Charts and hydrographs

How much data can you cram on one page. Cheatsheets test the limit and expand your mind.

Lake not the blame (this time)
Closed gate but rising flows downstream?

With The Lake near its annual low …

And the Kissimmee River at a similar ebb:

A semi-complicated hydrograph summarizing some key indices for Lake Okeechobee over the past two years, including rainfall, lake stage, inflows from the Kissimmee River and discharge through the S-79. See the complete cheatsheet for the lake.

Why then have discharges down the Caloosahatchee River’s S-79 into the Estuary suddenly spiked to over 5,000 cfs, which in layman terms is around 34 Fenway Parks filled to the top of the 37.5 foot high Green Monster every day? Answer: Blame all the rain in the Caloosahatchee Watershed, not the Lake. The S-77 which controls Lake flows into the C-43 are closed, and is therefore recording no flow.

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Tidbit: At 13 feet above sea level, Lake Okeechobee is about 8 feet below the level it naturally overflowed its southern shore into the Everglades prior to drainage.

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.

Handy Hurricane Calendar
Peak storm season is still 3 months away

Confused by Florida’s convoluted hurricane history?

If so, this calendar graph may come in handy.

When hurricane strength storms made Florida landfall

There’s more to this graph than meets the eye:

The dots show the year, month, and strength of each storm which made Florida landfall over the past 110 years. Clicking on each dot transports you to a detailed write-up of each storm. The “outer” dot plots each storm’s intensity at peak strength and the “inner” dot at the time it made landfall.

Major patterns?

September is Florida’s big month. Late August and October also light up the chart. And three is the most hurricane-strength storms that have made landfall in the peninsular state in any one year. We almost had four in 2004 but the eye of Ivan made its way into land on Alabama shores.

When and where storms form by month

That leads me to one caveat, and its a big one:

The graph only includes “hurricane strength” storms that made “Florida” landfall. That rules out many a monumental rainmaker (i.e., Fay) and any storms whose eye crossed just across state lines.

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Tidbit: In the Atlantic, hurricane season starts June 1, while in the Pacific it starts May 15. Both end on November 30.

It’s not like those winds and waves stop at county lines.

water table

Rainy season begins on a dry note
As usual (and despite the April rains)

The start of one season …

Usually means the end of the season that came before.

History of drought in Big Cypress Nat’l Preserve

Well, hold your horses. While Memorial Day Weekend does mark the unofficial start of south Florida’s summer wet season, and to be sure from this point on we can expect the regular build up of afternoon clouds and thunderstorms — it may take a few couple weeks before the swamp starts filling up, or it could happen in a day. Until that time and until that day, the swamp is still in a state of drought. Not as deep as last year. But as you can see on the hydrograph above, it wasn’t until early June that the water table bottomed out. June is soaking in and filling up month. What we do know is that probably by July and definitely by August the swamp will get its water back.

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Meteorological Proverb: “All droughts end in flood”

temperature check

High humidity blues
And why shade matters

Temperatures don’t rise as high in south Florida …

As they in the Great American Southwest.

Let’s just say both are hot in their own way

But the humidity is off the charts. Actually, technically speaking, it’s still on the chart. But did anybody else notice this week how the wave of heat hits you the moment you open the door. The thing about summer in south Florida — it’s so thick, it almost feels like you’re wearing a sweater, even though you’re only in short sleeves. The caveat is you better keep a sweater handy because it can get cool in the air conditioning inside.

Back to the comparison between Naples and Arizona on the heat index scale. There’s an old wise tale about how in Arizona, yes it’s hot — but its a dry heat, thus its cool(er) in the shade — in contrast to Florida that is so humid that the shade brings no reprieve. This just in: Shade matters in Florida. In fact, that’s exactly how you can spot a native (or a long-time year rounder) in a crowd. All the tourists will be standing int he sun, but the salty and seasoned old-timer will be predictably standing in the sand, no matter how small the sliver. Shade isn’t as cool as AC, but it may be Florida’s only sweater-free zone come summertime.

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Swamp Rules: Count on summer nighttime lows to stay at or above 70° F all summer long. That doesn’t mean it can’t get shivery cold after a June downpour.