Monday, December 19, 2011

Can't let go

Here are the current Meteosat water vapor channel and MIMIC total precipitable water satellite images:
Looking at these, you might say that while by now the MJO should have moved on across the Pacific, it seems it hasn't; the center of convection seems to be somewhere in the Maritime Continent (aka Indonesia), with the eastern Indian ocean still being somewhat active, despite the title of my last post. The RMM index would agree with you. By that measure, the MJO continues to tool around somewhere between phase 4 and 5, unable to decide if it wants to move on east, go backwards, or die altogether:
Consistent with this the westerly wind anomalies are persisting - actually picking up again - over the Indian ocean:
And the recent soundings at Addu Atoll, such as the latest one, look not too far off what one would expect with the active phase - something like what we saw in the buildup. Not really busting loose, but not far from it. High humidity (consistent with the MIMIC picture), with dew point not much less than temperature, and healthy westerlies in the lower troposphere: Why can't the MJO make up its mind? What's going on?
This is not too uncommon really. In fact the spectacular behavior we had for the first two months of DYNAMO - with two healthy MJO cycles coming through like clockwork in two months - was somewhat unusual. What's interesting is that the forecast models reasonably well predicted this current slowdown (though perhaps the amplitude is staying a little stronger than predicted). What did they see? What atmospheric conditions cause the MJO to either move forward or stall, or to strengthen or die?


  1. I'm not sure I would say that the models did a good job predicting the slowdown. It seems that every time I look at the forecasted RMM the models are always trying to kill the amplitude as well as the eastward propagation. It's as if they are predicting a slowdown more often than not.

    I think this has a lot to do with something Dave Raymond suggested in a paper on moisture modes and the MJO. His results seem to say that the GFS is unable to support moisture modes because the model physics won't allow a net import of moisture into the column over an extended period.

    I have a suspicion that other operational models may have a similar issue. However, I also remember the initiation of the current event was predicted rather well, so there's got to be a lot more to the models' performance in regards to the MJO.

  2. The stopped clock is right twice a day theory eh? Well there may be a little truth to it, but as you say I think the models - at least some of them - deserve a little more credit than that.