Prescribed burns lit up GOES-16 imagery on April 11 in the eastern half of Kansas. The 2 km 3.9 um IR channel shows an abundance of hotspots across the region during the day. The 0.5 km 0.64 um visible channel reveals widespread smoke. Ozone alerts were issued for parts of Kansas given the increased particulate matter in the air.
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”
During the overnight hours of March 19-20, 2017, an amplifying upper level shortwave moved off the Mid Atlantic coast and led to the rapid development of a mesoscale oceanic cyclone across the Gulf Stream east and southeast of Cape Hatteras. The upper level feature moved south and southeast along the backside of a deep upper level long wave trough near 68W. The global models including the GFS and ECMWF were not well initialized with the upper level shortwave and consistently, over the previous several model runs, were only indicating a weak trough would develop at the surface. Conversely, the 4km NAM and HRRR were each showing surface low development and significantly higher associated surface winds than shown by the coarser global models. OPC forecasters had been carrying storm warnings across a few offshore zones through 00 UTC March 20, 2017.
Animation of the 20 March 2017 00 UTC 4 km NAM pmsl and surface winds. Yellow boundaries delineate the OPC offshore forecast zones. Click here to open in a new window.
The GOES-16 water vapor imagery, including the 6.9 um mid-level and 6.2 um upper-level, suggested that the mid/upper shortwave was more amplified than initialized by the global models. The feature was also apparent in the GOES-16 7.3 um lower-level water vapor imagery, indicating it may be vertically stacked or at least extend through the lower levels. The three water vapor channels alone indicated there was likely adequate forcing through the upper and mid levels, and even into the lower levels, to support the development of a surface low. However, the low level circulation analyzed in the GOES-16 3.9 um shortwave infrared imagery confirmed the presence of the surface low. In addition, the enhanced baroclinicity the system encountered as it tracked across the Gulf Stream likely played a big role in the storm’s intensification. The sea surface temperature (SST) gradient along the north wall of the Gulf Stream can be seen in the GOES-16 3.9 um shortwave infrared animation.
GOES-16 6.2 um upper-level water vapor animation valid 2102 UTC 19 March 2017 – 0902 UTC 20 March 2017. *Preliminary, Non-Operational Data* Click here to open in a new window.
GOES-16 6.9 um mid-level water vapor animation valid 2102 UTC 19 March 2017 – 0902 UTC 20 March 2017. *Preliminary, Non-Operational Data* Click here to open in a new window.
GOES-16 7.3 um lower-level water vapor animation valid 2102 UTC 19 March 2017 – 0902 UTC 20 March 2017. *Preliminary, Non-Operational Data* Click here to open in a new window.
GOES-16 3.9 um shortwave infrared animation valid 2102 UTC 19 March 2017 – 0902 UTC 20 March 2017. *Preliminary, Non-Operational Data* Click here to open in a new window.
Upon reviewing the GOES-16 imagery and evaluating the most recent model guidance, the overnight OPC forecaster extended the storm warning through the night period, and also expanded the warning to include the outer mid Atlantic offshore waters. The significantly improved temporal and spatial resolution of the GOES-16 imagery, along with the additional water vapor channels, allowed forecasters to better diagnose the strength of the upper level shortwave and also, the presence of the surface low, which then gave forecasters more confidence in amending the warnings. Even as the both the upper level feature and the surface low appear to shear and weaken in the three GOES-16 water vapor channels and 3.9 um shortwave infrared band around 06 UTC, there was a ship which reported gale force winds (35 kt) at 06 UTC well southwest of the surface low.
Thanks for reading!
James Clark (OPC) and Michael Folmer (CICS)
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”
A strengthening upper trough/low centered over Wyoming spawned convection across the Central Plains during the afternoon/evening of April 9. The strongest of these storms developed along an area of convergence in far SW Nebraska during the late afternoon hours. The convective system moved west to east across southern Nebraska through the evening hours. Severe wind was the primary initial hazard with these storms, with a transition to severe hail occurring as they tapped into an environment characterized by steeper lapse rate.
Numerous strong/severe storm cloud top signatures were apparent in the GOES-16 IR Window channel imagery. The higher spatial (2 km vs 4 km) resolution makes these features more obvious, and improved temporal resolution (routine 5 min vs 15 min over CONUS) ensures important features are not missed. Overshooting tops, Enhanced-V’s, and thermal couplets were all apparent with the convective system. These features were long-lived, indicating sustained strong updrafts. Since these features were associated with severe storm reports early on, a forecaster could be confident that the storms would continue to produce severe as long as the signatures persisted.
GOES-16 10.4 um IR, annotated.
Overshooting tops, characterized by a localized region of cool cloud top temperatures, indicate the location of a robust updraft. Dworak, 2012 found Overshooting Tops were associated with severe weather reports over 40% of the time during the warm season. These features also pose a hazard to aviation. Enhanced-V’s are directly tied to overshooting tops, and are characterized by a V (or U) of relatively cool cloud top temperatures downwind of the overshooting top. The signature is formed as flow is forced around the overshooting top. The thermal couplet signature refers to the couplet of cold temperatures of the overshooting top and relatively warm temperatures immediately downstream of the overshooting top and within the enhanced-V.
“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”
