Undular bore approaching Puerto Rico

March 14th, 2013 |
GOES-13 0.63 µm visible channel images (click image to play animation)

GOES-13 0.63 µm visible channel images (click image to play animation)

Hat tip to Luis Rosa at the National Weather Service forecast office at San Juan, who alerted us to the presence of an undular bore that was moving southward toward Puerto Rico on 14 March 2013. The southward propagation of the wave clouds associated with the bore can be seen on McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above; click image to play animation). The passage of the bore also seemed to have an effect on the erosion of the marine boundary layer stratocumulus clouds.

An AWIPS image of 1-km resolution POES AVHRR 0.86 µm visible channel data with overlays of surface reports and the surface analysis (below) showed that a cold front was situated about 500 miles northwest of Puerto Rico — so the undular bore was located far in advance of this frontal boundary. As seen on the animation of GOES-13 visible images above, the wave clouds of the bore had dissipated by the time of the AVHRR image (17:38 UTC); at St. Thomas, Virgin Islands (station identifier TIST) the winds briefly shifted to northeasterly at 18-19 UTC, though it is unknown whether this wind shift was related to the arrival of the bore.

POES AVHRRR 0.86 µm visible channel image with surface reports and surface analysis

POES AVHRRR 0.86 µm visible channel image with surface reports and surface analysis