|GFS model forecast for overall atmospheric moisture content in the boundary layer (that in which weather occurs) for Wednesday Evening at 8:00pm|
BEYOND: With that said, next comes the big period in question. Latest model guidance (NAM/GFS) have returned to the previous state of mind, bringing the Atmospheric Tsunami of Moisture northward. By all appearances, the old frontal boundary that finally pushed through a few days ago, which was partly responsible for the severe thunderstorm warnings, had stretched out and become a bit elevated around 5000 ft will re-emerge and lift northward as a warm front as seen above. And the result, lifting and dragging northward of deep layer atmospheric moisture as a calling card.
Guidance is close to a- glee-ment for now, but previous runs showed nothing like this at all. For now, it is worth at least being aware of. Whether that Deep Purple is 'Smoke on the Water" (or a Smoke Screen) showing high precipitable water values will actually arrive right on the Summer Solstice to South and South Central and to as far north as the I-4 Corridor for the first full day of astronomical summer is yet to be known for sure, as this was a quick shift in guidance. This can only be determined with greater assurance (or not) in future model runs.
After further evaluation, it seems by all appearances is that what guidance is awaiting arrival of is an anomaly or perturbation in what would be an otherwise un-fazed environment known as an observed and named phenomenon called the MJO or Madden-Jullian Oscillation.
If this is correct, or something close to this does occur, chances are the first 72 hours will be the most rainy, but once the atmosphere by then worked over and fully saturated for that long of time occurs, even though the atmospheric moisture remains high, chances are it will most cloudy . But before then, guidance shows up to 4 or more inches could fall in various locales between Thursday through Saturday. Much depends on what is to be depicted in the next few runs which come out every 6 hours..So not to hang the hat on this one just yet. For all we know, next model run will revert to something completely different, as was the case earlier/over-night. But do not be surprised if you see something like this on the news.
The MJO is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian Ocean and Pacific Ocean. The anomalous rainfall is usually first evident over the western Indian Ocean, and remains evident as it propagates over the very warm ocean waters of the western and central tropical Pacific. This pattern of tropical rainfall then generally becomes nondescript as it moves over the cooler ocean waters of the eastern Pacific (except over the region of warmer water off the west coast of Central America) but occasionally reappears at low amplitude over the tropical Atlantic and higher amplitude over the Indian Ocean. The wet phase of enhanced convection and precipitation is followed by a dry phase where thunderstorm activity is suppressed. Each cycle lasts approximately 30–60 days. Because of this pattern, The MJO is also known as the 30–60 day oscillation, 30–60 day wave, or intraseasonal oscillation.
For more information: http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/mjo.html