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1. The divergence damping routine, which damps all gravity-inertia and external modes, is changed to increase damping of the external mode.
2. During the NDAS, divergence damping is increased to 5x that used during the 84 hr NAM free forecast.
3a. Numerous changes are made to convective parameterization:
- Triggering of deep and shallow convection is considered only for grid points with positive cape throughout a parcel’s ascent; the search for parcel instability is extended to include not only whether the most unstable (highest theta-e) parcel can support convection, but also whether parcels originating at higher levels become positively buoyant when lifted to their LCL. Convective adjustments are made with respect to the parcel associated with the greatest instability (largest CAPE).
- The search for the most unstable parcel is extended from the lowest twenty percent of the atmosphere to the lowest 40 percent of the atmosphere.