Imagine the clouds for a moment…
Probably you’re thinking of looking up at a few wisps of cirrus on a sunny day, or driving through a fog bank early one morning, or flying down the road in pursuit of rolling storm clouds. But if you ask a pilot the same question, he or she will no doubt recall staring at a building thunderstorm straight in the face and hoping they can zip over the top it before the tops get too high. Else perhaps they’ll remember wondering just how low the ceilings will be as they make their approach into San Francisco.
It’s all about the heights.
In fact, in the vast majority of the products issued by the AWC forecasters are required to list both bases and tops of each threat. This is where the Cloud Top Height imagery (from the ACHA suite) really will come in handy. Derived by a fairly complex algorithm, it simply generates a satellite based estimate of the heights of the cloud tops (in feet). With that data and several specifically designed color bars in hand, it can be molded into an aviation specific forecasting tool.
Shown here are two versions of the Cloud Top Height imagery from 1445 UTC this morning. This first version is used as a convective tool, and flattens out any cloud tops below 18,000 feet, or essentially any clouds below Class A airspace. With lightning (GLD and NLDN strikes) overlaid, the higher clouds associated with convection are easily visible. Note the storms just off the Gulf Coast and the associated convective SIGMET that was issued. With far fewer observations over the water, the additional satellite information is very valuable, particularly for the helicopter operations in this area (did you know there are roughly 650,000 chopper flights a day over the Gulf?!).
The second version (below) is used as a tool for better identifying lower clouds. It’s the exact same image as above, but with cloud tops above 18,000 feet, or Class A airspace, flattened out. Instead of highlighting convection, it instead highlights lower features, like the thick mid-level stratus deck off the coast of New Jersey and Maryland, and also the stratus clouds producing snow over the Great Lakes. Overlaid with IFR and mountain obscuration AIRMETs, as well as observed ceilings, it can aid in identifying low ceilings. However, aside from this, it can also be a useful tool for estimating the heights of lower cloud layers that may be producing icing or turbulence.
Again, it’s all in the heights. Whether one is forecasting for icing or winds or convection, it is vitally important to know where exactly an aircraft may encounter those threats, especially in otherwise data sparse areas like over the ocean. In fact, while this post actually highlights the GOES version of the imagery, it is also being generated over a global and northern hemispheric domain to address that very issue!
Thanks for reading!
~Amanda Terborg, AWC Satellite Liaison
Can you describe what forecast products this would be an input for and where does it work best (over land or water)
On the convective side, it would be used to identify tops for Convective SIGMETs. However, it can also be used to identify tops for layers of turbulence and icing in G-AIRMETS and/or SIGMETS for these same threats.
Also, I don’t know that there is a difference in actual performance over land vs. water, but it definitely provides the most benefit to the forecasters out over the oceans.
Amanda, great write up. Are these products available for ingest into AWIPS for WFOs? Thanks!
Hi Adam. Thanks for your comment.
Yes and no… this blog post features cloud tops/altitude in feet, which are not yet in AWIPS, though easily could be if you are interested. Else, the cloud tops in meters ARE available for AWIPS via the CIMSS LDM. Also, the color bars used for the post are only available for the AWC at the moment but I’m happy to share.