The Australian Bureau of Meteorology keep substantial records, and the BOM's weather-recording ability is far-reaching. The BOM's synoptic charts reach extends into the MH370 search zone - and their archived records of their observations are publically and easily accessible.
On the webpage below, one can acquire the archived records of the synoptic charts for Australia, whereby the area of the "7th arc" and the current search zone are covered by the synoptic charts.
If one selects the archived period from the 8th March 2014 to say, the 17th March 2014 - then that would encompass the first 9 days after MH370's disappearance (incidentally, the synoptic chart for 8th March is timed at 0000 UTC - which coincides very closely with the flight end time).
From that archive (from which you can select individual chart images, or a loop), we see that MH370 - if it crashed in the current search zone - crashed in an area which was essentially a fairly calm centre of a high pressure system.
The weather patterns in March in this region are fairly stable, slow-moving high-pressure systems.
Naturally, the winds are stronger the further they are from the centre of the high - but in general the winds are steady and consistent.
The prevailing surface winds would be the primary factor affecting the movement of MH370 wreckage in the fortnight to a month following the crash.
After that period, sea currents could have had increasing input into the wreckage movement. In general though, the primary sea currents in the Southern Indian Ocean, follow a counter-clockwise pattern.
The weather pattern for the current search zone was quite steady and stable for more than a week following the crash day.
This was the period when there was no air searching of this zone, the searching was concentrated around SE Asia. The search did not extend to the Southern Indian Ocean until 17th March 2014.
Thus, there were 9 days when there was no search activity in the zone where the ATSB is now convinced the aircraft was lost.
During that 9 days, the current search zone was subject to South-Westerly winds in the area below about 32-33 deg S - progressing to moderate-strength Southerly winds between the current search zone and the W.A. coast - and increasingly stronger Easterly winds in the Northern sector of the search zone, and closer to the Northern part of the W.A. coast.
In effect - if the flight crashed in the Southern sector of the current search zone, any remnant floating wreckage - of which there would have been enough to be found by air observations - would have commenced its movement in a North-Easterly direction towards the W.A. coast.
However, after several days, the wreckage movement would have then been Northwards, then Westwards, as the stronger Easterly winds in the Northern sector would have then been speeding up the wreckage movement - away from the W.A. coast - and away from the aerial and sea search efforts, that have been transferred to the Southern Indian Ocean, from the 17th March onwards.
IF the flight had crashed even further North, on the Northern edge of the calculated search zone, then the Westwards movement of the wreckage would have been immediate and even faster than if the flight crashed in the extreme South of the search zone.
The point I am making is that the fact that no floating wreckage that could ever be confirmed that it came from MH370, leads one to consider that a more Northerly crash site has a higher probability, than a deep Southerly crash site.
If the crash site was well to the South - and taking into account the 9 days delay in searching the Southern Indian Ocean - then the possibility of remnant floating wreckage being sighted in the initial SIO searches (both aerial and sea), would have been much higher, because the weather patterns would have favoured the movement of the wreckage towards the W.A. coast, even if only for the first fortnight.
There is also the interesting feature of the Indian Ocean Gyre rubbish patch. This rubbish patch was only discovered in 2010, and it circulates counter-clockwise with the IOG - with the rubbish seemingly taking 6 years to do a full circle of the Gyre - and with the likelihood that rubbish reaching the centre of the Gyre, in the central section of the Southern Indian Ocean, could stay in that region indefinitely.
BOM - Synoptic charts archive