Dean charges towards Jamaica; Erin returns

By: Dr. Jeff Masters , 3:37 PM GMT on August 19, 2007

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Hurricane Dean continues to pound Haiti and the Dominican Republic with high winds and heavy rain, and is headed for a very close encounter with Jamaica and the Cayman Islands. Early this morning, winds at Barahona on the southernmost point of land of the Dominican Republic hit 52 mph, gusting to 104 mph. Sustained hurricane force winds are expected to remain well south of both Haiti and the Dominican Republic, but a major spiral band has brought extremely heavy rain to the south portion of both countries.


Figure 1. Microwave satellite image of Dean taken at 7:17am EDT Sunday August 19. Think of this as a weather radar in space--the red areas show where the most intense thunderstorms in the spiral bands and eyewall are occurring. Note the incomplete double ring of echoes around the dark blue eye. Dean has two eyewalls, concentric around each other.

Jamaica and the Cayman Islands
Jamaica is already receiving high winds and heavy rain from an outer spiral band. How bad will it get? The big question is if the eyewall will move over the island. Unfortunately for Jamaica, Dean has two eyewalls, forming concentric rings (Figure 1). The inner eyewall is 15 miles in diameter, and the outer eyewall is 37 miles in diameter. Winds of Category 3 and 4 strength are blowing in both eyewalls, as seen in the latest data from the SFMR surface winds taken by the Hurricane Hunters. So, Dean's center has to pass more than 25 miles south of Jamaica for the island to be spared the worst of the hurricane. The nation's capital, Kingston, lies on the southern portion of the island, and will be the hardest-hit major city. The tourist city of Montego Bay is on the northern part of Jamaica, and will fare much better.

The same story holds true for the Cayman Islands. Grand Cayman, the southernmost of the islands, it at greatest risk. If Dean passes more than 30 miles south of the island, they will miss seeing the outer eyewall of Dean and will fare relatively well. It's going to be a close call, but it appears that both Jamaica and the Cayman will miss seeing the eyewall of Dean.

Mexico and Texas
Mexico will not be so lucky, and will receive a double beating. Dean is expected to make landfall twice, once near the tourist havens of Cozumel, and then again south of the Texas border. Mexico has to hope that the steering currents will be kind and take Dean south of the most heavily populated regions of the Yucatan. Hurricane Emily of 2005 grazed the southern tip of Cozumel Island as a Category 4 hurricane with 135 mph winds, and Dean may follow a similar path. Mexicans can take heart in the fact that Emily caused no deaths in Mexico, and damage was surprisingly light. Most of the tourist regions were relatively unaffected by Emily--it was Wilma two months later that really punished the Mexican Riviera.

As for Texas, it looks right now like only extreme southern Texas near Brownsville needs to worry about Dean. Hurricane Emily hit 90 miles south of Brownsville as a Category 3 hurricane in 2005, and I expect a similar story will unfold for Dean. Emily brought sustained winds of about 40 mph to extreme south Texas, a 4-5 foot storm surge, eight tornadoes, and heavy rains. Damage was minor.

Links to follow:
Radar in Piln, Cuba.
Radar from Guantanamo Bay, Cuba.
Morphed microwave animation.
Kingston, Jamaica observations.
Montego Bay, Jamaica observations.
Grand Cayman observations.

After Dean, what next?
There is an area of disturbed weather that has formed off the northeast coast of South America, 400 miles southest of Barbados. Wind shear is 20-25 knots in this region, and will stay too high to allow develoment for at least the next two days. None of the reliable computer models are suggesting anything will develop over the coming week. The ITCZ region between Africa and the Lesser Antilles is relatively quiet.

Erin returns
The remains of Tropical Storm Erin re-intensified this morning into a major storm that slammed central Oklahoma with rains up to seven inches and wind gusts of tropical storm strength. The radar presentation of Erin's remains (Figure 2) looks remarkable tropical storm-like. I've saved a long animation of this "landcane". Numerous flood watches, flood warnings, and severe thunderstorm warnings have been posted for Oklahoma today.


Figure 2. The remains of Tropical Storm Erin re-intensified into a remarkably tropical storm-like cyclone today.

Typhoon Sepat
Typhoon Sepat has moved inland over mainland China, after hitting as a Category 1 storm. Earlier, Sepat hit Taiwan as a Category 3 typhoon. No deaths occurred on Taiwan, but at least 15 died in China--11 of them in a tornado spawned by the typhoon.

I'll have a full update Monday morning, and may have a short update later today.

Jeff Masters

Hurricane Dean South coast Antigua (RHLK)
Hurricane Dean South coast Antigua

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126. kmanislander
4:34 PM GMT on August 19, 2007
I should have said all three islands are taking it seriously because we have two sister islands who, although much further to the NE than Grand Cayman, also share some risk but not as much as Grand Cayman
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124. paulfrmpasschristian
10:35 AM CST on August 19, 2007
that eye is really looking good, still may scrape the South edge of the island
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122. littlefish
4:35 PM GMT on August 19, 2007
Stay safe kman and all people on Jamaica (and elsewhere in Daen's path).
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121. KnowYourRole
12:33 PM EDT on August 19, 2007
Posted By: TXKiwi at 12:33 PM EDT on August 19, 2007.
Come on people... I'm not an expert by any means.. but megaloo / wxmongrel, those maps are generalized diagrams of where storms typically go. EVERY storm is different depending on the weather systems around it.

You can't look at Dean and say it hasn't hit the "fork", so it could go anywhere. The particular ULL /high situation etc dictate where it is likely to go, not some general roadmap prepared 6 months ago.


I agree TXKiwi. Every situation is different. Those maps are great info for historical information, but nothing more. I'm still waiting for someone to wishcast it to Florida today=)
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120. Tazmanian
9:33 AM PDT on August 19, 2007
the USA is not at of the woods by any means what so evere we have that ULL in the gulf and Erin in ok
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117. kmanislander
4:34 PM GMT on August 19, 2007
Thanks Ike
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116. Spoon
4:33 PM GMT on August 19, 2007
I asked last night but didn't get an anwser... why does it take so long for the GOES images to appear online? It seems like there is a 30+ minute delay from the timestamp to when it shows up.
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114. kmanislander
4:30 PM GMT on August 19, 2007
Hi MLC

Yea, we have our fingers, toes and just about everything else crossed at this time ( except the eyes of course ) !.

Will chat later. Just wanted to stop in briefly to let everyone know that the entire island is taking Dean very seriuosly regardless of what happens.
Ivan taught us a lot of valuable lessons .
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113. NorthxCakalaky
4:32 PM GMT on August 19, 2007
Posted By: Amystery at 4:32 PM GMT on August 19, 2007.

despite what alot of people were predicting when Dean formed, there isnt really anything to worry about in the Atlantic for at least a week...Dean might be the only thing memorable about this season(and it will not be memorable for most of the USA since it will not affect the USA). I am suprised the ITCZ is so not active...not ANYTHING on the horizon and we are entering in the end of August!



Thats a good thing!
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112. TXKiwi
4:30 PM GMT on August 19, 2007
Come on people... I'm not an expert by any means.. but megaloo / wxmongrel, those maps are generalized diagrams of where storms typically go. EVERY storm is different depending on the weather systems around it.

You can't look at Dean and say it hasn't hit the "fork", so it could go anywhere. The particular ULL /high situation etc dictate where it is likely to go, not some general roadmap prepared 6 months ago.

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111. IKE
11:31 AM CDT on August 19, 2007
Posted By: medic11402 at 11:31 AM CDT on August 19, 2007.
I find it interesting that once Dr. masters says that this is most likely a Non US event,,, it dies down in here...


Because most folks that post here are from the US and if it doesn't threaten them, their not around.

And good luck Kman..for you and your tropical paradise.
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110. Xion
4:30 PM GMT on August 19, 2007
Eye seems alittle more oval. Maybe in response to the blue mountains. The storm does not want to lose its eyewall.

You mean eyewalls.

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107. medic11402
11:28 AM CDT on August 19, 2007
I find it interesting that once Dr. masters says that this is most likely a Non US event,,, it dies down in here...
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106. Weather456
4:29 PM GMT on August 19, 2007
Posted By: littlefish at 4:27 PM GMT on August 19, 2007.

Thanx 456, did not realize it was one wave. The axis seems plausible, but the path the north component has taken and speed don't match with the lsoutherly part. Regardless, I think it is the 'blob' the CMC is putting over Fla. But no one rleiable is talking about it so I'm guessing it is a strong no-go for dvlpmnt. Still watching though. Dr M and NHC don't bring it up but mention your wave down south.


i was wondering that too.
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105. tallahasseecyclone
4:30 PM GMT on August 19, 2007
Could Erin stall the ULL?
104. WXMongrel
4:26 PM GMT on August 19, 2007
August

Link
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103. moonlightcowboy
4:28 PM GMT on August 19, 2007
G'morning, K'man, that is in our wish and prayers! STAY SAFE!!!
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102. Weather456
4:23 PM GMT on August 19, 2007
Posted By: littlefish at 4:23 PM GMT on August 19, 2007.

456, there's some decent vorticity with the south wave you mentioned and very little with the northerly area and they both have shear (in difft directions). so again I doubt either will develop. But if the 18N one did, it'd be staring down the east coast. Mostly Fla I think like the CMC shows, but there's a trough coming across US that could spit it north quite a bit. But hey, it needs convection before conjecture can start:) Hope Jamaica's prayers are answered and Dean slides south.


Yeah, I mentioned that earlier:

Tropical Wave Update

A tropical wave continues to move west across the Tropical Atlantic along 10N/53W-20N/50W. The wave continues to exhibit clear inverted V curvature in the surrounding mid-low level stratocumlus field on visible images. Also the wave is cleary indentified in potential vorticity charts, precipitable water imagery by SSMI satellite sensor and quikscat. A few buoys also show the classic northeast-southeast wind shift.

Low level vorticity, precipitable water, visible winds, visible imagery loops and buoy observations all indicate very well that a low pressure area continues to be located along a tropical wave near 11N/53W. The latest GFS MSLP of the Atlantic and Quikscat also depict the low pressure center very well.

The lastest TAFB anaysis also supports this finding and has the low at 1010 mb.

Shower activity remins minimal to moderate along these two features but one the models CMC develops this wave has moves northwest in either the northern Caribbean or Southwest North Atlantic.

by W456




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101. kmanislander
4:20 PM GMT on August 19, 2007
good morning all

We are pretty much ready here but are also encouraged by the shift S of the forecast track. Dean has been pretty consistent on the points since last night and if this holds true for the next 15 hrs we would be spared the core of the Hurricane.

Gilbert passed 60 miles S of us and did little damage. Lets hope Dean stays that far away or further.
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100. littlefish
4:24 PM GMT on August 19, 2007
Thanx 456, did not realize it was one wave. The axis seems plausible, but the path the north component has taken and speed don't match with the lsoutherly part. Regardless, I think it is the 'blob' the CMC is putting over Fla. But no one rleiable is talking about it so I'm guessing it is a strong no-go for dvlpmnt. Still watching though. Dr M and NHC don't bring it up but mention your wave down south.
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99. OUFan919
4:25 PM GMT on August 19, 2007
What happened here in Norman/Oklahoma City this morning was amazing! There were several reports of 70-80mph winds. It woke me up around 5am with incredible wind gusts! I turned the TV on and Erin looked like a Hurricane!! It was amazing to watch and go through!
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98. IKE
11:26 AM CDT on August 19, 2007
The 1545 UTC visible on Dean has it edging closer to the southern coast of Jamaica.
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97. tillou
4:22 PM GMT on August 19, 2007
Thanks WXMongrel and Melagoo. Im sort of new to this tropical weather stuff but since Katrina I've been paying a lot more attention to this stuff.
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96. KnowYourRole
12:25 PM EDT on August 19, 2007
Posted By: Melagoo at 12:24 PM EDT on August 19, 2007.
Dean hasn't hit the fork in the road to Mexico or USA


nice map...for September=)
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95. CapeBretonNS
4:23 PM GMT on August 19, 2007
Am i the only one thinking WTF?????
A huge cane in the ocean, An eyewall in Oklahoma
and frost in the east halfway through August ?????????
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94. ewolk08
4:24 PM GMT on August 19, 2007
i was talkin bout after jamica someone had mentioned after jamica it could head more north than expected
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93. Melagoo
4:24 PM GMT on August 19, 2007
Dean hasn't hit the fork in the road to Mexico or USA

august storms
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91. littlefish
4:18 PM GMT on August 19, 2007
456, there's some decent vorticity with the south wave you mentioned and very little with the northerly area and they both have shear (in difft directions). so again I doubt either will develop. But if the 18N one did, it'd be staring down the east coast. Mostly Fla I think like the CMC shows, but there's a trough coming across US that could spit it north quite a bit. But hey, it needs convection before conjecture can start:) Hope Jamaica's prayers are answered and Dean slides south.
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88. Tazmanian
9:21 AM PDT on August 19, 2007
yes 03 92L soon but not today
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87. guygee
4:19 PM GMT on August 19, 2007
Frost...
Downside - End of the Growing Season.
Bright side - End of the mosquito season.
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86. centex
4:19 PM GMT on August 19, 2007
Dean has been moving west the last 12 to 18 hours with bumps, wobbles to the north every few hours. But still looks like with even the northen small shifts the eye will pass to south of Jamaica.
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85. WXMongrel
4:20 PM GMT on August 19, 2007
IAmRooot...whew. Thought I was the only one seeing things. May want to ask StormW, 456 or some of the other vets when they join.
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84. Tazmanian
9:19 AM PDT on August 19, 2007
yes 92L soon but the nh dos not seen to happy about it yet so whats this wait and see
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82. Weather456
4:18 PM GMT on August 19, 2007
also littlefish....the axis of the wave tilts from the low pressure area near barbados to near 18N/48W so i see it as one wave.
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81. jamnkats
4:17 PM GMT on August 19, 2007
Posted By: Masquer08er at 4:09 PM GMT on August 19, 2007.
Why is Belize not being discussed? I understand the northerly componant. But, isnt a due west course plausible. Asking not casting. Thanks

I agree! Belize was our evacuation point. Now we're stuck here (Yucatan penninsula) waiting to see if we should head north or south. I just want to be gone already but now we have to wait and see where Dean is going to go.
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79. IAmRooot
11:20 AM CDT on August 19, 2007
WXMongrel & tillou.....i was questioning that also. maybe someone will provide an answer if enough people ask. i would like to know as well.
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78. Melagoo
4:16 PM GMT on August 19, 2007
tillou...I made that comment earlier. I am not a qualified forecaster, however, seems to me that steering winds have a more practical effect than models give credit to. This AMATEUR is guessing that after passing Jamaica a northerly correction is possible.

I think you may be right
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77. WXMongrel
4:18 PM GMT on August 19, 2007
Ok, experienced weather jockeys. What happens if Dean overtakes the nearly stationary ULL sitting in the GOM?
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76. setfree7
11:07 AM CDT on August 19, 2007
those 80mph winds were not from tornadoes in OK. they were straightline winds.
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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