This morning the National Weather Service (NWS) Operations Proving Ground (OPG) began a 6-week evaluation of 1-minute satellite imagery, a normal operating capability of the Geostationary Operational Environmental Satellite (GOES)-R Series. The overarching goal of the evaluation will be to provide quantitative and qualitative guidance to NWS management and the GOES-R Program Office on how 1-minute satellite imagery impacts NWS forecaster decision making in a variety of weather situations.
In total, eighteen participants from NWS Forecast Offices across the country will each complete seven simulations that were developed using satellite imagery collected during the 2013 and 2014 GOES-14 Imager Super Rapid Scan Operations for GOES-R (SRSOR) experiments. In all simulations, participants will provide feedback on how satellite imagery affects decision making processes, situational awareness, confidence, workflow, and workload. Furthermore, in three of the simulations, the forecasters will be split into two groups where one set is given 1-minute imagery and the other set is 5-minute imagery. This unique dataset will allow the OPG staff to investigate if 1-minute satellite imagery had added value when compared to 5-minute imagery for these cases.
Once completed in early April, OPG staff will write a report summarizing the statistical analysis and forecaster feedback that was gathered during the evaluation. In addition, results will be presented at the upcoming 2015 National Weather Association and 2016 American Meteorological Society Annual Meetings.
On Sunday April 27th, 2014, a moderate risk for severe thunderstorms was forecast by the SPC across eastern Kansas and Oklahoma, most of Missouri and Arkansas, as well as portions of Texas, Louisiana, Mississippi, and Tennessee. Before 12Z on that morning, convection developed along the dryline/Pacific cold front across central Kansas and Oklahoma. These thunderstorms became elevated as they moved east northeast towards Kansas City and western Missouri due to mid to lower tropospheric warm air advection. The early morning convection added uncertainty to the forecast as there was a question whether the atmosphere would recover and destabilize for convective initiation (CI) before the dryline and Pacific cold front moved through across eastern KS and western MO behind the morning convection.
Visible satellite image from GOES-13, METARs, NWS Convective Watches and Warnings, and manually analized surface features valid 1815 UTC 27 April 2014.
In the image above at 1815 UTC, although there was clearing right ahead of the dryline, extensive cloud cover and cool temperatures were present in the wake of the morning convection across eastern Kansas and western Missouri. Ninety minutes later, at 1945 UTC, temperatures started to rebound into the lower to mid 70s across southeastern Kansas and a cumulus field developed ahead of the dryline across eastern Oklahoma.
Visible satellite image from GOES-13, METARs, NWS Convective Watches and Warnings, and manually analized surface features valid 1945 UTC 27 April 2014.
One of the GOES-R future capability products, Probability of Convective Initiation, provides probabilistic 0-1 h forecasts of cloud objects achieving convective initiation (35 dBZ or > radar echo). Inputs into the algorithm are convective cloud properties from either GOES-13/GOES-15 and 20 Rapid Refresh model output fields. This fused product is excellent at providing guidance to the mesoanalyst or warning forecaster on which portion of a cumulus field will develop into convection. In the image below at 1945 UTC, there were low probabilities of CI within the newly developed cumulus field across northeastern Oklahoma.
Visible satellite image from GOES-13, GOES-R Probability of Convective Initiation [%], and NWS COnvective Watches and Warnings valid 1945 UTC 27 April 2014.
At 2045 UTC, 60 minutes later, the cumulus field developed northward into southeastern Kansas and probabilities increased to 60% within that cumulus field. This indicates a higher likelihood of CI and is starting to provide confidence to the forecaster that the atmosphere is destabilizing enough for the potential of CI.
Visible satellite image from GOES-13, GOES-R Probability of Convective Initiation [%], and NWS COnvective Watches and Warnings valid 2045 UTC 27 April 2014.
Another GOES-R future capability is the Convective Cloud-Top Cooling (CTC) product. This algorithm uses GOES-13/GOES-15 imager data and cloud phase information to provide situational awareness on which convective cloud objects are quickly growing vertically (i.e., a proxy for initial updraft strength). A stronger CTC rate is directly correlated with updraft strength and larger hail when compared to the WSR-88D maximum expected hail size algorithm. At 2125 UTC, 40 minutes after the elevated CI probabilities, two thunderstorms were developing across southeastern Kansas and northeastern Oklahoma. This is evident by the strong CTC detections in those areas.
Visible satellite image from GOES-13, GOES-R Convective Cloud-Top Cooling [K per 15 minutes], and NWS COnvective Watches and Warnings valid 2045 UTC 27 April 2014.
Fifteen minutes later, the first severe thunderstorm warning was issued on the thunderstorm with the northern CTC detection in southeastern Kansas. These two thunderstorms eventually developed into the supercells that produced the two EF2 tornadoes that affected Baxter Springs, KS (southern CTC detection) and Bates/Linn County, KS (northern CTC detection). Although the two products shown are GOES-R future capabilities, they are used today with GOES-13/GOES-15 data to demonstrate the algorithms and provide observational information of the convective environment that is not currently available with other datasets. When these two products are used together with observations forecasters are already comfortable with, situational awareness of the convective environment is elevated and more accurate short-term forecasts of convection may possibly be provided to partners.
~ Chad Gravelle, NWS Operations Proving Ground Satellite Liaison
The spatial resolution of infrared (IR) polar imagery (e.g., Suomi NPP VIIRS and MODIS) is currently superior to similar geostationary data over North America (~1km vs 4km). Unfortunately, there are relatively few polar passes a day over the contiguous United States. At best, there would be 2 passes over any one location every 12 hours for each polar satellite. This is one reason why it is challenging to introduce operational forecasters to the advantages in using this imagery.
This will all change over the next year with the National Weather Service’s (NWS) second generation Advanced Weather Interactive Processing System (AWIPS2), and the use of polar imagery will become more and more common within NWS Forecast Offices. This is because AWIPS2 will allow the forecaster to overlay multiple images to create GOES/POES hybrid satellite loops.
In the image below, this capability is shown using IR imagery from GOES-13 (10.7 μm), MODIS (~11.0 μm), and Suomi NPP VIIRS (11.45 μm) between 0615 and 0801 UTC on 28 March 2014 over the Southern Mississippi Valley.
IR imagery from GOES-13 (10.7 μm), MODIS (~11.0 μm), and Suomi NPP VIIRS (11.45 μm) between 0615 and 0801 UTC on 28 March 2014 (click image to enlarge).
When polar imagery is available from MODIS or VIIRS, it is overlaid on the GOES imagery which allows the forecaster to take advantage of the greater spatial resolution of the polar imagery. In the example shown above, there are GOES-13 images at 0615, 0631, and 0645 UTC, followed by a VIIRS image at 0655 UTC, two more GOES-13 images at 0715 and 0731 UTC, a MODIS image at 0740 UTC, and one more GOES-13 image at 0801 UTC. As the forecaster cycles through the images, you can envision how this capability would be beneficial. The increased spatial resolution from MODIS and VIIRS allows important details to be extracted which include the location and strength of updrafts/overshooting tops and the location where new convection is forming on the southwestern flank of the MCS. In addition, when deep convection is present, the parallax (GOES pixels are displaced slightly poleward from their correct position) that occurs with geostationary satellites is magnified and the polar imagery “corrects” the location for the forecaster. To see the full impact of these hybrid images, click on the image for a full resolution version.
AWIPS2 is currently being installed at NWS forecast offices throughout the country. +