WILL MJO PULSE RESULT IN BURST OF NAMED STORMS FOR THE ATLANTIC? WE ARE GOING TO FIND OUTSOON ENOUGH![]()
I wanted to write about a phenomenon that few people ever hear about except for those who really follow tropical weather. It is called the MJO for Madden-Julian Ocscillation. What is it? Here is a direct quote from the MJO resource page from the Climate Prediction Center's site
The MJO is an intraseasonal fluctuation or �wave� occurring in the global tropics. The MJO is responsible for the majority of weather variability in these regions and results in variations in several important atmospheric and oceanic parameters which include both lower- and upper-level wind speed and direction, cloudiness, rainfall, sea surface temperature (SST), and ocean surface evaporation. The MJO is a naturally occurring component of our coupled ocean-atmosphere system and the typical length of the MJO cycle or wave is approximately 30-60 days (Madden and Julian, 1971, 1972; Madden and Julian, 1994; Zhang, 2005).Another way to look at the MJO is that when it is favorable for convection we essentially have a period of favorable upward motion in the atmosphere. This then leads to increased convection which in turns favors the genesis of storms- and specifically, tropical cyclones. Computer models predict the progress of the MJO and can be helpful in understanding when a certain region of the tropics is likely to have conditions conducive for development. It is not a cure-all 100% piece of the puzzle but the MJO can be a key indicator that we are entering a period where tropical storm formation is more likely than not. Make sense so far? So, looking at the graphic I have posted, the browns and rust colors indicate sinking air and conditions generally unfavorable for tropical convection. The green areas, especially the darker greens, indicate large scale upward motion in the atmosphere and hence the possibility for ripe conditions aloft. The map shows the next 15 days as predicted by the GFS model. We can see that as we progress through the next two weeks, a strong pulse of upward motion moves in to the southeast Pacific and then in to the western Atlantic Basin- including the Gulf of Mexico. Here is another quote from the CPC site regarding the MJO's influence on tropical cyclone formation:
The MJO is known to modulate tropical cyclone activity in the Indian Ocean, Pacific Ocean, Gulf of Mexico, and Atlantic Ocean (Maloney and Hartmann, 2000a; Maloney and Hartmann, 2000b; Higgins and Shi, 2001). For example, although tropical cyclones occur throughout the Northern Hemisphere warm season (typically May-November) in both the Pacific and the Atlantic basins, in any given year there are periods of enhanced / suppressed activity within the season. The MJO modulates this activity (particularly for the strongest storms) by providing a large-scale environment that is favorable (unfavorable) for development. For example, westerly wind anomalies at the surface in and just behind the area of enhanced convection of the MJO may generate cyclonic (anticyclonic) rotation north (south) of the equator respectively (Figure 2). At the same time, in the upper levels, anticyclonic (cyclonic) rotation develops along and just behind the area of convection (Figure 2) resulting in a means to reduce vertical wind shear and increase upper-level divergence � both of which are favorable for tropical cyclone development and intensification. The strongest tropical cyclones tend to develop when the MJO favors enhanced precipitation. As the MJO progresses eastward, the favored region for tropical cyclone activity also shifts eastward from the Indian Ocean to the Pacific Ocean and eventually to the Atlantic Ocean (Figure 10). While this relationship appears robust, we caution that the MJO is one of many factors that contribute to the development of tropical cyclones. For example, it is well known that SSTs must be sufficiently warm and vertical wind shear must be sufficiently weak for tropical disturbances to form and persist.So what does this all mean for the next two weeks or even longer? It might turn out to mean absolutely nothing- and we don't see any additional development in the tropics. However, it more than likely indicates that we will see an increase in activity in the southeast Pacific first, followed by one or two tropical storms forming in the Atlantic- probably west of 60W longitude. The models are not indicating anything specific as of yet but with this pulse moving through, it may only be a matter of time until we see something significant develop. There is no way to know when where and how strong but this large piece of the tropical cyclone puzzle is interesting to monitor and helps to know when to really start looking. Climatologically speaking, the next two weeks would be a favored time of year anyway as we see a mini-spike in activity during this period over the last 100 years. The bottom line is that we continue to see a nice quiet tropics for the most part but IF something is going to come along and spoil everything, it is my opinion that it will happen within the next two weeks. This makes logical sense but is in no way a prediction on my part. The odds are that we will be just fine but again, I emphasize that IF there is going to be a hurricane problem for ANY land area, I think it will come between now and the end of the month. This sounds a little obvious considering that once we reach November the chances really diminish but this pulse is fairly strong in the models so we'll have to see what happens- if anything at all.!
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Interessant
Meer over de MJO -->
Wiki: MJO