Tuesday, August 23, 2011

Why does the path keep moving east?

Forecasters were talking Sunday about Hurricane Irene slamming into south Florida. By Monday morning, it was north Florida. Later in the day, it was Charleston, and then Myrtle Beach.

Tuesday morning, it was Wilmington, then Morehead City. Now it looks like the Outer Banks -- or maybe not at all.

The continued eastward adjustment of Irene's predicted path has frustrated those responsible for planning emergency preparedness, although I'm sure nobody in south Florida is complaining about not being hit by a big hurricane.

But why the continued adjustments?

For starters, forecasting the path of a hurricane is not an exact science. You already knew that. Fifty years ago, meteorologists were hard-pressed to forecast the path 48 hours in advance. Now, they almost always get it right within 72 hours. It's the predictions beyond 72 hours that cause the problems.

As you might know, the path depends on a lot of factors.

In Hurricane Irene's case, the storm is expected to move into a weak area between two strong high pressure systems -- the "Death Ridge" over Texas (so named because it has been absolutely immovable this summer and has been death to any cold front or storm system that approaches), and the Bermuda high in the Atlantic.

Frequently this summer, circulation around the eastern side of the Texas Death Ridge has sent cold fronts into the Southeast. That's why we've had a lot of rain this summer and a few episodes of below-average temperatures.

That "weakness" between the two highs is called a trough, or a dip in the atmospheric flow. Hurricanes usually follow a path into such a weakness, and what happened with Irene is that computer models had a difficult time several days ago predicting how far south that trough would expand.

Imagine the trough as a roller-coaster, with the low end of the ride along the East Coast. Small low pressure systems riding along that trough can help steer a hurricane up the right side of the trough's path -- northeast, away from the U.S. coast.

Actually, we've seen this happen frequently in recent years. The last year I can remember when hurricanes barreled directly into the East Coast was 2004, when Frances and Jeanne pummeled Florida's Atlantic coast.

Some meteorologists think that as long as the Texas Death Ridge is in place (and who knows when that will break down!), the East Coast will have some built-in insurance against tropical storms and hurricanes.

Bill Reed, director of the National Hurricane Center, said in a morning news conference Tuesday that it's been tough, predicting exactly when Hurricane Irene will get caught in the upper-level flow, forcing a turn to the north and eventually the northeast. He's still not certain about the path, saying it could move back to the west or to the east.

I'm betting the east, because of the old weather saying, "The trend is your friend." And in Irene's case, the trend has been eastward.

26 comments:

Anonymous said...

What I heard was that residents in Florida turn their fans to the east, and all of the people at the beach blow air that way, too.
Who is to say what really happens?
Ok,ok,ok, I heard it from Rick Perry and Michele Bachmann....

Anonymous said...

Is everything about this country turning to the right ???

J said...

I absolutely do not wish major damage on anything or anyone, but I was kind of hoping the rains of the hurricane would come our way. It would keep the temp down. And before anyone says it, it has NOT cooled down. I don't know why meteorologists start calling the weather "cool" when the high is 89. That's still hot as far as I'm concerned.

Anonymous said...

I still think Irene has a surprise up her sleeve.... GA-FL border was my original call - but i don't have all the data the models are being fed so I can't argue with them.

Anonymous said...

I've had my fill of that scientifical lobal swarming nonsense.

Anonymous said...

J 1:53 -
I hope it is not that, the rain in vain falls mainly on the coastal plain.

Anonymous said...

Anon 1:55 -
Don't worry, pretty soon those models will regurgitate all of that data they were fed.
You know how models are these days.

Anonymous said...

"a weak area between two strong high pressure systems -- the "Death Ridge" over Texas (so named because it has been absolutely immovable this summer and has been death to any cold front or storm system that approaches)".

How do you get away with calling the Tea Party "the Death Ridge"?

Anonymous said...

To Anon 2:16,
"...the Texas Death Ridge has sent cold fronts into the Southeast."
And Rick Perry just left Rock Hill yesterday. Bachmann left last week.

Anonymous said...

Hurrican Irene was just tryng to steer clear of that NCAA-University of Miami storm. Didn't want to be upstaged.

Anonymous said...

NC State SUCKS so badly in Football that it is pulling the stinking storm east!

Anonymous said...

You meteorologists make me sick. Why don't you bring those meteors that you worship out into the true light of AMERICAN day??
But, NOOoooo.....you can only see them at night, in the dark, when the conditions are just right...
'NUFF SAID !!!

Anonymous said...

Whatever happened to "separation of church and stratus" ????

Anonymous said...

And the tin foil hat makes its appearance at 02:40.

Anonymous said...

J 1:53. You're not native are you? 89 degrees in mid to late August IS absolutely a "cooling off" for Southern Piedmont NC. Just remember, we'll have 70's into mid-November, while watching the Great Lakes snow on TV.

Anonymous said...

Wouldn't it be original if Irene kept going west and created its own atmosphere leaving everyone stunned.

Anonymous said...

That is what Michele is already doing.
Irene should be her own original catastrophe.

Anonymous said...

By the way, anon 4:44-
Don't post a comment if you can't bring enough ganja for everybody.

Anonymous said...

This has been a strange storm. I knew GA-FL border was out. Hasn't been a storm there ever. Figured it would be Charleston or McClellanville like Hugo.

Anonymous said...

We and the aquifer do need the rain.

Anonymous said...

Second generation Floridian here, have learned from experence not to trust the predicted paths. Being a block off the intracoastel across from the Sebastian path I will always prepare when they are this close especially when they ride north of the lower islands. Troughs and Texas hold ems can play a part, although the gulfstream plays a bigger card on the table.Jeanne was never to hit our shores and we were the only house for miles with boards on the windows and a generator,meaning running water for our neighbors to shower and wash clothes. army corps did not have time to open the locks what a mess that was, national guard finally showed up a week later with much needed MRE's and h2O with hours of lines for basics. Thank god for the salvation army food trucks. Remain cautious and don't always go by what the predictions say. I predict my house will be prepared.

Anonymous said...

Sorry for the misspelling I meant the Sebastian pass same as the Sebastian Inlet only growing up the daughter of a fisherman we always call Inlet's, Passes. Also Francis was not predicted correct either and was supposed to go north only to come in south threw the Ft. Pierce pass hovering over us for hours and hours, my memeory of that was waking up and looking up at the sky while the roof was flapping in the wind, saying so much for predictions and opening an ice cold can of budweiser.Out of the worst predictions in my lifetime, I have to say Andrew and Katrina were the worst. Note to the wise, when theres a monster lurking in the mist, board up your doors and windows and be prepared to hunker down for a few days.From a Florida girl who knows Hurricanes are unpredictable.

Anonymous said...

Oops I meant memory. Be careful out there, they are much more easier to ride out, if your prepared.

Anonymous said...

Head East? "Never Been Any Reason"

Anonymous said...

1:30pm comment - Well played.

Anonymous said...

In Sebastian, Fl. light bands are coming threw, going to be intresting to see what she wants to do after she gets over open water, still not trusting the predictions.Waiting and watching cautiously.Florida girl.