" for the next day. It is stressed that the SPC outlooks should not be viewed as a gauge in determining a "GO”, “NO-GO" decision. The forecasting objectives of SPC are vastly different then MOCISE's. If the evening status message is a “STAND-BY”, information leading to the decision delay will be explained.

When the evening status message and forecast discussion contains a "GO” or "STAND-BY" condition, morning forecast will occur. Forecasting emphasis will be placed on current remote sensing instruments. The forecasting time frame will preclude the use of 12Z soundings and numerical guidance. Forecasts will include but are not limited to, boundary(ies) placement and movement, expected time of convective initiation, supercell type(s) given the probability of supercells and likely motion, as well as tactical operations for that day. In formulating his decision, the FC will also consider how the terrain and vegetation in the target area may effect operations; the relative amount of data already for various study objectives. The feasibility of reaching the target and thus insuring that the teams arrive at the potential boundary area before initiation of deep convection will be carefully examined. Once the FC has made a decision for the day, a second email will be sent containing the mission status. The email will be sent to all participants no later than 1700 UTC. It is possible that a morning status message will be a “STAND-BY”. If that is the case, information pertaining to this decision will be conveyed along with a time frame for a later update. The majority of MOCISE participants are TTU grad students and in close academic proximity to the FC. This group of participants will be updated verbally in addition to the email. The students’ exam schedules will be taken into account in determining the "GO" "NO-GO" decision.
 

Data sources and archival:

Several sources are providing specialized real-time data and the archiving of remote sensing and model data. Jim Bresch with the Mesoscale and Microscale Meteorology Division, at NCAR, will maintain a real-time MM5, 30-km resolution sector centered over Oklahoma. Eric Nelson with the College of DuPage, neXlab, is providing a Southern Plains ETA sector. TTU will maintain the ingestion and archive NIDS, satellite, soundings, ACARS, profiler, and surface data. Archived level II WSR-88D data will be ordered as needed through NCDC. The LBB WFO will archive the ETA model output and the KSPR Campbell mesonet site. Observational field notes and mission summaries will be maintained by the FC. These will be made available on-line as time permits. The mobile mesonet and M-CLASS data will be available to the community after rigorous quality assurance steps have been completed.