Monsoon_Burst

See attached from Darwin profiler.  The 19Z 'flight' was recorded during  a
long period of heavy rain - I don't know how accurate is up near 250 hPa
but the general idea probably isn't too far off the mark.

Max wind gusts at Darwin Airport so far tonight 44 knots.

Andrew Tupper

John  McBride

Following up from Andrew's image on the very deep westerly flow at Darwin:

 Wasyl Drosdowsky wrote a paper a few years ago on the interannual variability of the monossn at Darwin (Drosdowsky, W., 1996: Variability of the Australian Summer Monsoon at Darwin: 1957-1992. J. Climate, 9, 85-96.).  One of his main points was that a major monsoon burst involved deep westerlies, up to about the 300 hPa level.  This was observed also during the monsoon bursts in the 1986-87 AMEX experiemnbt: see for example Fig. 12 of Gunn, B.W., J.L.McBride, G.J.Holland, T.D.Keenan, N.E.Davidson and H.H.Hendon, 1989: The Australian Summer Monsoon Circulation during AMEX Phase II.  Mon. Wea. Rev.,  117, 2554-2574.

The relevance of this is that we have had this (apparently MJO-inspired) monsoon burst since about the 1st or 2nd of Febrary; but over that first week there were no deep westerlies.

Something happened a few days ago, whereby the westerly burst is deep.  On my web-page I have put up a sequence of satellite image, 850 flow and 850-500 Deep-layer mean for two days: 00 UTC 7 Feb and 00 UTC 9 Feb.  If you look at the deep-layer mean, you see an enormous difference.   On the later day (the 9th) there is a deep westerly flow averaging (over the depth) 20-40 kts.  Two day previously the depth-averaged flow was 10-15 kt easterly.

So... something happened between 00 UTC 7 Feb and 00UTC 9 Feb..... What?.... Stay tuned... I'm going to have to give this one some thought.... (But in the meantime, I'm confident our mate Noel will have something to say)

John McB
 
 

850_0202_07_0000.gif	850_0202_09_0000.gif	850_500_DLM_0202_07_0000.gif	850_500_DLM_0202_09_0000.gif	satpic0202_06_2100.gif
satpic0202_09_0000.gif