monsoon trough question

[weatherwindow]

monsoon troughs exist in several area around the world....this question concerns only the semi-permanent eastern pacific monsoon trough, off the west coast of central/south america....that said, this trough occasionally, intrudes into the southwest and, even less frequently, into the western caribbean. these intrusions tend to occur early(may, june) and late(late sept, oct) in the season...even less frequently, the vorticity involved in the monsoon circulation is involved, directly or together with other factors, in tropical cyclogenesis in the caribbean, the latest example being wilma...my questions are: 1) what synoptic setup presages the movement of the trough into the carib...2) why are these intrusions relatively rare.....thanks for everyones assistance in advance.....rich

[philnyc]

Hi Rich,
That's a great question and one complex situation. I have notes on this somewhere, so I'll try to find them and get back to you, but I'm not sure when yet. Since the monsoon trough always works with the ITCZ, I would start by looking at the climatological mean vector winds and surface pressures from the western Caribean to the east Pacific from 30S to 30N. You'd probaby want to build charts for each month from June to November. Then you could look at the same charts from 2005 when Wilma was active, and then the matching synoptic charts at that time. That's where I'd start anyway.

[weatherwindow]

thanks phil....anymore that you may find will be greatly appreciated...if anyone could, graphically or in text, just describe the synoptic setup in the eastern pacific and sw caribbean in the days prior to the birth of wilma, it would give me a lot of insight into the problem....thanks again rich