ETT Model Fields 0001 UTC 07/08/2005 to 1200 UTC 08/08/2005

This sequence shows water vapour and infra red imagery from 0000UTC on 7 August to 1200 UTC on 8 August 2004. The sequence shows the re-intensification phase when ex-hurricane Alex engaged with the upper trough and rapidly developed in to a vigorous depression.

Is this 1000 height?.

The height of 1000 hPa illustrates the rapid development of the depression during the re-intensification phase.

At the start of the sequence the 500 hPa contours show a large upper low south-west of Iceland. As ex-hurricane Alex moves across the Atlantic the trough originally on the south-west quadrant of upper low extends southwards and sharpens.

As with the 500hPa contours the 300 hPa contours show a large upper low south-west of Iceland. As ex-hurricane Alex moves across the Atlantic the trough originally on the south-west quadrant of upper low extends southwards and sharpens.

The jet stream on the western side of the upper low accelerates and the trough engages with the ex-hurricane and a rapidly deepening depression results.

The height of PV=1 unfortunately as the dry stratospheric air descends at the base of the trough the height of PV=1 contours get cut-off! However, it can be seen prior to this that there is an intense are of PV associated with the dry intrusion on the southern side of the depression.

The 850 hPa theta contours, as expected, show a tight gradients in association with the warm and cold fronts. The gradient is more marked in association with the cold front as the cold air plunges southwards to the rear of the depression.

At the beginning of this sequence the isotachs show small areas of maximum jet speed of just over 60 ms^-1. As the jet stream propogates it accelerates showing a peak of greater than 65 ms^-1.