morning glory

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A characteristic sudden squall often experienced in the southern Gulf of Carpentaria in Australia, but suspected to exist in less extreme form elsewhere in the world. Often accompanied by one or more long roll clouds that typically travel at 40–50 km h−1, each with associated subsidiary gusts. The strongest morning glories arise through the interaction of sea-breezes that initially propagate towards one another from both sides of the Cape York Peninsula. When they interact, they create a hydraulic jump, similar to a river bore, with an abrupt uplift at the leading edge, and a corresponding pressure jump of about 1 hPa. The morning glory itself propagates in the same direction as the stronger sea-breeze (usually that from the Pacific Ocean). Wave motion behind the front gives rise to the bands of cloud, but after the glory has passed there is a persistent increase in the depth of the low-level cold air and in atmospheric pressure.

Similar interaction may occur between a sea-breeze front and a cold front, and such southerly morning glories have been observed in association with cold fronts moving north or north-east over northern Australia. See also undular bore.

Subjects: Meteorology and Climatology.

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