In accordance with the NWS mission of mitigating costs to interstate commerce through accurate and timely weather forecasts and warnings, and as part of it's total lightning information initiative, NWS MLB will exploit all available lightning detection systems - Lightning Imaging Sensor Data Application Demonstration display system (LISDAD), Lightning Detection and Ranging (LDAR), Lightning Position and Tracking System (LPATS), as well as the lightning alert in the Integrated Terminal Weather System (ITWS) to improve it's Terminal Aerodrome Forecasts.
 

Background

Since April of 1996, the National Weather Service (NWS) Office in Melbourne, Florida (MLB) has routinely issued Terminal Aerodrome Forecasts (TAFs) four times daily for the following four sites: Daytona Beach International Airport (DAB), Orlando International Airport (MCO), Melbourne International Airport (MLB), and Vero Beach Municipal Airport (VRB). During the convective season (generally late May through September) the MLB aviation forecaster routinely issues TAFs which include forecasts of afternoon thunderstorms (TS) for a period of between three [3] and six [6] hours, with four [4] hours being the most common time span specified.
 

NWS Melbourne forecasters are well aware of the importance of balancing airlines' needs for both cost-effectiveness and safety when it comes to composing TAFs. The inclusion of TS and accompanying IFR ceilings/visibilities in either the prevailing or TEMPO group of a TAF has significant consequences with respect to airport operations particularly if it is a major hub (Ott and Ladd, 1994).
 

For instance, not only are the number of arrivals/departures reduced during TS/IFR conditions, but any aircraft whose destination airport contains a forecast of prevailing or TEMPO TS must carry additional fuel so that it may reach a designated alternate destination airport should the weather not permit a landing at the planned destination airport. Carrying this extra fuel costs the commercial carriers more money, and if TS are inaccurately (excessively) forecast, the cost incurred by a commercial airline can become exorbitant.
 

Climatological study

An initial study will be undertaken by the aviation focal point to ascertain the time of both onset and dissipation, as well as the duration of thunder (lightning) events at the four airport terminals for which MLB is responsible, during the convective season. This will be done using locally archived SAO and METAR data from 1994-97. These events will then be stratified according to regime by correlation to morning soundings (10-15Z) from the Cape Canaveral Air Force Station (CCAFS), after which mean start, stop and duration times will be compiled.
 

Sub-Initiative Goals for Exploitation of TLI  as a complement to WSR-88D, ITWS, etc.

Without a compromise to safety...

1) Minimize/optimize the usage of thunderstorms (TS), convective wind gusts (GxxKT) and associated IFR ceilings/visibilities in both the prevailing and TEMPO groups of the TAFs in the 0 to 4 hour time frame, with emphasis placed on the 0 to 2 hour time period. example
 

2) Narrow the time frame in which "extreme" thunderstorm related aviation weather - defined here as LIFR ceilings/visibilities, wind gusts in excess of 30KT - to one hour or less within the 0 to 2 hour time frame, when warranted.  example
 

3) Decrease usage of TS in the TEMPO groups of the TAFs in the 6 to 24 hour time frame as appropriate. Emphasize/encourage the use of PROB30 and PROB40 within this time period when appropriate.
 

4) Establish that the use of "TS VCSH" as a prevailing weather group is preferable over the use of "VCTS". 
 

Operational Methodology

1) *TENTATIVE* The plan view of the LDAR display system will be modified with the placement of 20nm diameter circles around each (DAB, MCO, MLB, VRB) of the four TAF locations. LDAR will visually alert the aviation or AMU forecaster to the presence of lightning within either 20nm (yellow) or 10nm (red). LISDAD will also have a variation of this functionality.

Currently, both LDAR & LISDAD are being reprogrammed to accommodate these requirements. (SOO, 07/97)

2) As part of his/her duties, the AMU forecaster will monitor all available lightning information systems and routinely coordinate with the Aviation/Short term forecaster regarding the presence (or lack thereof) and trend of lightning activity in the proximity of the aforementioned TAF sites.

3) The 88D, LISDAD and ITWS will continue to be monitored for the presence and movement of boundaries which may initiate electrified convection near the TAF sites.
 

* Obviously, workload and staffing during the remainder of Stage 1 will need to be considered, since the sub-initiative goals will likely increase the number of TAF amendments issued for each terminal location.