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Major Hurricane Irene live tracking


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TROPICAL STORM IRENE TROPICAL CYCLONE POSITION ESTIMATE

NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011

200 AM AST MON AUG 22 2011

AT 200 AM AST...0600 UTC...THE CENTER OF TROPICAL STORM IRENE

WAS ESTIMATED BY FAA DOPPLER RADAR AND RECONNAISSANCE AIRCRAFT

TO BE NEAR LATITUDE 18.2 NORTH...LONGITUDE 65.9 WEST...OR ABOUT

15 MILES SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO.

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Updated the radar loop, made it longer by collecting more frames and also slowed the speed a bit.

(Radar loop from 12:12am EST to 1:42am EST)

You can tell the latest movement.

Looks like the interaction with land is what may have tugged the center north, especially seeing the structure of the center "consolidate" the southern flank up into the circulation center. Seems to be heavier convection intensifying on the norther quadrant, is it maybe a dilemna whether the Center is tugged off the Island by lopsided convection or trapped on the island due to frictional forces? I'm wondering about the latter since it seems to have shiften to a more WNW track over the past 1-2 frames rather than a NW track...(wobble). Or maybe not? Hard to tell.

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Phil,

If this straddles the coast of Florida, won't land friction pull it inland? One track showed it parrallel almost the entire coast of Florida and I was wondering if that would be possible.

The effect is less when the terrain is not as significant. However, there are examples even in relatively flat terrain where if mean flow is very weak that TCs can gravitate towards the coastline. The most obvious example I can think off off the top of my head was Hurricane Isidore (2002)

2r43jma.gif

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This run has a landfall on the NC/SC border as a Major, so much for "consistancy"...if it ever existed it's history now. GFS/West, CMC/West, ECMWF/East. Hard to tell where to go...ECMWF has been very consistant, sticking to my original thoughts on a SC landfall, not that it matters.

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This run has a landfall on the NC/SC border as a Major, so much for "consistancy"...if it ever existed it's history now. GFS/West, CMC/West, ECMWF/East. Hard to tell where to go...ECMWF has been very consistant, sticking to my original thoughts on a SC landfall, not that it matters.

ECMWF is further east than that. it approaches the NC/SC border but turns toward the NNE. At 12z sunday it's got a strong-looking cane near Hatteras. Gets bald head island pretty good on it's way by.

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Here's another tibit that might help solve this mid-level subtropical ridge question. 00z Bermuda sounding shows that the current 500mb height is at 5920m which is a good 20m lower than yesterday at 12z... thus the ridge has weakened slightly in the last 12 hours.

24vjvx3.png

Comparing it to the initialization of the models, it seems that the ECWMF seems pretty reasonable, while the GFS is a little bit too weak on the 500mb height initialization at 00z. However, the GFS has a weaker surface initialization of Irene, while ECWMF is much stronger, which might be able to explain the more northward solution initially from the ECWMF.

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Here is a good paper on island effects on the propapgation of TCs

http://orca.rsmas.mi.../Wang_Chang.pdf

In this paper the basic idea is that there is a trough that is formed on the lee side of a mountain range, while a ridge develops on the windward side... in theory the TC would be drawn towards the trough causing the cyclone to move towards the island. That explains why you often see TCs trying to hang around land, because the leeward trough that forms will shift depending on the orientation of the wind direction.

Furthermore... if the mountains are tall enough, the llc is impeded by the height of the mountains and is essentially stuck... in this case the lee trough that forms on the lee side of the mountain range ends up developing into the new llc for the cyclone. When the upper level portion of the circulation (the part that is taller than the mountain) moves over the mountain pass, the llc circulation that forms from the lee trough reconnects with the upper level circulation and the cyclone can now progress in a more uniform fashion.

This is application of the Bernoulli Principle: airflow through a constricted medium. As the winds progress up the sides of mountains, they increase in velocity which decreases the pressure. So you end up with a pressure gradient between the bottom of the mountains and the tops. As stated, on the leeward side the velocity is at a maximum and then the winds will decrease in velocity coming down which creates a pressure gradient also. So, what you really have is a trough along the mountain range. If there is blocking, this would produce a ridge as well.

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More latitude gained.

LOCATION...18.3N 66.1W

ABOUT 10 MI...20 KM SW OF SAN JUAN PUERTO RICO

ABOUT 70 MI...115 KM ESE OF AGUADILLA PUERTO RICO

MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H

PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H

MINIMUM CENTRAL PRESSURE...989 MB...29.20 INCHES

Also

DATA FROM THE SAN JUAN FAA DOPPLER WEATHER RADAR INDICATE THAT

MAXIMUM SUSTAINED WINDS ARE NEAR 70 MPH...110 KM/H...WITH HIGHER

GUSTS. SOME STRENGTHENING IS STILL POSSIBLE THIS MORNING...AND

IRENE COULD STILL BECOME A HURRICANE WHILE OVER PUERTO RICO DURING

THE NEXT FEW HOURS. SOME WEAKENING IS POSSIBLE THIS AFTERNOON

AND TONIGHT AS THE CENTER MOVES NEAR OR OVER THE DOMINICAN

REPUBLIC. SOME RESTRENGTHENING IS EXPECTED LATE TUESDAY AFTER THE

CENTER MOVES BACK OVER WATER.

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Based on the new Euro and the GFS ensembles, as well as the majority of the hurricane models (throwing out the obviously out to lunch GFDL) I still think NHC is too far left. I pretty strongly feel this will hit NC or SC. The strength is problematic, but a cat 2 at landfall might be a good first guess.

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The ECWMF at 96 hours is in about the same position compaired to 12z, but not as far to the west at the 00z GFS.

At 120 hours its actually east of the 12z ECWMF track and looks more like a SC/NC track.

23rtkko.gif

Impressive....a 943mb (27.85" for us old timers) hurricane 200 miles due south of the SC/NC border.

Anything even vaguely similar to that scenario will make for one wild weekend along our coastline. And the hours remaining on each model run gets less and less and less....

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Impressive....a 943mb (27.85" for us old timers) hurricane 200 miles due south of the SC/NC border.

Anything even vaguely similar to that scenario will make for one wild weekend along our coastline. And the hours remaining on each model run gets less and less and less....

ECMWF tends to go a little crazy on the strength. 943mb is most likely too low.

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