weather event

Big Saharan Swamp?
And during soggy season no less

Umbrella be darned,

It’s almost impossible not to get caught in a rainstorm come summer time in the swamp, and getting thoroughly drench.

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But a dust storm? And from the Saharan Desert, no less? And during the soggy summer season in south Florida? Now that’s something if I were to warn you about, you would find hard to believe, and equally uninterested in preparing for. The good news: The plumes of Saharan-desiccated dust blowing in on the wings of the Trade winds are not on the same scale as an Oklahoman sand storm during the Dust Bowl. But it does give one pause for thought: The weather is south Florida’s famed summer rain machine isn’t as isolated as we think. External forces can both stoke and stymie its might, and sometimes completely shut it down as often happens when a hurricane passes off shore up Florida’s east coast (i.e. pumping down drier northern air).

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Tidbit: The Sahara Desert measure 3,000 miles from east to west (about the distance between New York City and San Francisco) and about 1,000 miles from north to south (the distance between Chicago and Houston). Now that’s one big desert!

big weather

First Big Rain Day of the Year
One down, four more to go

Well, it’s been over a half year …

But finally we got another Big Rain Day (BRD).

Historic calendar of Big Rain Days (BRDs) in south Florida. Black drops show the BRDS. Orange circles show the “little to no rain” days. Baby blue and blue-ringed circles are somewhere in between.

And I know what you’re thinking — what exactly is a BRD? According to the official Go Hydrology Dictionary, a Big Rain Day (BRD) is any day that an average of an inch or greater is recorded across all of south Florida.  For that to happen requires a lot of rain to fall everywhere. The weekend storm makes it the first BRD of both the new water year (starting in May) and the calendar (starting in January) year, too.

Annual number of BRDs per year, 1990 to present

On average, south Florida averages about five BRDs per year. The most in recent history was 2005 with ten BRDs followed by the least in 2006 when we only got two.

In terms of when they occur, this is where it gets interesting. June leads the way with 18 percent, accounting for about one in every five every BRD. The lowest are February and July. Okay, February makes sense — It’s the heart of the dry season. But July? Isn’t that the smack dab in the middle of the rainy summer months?

Distribution of BRDs by month

Answer: Correct, it is. Unlike the June that is still juiced with upper-level instability from continental fronts, come July that instability dissipates with the full maturation of the Trade Winds out of the east. The result: July reliably brings us the “bread and butter” summer storms, but not the big rainmakers that define the start and end of the wet season.

In summary, it feels good to get the first BRD of the year. Now, on average, four more to go.

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Did you know? On average, June is south Florida’s rainiest month, and August second.

spring

Fog flow
The ghost of sheet flow past

Morning fog in Florida …

Can sometimes be very thick.

Not to be confused with sheet flow

Other times it hovers just over the surface like a blanket that burns away rapidly in with the rising sun. That’s what happened this morning. The thing about fog: It’s really hard to photograph, especially without good camera equipment and a lot of patience. In this case I just hopped on the guard rail and tried to campfire the ephemeral layer of moisture while it was still there, and in doing so also watched it slowly fade away. Five minutes later it was completely gone.

animation switch short

Looking back on Eta
Last year's game changer

Today (or is it tomorrow) …

Marks the one-year anniversary of Eta.

Playlist of videos (i.e. plural) I took during Eta

You know it’s a Big Rain Day (BRD) if you pause a year later (even two, or three) to think back and reflect on its size and extent. Eta was a big as it was unexpected. All signs were pointing to an early and deep descent into winter drought. Not only did Eta give the swamp an extra boost, its bounty from Eta fell just as the regional evapotranspiration machine was shutting down. That gave the water staying power, too. Or rather, slow-flowing power. Where does water go when you get that much water in the swamp? Answer: Nowhere fast.

The storm reminded me of Hurricane Mitch back in 1998. It too instantly reset the swamp clock to peak sheet flow time. Actually, Mitch may have been the bigger of the two. But they are more similar than different and should go down as the twin November game-changing storms of note.

Did summer just end?
Just when it was getting interesting

It was shaping up to be a subpar summer …

And then September kicked into high gear.

The swamp finally peaks, but for how long?

Back to back weeks pushed the swamp to its annual peak.

Then came the recent front of dry air?

Overnight the rain machine shut down.

Or is there still time for it to rev back up?

A flooded marl prairie with periphyton

I‘m never one to complain about the start of fall, but seriously – summer was finally starting to get interesting. It’s good to see the swamp’s sheet of water spreading out.