CI over New York

Another busy day for the EWP forecasters, as severe thunderstorms have erupted over the mid-Atlantic region. As so, screen captures from AWIPS have been tough to come by. Therefore, these next screen shots come from NAWIPS.

SATCAST CI has performed very well over the New York and Pennsylvania areas this afternoon. The following satellite image is from 1945 UTC. SATCAST forecasted CI over south central New York. Approximately 13 minutes later, radar reflectivity exceeded 35 dBZ on the base scan. While not the largest lead time, in another large CAPE environment, SATCAST is performing well.


SATCAST is performing quite well today pinpointing areas where storms will develop in the future. Even in Florida, where the dynamics are not as impressive, storms developed with help from convergence by the sea breeze, and SATCAST provided a very good forecast.

Pseudo-GLM Perspective on Oklahoma Storms

This week started with two very active days within the OUN CWA which allowed EWP forecasters to incorporate pseudo-GLM products into their warning operations. Despite the dense radar coverage, forecasters used the total lightning products and provided some interesting insights.

Day One – Monday 23 May
Two storms developed in Northwest Oklahoma and exhibited very different lightning and radar signatures. The northern storm formed in Major County, exhibited very large IC flash rates, and produced large hail. Conversely, the flash densities were much smaller in the southern storm which produced a brief tornado. This observation illustrated the variability between two storms that occurred in a similar environment and emphasizes the importance of continued research on the relationships between lightning and radar within individual storms.


The greatest pseudo-GLM densities (> 30 flashes/ km/min) accompanied a large storm cluster which followed the merger of two strong storms. The 3D-Var products indicated a strong updraft throughout the length of this storm cluster which helps explain the high flash rates.


Day Two – Tuesday 24 May
The high risk forecast and model-derived products all indicated a very active day was in store. The CI products identified the initial convection 15-20 minutes prior to the first pseudo-GLM signatures. Flash rates increased rapidly in the earliest convection, and the first tornadic storm occurred as two isolated storms merged near Weatherford, OK. Flash rates spiked as the two storms merged, coincident with an increase in mid-level rotation. These combined observations increased forecaster confidence as they issued the first tornado warning of the day.


The EWP forecasters observed that the greatest pseudo-GLM flash densities consistently tracked ahead of the main updraft and actually helped to identify changes in storm motion. On several occasions the pseudo-GLM densities also indicated that the main center of rotation was shifting prior to the identification of new rotation tracks by the multi-radar multi-sensor algorithms.


Although lightning jumps preceded many of the tornados, forecasters commented that they would have liked to examine time trends for individual storms. This has been a common theme during previous spring experiments, and was not fully accounted for by plotting swaths of the pseudo-GLM products.


- Scott Rudlosky

Overshooting tops are being detected with the severe/tor warned storms over Indiana

The UWOTTC algorithm is consistently identifying overshooting tops over the state of Indiana. The above sequence of images (valid from 1902 UTC to 1945 UTC) shows numerous overshooting tops and their associated visible imagery counterparts. No thermal couplets have been detected with any severe storms as of yet, but this is not a surprise with how hard it is to detect the couplet features with the course resolution of GOES imagery. ABI is how long away??? See NWS all hazards image capture (top image) to see associated concurrent warnings.

UWCI consistently capturing best developing convection in central and north central Arkansas

The above sequence of images shows how UWCI nowcasts (upper right panel of images) are consistently picking out the best developing convection. Without the bane of cirrus affecting the algorithm processing, cases such as this show that satellite products can be of good use for situational awareness.

SATCAST CI detected underneath cold core low

Oklahoma was under the gun yesterday, but is under a completely different convective regime today. As the cold core low continues to shift eastward, clear morning skies have created an area of convective instability that has led to convective shower development.

SATCAST has been developed to try and diagnose convection of all types, not necessarily areas of severe weather. SATCAST forecasted CI in northern Oklahoma at 1832 UTC (upper panel of top image). 38 minutes later at 1910 UTC, radar reflectivity exceeded 35 dBZ at -10 C (bottom left panel of bottom image). No severe weather will come of this activity, yet it provides forecasters with the ability to let the public know via short term forecasts that convective showers are developing, and changes to outdoor plans may need to be changed.

Overshooting tops detected over central MO

Overshooting tops are being detected in central MO. The above image (valid 1855 UTC) and an earlier image shown below (valid 1832 UTC) show the OT detections (red spots) superimposed over their associated regions in the visible.

These OTs are associated with storms warranting tornado warnings over the same area. See warning image below. No thermal couplet signatures have been detected as of yet.

UWCI also capturing developing convection in central IL

UWCI (upper right panel of 4 panel display) was also capturing developing convection in central Illinois with an initial nowcast of 'CI Likely' and 'CI Occurring' valid during the 1625 UTC satellite scan (above image). This developing storm later produced it's first CG lightning strikes at 1700 UTC (bottom right panel of following image).

The image below is just shown for the purpose of stating that UWCI is picking out the storms along the developing line that are continuing to thrive. Image below is valid at 1815 UTC.

NSSL-WRF simulated GOES-R products

GOES-R visiting scientists discussed with NSSL scientist Jack Kain about the possibility of creating NSSL-WRF simulated GOES-R convective initiation products. Since the model has very short time-steps (24 seconds), following cloud 'objects' via the SATCAST overlap method should be relatively simple. From this, a cloud top-cooling rate and other CI fields, such as cloud-top glaciation, would be easy to produce. Hopefully in the future we may be able to start producing this and other unique GOES-R products that we can not currently produce from observational sensors.

UWCI capturing initiating convection in S MO

UWCI (upper right of four panel) captured convection initiating in south central Missouri. Looking at the bottom image posted above, which was valid 1725 UTC, we get 'CI likely' along the southern end of a building convective line. The very top image is valid 50 minutes later when the storm has matured and produced the first signs of CG lightning strikes (lower right panel). The upper section of the newly convective line was labeled with ice cloud type earlier in it's development, therefore not allowing UWCI to be produced for this part of the line.

CI beginning to occur over south central MO

Despite EWP operations being canceled for today, monitoring of experimental products continues. As the strong cold core upper level low continues to churn eastward, new thunderstorm development continues to erupt in Missouri as daytime heating combined with mid-level cold air advection erode the cap. SATCAST CI has recently forecasted new convection to develop in this region. An example is presented in the images below:

In the upper image, SATCAST is predicting convection to fire somewhere near the circled area at 1645 UTC, as SATCAST currently predicts which cloud objects are forecast to initiate, but now exactly where it will do so. Not there is no convection currently at the same time (lower right panel in top image).

In the lower image, radar imagery shows greater than 35 dBZ at 1726 UTC, approximately a 41 minute lead time. No lightning had been generated as yet, but the storms to the north have quickly become severe, and it sure appears as storms form further south, that they will also become severe.

In a future blog post, we will try to look at other areas of the country where severe weather is not anticipated if the weather cooperates.