Nearcast training for severe

UW-CIMSS scientist Ralph Petersen explaining the Nearcast product to EFP participants
This morning UW-CIMSS scientists Ralph Petersen and Bob Aune sat down with the EFP's severe desk to help train the participants on how to use the Nearcast product during morning forecast operations. UW-CIMSS provides us with 10 fields from the Nearcast product, which includes individual layers of theta-e and preciptable water (PW), which are then differenced to provide the differential theta-e and PW water fields that we typically use for forecasts. The most effective way to help forecasters understand what they are looking at in these differential fields is to start with the individual layer PW and theta-e fields and then the forecaster can mentally calculate the differences and compare to what the product is showing them. Ralph and Bob helped the participants understand how the Nearcast can assist them in making their forecasts by pointing out that the Nearcast fields will show you where relatively convectively stable and unstable areas are. Because no forcing mechanisms are included within the Nearcast's output, it doesn't guarantee where convection will occur, but it can help narrow down where you should be focusing your attention. If there is an area of strongly stable air, you're not likely to have any deep convection, even if there is some sort of light forcing present. This may be especially useful within SPC operations for forecasters issuing mesoscale discussions (MD) to determine where a severe thunderstorm or tornado watch will or will not be needed. It may also be useful during the early afternoon convective outlook updates to help trim areas that will not be expected to have thunderstorms later during that day. Following the group training, Steve Weiss (SPC SOO) asked if I would be willing to work with the forecasters in operations this summer in exposing this product to them. In addition, we expect to provide a training session within the SPC's bi-annual forecaster training this fall to help expose all of the SPC personnel to the product.

Impressions of a first day...

Sitting through the various discussions on the likelihood of the development of CI, it quickly became apparent that the low pressure system moving eastward along the Canadian border was garnering plenty of interest from the 3 main desks located in the HWT. Watching it through the morning with the morning shift of EWP forecasters, the area remained on the "it's going to be an interesting day" and "it didn't really produce much" line, due to the favorable conditions in moisture and afternoon heating being held back by a pretty definite cap that may or may not break sometime before 00Z. Moving in the afternoon, warning portion of the EWP program, conditions remain decent, yet the cap is still firmly in place. Interest in the CI products is in the forefront of the forecaster's minds and the handy, four panel, product is up on the main screens of the AWIPS displays of all four forecasters present.

In all, so far, SATCAST has been indicating CI sporadically in and around the North Plains for most of the afternoon. Taking into account the capped environment, the algorithm has been picking up the signal of rapidly growing clouds, as it is trained to do, yet convection has been slow to develop in CWA's of Grand Forks and Duluth. This has resulted in some red objects (in the area of interest) that will likely not verify, due to the capped environment and some interfering cirrus atop the low pressure system as it moves east.

So far, the forecasters have still indicated an interest in the product as the afternoon has progressed. Being able to look at the data in a loop has allowed for an awareness of the environment, allowing for the forecaster to be "queued in" to an area of interest. As an example, the UAH CI algorithm has indicated a consistent CI signal moving across western North Dakota that verified about 35 minutes later on radar (according to the notes of forecasters assigned to the Grand Forks CWA).

It is still early, we will see how things evolve after a quick dinner break..

Nearcast in short-term warning operations

EWP forecaster issuing an experimental severe weather outlook using the Nearcast output.
EWP forecasters have come up with some novel ways to utilize the Nearcast differential precipitable water/theta-e forecasts within their warning operations. Generally we think of the Nearcast as a forecast tool, but the EWP forecasters have been using it to issue warnings and severe weather statements (see image above). Forecasters have been analyzing increased near-storm convective instability as depicted in the 0-2 hour forecasts from the Nearcast product to help increase their confidence that the storm will intensify. Conversely, the Nearcast is very useful to show when storms will die if the storm is expected to move into an area with very low convective instability or dryer atmospheric columns. This is another example of how forecasters will find some additional utility of these experimental products that the developers may not have originally intended.

Final week of the experiment...

Today marks the first day of the 5th and final week of this year's Spring Experiment. This week the EWP rejoins the EFP from its week off and resumes normal activities. Today the EWP will be providing forecasters with a load of training material as they prepare to use the experimental products during real-time forecast/warning operations. Following the 4-hour PowerPoint session we will have the forecasters work through a WES case to get familiar with where the products are, what they look like and how to use them within their AWIPS workstations.

UW Overshooting Top Algorithm Hits Storm Prior to Springfield, MA Tornado

Yesterday, 1 June 2011, climatologically rare tornadoes hit New England. The University of Wisconsin Overshooting Top algorithm identified an overshooting top with a severe thunderstorm at 2002 UTC 1 June 2011, just west of Springfield, MA (right). The overshooting top magnitude is filled atop the GOES visible imagery. The overshooting top identification occurred 28 minutes ahead of the first tornado report in Westfield, MA at 2030 UTC (a western suburb of Springfield).

UW Nearcast Product and Developing Convection

The GOES Sounder Nearcasting product is being used today on the EFP CI-desk to identify possible forcing mechanisms for the deep convection. In the image below the nearcasting theta-e difference is shown, valid 1700 UTC 01 June 2011. Strong convection has been ongoing and continually developing in eastern to north-central Kansas along the minimum (maximum instability) and northeastward toward the strong gradient in the nearcasting theta-e difference. It was noted this gradient is also coincident with a strong dewpoint gradient at 850 hPa. It is believed southerly flow across this gradient is helping force the convection. Further east across the Mid Atlantic region, convection was developing largely in the minimum of the theta-e difference, with a strong gradient to the west as low-level moisture decreases behind the front. It has also been noted there are many other areas of strong potential instability indicated by the nearcasting product, however there is not deep convection associated with many of these areas. One hypothesis is there needs to be not only instability present, but also a forcing mechanism. Possible forcing mechanisms maybe inferred by a strong gradient in the instability indicated by the nearcasting product, suggestion strong temperature and/or moisture advection.

NSSL-WRF Simulated ABI Imagery and CI forecast

This morning on the EFP CI-desk, the simulated ABI imagery from the NSSL-WRF provided guidance on location and timing of initial CI location for many of the forecasters. As can be seen in the image below, there was a tight cluster of forecasted first CI location points over the higher terrain of northern New Mexico. The simulated ABI band 13 image valid at 1900 UTC shows newly developing convention over northern New Mexico. A few other forecasters favored convective initiation along the moisture gradient in the lower troposphere in eastern Kansas. (Ongoing storms northwest of Salina, Kansas were excluded from the forecast area.)

UW CTC Highlights Most Rapid Development of Convective Line

The UW Cloud-Top Cooling (CTC) rate cannot only be used to nowcast convection initiation, but also highlight the most rapid vertical growth along a line of developing convective clouds. Below is the GOES visible imagery/UW CTC valid at 1732 UTC 31 May 2011 and base radar reflectivity at the same time. The entire line of towering cumulus over central Michigan looks similar on visible imagery, but the UW CTC highlights (green circle) the most rapidly growing and hence precipitating portion of the line (also green circle).

Simulated ABI Radiances Compared to GOES Observations

This week there is no EWP running so all support is geared towards the EFP. Early Tuesday on the CI desk of EFP, the NSSL-WRF simulated ABI radiances were compared to the current GOES observations for judging the timing/placement of the upper level vorticity maxima/upper level dry intrusion over the Central US, as well as impact of cloud cover on convective intiation forecasts over the western Great Lakes.

Below are the 15 UTC simulated ABI brightness temperatures (top) and observed GOES brightness temperatures (bottom). The consensus of the forecasters on the CI desk was the NSSL-WRF had excellent placement of the upper level vorticity as depicted by the water vapor channels. On the other hand, the NSSL-WRF struggled to capture the intensity and magnitude of a band of clouds and decaying convection over the Upper Mississippi Valley/western Great Lakes. The images below show the GOES observed clouds are much more expansive and have colder brightness temperatures than the simulated ABI clouds from the NSSL-WRF. Discussion is ongoing on how these clouds will impact convective initiation timing and location later today.







FLASH utility to toggle between images

Discussing RGB imagery

A forecaster from Austria visited the HWT this week and I asked him to give a short briefing on the use of satellite data over Europe to the EWP forecasters to help them understand some of the capabilities that we will have with GOES-R with respect to the utility of RGB imagery. Over Europe, the use of radar and surface data is relatively limited to the level that we use it here in the US because of the difficulty in obtaining data from the private companies, not to mention other neighboring countries. Scientists and forecasters in Europe have found innovative ways to combine imagery into products that help identify surface features, cloud types, volcanic ash, as well as moisture and jet streaks. These techniques are not commonly used within normal WFO operations within the US, mainly because of the lack of spectral data available from our current operational satellites. EWP forecasters got the chance to have a look at what they use routinely over Europe and found the briefing very interesting and are excited to use this sort of information in the future.