Monday, July 12, 2010

Tropics Still Quiet...

With the amount of SAL in the Atlantic basin, I'm not really surprised at the lack of activity... It has already started to dissipate, and we should continue to see that trend continue over the next week... All that rising motion (warm ocean water) in the Atlantic basin should slowly "mix out" the SAL... With the MJO pulse swinging into octave 1 again, and with it forecasted to swing out even more into octaves 1 & 2, I really think the tropics will pick up in the Atlantic basin in the next week or so (7-10 days)... Studies have shown that hurricanes are four times more likely in the Gulf of Mexico and the western Caribbean during the "rising" phase of the Madden-Julian Oscillation... I've talked about the MJO in fairly good detail before, but I'll cut and paste a section from my 2010 Atlantic Hurricane Season Thoughts/Ideas (From May 5th) on the 8 octaves related to forecasting tropical development in the Atlantic basin:

"7) MJO Forecast: As many of you know, an enhance in rising motions caused by the MJO pulse statically can lead to a 4 x likelihood of tropical development in the Gulf of Mexico and western Caribbean... Off the CPC site, you can get a very useful 15 day MJO index forecast and also the 40 day wave MJO index... To really simplify this, the MJO tends to organize in the Indian ocean where there is a lot of rising motion... As it moves across the Pacific, you can basically follow this rising motion through the 40 day wave and forecast it through the 15 day MJO forecast... When I talk about the 40 day wave I'm talking about how the MJO pulse typically takes 40 days to make it through all 8 octaves representing different areas of the globe... Of course it can move faster or slower depending on a lot of factors..

During an El Nino phase when you have warm waters in the Pacific, this MJO phase almost gets stuck because of the already warm waters and rising motions associated with it... If you think about it, a neutral phase is the best time to use this MJO 15 day forecast since it is not likely to be affected by the warm waters during El Nino or the cold waters during La Nina... In theory, the neutral phase should allow us the best forecast on the movement of the MJO pulse... Since we are now/shortly entering a neutral phase we can probably put a lot of stock into this 15 day forecast! Right now the MJO pulse is in octave 2 and about to enter octave 3... Again, this is really going to simplify things, but in general when the MJO pulse is in Octaves 3,4,5, & 6 you typically have quiet weather as far as hurricane activity is concerned in the Atlantic... When the MJO pulse enters 7, 8, 1, & 2 you typically have more active weather as far as hurricane activity is concerned in the Atlantic... I have found octaves 8,1, and 2 seem to be the best for development in the Atlantic, while octaves 7 and 3 are ok/average!

Is this perfect? Of course not, as I've seen hurricanes develop whether we have MJO rising motions or not... I could be wrong but I'm pretty sure hurricane Charley developed during a "sinking phase/pulse"... However, I've seen this work a lot (2008 season especially)and it will be interesting to track it currently since again we are entering a neutral phase... The 15 day forecast has the MJO pulse almost entering octave 7... So in about 20 days or so we should see enhanced rising motion associated with the MJO pulse in the Atlantic (entering octave 8)... Plus this rising motion should last about 20 days or so... Again, it typically take 40 days for the MJO pulse to move through all 8 octaves when things go smooth like you would typically see in a neutral phase... The precipitation graphical forecast shows the MJO pulse entering the Atlantic about 20 days out, so it will be interesting to see if it verifies... It does make a lot of sense! Also, it will be interesting to see if this will lead to some tropical activity in late May/early June? I know this is very complex and trust me I don't understand everything about it at all, but because of my good friend Justyn Jackson & my internet teacher Joe Bastardi, I have a decent grasp on this.... I hope it made some sense?"


  1. Right now is a perfect example of how you can not completely base your forecast off the MJO. We are in a supportive phase...but with all that dry air and shear it is going to be tough to develop a cyclone in the next 5 days at least. (I know you know this, but just pointing it out.)

  2. Like anything in weather forecasting, relying on one forecasting parameter is a setup for disaster! It would be like only looking at CAPE in severe weather forecasting... I do agree with you Ryan, as I stated in my post that I don't expect tropical activity for a week or so... The further out the MJO pulse goes from center, the more favorable it will become... On that same note, you can't just look at the MDR for tropical development, you have to be aware of home grown development as well...

  3. Also buddy, I think it's funny that today Joe Bastardi is now forecasting tropical activity in the next 7-10 days as well... Beat him by 12 hours or so! haha... I honestly just laugh, because obviously it just means I think A LOT like him now! :-)

  4. you are the bomb, Greg! i enjoy your analysis and am learning a lot from you. keep up the great posts, i'm looking forward to each one. and of course, the increase in activity! so long SAL!