Wednesday Observations 6/4: The Day with No Radar

 Today in the testbed all three forecaster groups were told to act as if they did not have any radar at their disposal, with offices in Albuquerque, Midland, and St. Louis.

Starting the day in Albuquerque CWA...The forecasters were quick to use OCTANE and GREMLIN to identify the strongest storms, and they picked out a storm just west of the city of Albuquerque. Increasing reflectivity values from GREMLIN, along with divergence signals from OCTANE Speed and the Cloud-Top Divergence products. Animation of GREMLIN and OCTANE (with radar included) are included below. The forecasters also leveraged the 12Z sounding from ABQ with its freezing levels, mid level lapse rates, and the wind profile.

GREMLIN 4 panel with the MESO scene (upper left), CONUS (lower right), MRMS composite reflectivity (upper right), and ABI MESO Clean-IR (lower left).

OCTANE with Speed (upper left), and the cloud top cooling and divergence flavors.

12Z Sounding from ABQ.

As the forecasters debated on issuing a warning, the 'real' NWS Albuquerque office issued a severe thunderstorm warning for 60 mph winds and 1 inch hail.

After some additional discussion, the HWT 'fake' Albuquerque office issued their own severe thunderstorm warning, also for 60 mph winds and 1 inch hail. They used LightningCast probabilities and ENTLN/NLDN flash locations to identify the thunderstorm 'core'.

Shifting to the Midland CWA...The forecasters in this office were watching for initiating convection just across the US-Mexico border in the higher elevations west of the Big-Bend region. There was discussion of the environment and how supportive it was for deep convection, especially related to the moisture/instability return from the Gulf during the forecast period.

OCTANE speed, cloud top divergence, and cloud top cooling products all showed the first robust updraft tapping into this instability with increasing speeds and strong cloud top cooling signatures followed by cloud top divergence.

The GREMLIN product from the MESO scene also reflected this cooling signature and strong gradients with increasing simulated reflectivity values. These values continued to increase until the HWT MAF office issued a severe thunderstorm warning. With 5-10 minutes of the warning, GREMLIN exceeded 60 dBZ. Another storm to the southeast also initiated and quickly intensified, with GREMLIN values also exceeding 60 dBZ.

We talked about the skill of GREMLIN to identify discrete convection and how realistic the values compared to our expectations from this machine-learning, satellite-based perspective. The takeaway from the forecasters was that GREMLIN has an easier time showing greater reflectivity values in discrete convective cores than multi-cell convection. 

I also looked at the ALPW product, and noted that the surface to 850mb layer showed the returning moisture, though I wonder if forecasters would like to see more frequent updates than hourly. I didn't have the chance to ask about this due to the active discussions during operations, but this seems like it would be the 'ideal' case since there was little cloud cover so sampling the lowest layers would be easier for the polar-orbiting sounders. How much this can help NWS forecasters searching for observations in remote areas is to be determined, but the product seemed to fit the conceptual model for the case.

-Dr. Thunder