Early fall surprises swamp?

Another perplexing rumor:

Is luckless forest on onerous last straw?

An inauspicious start? - Usually verdant spring cypress inexplicably brown to autumnal hue!

I was shocked to learn (and see for myself) that all the recently greened out cypress needles had browned and fallen to the ground all in a single night, returning what once were verdant green forests back into their dormant winter state ...

Or are they dead?

April in the swamp, really? Spring looks downright foolish without green trees.

Whatever it is going on …

This has the makings of one heck of a cruel joke!

Rain chart for south Florida

Chart of weekly, monthly, and yearly rainfall for south Florida:
We've had a low annual total this past year (May 2010 - Apr 2011) 

Drought battles Big Rain Day

Big Rain Days get all the attention …
On Monday we had our second of the year,

But what about all those dry season days in between when it doesn’t rain at all:

Don’t they count, too?

Over the long run, Big Rain Days are no match for south Florida's spring drought

Just to refresh your memory, a Big Rain Day (BRD) is any day in which south Florida (as an aggregated whole) averages one inch or more of rain. One inch of rain isn’t all that unusual for any single gage, but as a regional average it’s a pretty rare event:

On average over the past 20 years we’ve averaged around six BRDs per year.


On the opposite end of the spectrum are Florida’s prolific days of pure sun.

They may register “zero” in all the rain gages but on the ground are an invisible indication of water “pointing up.” Evaporation and transpiration drop the water table down.

June and September have the highest monthly occurrence of BRDs,
but forty percent of them fall during the dry season (Nov-Apr)

The calendar chart below highlights these two extremes:

• Big Rain Days (BRDs) are plotted as blue rain drops. Fay totaled 5.7 inches over a single day but it’s Mitch with 5.3 inches in November 1998 that wins the one day prize.
• Insignificant Rain Days (IRDs) are plotted as orange suns and include any day which recorded a south Florida wide average of 0.05 inches of rain or less.

Two interesting patterns emerge:

1. BRDs appear to have a good chance of occurring any time of year, both during the wet season and the dry season (see bar chart above). Why? Despite getting 3/4ths of our rain during the summer wet season, those showers are often localized in nature. In comparison, a winter cold front can spread water across all the basins in one fell swoop.
2. IRDs rule the dry season skies. Yes, a BRD or lesser rain may aperiodically pass through, often achieving a “dry season’s month” worth of rain in a single day (and momentarily bumping the water up), but it’s the long-run of semi-consecutive IRDs which usually win by late spring: Surface waters have vanished and wildfire is on the prowl.

This chart displays the distribution of south Florida's two meteorologic extremes:
Periodic Big Rain Day versus long-stretches of unending sun

So, to answer the question:

Yes, all those “zeros” of no rain add up to quite a big sum!

Monday's big rain on Kissimmee

Radar-derived 24-hour rain total for south Florida, courtesy of SFWMD.
Rains were heavy on the Kissimmee but light in Big Cypress Nat'l Preserve.

Okeechobee over the years

How low is the Lake?

Lower than April 2009, but still higher than the drought years of 2001, 2007 and 2008.

Chart of current Lake stage compared to previous years of interest

Monday’s big rain fell heavy on the Kissimmee.

What effect that has on the Lake we’ll know by week’s end.


New water restrictions are in place regardless.

Clouds of cold front bring rain

Walk into the dry side

There's the dry season ...

And then there's the "dry season."

The second half of the meteorologic dry season, say March through May, coincides with an equally parched landscape to impart the swamp with the full effect of drought. In this case, a shallow sliver of water is still holding on in the center of a cypress dome, but it was filmed in the beginning of May.

Even with today's rain my guess is, as the month draws to a close, that puddle is gone.

Watch out below!

Royal Palms shed their fronds when you least expect it:
Pedestrians should keep a careful eye on the sidewalk below.

Royal palm of the wilderness

This Royal Palm is over 100 feet tall.

Even more surprising is seeing one in the wild.

Royal Palm as seen on the Big Cypress Bend Boardwalk

My understanding is that they are native to south Florida, but somewhat rare to find anymore in the wild. More typically you’ll see them planted in alignment along scenic stretches of road in town.

But watch out on the sidewalk below!


Their fronds (and husk) are quite big, on the order of ten feet long, and crash down from 100 feet high just when you least suspect it. I was startled by one once but have never been hit …

Knock on wood!

Fire and water

This hydrologic monitoring station escaped the fire unscathed

"This wheel's on fire"

Absent water, fire takes center stage in the swamp.

Add in some wind and suddenly it has wheels, a wall of flames and fumes are on the move, leaving in its wake charred earth and a lot of ash.

That’s where the wildland firefighters step in to contain it …

Not that they don’t mind a little back up in the form of a big rain!


Photo is from Deep Fire of May 2009.

Dome and dwarfs

Cypress domes are often surrounded by a marl prairie of dwarf cypress

"No name" swamp

Among the swamps most puzzling paradoxes is this:

None of its cypress domes are named.

Shallow pool of water in the middle of a dome, March 2011

Pine Islands are commonly given proper names – Thompson Pine Island to name one – as are many of the hardwood hammocks – such as Lime Tree and Iron Pot – and, to the east in the Everglades, most of the River of Grass’s larger tree islands such as Gumbo Limbo, Choctaw and Johnny Buck.

At first glance that seems to imply a preference for naming high ground.


But think again:

Most of the swamp’s linearly aligned formation of deep-water cypress – called strands – are marked on the map with names – such as Gator Hook, Barnes , Skillet and Gannet – as are most of the major marshy sloughs – Mullet and Lostmans Sloughs to name two.

Even the "middle of the road" marl meadows bare names – including Airplane, Wagon Wheel, and Lost Dog Prairies.


Most shocking of all?

Cypress domes are arguably the swamp’s most iconic and abundant land form. I could spend a year trying to explore them all and probably only cover a few, yet be all but guarantee that I’d never for a moment get bored.

They are sanctuaries of cool water where sun and shade intertwine that arch from a perimeter of dwarf cypress into a rounded apex of cascade of towering trees which at their highest point collapse into a gothic display of orchid-hiding pond apple forests and open water pools.

Water's edge (and receding fast)

Actually, I kind of like the idea they aren’t named:

The world could use some more places like that.

L28 Interceptor

View of the L28 Interceptor looking south just north of I75 Alligator Alley
February 2011

Which L28 was that?

There's over 600 miles of major levees in south Florida.

Even more confusing than that is that several of them go by the same name.

Or sort of:

As described in the video, the L-28 for example includes the tieback, interceptor, gap, borrow, north ... and probably more, all of which are separate canals.


That's why hydrologists spend lots of time studying maps!
(And even then we still get confused.)

South Florida Rain Chart

Rain has been scarce the past two months:
That's setting the stage for a spring nosedive in the swamp.

Phases of Florida's endless summer

When does summer begin in Florida?

The graph below combines three aspects that we commonly associate with summer weather in Florida: rainfall, air temperature, and hurricane frequency.

Chart highlights three aspects of south Florida's seemingly endless summer

The wet season of regular afternoon showers won’t get started for another 60 days and hurricane season doesn’t get revved up into full gear for another 60 days after that, but air temperatures are already turning hot.

Late March begins an 9 month span (lasting through November) in which average daily daytime high temperatures break the 80 degree plane.

Cloud shadow over pinelands
March 2011

Florida’s summer unfolds in several phases:

It starts with cloudless heat-searing sunny skies of March, followed by a drought-parched landscape of April and May, then comes the humidity and regular showers of June through August punctuated by the threat of big storms in September and October until finally, usually around November, a cold front pokes through and then by sometime around Thanksgiving summer weather finally comes to an end ...

Or at least, daytime highs drop back below 80 degrees.

Finding shade where you can is key to surviving Florida's searing summer sun.

Wide brim hats, limiting exposure and activity during peak sun hours, long sleeves, umbrellas, sun screen and drinking plenty of water also helps.

Lots of evapotranspiration

Even that cypress-enclosed two-acre marsh is mostly dry
March 2011

Drier than spring drought of 2009?

The slough has shallowed Everglades National Park’s Shark Slough.

Currently it’s dropped down to under a foot deep.

Slough stage is slightly lower than the same point in 2009.
Click here to see the historic record, 1950 to present.

That makes it 8 inches shallower than March of last year and, if you can believe it, an inch or so shallower than the March of 2009. That was the spring that Shark Slough went peat-parching dry as a bone which is rare for the Everglades. Usually sloughs hold at least a few inches of water all year long.

On average waters don’t bottom out until early May.


That gives us all of April and into May for a deep dry season drop.

70°F is our wet season indicator

Nighttime lows in the high 70s have been the norm the past few years

Summer return interval

It’s no longer a question of when winter ends …

But whether or not (and if so, when) summer starts.

Temperature comparison of this winter (blue) to last winter (red)

The past few daytime highs have approached the 90° F mark in Naples Florida, but as of yet we haven’t broken that plane. Usually it doesn’t happen until April or May (as indicated by the “blue dots” on the graph below) but it can happen as early as March during hot spring spells as was the case in 2002 and 2003.


Once that plan is broken, summer temperatures sort of plateau:

Only rarely do daytime highs approach the high 90s and it’s as monumentally rare to have temperatures rise above 100° F in coastal south Florida as it is to experience a winter freeze (below 32° F.)

Count on daytime highs to rise into the 90s (but not much higher) all summer long

Of course it’s not the daytime high that we use to measure summer in Florida, but rather the nighttime low instead which, when it consistently stays above 70° F for the night, is our bell weather that the summer rains, better known as our wet season has begun.


In part, it’s those afternoon rains (and clouds) that keep daytime temperatures in check. Latitudinally speaking you could almost call 90 degrees "cool" for someplace as far south as the Everglades.

A "cool" 90 degrees for half the year?

Maybe "hot and humid" is more like it.

Pinelands get new recruits

Slash pines are fire tolerant but don't much like getting their feet wet

Fire return interval?

How frequently do the slash pine burn?

February 2009

February 2011

In this case it's been about two years.

Little puddle

As of early March a thin pool of water was still holding on in this dome.

Dungeons of the deep

The term "dome" implies an open air arena ...

as in say a swamp stadium or a cypress coliseum.

But don't forget that the tall cypress trees are located in the lowest part of the swamp like a shallow cellar and who at first glance wouldn't say that these pointy knees confer a certain dungeon feel.

Not that I ever feel "locked up" in the swamp.

Very tall knees

Next time I'm out I'll have to to measure a few

Cypress knee growth spurt?

Is it me, or are these knees particularly tall and pointy?
Or maybe it's just the water's dropped down so far instead.

Probably a combination!

Past 600 months of rain

Dot size and color indicate historic monthly rainfall for south Florida, 1960 to present.  Our biggest rain month of the past decade was June 2005.  Notice how the driest months fall during the winter and spring, also our peak water usage months.

60 day weather outlook

As indicated by the abundance of red on the map ...

It's been a dry "past 30 days" in south Florida.

The map is interactive:

Just click inside the individual basins to view weekly, monthly, and yearly bar charts for each basin. Or you can click on the "dot" within each basin to view the historical period of record from 1950 to present plotted in calendar format. The calendar charts nicely highlight south Florida's seasonal wet/dry cycle -- 8 inches and higher of rain during the hot half and closer to the neighborhood of 2 inches during the dry cooler half.

As to what we can expect over the next couple of weeks ...

Look for the dry pattern to continue for at least another 60 days.

Deepest Lake of Collier County

Deep Lake, as seen looking east into Big Cypress Nat'l Preserve

Swamp's deepest lake is only a speck

The Big Cypress Swamp in total comprises some 2,500 square miles. But it's water column is incredibly small in the sense it is Shallow ...

Even its deepest and isolated pockets are only 3-5 feet deep.

The exception is Deep Lake which, as its name implies, is deep.

But measured from bank to bank it's under 300 feet across.


That makes it the swamp's deep spot, if also only a speck.

40 nights in the 40s?

Almost, only 39 nights dropped into the 40s or below this winter

Refreshing winter days added up

Winter appears to be gone:

After a month without having one Naples, Florida experienced the bone crushing cold of another day in which the daytime high did not break over 70° F.

Chart showing days in which Naples daytime high temperature didn't break above 70°F 

That’s not cold by Continental Standards …

But here in the south Floridian Peninsula we call that a refreshing winter day.


Up north on the continent the cold days are usually greater in number and more contiguous in nature which when bundled up together form a multi-month time span commonly referred to as the Winter Season.

Winter on the peninsula isn’t a “season,” but is rather measured in a handful of haphazard “days” instead.

Chart showing how this winter stacks up to previous winters

How many did we total this year?

We had one in November, sixteen in December, nine in January, three in February and – a month later – now one more in March … which I am assuming is also our last.

That adds up to 30.


Or in other words, about a month.

Intersection in the swamp

Aerial view of airboat country in the southeast corner of Big Cypress Nat'l Preserve

Swamp has size of 51st state

How big is the swamp?

Big Cypress Nat’l Preserve alone is expansive enough to be called a "state."

Comparable in size, yes, but the swamp has considerably less congestion

By state-like I mean as big as Rhode Island, or in other words 1,214 square miles … or almost. Big Cypress Nat’l Preserve covers some 1,139 square miles.

I call that close enough.

Two gulls on the beach

"All aboard who's going aboard!"

Here’s an unusual sight from Naples Beach.

It didn’t strike me as being a symbiotic relationship …

But what do I know:


Maybe this gull and pelican are just good friends.

Spanish moss

As seen in Robert's Lake Strand earlier in the winter

New sub species of Spanish moss?

The flowers of Spanish moss are “tiny and inconspicuous.”

Really? – Not according to this photo at least.

Could it be a special sub species found only in the swamp?

Trick photography more like it.


The photo shows two plants intertwined:

An epiphyte and a flowering vine.

Getting greener

Eastern edge of Deep Lake Strand looking north

Swamp's final disappearing act of spring?

Patterns jump instantaneously up high in the sky ...

That on the ground you could never fathom to see.

Swamp's patterns are especially obvious in the winter with the cypress still bare

In the video I use the word "transparent" which I don’t mean to be construed in the sense that it's invisible, as in "I can't see it at all," but rather to imply that it's clear as glass ...

As say a big bay window with the most coveted view.

Everyone's first flight is eye opening in that way.

Thirteen years later I'm still sort of in awe.


Note: My boot is not to scale.

Marsh below in Mullet Slough

Late February looking west a few miles south of I-75 

Precipitation turned upside down

Mention the word precipitation to a Floridian …

And the first thing that comes to mind is “rain.”

Evapotranspiration outpaces rainfall during south Florida's dry season

But rain isn’t the only show in town dictating how the swamp’s water responds.

There’s also evapotranspiration which – starting in spring – starts to switch on to full gear.


The black bar in the graph shows what I call net precipitation as computed week after week from May 2008 to present. The background blue shows recorded weekly rainfall as a basin-wide average for the swamp and the background red shows an estimate of evapotranspiration over the same week.

A week of no rain means a seven days of unfettered evapotranspiration.

String a couple of those together during the spring turns precipitation on its head.


What looks like blue sky and sun to most ...
is just rain falling upside down to me.

Green out from below

As seen in a middle of a cypress dome looking up

Swamp turns green without any water?

Usually we think of the spring green out with rising river levels.

At least if you grew up on The Continent you do.

Graph displaying this spring's dry down (an early one) compared to previous years

Not down here on The Peninsula in south Florida:

Spring is the time when water levels are on the nose dive down.


Cypress trees find a way to green out anyway.

And more than that, the thirsty needles wick away at what water's left in the form of tightening grip of increased evapotranspiration.

Verdant green regrowth following a wildlands fire, in this case a controlled burn,
in a marl prairie south of Tamiami Trail

That makes spring in the swamp a peculiar mix of wildfire char followed by regrowth and diminutive wildflower blooms plus the green out.

The swamp ecosystem is always in motion even when its dry.