May 23, 2018

"June-like" May?

May can go either way:

Some years "dry" and other years "rainy."

Bar chart showing monthly rainfall in Big Cypress National Preserve compared to the long-term median (white line), normal range (dark gray band) and historical record (light gray band).

With a week still to go, it's safe to say we are "rainy."

The new question is be will the May total end closer to June ...

Stay tuned!

May 22, 2018

Exposed roots

Pond apple forests are a common sight ...

In the center of cypress domes.

Pond apple forest
as seen in spring 
This year they exposed to air for 2 months.

May 21, 2018

Roots of the pond apple

How do we measure the duration of drought in the swamp?

Answer: By the number of months the roots of the pond apple trees are exposed.

Bar chart showing the annual duration of deep drought
in Big Cypress Nat'l Preserve as calculated by the number
of months the roots of the pond apple trees go dry.

That happened 2 months this year.

That's about three weeks longer than normal year.

And over two months shorter than the "drought of record" in Spring 2011.

May 20, 2018

Swamp extremes

You know it's really wet in the swamp ...

When the water's edge creeps into the pine islands.

Water in the pines!
As seen in August

And you know its really dry in the swamp ...

When even the alligator holes in the middle of the cypress domes go dry.

A last gasp puddle
in the middle of a cypress dome
as seen in early April

It's going to take a little while,

But after a long dry season the swamp is finally starting to fill back up.

May 19, 2018

"Fake" shutters

Early-season hurricanes are not the norm,

But they do happen from time to time.

Agnes (June 1972) sticks out in my mind.

It goes in the record books as my first hydrologic memory, not as a Floridian – where it made landfall, but as a native Marylander where I was born, and where the storm passed through on its way up the Atlantic Coast.

I was only 3 years old at the time.

My mother and father judiciously had us take cover under ground, not for the reason we didn’t have shutters on our windows – we did, but because those shutters were fake!

The so called "ornamental shutters" were made of flimsy plastic, manufactured too narrow to cover the full width of glass, and – the final insult – drilled permanently into the wall siding.

They looked great on a sunny day, but that was about the good of them!

But Marylanders are nothing if not innovative: we found safety in the basement … and after the storm passed, also found a thin sheen of water on the slab floor.

That discovery marked the beginning of my father’s futile attempts to battle a chronic moisture problem in our basement, predictably ending each time with him admitting defeat (tinged with a sense of awe) to the subterranean river that coursed beneath our house.

May 17, 2018

Swamp has four seasons (not two)

South Florida's two meteorologic seasons ...

Turn on and off like the flip of a switch.

iagram depicting the two meteorologic
(inner ring) and four terrestrial (outer ring) seasons
of the Big Cypress Swamp

But at a landscape level,

There is actually a lag.

As a result, the swamp has four seasons (not two) as described below.
  • Soaking in season. The early part of May is usually the crunchiest time of the year to walk through the swamp: water is absent except in the deepest pools. By month’s end the wet season will have started, followed by June – the rainiest month of the year; yet only rarely do waters peak this early. Late May through June is usually a “soaking in” season for the preserve.
  • Sheetflow season. The onset of summer, lasting into early fall, coincides with an extensive but ephemeral sheet of shallow flowing water in the swamp. Its flowing aspect is achieved when waters rise to the base of the pine flatwoods (i.e., equating to a depth of two feet in the center of the cypress domes). The depth, spatial extent and flow rate of sheetflow typically peak between late August and early October.
  • Hydrologic Interregnum. Starting with the demise of sheetflow in mid fall and lasting through winter is the hydrologic interregnum. This is an approximate five month period in which “wet season” water is still present on the ground, but atmospherically the “dry season” has set in, thus initiating the slow demise of the swamp’s expansive sheet of surface water. The duration of surface water in any one spot is largely habitat dependant, but may also be sustained by winter rains, particularly during El NiƱo years. Pinelands go dry first, followed by marl prairies which eventually leads to a retreat of waters into the tall cypress and pond apple swamp.
  • Spring drought. The swamp ebbs to its low water mark in April and May due to the cumulative effect of months with little rain and increasing rates of evapotranspiration (rising temperatures, expanding hours of daylight, and plant transpiration). During this period, surface water is practically absent from the swamp other than smallish (typically less than an acre) and isolated pools called dry season refugia.

Currently, we are in the "soaking in" season now.

"Meteorological" line(s) in the atmosphere

Just when we thought the answer was beyond our grasp,

The start (and end) dates of the rainy season have been officially defined.

It's official:
From now on the rainy season
starts on May 15th and ends
on October 15th.
Part simplification and part historically based,

Meteorologists are most happy about finally putting this pesky question to rest.

Instead of getting bogged down in the verisimilitude of each and every year, meteorologists made the decision go by the long-term trend of when, on average, the atmospheric conditions conducive to regular summer showers starts and ends.  Interestingly, the maiden year of the decision has turned out to be exact.  The rainy season pretty much started two days ago on the 15th!

We'll see if the end of the rainy season similarly behaves.

May 16, 2018

Lots of "soaking in" ahead

Has the rainy season begun?

Well, it's definitely more humid.

History of May and June rainfall totals
for Big Cypress Nat'l Preserve from 1990 to present

And yes, the afternoon clouds appear to be taking shape,

But the water table is still bottomed out.

Still lots of "soaking in" (and filling up) to do in May and June.

May 15, 2018

When Big Rain Days Strike

When it comes to Big Rain Days (BRDs),

South Florida gets about 5 of those per year.

Monthly distribution of when Big Rain Days
occur in south Florida, 1992 to present
As for the month,

They can happen any time of year (see above).

June happens to be the most plentiful, accounting for one of every five.  Interestingly, July is the lowest despite being a core rainy season month (i.e. about 8 inches of rain on average) due to the fact that upper atmospheric instability (still present in June) tends to decrease once the Easterly Trade Winds kick in.

May 14, 2018

Swamp sponge soaks up rain

It's official:

South Florida had its first Big Rain Day (BRD) of the year.

Calendar chart showing daily rainfall across South Florida. The big black rain drops indicate Big Rain Days (BRDs), i.e. any day in which all of south Florida averaged an inch or more of rain.  Usually we average about 4-5 of those per year.  Mother's Day was our first BRD of 2018 and our first one in over 6 months (i.e. late Oct 2017).
But, I wouldn't call it the wet season just yet.

The reason?

Not much of it got past the swamp sponge.

As a result the water table is still pretty much bottomed out.

May 10, 2018

What a difference a headwaters makes!

The Everglades has a reputation ...

For being wetter than the Big Cypress.

Quick look at water depth
(above the slough floor) in the Everglades
compared to water depth (below the center
of the cypress dome floor)
in the Big Cypress

That's only because the Everglades is connected to its headwaters.

The Big Cypress in comparison has to rely on direct rainfall.

For the most part its historic headwaters have been cut off.

Mother's day storm?

I never like "calling the rain" ...

Before it happens.

Rain forecast
for Sunday, May 13th

But it looks like Sunday could see some plentiful rains.

(Still not comfortable guessing how much ...)