1. Changed the value used for the latent heat term in the exponent for calculating equivalent potential temperature (ELIWV) in subroutine BMJ to use the same value that is used in the BMJ lookup table (ELIWV=2.683E6). A higher value (ELIVW=2.72E6) was previously used in the model integration.

1. Parameter ELEVFC changed to 0.6; the search for the most unstable parcel is done from the surface up to ELEVFC*Plow, where Plow is the midlevel pressure of the lowest layer.
2. In response to the high precipitation bias that developed in parallel, the search for instability is extended to include not only whether the most unstable (highest theta-e) parcel could support convection, but also parcels originating at higher levels where when lifted to their LCL would be positively buoyant.
3. Water loading effects were included in assessing the buoyant instability of parcels, from which a revised (lower) cloud top is determined to be at the highest level of positive buoyancy.
4. At "swap points" (see item #2 in 2006/09/01/00 entry) the first-guess estimate for the top of shallow convection is based parcel instability using the same criteria as for deep convection, but not to exceed the upper limit for shallow convection (0.2 times the atmospheric pressure depth, or nominally 200 hPa for a surface pressure of 1000 hPa). A final adjustment is made to the top of shallow convection, in which it can extend to higher altitudes if (1) the mean ambient relative humidity in the cloud layer exceeds a threshold relative humidity (usually near 90%), and (2) the pressure-integrated parcel instability (similar to CAPE) must be greater than 0. The threshold relative humidity is based on the relative humidity at cloud base that is consistent with a deficit saturation pressure of 25 mb.

1. Horizontal diffusion parameter COAC in module_initialize_real has been changed back to 0.75, and the diffusion variables HDAC and HDACV have been multipled by 1.6/0.75=2.133333 just prior to the call to HDIFF in solve_nmm. Done at 12z 9/5 in the ops NAM and 18z 9/5 in the ops NDAS
2. Revert to using the original 1/2 deg RTG_SST analysis (Wanqiu Wang's 2dvar analysis module, was used in the ops NAM-Eta) instead of the 1/12th deg RTG_SST (using Dave Parrish's 2dvar module) due to a persistent cold SST bias near Alaska and in Hudson's Bay the 1/12th deg SST product. Done at 06z 9/6 in the ops NDAS/NAM

1. Parameter ELEVFC changed from 0.8 to 0.7; the search for the most unstable parcel is done from the surface up to ELEVFC*Plow, where Plow is the midlevel pressure of the lowest layer.

1. The triggering of deep and shallow convection is considered only for grid points with positive CAPE. The CAPE is calculated only over the cloud layer (i.e., the lifting condensation level [LCL] of the most unstable parcel [MUP]) using Zavisa's existing "FIRST ENTROPY CHECK" code, which includes virtual temperature effects. The code was modified slightly to ignore the contribution to CAPE from subcloud effects (when the MUP is subsaturated).
2. "Swap points" are when a grid point fails the entropy check for deep convection but has positive CAPE and is considered for shallow convection. During these situations the cloud top is assumed to be where the relative humidity increases most rapidly with pressure (decreases most rapidly with height, as often associated with inversions). If the calculated CAPE over the shallow cloud depth is negative, then the cloud top is reduced until the CAPE over the cloud depth becomes positive.
3. During melting precipitation ice particles are assumed to have the same mean diameter (1 mm) as at the freezing level. The change is expected to alter heating and cooling profiles in stratiform precipitation, and preliminary results suggest improved forecasts of temperature and humidity profiles in stratiform precipitation associated with mesoscale convective systems.

1. T_ICE changed from -30C to -40C. The new value is consistent with the temperature of homogenous nucleation and the rapid freezing of cloud droplets to ice crystals.
2. T_ICE_init changed from -5C to -15C based on aircraft icing observations.

1. Modified the SST preprocessing job to use new climatological values for Great Salt Lake water temperatures from the University of Utah; a cosine fit to the bimonthly observational data from Saltair Boat harbor (from 1972-1989). From Steenburgh et al., 2000: Climatology of Lake-Effect Snowstorms of the Great Salt Lake. Monthly Weather Review, 128, 709-727.
2. Modified the SST preprocessing job to use monthly climatological values of water temperature for the Salton Sea in southern California
3. Modified the SST preprocessing job to use monthly climatological values of water temperature (obtained from the Army Corps of Engineers) for Fort Peck Reservoir in Montana

1. Remove any restrictions to horizontal diffusion between water points at different elevations (e.g., between erroneously sloping water points and water points at sea-level)
2. Change in start_domain_nmm to redefine z0=z0base (veg component) + z0land, removing terrain height component
3. Code changes to allow horizontal diffusion at grid points along coastal/ice boundaries where the slope between neighboring grid points is > 6 m
4. COAC increased from 0.75 to 1.6, increases Smagorinsky constant for lateral diffusion from 0.27 to its maximum value of 0.4
5. Enhanced vertical diffusion: change parameter EPSL in module_bl_myjsfc from 0.1 to 0.32.
6. Turned on assimilation of sfc temperatures in GSI analysis

1. turn off MSU satellite data
2. tighten the gross error checks for all conventional data
3. increase iteration number from 50 -> 75
4. +/- 15 minute window for all surface obs (was +/- 1.5 hours)

1. Begin use of latest (March 2006) GSI release
2. Use NMM-based background errors computed using an ensemble/Monte Carlo approach

E = 1-.exp(-0.75*D),

as defined over a contiguous cloud layer was changed to

E=1.-exp(-1.66*1.5*D)

The 1.66 factor agrees with the equation in the WRF RRTM, while the extra factor of 1.5 accounts for the larger absorption coefficients used in NCAR's RRTM to convert from cloud mixing to optical cloud depth.