Convection in the Northeast.

The first week of this year's summer experiment is almost completed.  The week has certainly gone by quickly.  Today the high-resolution model evaluation and verification desk had a bit more time to put together a quick post. 

We were focused primarily on the timing and location of convection impacting the northeast.  One of the products used for this diagnostic was the probability of a lightning strike. The image below is a loop from 12Z-06Z centered over the northeast.  The field is the probability of a lightning strike within 20 nautical miles of a grid point, as calculated from the AFWA mesoscale ensemble prediction system.  This product indicated a significant lightning threat moving through Nova Scotia and Maine during this time.

AFWA probability of a lightning strike, 12Z-06Z.

Similar to the previous post, we took a look at spaghetti diagrams of the Air Force Weather Agency ensemble and the Storm Scale Ensemble of opportunity. Both ensembles indicated that the threat would primarily be cellular in nature.  The AFWA ensemble progressed the system more quickly and further east than did the SSEO.  Upon investigating the initial conditions for these ensembles, it was determined that this was likely due to the fact that all of the SSEO members were initialized off the 00Z operational NAM, while the AFWA members were initialized from 12Z and 18Z global model runs from the previous day which had the surface trough further east in earlier model runs.

The AFWA ensemble also developed more cellular convection southward, stretching across Pennsylvania. To get an idea of the potential impacts these solutions have on aviation operations, the top 25 jet routes have been plotted in each of these figures.  The AFWA solution then indicates more constraints to aviation traffic flow.

AFWA paintball plot of areas of simulated composite reflectivity >= 40 dBZ

SSEO paintball plot of areas of simulated composite reflectivity >= 40 dBZ

Convective Timing

This morning's analysis of the high-resolution ensemble models focused on the ongoing convection in the southeastern US.  One of the questions asked was when would convection clear out of the Atlanta, GA area.  One of the tools used were spaghetti/paintball plots showing the location of each of the individual members of the ensembles.  These graphics allow a quick visual of the solutions presented by the various ensemble members.

Spaghetti plot of AFWA ensemble members with composite reflectivity >= 40 dBZ, valid 17Z.

Spaghetti plot of SSEO ensemble members with composite reflectivity >= 40 dBZ, valid 17Z.

In general, more spread was observed in the AFWA ensemble than in the SSEO.  Timing was fairly good, with the location of leading edge of convection depicted in the same general area in southeast Georgia.

Radar and aircraft observations valid at 17Z.