While a pretty large EWB was taking place, SOI values were negative when they should've been positive. Easterlies are usually dominant across the equatorial pacific when the pressures are lower in Darwin and higher in Tahiti (positive SOI), and vice versa in regards to westerlies. So right now we're going to see some positives in the range of +8 or higher while the winds shift and become predominately westerly. Yet down the line, we'll see the dailies tank while the westerlies relax. So the lag is that the 30 day SOI takes time to reflect real time events and can give false impression. Which is why experts like Dr. Ventrice don't use it... but the CPC and BOM swear by it. The 90 day average is pretty solid but takes a loong time to show changes in the atmosphere.
Thanks so much for your response, it was very helpful. Now I see the correlation between the winds and the SOI and how it can lag behind.
Would the equatorial SOI be a better measure do you think? I've seen it mentioned a few times, but never as much as just the regular SOI. Just did some quick searching and found a link for some data, although it only shows monthly means, not dailies or 30/90 day averages like the regular SOI.
February mean was -1.4 though, and March was -1.2, hopefully April will update within the next few days.