Layered clouds and the Cloud Base Height product

After yesterday's West Coast scenario at the C&V desks (another post to come about that), today's domain has shifted to the east and central CONUS. A stubborn, slowing moving system continues to plod SE, bringing with it scattered showers and storms, along with a broad area of clouds in the lower Mississippi Valley. The satellite derived Cloud Base Height (CBH) product brought around an interesting perspective as forecasters began spinning up for the day.

As noted in the AWT Winter Experiment earlier this year, the CBH product does well in areas of single layer clouds. However, in the presence of multiple layers of clouds it tends to 'see' only the base of the top most layer, thereby overestimating the true base. Such was the situation again this morning, although a closer look actually provided many more details of the cloud environment.

20160818 1430 UTC Cloud Base Heights overlaid on GOES-13 visible imagery in AWIPS-2 D2D; dark blue < FL030, blue = FL030-060, light blue = FL060-090, cyan = FL090-120, green = FL120-150, light green = FL150-180, yellow = FL180-240, light orange = FL240-300, orange = FL300-360, red = FL360=420, and pink > FL420

Embedded convection down in central Texas resulted in some cirrus blowoff, visible in the reds and oranges. A higher cirrus layer also extended up through Arkansas. Near Memphis was the classic signature of transverse waves. The CBH product actually indicated lower ceiling heights (~6,000 feet) in the valleys and higher (16,000 feet) in the peaks of the waves. Further south into northern Lousiana was an area of scattered showers, where the CBH estimated ceilings of between 9,000 - 10,000 feet.

Lastly, there was a fog an low stratus deck in Oklahoma. The CBH identified this as having ceilings of >3000 feet. You will note that not all of these ceilings were picked up by the CBH product. This could be due to the time of day and transition between the night and day algorithm calculations. With addition of visible cloud properties, the algorithm has more data to work with as it estimates the ceilings.

The CBH product, while not particularly capturing the 'true' ceilings accurately in some cases, actually provided a detailed analysis of the cloud situation. It was also pretty accurate as compared to the observed flight rules at the time seen below.

20160818 1315 UTC visible imagery and observed flight rules. Noted cloud details from the CBH product are also included.

Having additional situational awareness about the current cloud situation can provide very valuable insight into future ceiling forecasts, particularly in the C&V grid editing process.