Many, including me, read the National Weather Service office's forecast discussion, which they put out four times a day, to see what they're thinking. In this afternoon's take, they had this:
"THE SOURCE OF SOME OF THE MOISTURE IS MADDEN-JULIAN OSCILLATION INDUCED TROPICAL CONVECTION OVER THE FAR WESTERN PACIFIC AND TROPICAL CONVECTION TO THE SOUTH OF THE HAWAIIAN ISLANDS AS DEPICTED BY GLOBAL-COMPOSITE SATELLITE IMAGERY AND PRECIPITABLE WATER IMAGES FROM THE NOAA POLAR ORBITING SATELLITES. "
While that sounds like perhaps the latest sports game on Playstation, the Madden-Julian oscillation is actually a pattern in the Pacific where you get really big blobs of tropical moisture followed by big areas where there's no tropical moisture, and this alternating pattern then moves around the globe.
This alternating pattern is evident around the globe, and has about a 30-60 day cycle, and within the cycle, there are times the "MDO" is going strong and times when it is very weak and hardly noticeable.
Anyway, we're in a strong phase now, and the jet stream has tapped into a bulk of that tropical moisture south of Hawaii and is sending it our way.
This is how we typically get our very wet and warm storms, as is expected to occur on Thursday and Friday. And the Hawaii origin is how we get the name you might have heard off when we get these warm, rainy storms: the "Pineapple Express".
(Much easier to understand than that MJO, IMO...)
So when it's pouring buckets later this week and your colleague says "Man, where is all this rain coming from", you can impress them with the neat weather terminology...
And just hope he doesn't run out to try to buy the video game :)