CAT 5 Hurricane Dean - Archived threads

[mempho]

150mph, Category 4 at 5:00

[CrazyC83]

Jamaica insured damage: up to $2 billion (total up to $4 billion)

http://www.bloomberg.com/apps/news?pid= ... 00fwQOe.0Q

[cycloneye]

AT 500 PM EDT...2100Z...THE CENTER OF HURRICANE DEAN WAS LOCATED
NEAR LATITUDE 18.2 NORTH...LONGITUDE 84.2 WEST OR ABOUT 270 MILES...
435 KM...EAST OF CHETUMAL MEXICO.

[Sanibel]

I'm not going to argue large low pressure pan dynamics in here. But pressure is a main factor.

This coast has reefs that keep the worst surge down, but then has the opposite in shallow bays.

Winds and geography are the two main factors that enhance surge.

Charley had 145mph in the Bay of Bengal shallows off Sanibel and had no surge.

[dtrain44]

NHC Discussion at 5 EDT:

"COMMUNICATIONS PROBLEMS ARE PREVENTING THE RECEIPT OF MOST DATA FROM
THE AIR FORCE RECONNAISSANCE AIRCRAFT THIS AFTERNOON...ALTHOUGH A
1930Z VORTEX FIX WAS RECEIVED. AT THAT TIME THE MINIMUM PRESSURE
WAS 918 MB...WITH MAXIMUM FLIGHT-LEVEL WINDS OF 151 KT. EARLIER IN
THE FLIGHT...A PEAK SFMR WIND OF 123 KT WAS OBSERVED. DVORAK
CLASSIFICATIONS FROM TAFB AND SAB WERE 127 KT AT 18Z. BASED ON
THESE DATA...THE INITIAL INTENSITY IS HELD AT 130 KT. ALL OBJECTIVE
GUIDANCE SHOWS ADDITIONAL INTENSIFICATION OVER THE DEEP WARM WATERS
OF THE WESTERN CARIBBEAN...AND DEAN COULD REACH CATEGORY FIVE
STATUS BEFORE MAKING LANDFALL. A 15Z MICROWAVE PASS SHOWS A PARTIAL
OUTER EYEWALL...BUT THIS WILL PROBABLY NOT HAVE ENOUGH TIME TO
INDUCE ANY WEAKENING BEFORE LANDFALL. DEAN IS EXPECTED TO MAINTAIN
HURRICANE STRENGTH AS IT TRAVERSES THE YUCATAN PENINSULA...AND
APPROACH MAJOR HURRICANE STRENGTH AGAIN BEFORE ITS FINAL LANDFALL.

THE INITIAL MOTION IS 275/17. DEAN IN EXPECTED TO MAINTAIN A TRACK
BETWEEN WEST AND WEST-NORTHWEST TO THE SOUTH OF THE WESTWARD-
BUILDING SUBTROPICAL RIDGE. MOST OF THE DYNAMICAL MODEL GUIDANCE
HAS TRENDED SOUTH AND THE OFFICIAL FORECAST HAS BEEN NUDGED
SOUTHWARD. ALL THE LARGE-SCALE MODELS TAKE THE MID-LEVEL VORTICITY
OF DEAN WEST-SOUTHWESTWARD ACROSS THE MOUNTAINS OF CENTRAL
MEXICO...AND THE OFFICIAL FORECAST NOW SHOWS A LEFTWARD BEND OF THE
TRACK AFTER FINAL LANDFALL. I DO NOT ACTUALLY EXPECT A WELL-
DEFINED SURFACE CIRCULATION TO EXIST AT 72 HOURS...BUT A POINT IS
PROVIDED SO THAT IT DOESN'T APPEAR THAT THE TRACK ENDS IN THE GULF
OF MEXICO."

Same line on potential for intensification - but we've been hearing that for the last day.....

[tolakram]

http://www1.cira.colostate.edu/ramm/rms ... PICAL.html

The loop is updating every 10 minutes now.

[Cyclone1]

I'm not going to argue large low pressure pan dynamics in here. But pressure is a main factor.

This coast has reefs that keep the worst surge down, but then has the opposite in shallow bays.

Winds and geography are the two main factors that enhance surge.

Charley had 145mph in the Bay of Bengal shallows off Sanibel and had no surge.

Did you fuse two sentences by mistake? Charley was small, and it had just rapidly intensified, which explains lack of surge. I forgot to mention size. The Bay of Bengal... has very little to do with Hurricane Charley.

[flamingosun]

Has anyone heard any news out of Roatan?

[Derek Ortt]

looks to hit very near Chetumal, which is at 18.5N

[Wthrman13]

I'm not going to argue large low pressure pan dynamics in here. But pressure is a main factor.

This coast has reefs that keep the worst surge down, but then has the opposite in shallow bays.

Winds and geography are the two main factors that enhance surge.

Charley had 145mph in the Bay of Bengal shallows off Sanibel and had no surge.

Umm, Sanibel, I don't mean to be rude, but what are you talking about? As far as I know, there is no such thing as "low pressure pan dynamics". Cyclone1 was correct, the overwhelming cause of storm surge is the action of wind on the surface of the ocean, which can be enhanced by the ocean floor topography and the orientation and shape of the shoreline. The low pressure does play a role, but it is a very small one compared to these other factors.

[mempho]

The surge in Charley did not have time to build. Surge lags behind a storm's strength. Katrina had a Category 5 surge because the surge values had not come down from it's Cat 5 status. Charley was the opposite.

[crm6360]

I'm not going to argue large low pressure pan dynamics in here. But pressure is a main factor.

Pressure exerts little influence on the surge. Do some background research before making such statements. Katrina's surge was a result of its peak winds over the open gulf, the very large wind field, and its perpendicular approach to the coast.

It is annoying when people make claims that lack scientific underpinnings and then stick by it as if it were fact.
Being new to the board, it seems like many people here spend more time posting statements based on emotion rather than pure reason and objectivity.

[Sanibel]

I forgot to mention size.

Exactly. This is a large, burly hurricane. Charley was small. Charley was 945 or so in pressure. Dean - 918. Different characteristics result in different damage. Charley was a 'weaker' category 4, Dean a stronger one. Because of size and pressure. Pressure is why large Katrina made so much surge. It had a low pressure pan that acted like a plow. Charley had a very steep gradient and didn't.

Umm, Sanibel, I don't mean to be rude, but what are you talking about? As far as I know, there is no such thing as "low pressure pan dynamics".

Talk to Derek, that's where I got it. I don't want to draw off-topic complaints, so Ill just say Katrina existed in a low pressure pan of broad 2005 low pressure in the west Atlantic. In this scenario a broad shouldered storm making a right turn into the GOM coast was able to plow more water. That's why Camille had a narrower surge field.

[Derek Ortt]

surge does NOT lag the intensity, that is a horrible myth that has spread.

katrina' surge was size related, not because it was a cat 5

[Wthrman13]

For a really cool aliasing effect, check out the mesovortices in the eye of Dean in the zoomed visible satellite loop on the RAMSDIS website (http://www1.cira.colostate.edu/RAMM/Rms ... pical.html). The sampling rate of the satellite creates an illusion that the mesovortices are rotating clockwise about the center like you sometimes see when you look at the spokes on a tire or the blades of a helicopter.

Yep, I noticed that too. Very cool! Check out this page (if you haven't already), which shows the effect, and then a higher temporal resolution loop which removes the illusion:

http://cimss.ssec.wisc.edu/goes/blog/

[WxGuy1]

NHC Discussion at 5 EDT:

Same line on potential for intensification - but we've been hearing that for the last day.....

Just so that we fair to the NHC, they've been saying that there has been POTENTIAL for Dean to strengthen into a Cat 5 hurricane. If Dean does not do so that doesn't mean that the NHC forecast is a bust. Indeed, they have correctly and prudently noted the POTENTIAL for intensification.

I know you weren't blasting the NHC, but I just wanted to make sure nobody misinterpreted the "potential for intensification to Cat 5" to mean "Dean will intensify to Cat 5".

[Cyclone1]

I forgot to mention size.

Exactly. This is a large, burly hurricane. Charley was small. Charley was 945 or so in pressure. Dean - 918. Different characteristics result in different damage. Charley was a 'weaker' category 4, Dean a stronger one. Because of size and pressure. Pressure is why large Katrina made so much surge. It had a low pressure pan that acted like a plow. Charley had a very steep gradient and didn't.

The pressure of a 965mbar, 100mph category two hurricane can create a 2-3 foot surge. Winds from a 965mbar, 100mph category two hurricane can create a 6-8 foot surge. 12+ foot surge in place with a coastline that curves inward (such as Long Island).

Pressure < Wind+Geography

[Wthrman13]

I forgot to mention size.

Exactly. This is a large, burly hurricane. Charley was small. Charley was 945 or so in pressure. Dean - 918. Different characteristics result in different damage. Charley was a 'weaker' category 4, Dean a stronger one. Because of size and pressure. Pressure is why large Katrina made so much surge. It had a low pressure pan that acted like a plow. Charley had a very steep gradient and didn't.

Again, respectfully, you are incorrect sir. Low pressure has very little to do with it! It's all about the winds: the strength, time duration, and fetch.

I might add, that if the pressure was a main factor, the surge would be just as bad on the side of the hurricane where the winds are blowing off the land. In fact, that is not the case.

[Matt-hurricanewatcher]

I would love for another pass through the eye and northeast quad about now,. Dean looks very good.

[Derek Ortt]

http://www.nwhhc.com/atl042007.html

A Hurricane WARNING, not a TS watch is needed to Veracruz. I am not entirely sure what the Mexicans are thinking there and a watch probably is needed north of Veracruz at least to la Pesca, but to be safe to the US/Texas border

Prepare for cat 5 winds between the Belize/mexican Border to Tulum. Expecting landfall not far from Chetumal