Simulated Satellite and HRRR verification

At the experimental CAWS desk this morning forecasters are discussing the placement of scattered convection in the Northeast later this afternoon. Part of this involved looking at the simulated satellite imagery from the various models, not only to determine that placement, but also to determine performance.

For the latter, forecasters first looked at the 1300 UTC HRRR simulated satellite from the CIMSS HRRR validation website shown here in Figure 1.

Figure 1. HRRR simulated IR (left) and actual GOES-13 IR imagery at 1300 UTC on August 10th.

Immediately noticeable are two things in relation to the MCS over the Memphis area: 1) The placement of the HRRR is very good and 2) the IR temperatures are significantly colder in HRRR. This suggests that while the location of any expected convection will be relatively accurate, the intensity may be overdone.

This in mind, forecasters shifted further into the future, aiming to identify potential areas of convection later in the day. Below in Figure 2 is the HRRR forecast for 1800 UTC.

20150810 1300 UTC F0600 (1800 UTC) HRRR simulated IR

The modeled IR imagery is indicating scattered convection over central Ohio, as well as some convection across Alabama and Georgia. Keeping in mind the overdoing of the earlier convection, forecasters believed that it would remain more scattered across the latter area and isolated across Ohio.

While scattered and isolated convection isn't a big issue for a local WFO office, it can have a significant impact to aviation. Atlanta center is well versed in dealing with summertime convection in the afternoon and in this case may not require a CAWS, simply rerouting traffic on an as needed basis (i.e. ad hoc). However, an experimental CAWS was issued for the forecast convection over Ohio. While only expected to be isolated in nature, any convection that develops in this extremely busy airspace causes disruptions and requires a more complex plan to reroute traffic. Figure 3 below shows the CAWS issued by experiment participants.

20150810 experimental CAWS issued at 1453 UTC

This CAWS indicated scattered thunderstorms would be occurring by 1900 UTC and could potential affect all east/west traffic into and out of the Northeast U.S.