Undular bores over the Gulf of Maine

April 27th, 2017 |

** The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. **

As pointed out by NWS Caribou:



numerous packets of wave clouds associated with undular bores were seen on GOES-16 Visible (0.64 µm) imagery over the Gulf of Maine on the morning of 27 April 2017. A longer animation with surface wind plots (below; also available as an MP4 animation) revealed the presence of 3 distinct bore structures: the largest and most well-defined which was moving eastward; a second (and much smaller) off the coast of Cape Cod which was moving southeastward; and a third which as moving northwestward  (and eventually intersected the northern end of the primary eastward-moving bore).

GOES-16 Visible (0.64 µm) images, with surface winds (knots) plotted in cyan [click to play animation]

GOES-16 Visible (0.64 µm) images, with surface winds (knots) plotted in cyan [click to play animation]

A comparison of GOES-16 and GOES-13 (GOES-East) Visible images (below; also available as an MP4 animation) showed that undular bore wave cloud structures were more clearly clearly seen with the higher spatial spatial resolution of GOES-16 (0.5 km at satellite sub-point, vs 1.0 km for GOES-13). The comparison also showed that the visible imagery from GOES-13 (launched in May 2006, and operational as GOES-East since April 2010) was not as bright as that from GOES-16; this is due to the fact that the performance of GOES visible detectors tends to degrade over time.

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images [click to play animation]

GOES-16 Visible (0.64 µm, left) and GOES-13 Visible (0.63 µm, right) images [click to play animation]

So what caused these undular bores to form and propagate across the Gulf of Maine? Such gravity waves are ducted within strong temperature inversions — and rawinsonde data from Chatham, Massachusetts and Yarmouth, Nova Scotia indicated that such inversions were in place above the surface that morning. The northwestward-moving bore could have been initiated by surface outflow from thunderstorms associated with a mid-latitude cyclone (which was producing storm force and gale force winds: surface analyses) — GOES-16 Infrared Window (10.3 µm) images (below; also available as an 88 Mbyte animated GIF) showed these thunderstorms which developed within the warm sector of the coastal low pressure system. However, the forcing mechanism(s) that generated the eastward and southeastward moving bores remains somewhat of a mystery.

GOES-16 Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 Infrared Window (10.3 µm) images [click to play MP4 animation]

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