This blog entry will consider the synthetic IR imagery from the NSSL 4-km WRF-ARW model for 19 April 2011. There were many severe weather reports on this day:
The synthetic IR imagery from the WRF-ARW model from 1200 to 2300 UTC (from the 0000 UTC 19 April 2011 model run) is given here:
The synoptic scale feature of interest is a trough that is moving eastward across the Plains. A surface low (not shown) is forecast to move across Missouri with an attendant warm front towards the northeast and a trailing cold front to the southwest. There are indications of the cold front in the synthetic imagery, note the arc of colder brightness temperatures extending southwest from Missouri to north Texas then bending northwest across the Texas panhandle by later in the day. A dryline is forecast to move eastward across Texas, it intersects the cold front near the Oklahoma border by late afternoon. Model brightness temperatures are warmer on the dry side of the dryline during the afternoon. The model has partial clearing in the warm sector ahead of the surface low in eastern Missouri and portions of Illinois. Initial afternoon thunderstorm development is forecast in this area. Shortly thereafter, thunderstorm development is forecast by 2200 UTC in southeast Oklahoma and northeast Texas. By 2300 UTC, thunderstorms are forecast in between these two areas from northwest Arkansas into southwest and central Missouri.
Let’s look at what happened by examining the GOES IR imagery during the same time period:
After the departure of a morning MCS, clearing took place in eastern Missouri and the southern half of Illinois which allowed destabilization to occur south of a warm front and east of the surface low. The cold front and dryline in Oklahoma and Texas do show up during the mid-afternoon hours but the lack of contrast by later in the day makes them more subtle than the synthetic imagery. Toggle on the surface winds (from the RTMA) so you can confirm where the various low-level boundaries are located. The initial afternoon storms developed in southeast Oklahoma along the intersection of the cold front and dryline with thunderstorm development in eastern Missouri soon thereafter. Later, convection develops in between these two regions in northwest Arkansas / southwest Missouri.
The synthetic imagery from the WRF-ARW model depicts a similar evolution to thunderstorm development compared to what actually happened. Monitoring cloud cover trends and identifying the various low-level boundaries throughout the day can assess how much confidence one should have in the model forecast. Be aware that at times, various low-level boundaries may show up differently in the synthetic imagery compared to GOES imagery.
For more information on severe weather applications of the synthetic imagery from the NSSL 4-km WRF-ARW model, you may take this VISIT training session: