A mountain wave event impacted Colorado on 4 November 2017. A 100+ knot, westerly upper-level jet developed over the state during the night of the 3rd into the morning of the 4th. The strong winds aloft quickly mixed to the surface as the mountain wave took shape over the eastern mountains and adjacent eastern plains. A high wind warning was issued for the Palmer Divide south to the New Mexico border for the eastern mountains and adjacent plains for wind gusts up to 60 mph. Numerous reports of winds in excess of 60 mph were recorded. GOES-16 provided unique views of the mountain wave clouds associated with this event.

Lee wave clouds set up over eastern Colorado early on the 4th as the strong westerly flow interacted with the north-south oriented mountain ranges. These clouds are identified in GOES-16 10.3 um IR imagery as stationary and are relatively cold compared to other clouds in the region (Figure 1).

Figure 1: 4 November 2017 GOES-16 10.35 um IR Window over Colorado. Full res

The three water vapor channels from GOES-16 show expected subsidence immediately upstream from the wave cloud (warmer region; Fig. 2). Additionally, one can diagnose ripples, or small wavelength waves, in the clear air moisture fields, as well as on the top of the wave cloud at times. These features indicate potential turbulence for aircraft pilots.

Figure 2: 4 November 2017 GOES-16 Water Vapor Imagery centered over Colorado. Full res

The 0.64 um, 0.5 km VIS shows the ripples atop the wave clouds, along with the wave clouds themselves, with much more spatial detail (Fig 3).

Figure 3: 4 November 2017 GOES-16 0.64 um VIS over Colorado. Full res

The 1.3 um channel, which is sensitive to water vapor absorption in the lower atmosphere (where most of the moisture resides), highlights the mid/upper-level wave clouds clearly atop the dark background and other, less reflective clouds (Fig 4).

Figure 4: 4 November 2017 GOES-16 1.38 um Near-IR over Colorado. Full res

The 10.3 – 3.9 um difference also distinguishes the mountain wave clouds during the daytime. The reflectance of solar energy off of the small ice particles in the cloud (in addition to the longwave emission component) results in a warmer temperature in the 3.9 um channel versus the 10.3 um IR window, and therefore relatively high negative values when taking the difference.

Figure 5: 4 November 2017 GOES-16 10.3 – 3.9 um Difference over Colorado. Full res

-Bill Line, NWS

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