Hurricane Dean--9th strongest hurricane on record

By: Dr. Jeff Masters , 2:46 PM GMT on August 21, 2007

Hurricane Dean powered ashore in Mexico's Yucatan Peninsula this morning as a Category 5 hurricane with 165 mph winds. The pressure of 906 mb measured by the Hurricane Hunters shortly before landfall at 4:30am EDT makes Dean the ninth strongest hurricane on record in the Atlantic. This is the third lowest pressure at landfall behind the 1935 Labor Day hurricane in the Florida Keys and Hurricane Gilbert of 1988 in Cancun Mexico. Dean is also the first Category 5 hurricane to make landfall in the Atlantic Basin since Andrew of 1992.

Figure 1. Dean at landfall, as seen by the Cancun radar. Image credit: Meteorological Service of Mexico.

Radar images at landfall (Figure 1) show that Dean came ashore just north of Chetumal, Mexico, a city of 130,000 people. Dean's center passed about 15 miles north of the city, and Chetumal missed the strongest Category 5 winds of the storm. The strongest winds from Dean were in the right front quadrant on the northern side, since the forward speed of the storm adds to the rotational speed of the winds there. It appears Chetumal was just at the edge of the southern eyewall, and probably experienced sustained winds of Category 3 strength, 115 mph. We don't know, since the weather station stopped reporting data long before the storm arrived. However, a wind analysis done by NOAA's Hurricane Research Division (Figure 2) supports this estimate. The coastal area north of Chetumal where Dean's greatest fury was unleashed has a cruise ship port and a stretch of beach front development, and this region probably suffered near-total destruction.

Figure 2. Dean's winds one hour before landfall. Winds are in knots, multiply by 1.15 to convert to mph. Locations of Chetumal and the Costa Maya Cruise Ship Port are marked. Winds of Category 1 strength (65 kt) are colored yellow, and winds of minimal Category 3 strength (100 knots) are colored pink. Image credit: NOAA/Hurricane Research Division.

Further north, it appears that Cozumel probably got sustained winds near tropical storm force, 39 mph. The weather station there stopped transmitting data before the storm arrived. Cancun's winds topped out at 29 mph, gusting to 54 mph. To the south, Belize City has had top winds of 23 mph, gusting to 35 mph, so far this morning. On the western side of the Yucatan Peninsula, the winds are starting to rise at Campeche. Dean's center will pass south of Campeche, and bring tropical storm or Category 1 hurricane-force winds to the city.

Dean is powerful enough to survive the crossing of the Yucatan as a hurricane, and I expect it will be a Category 2 hurricane with 100 mph winds when it pops out into the Gulf of Mexico later today. Hurricane Janet of 1955, which hit near Chetumal as a Category 5 storm with 170 mph winds, weakened to a Category 2 storm with 105 mph winds when it popped out into the Gulf of Mexico south of Campeche. Janet was moving at about the same speed Dean is, so I expect Dean will behave similarly. Once out over the warm waters of the Gulf of Mexico, Dean has time to intensify by perhaps 15 mph before it makes a second landfall near Poza Rica. Dean will finally dissipate in the mountains about 100 miles north of Mexico City, and could bring heavy rains to the Mexican capital. No hurricane has ever survived the crossing from the Gulf of Mexico to the Pacific over the wide, mountainous portion of Mexico.

Links to follow today:
Campeche, Mexico observations.
Radar from Cancun, Mexico.
Belize City observations.
Morphed microwave animation.

Disturbance 92L
An area of disturbed weather associated with a tropical wave, 92L, is a few hundred miles north of Puerto Rico. This disturbance is less organized than yesterday, despite some rather favorable upper-level winds. There is some dry air to the north that may be interfering with organization, and there is probably not enough turning motion available from this tropical wave to get 92L spinning. I don't expect significant development today given its current state of disorganization, but 92L deserves close scrutiny over the next few days. None of the reliable computer models develop the system.

My live appearance tonight on Internet Partnership Radio
I'll be the guest tonight on the Internet Partnership Radio ( Tonight's show is called "Center of Circulation", and consists of global severe, winter, and tropical weather news/topics with up to the minute advisories, watches and warnings, safety & preparedness info, and periodic special guests. The host is Charlie Wilson. I hope you can listen in!

I may do a short update this afternoon, and the next full update will be Wednesday morning around 10am EDT.

Jeff Masters

Dean 2007 (nickmini)
A roof dumped atop another house
Dean 2007

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18. Bonedog
11:09 AM EDT on August 21, 2007
chovy probably renamed. Several systems disipated to just Tstorms that refired in the pac and got renamed.

monster the difrence with other countries is the lack of buracracy. No one bitchs as to who is in charge or does what and when. They have an emergency plan and just go. Military moves in to secure and assist, red cross does recovery and its thing, finally after its all said and done the areas go back to their normal government establishment.
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10:10 AM CDT on August 21, 2007
ckovy they get a new name
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16. hcoogcanewtcher
3:08 PM GMT on August 21, 2007
model runs for 92L...who knows???

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15. ckovy
3:08 PM GMT on August 21, 2007
According to Dr. Masters, no Atlantic hurricane has ever survived crossing Mexico.

But, what if one did?

Would it retain its Atlantic storm name or be renamed with a Pacific storm name?
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14. monstersmom
3:04 PM GMT on August 21, 2007
bonedog, thanks. i'm from new orleans and after katrina in a city with modern infrastructures and the delay in assistance, I worry about anyone going through a hurricane of any type.
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13. Bonedog
11:04 AM EDT on August 21, 2007
as far as rescue and provisions I did hear a report that the International Red Cross did activate their SAR teams from around the globe to be inplace to be used if necessary.

Food and Water were stocked at the shelters and they will be destributing chlorene tablets to disenfect potable water sources after the storm has passed.

The Mexican Government learned quite well from the 05 season and steps were inplace even before this season started. They dont waste time on buracracy there. They just push the GO button and the ES crews get to work. They even preplace the military and SAR teams so as soon as its safe for them to come out from cover they go to work.
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12. Bonedog
10:58 AM EDT on August 21, 2007
monster the Red Cross was inplace the days before the landfall, also the Mexican Government 24hrs prior activated their military on DN3 status which is like activating our troops to affected areas with full support behind them.

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11. StormHype
2:59 PM GMT on August 21, 2007
Update: 92L will never see US land. It's a fish blob. End of discussion.

Now back to Dean...
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10. PascagoulaGal
2:57 PM GMT on August 21, 2007
Emagirl This is awsome.

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9. RNluvsWeather
2:56 PM GMT on August 21, 2007
what about possible 93L? Anything going on there?
Thanks for the updates :) Love the info!!!!!
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8. monstersmom
2:55 PM GMT on August 21, 2007
Does anyone know what resources are in place to go into the affected areas for rescue, healthcare, food/water provisions?
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7. stormhank
2:53 PM GMT on August 21, 2007
Thanks DR. M. for update..
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6. philliesrock
10:53 AM EDT on August 21, 2007
Dr. M, what time does the show start? I would love to listen.
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5. floridagrrl
2:53 PM GMT on August 21, 2007
I am learning so much from Dr. M. We homescool - the kids thank you, too.
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4. emagirl
2:51 PM GMT on August 21, 2007
dean now a cat 2 with 105mph winds
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3. Miamiweather
2:49 PM GMT on August 21, 2007
Thank you for the update Dr. Masters
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2. ryang
10:47 AM AST on August 21, 2007
Thanks for the update...
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1. PascagoulaGal
2:47 PM GMT on August 21, 2007
Thanks for the update DR. M
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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