Flipping the switch

2008 wet season is “flip of switch” away

Rain Or Shine Report for May 20

What if we could just “flip a switch” to the sky?

Turn blue skies into rain.

Stop downpours at a moments notice just as flood waters are about to overflow the bank.

Unfortunately, such a switch does not exist … at least literally.

But come middle May, landscape parched and water pretty much out of site, we find ourselves waiting for the great meteorologic hand in the sky to “flip the switch” on Florida’s fabled summer rain machine.
Looking out my window, here at work in Ochopee, the cumulus humilis clouds – they’re the whiffs of moisture that look like popped popcorn – are already taking up as much space as clear blue sky – and its only 10 am.

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That’s a good sign that the summer rain machine is trying to rev up its engines … and flip that switch. .

And there’s also a pretty stout wind blowing from the south – enough to lift and unfurl the flag to the north. Is that a sea breeze, or prevailing on-shore wind from the Gulf?

Those cumulus humilis are the morning seeds of the cumulonimbus giants that rise out of the Everglades in the afternoon. And it’s that sea breeze (if it is one) that fuels the fire for taking them higher (giving them vertical lift), and, eventually, pushing them together into the gargantuan fronts that blot out the sky and make us take cover from the rain.

But first thing first. In the short run we’ll be content to see some isolated cumulonimbus dot the peninsula with showers.

It takes fertile atmospheric soil to grow the clouds to their full flowering phase, which in this case, is making them rain makers. And the full-blown fronts don’t come until later in the wet season usually.

So often in life we find patterns. And learn to live by them.

For Floridians the start up of the wet season is one of those patterns, and yes, it is like “a flip of the switch”.
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But the term “switch” implies two things: one, that there is no middle ground, that it goes straight from night to day, with no dawn in between, and that two, that we have control of turning it ON and OFF.
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The latter isn’t the case.

With 19,000 acres (30 square miles) burned or burning within the bounds of Lake Okeechobee levee and another 36,000 acres (56 square miles) Mustang fire in Everglades National Park, not to mention the 12,000 acres in Brevard County (19 square miles) – reaching for and flipping that switch would be a no brainer, if only we could.

In the absence of that switch, we are fortunate to have the next best thing: lots of rain data.

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By studying the historic patterns of that data, we can glean some sense of understanding that in a small way gives us a sense of control. Data is the lantern in the darkness that give us the dim light that illuminate our way down the path of what might come next.

In different corners of the southern peninsula I’ve heard equal doses of level headed projections that the rainy season is right around the corner, and others who will “believe it when they see it.”

If seeing is believing, you can either look out the window (at the clouds), or take a look at the graphs below.

The first graph shows cumulative rainfall, from April 1st to the end of June, from 1998 to present. It shows where that cumulative rainfall total of this year stacks up to the previous ten years.

What immediately jumps out is the lack of rain we’ve seen since the start of April.

But take a look at 2005. That was the June of that +20 inches fell throughout southwest Florida. But the preceding May and April were very dry, very reminiscent of what we’re experiencing now.

My point?

All bets are off once the summer rain machine kicks in.
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But truth be told those 20 inches of June 2005 rain weren’t 100 percent from our traditional summer rain machine, but rather from a series of late-spring low pressure systems blowing in from the west across the Gulf.

So the rain machine had help.

Interestingly, also take a look at 1998. It shows the lowest cumulative rainfall through June of all the other years. That’s interesting because it also was an extraordinarily wet El Nino influenced winter. Thinking back to fire severity, it was that winter and spring-time wetness that fueled the undergrowth that later dried out and provided fuel for the late spring blazes. That’s similar to our current condition.

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But getting back to the original question:

When does the wet season switch flip to ON?

The second graph below plots the median daily rainfall from April 1st through June 30th for the 10-year period between 1998 and 2007.

That’s a pretty clear signal.

So for arguments sake, mark your calendars for the last week of May for this year’s official ribbon-cutting ceremony for the much anticipated 2008 wet season.

Hopefully we won’t be “rained out” … or hydrologically speaking, hopefully we will.

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