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Overview

The NCWF product, designed and implemented by the NCAR, provides a diagnosis of the current locations of convective hazards to aircraft as well as a depiction of future locations of existing convective hazards for lead times of 30, 60, 90, and 120 min given in a probabilistic sense. Both the convective hazard detection field and the forecasts update every 5 minutes. The NCWF product is currently available on the Experimental ADDS Convection page as well as the Experimental ADDS Flight Path Tool. The target users of NCWF2 are general aviation, airline dispatch offices, and FAA TMU's. NCWF was developed by the Convective Weather Product Development Team through sponsorship by the FAA's AWRP. The Convective Weather Product Development Team consists of MIT Lincoln Laboratories, National Weather Service's AWC, and the NCAR.

The Base Interest or Significant Weather field indicates where precipitation with VIP >= 1 is falling. The product is the result of combining the VIL field generated from the WSR-88D national radar mosaic by Unisys© with the cloud-to-ground lightning data from the NLDN. The Significant Weather field is depicted based on a 6 level intensity scale (Figure 1). The 6 levels fundamentally correspond to the VIP levels that were developed to convey storm intensity for aviation interests.

: Figure 1: VIP Levels

NCWF-2 produces rapidly-updating probabilistic forecasts of convection that has deemed hazardous to aviation. As mentioned above, the system produces 30, 60, 90 and 120 min probabilistic forecasts every 5 minutes. This frequent update cycle is required to capture rapidly changing nature of thunderstorms which evolve over very short time scales (order 30 min). The goal of this system is to continuously provide the most up-to-date information on convective activity across the CONUS for aviation users including aviation weather forecasters, airline dispatchers, general aviation, and FAA TMUs and CWSUs. Forecasts are produced through the following sequence of steps:

detection
motion determination
trending
extrapolation
conversion to probabilities
dissemination and display.

The NCHD is intended to indicate areas of thunderstorms that pose an aviation hazard. This field is generated by performing automated Quality Controls to the WSR-88D national mosaic of VIL, removing areas of the light precipitation and filtering out areas of stratiform precipitation from the Significant Weather field. Probabilistic forecasts of 30, 60, 90 and 120 min are then generated using the NCHD field, observed tracks and trends in the NCHD, environmental conditions provided by the RUC model run by NCEP, and climatological information. The probabilistic forecast indicates the likelihood or chance that storms posing an aviation hazard will exist at a particular location at a given time.

The NCWF forecast product is not intended to forecast thunder storm formation, but does very well with long-lived mature systems. The NCWF forecast products also includes information on storm trends which are represented as areas of decreased/increased probabilities depending on whether the storm was observed to be dissipating or in a region favored for growth. While NCWF does not explicitly treat storm initiation, the growth algorithms will capture new storm formation in the vicinity of existing storms. Work on improving automated methods for forecast initiation, growth and dissipation of storms and extending these forecasts to longer lead times through blending with probabilistic NWP forecasts is ongoing.