May 4, 2011

Watched pot never boils!

When will the summer rains begin?

I was relieved to find a newspaper article that suggested it would be on time, entitled Southwest monsoon rainfall “most likely” to be normal – although use of the term “monsoonal” struck me as odd since the standard parlance for the Florida peninsula is “wet season” instead.


Comparison of Florida and India's summer onset and annual rain totals


In general, the wet season starts by early May in Miami and then by mid month (in the form of spot rains) spreads through most of the rest of the peninsula, until finally, by early June, reaching the Panhandle and Jacksonville coasts.


The meteorological wet season tends to “turn on” like the flip of a switch.

But getting it to soak in and fill back up takes time. Unless we get a lot of rain all at once (i.e., May 2009,) the swamp will likely take longer to fill back up by merit of the especially deep drop of the winter water table. A this point, only the deepest refugia pools still hold water. And by deep, I mean deep – as in Deep Lake (i.e., 90 ft deep) and a few others. For more information on the drought, please read this recent SFWMD/NWS Press Release, ominously entitled "Drought Expected to Last into Dry Season."


Deep Lake looking east, May 2011


As for that newspaper article, once I clicked in I saw my mistake:

My news search for “southwest rainy season” had spanned the globe and found a meteorological forecast for the Indian peninsula instead. But I wasn’t disappointed, in fact fascinated: the top of the article had a vividly-explained map depicting the chronological onset of its summer showers across the Indian peninsula which, it turns out, start up later than Florida.


The difference between the two is that our rainy season is characterized by a daily reversal of winds (i.e., sea breeze and land breeze) whereas in India the winds blows a reliably and constantly (i.e., both day and night) “onshore” into the upper atmosphere low that settles in over the peninsula.

Notice how a big week of rain in May 2009 ended the drought.
Could the same happen again?
Florida’s rains are fueled by daily formation of lower-atmosphere lows instead.

However, it should be noted it is the lingering up upper-atmosphere instability of the continental spring (which can extend into June) that often bring south Florida some of our biggest weeks of rain. That's what gave us the big week of rain right out of the wet season gate in May 2009. Fast forward two years later and we are in the same deep dry season boat, watching (and waiting) for the wet season pot to boil.


The sooner the better!

1 comment:

Janie said...

Interesting compare/contrast of the Indian wet season with Florida. Surely your pot will boil soon.