Extremely dangerous Dean heads for Jamaica
Hurricane Dean put on an impressive round of rapid intensification last night, deepening 49 millibars in just 24 hours. Dean is now a major Category 4 hurricane with 150 mph winds. Reports from Hurricane Hunter aircraft show that Dean has likely peaked in intensity, and may be undergoing an eyewall replacement cycle. The eye has shrunk from 20 miles in diameter yesterday down to 13 miles in diameter this morning. This inner eyewall will probably shrink even more and collapse sometime in the next day, to be replaced by a new outer eyewall 30-40 miles in diameter. Dean's winds may decrease to the lower end of the Category 4 scale, 135-140 mph, if that occurs. The inner eyewall and the new outer eyewall that is forming can be seen on a microwave satellite image from this morning (Figure 1). The 11:02am EDT eye report from the Hurricane Hunters said that the southern portion of the inner eyewall was missing, so the eyewall is probably collapsing now.
Figure 1. Microwave satellite image of Hurricane Dean at 7:31am EDT Saturday August 18. Two small partial rings of strong echoes, marking the boundaries of concentric inner and outer eyewalls, are visible. Image credit: Navy Research Lab.
Dean pounded Martinique, St. Lucia, and Dominica yesterday, and the storm's death toll now stands at three. A 62-year old man died on St. Lucia while trying to save his cow from raging flood waters, and a rain-triggered landslide killed a mother and child in their home in Dominica. Martinique suffered the worst damage, with 100% of the banana crop destroyed, 70% of the sugar cane crop gone, and considerable damage to buildings on the south end of the island. Lesser damage occurred on Dominica and St.Lucia, and overall, it appears that the Lesser Antilles islands were fortunate to get off so lightly.
Puerto Rico
Dean's eye is visible on long range radar out of Puerto Rico. A major spiral band of rain moved over Puerto Rico at about 11am EDT, and will bring up to four inches of rain to the island today. Radar estimated rainfall from the Puerto Rico radar shows up to two inches had fallen as of 1pm EDT. The wind/pressure plot from Buoy 42059 south of Puerto Rico shows that Dean passed just north of that location this morning, bringing wind gusts to 66 knots.
Dominican Republic
The tourist town of Punta Cana on the east tip of the island reported sustained winds of 34 mph, gusting to 46 mph this morning. The capital city of Santo Domingo can expect sustained winds of 40-45 mph today as Dean makes its closest pass to the south. Heavy rains of 1-3 inches in non-mountainous area will create some minor flooding problems in these areas. Mountainous area along the south coast of the Dominican Republic, particularly in the rugged Barahona Peninsula that juts farthest south into the Caribbean, will receive higher rain amounts and are at great risk of life-threatening flash floods.
Haiti
Dean will make a very close passage to the south of Haiti's mountainous southern Peninsula, and the capital city of Port-au-Prince could experience winds just below hurricane force. A Category 4 or 5 hurricane passing so close to Haiti is a serious threat. Deforestation has denuded the mountainsides of protective tree cover, and flood waters will wash down the mountains into populated areas. The only saving grace in this situation may be the relatively rapid forward speed of Dean, which will reduce the amount of rain that will fall, compared to other hurricanes that have affected Haiti.
Jamaica and the Cayman Islands
Jamaica is my greatest concern. A direct hit by Dean would make it the worst hurricane strike on Jamaica for over a century. Jamaica has not received a direct hit by a Category 4 or 5 hurricane since perhaps 1832. The worst strikes of the 20th century were Category 3 Hurricane Gilbert of 1988 and Category 2 Hurricane Charlie of 1951. The Cayman Islands also have much to fear from Dean. Dean could rival Ivan as the Cayman's worst hurricane strike of the past century.
Cuba
Mountainous regions in Cuba area also at risk of dangerous flash flooding from Dean. However, civil defense is so good in Cuba that I don't expect any loss of life. Portions of south Cuba will experience sustained tropical force winds.
Mexico
The models have come into much better agreement this morning on the longer term forecast, and it looks very bad for Cancun and Cozumel. Dean will give those resort areas a pounding like they received from Hurricane Emily (Category 4) in 2005, and Hurricane Gilbert (Category 5) in 1988. Dean will probably not be as bad as Wilma (Category 4) in 2005, since Wilma stalled out over Cancun for three days as a major hurricane. Dean is moving quickly, and will not linger long over any of the regions it strikes.
Texas and Louisiana
Things are looking much brighter for Louisiana, as the GFDL model has come in line with all of the other models in predicting a landfall in Southern Texas or Northern Mexico. It now appears likely that Mexico's Yucatan Peninsula will knock Dean down a category or two before it can approach the Texas coast. The upper level low that was forecast by the GFDL to potentially steer Dean northwards appears to be weakening and moving westwards, out of the way of Dean. You can watch this upper level low on water vapor satellite loops. It is the counter-clockwise spinning region that has moved west off the Florida coast into the eastern Gulf of Mexico. If this low continues to weaken and move westwards, it will not be able to swing Dean northwestwards towards northeast Texas and Louisiana. If Dean does manage to catch up to the upper level low, the counter-clockwise circulation around the upper low will bring some south-to-north winds over Dean that would steer it on a more northerly track into the Gulf of Mexico.
The NOAA jet is scheduled to fly tonight and Sunday morning, so we should have some excellent model runs available Sunday morning and afternoon.
I'll have a short update tonight by 9pm, and a full update Sunday morning by noon. Tonight's update will focus on Jamaica, and I'll post the relevant radar and current condition links to follow the storm's path. I'll talk about Typhoon Sepat, as well.
Jeff Masters
Reader Comments
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lf, it is really great when it has just been updated also!!!
Carry over response from previous blog concerning MIMIC.
I started looking at the ULL after I got back home last night because it was drawing from as far SW as the W Caribbean. I also notice that (at the time) Dean was moving W roughly 2x the speed at which the ULL was moving W.
Now, with the apparent change in motion of Dean, I'm wondering if they might not miss each other. The ULL maintains it's "forward motion" at roughly the same speed as last night. But, Dean's "westward motion" has been reduced by roughly 20-30% with this more northerly component to it's motion.
Bottom line - wait and see, I guess...
Link
A large ridge continues to cover most of the Southern Half of the United States, Northern Mexico and the Gulf of Mexico west of 90W. Broken to overcast skies with embedded showers are under the ridge over Northwest Texas and Arkansas associated with a 1008 mb low near 33N/101W...the remnants of Erin...and surface inflow by the low level jet.
Meanwhile...an upper low is moving west over Southern Florida, with a strong northerly upper flow developing between the two upper features. This flow is enhancing scattred showers over Alabama, Lousiana and parts of The Florida Panhandle. Showers are over the Northern Bahamas, South Floida and the Southeast Gulf caused by instability associated with our upper low. Elswhere across the region remains fair to partly cloudy with mid-high cloud advection mostly over the Northern Half.
The weather across the Southwest Atlantic is controlled by a surface ridge that continues to build west in times. Fair weather with light variable winds dominate.
by W456
Of course we just use them as guidance and thats it, but the NHC uses them to do their track... and eventually by tonight, the NHC track will shift northward substancially....
Looks like the GOM is just bubbling and waiting for anything to come in = DEAN MAJOR CAT 5
Link
Broward, that shows the ridge building in which should keep Dean on the W, WNW track.
URNT12 KNHC 181536
VORTEX DATA MESSAGE AL042007
A. 18/15:02:00Z
B. 15 deg 39 min N
068 deg 43 min W
C. 700 mb 2511 m
D. 80 kt
E. 196 deg 5 nm
F. 281 deg 091 kt
G. 194 deg 005 nm
H. 930 mb
I. 11 C/ 3051 m
J. 21 C/ 3038 m
K. 10 C/ NA
L. OPEN S
M. C11
N. 12345/7
O. 0.02 / 2 nm
P. AF304 0604A DEAN OB 15
MAX FL WIND 92 KT SW QUAD 15:00:30 Z
MAX FL WIND OUTBOUND 139 KT NE QUAT 15:05:30 Z
EYEWALL ON SOUTH SIDE LOOKING MORE RAGGED
Landfall.
WTF... What Ha Happened To The High Pressure?
Man The CMC is On Crack I Just know.
TWC Keeps Moving the Track South!!
Nickel TWC has the right idea,, it is reacting to the high that will be over most North GOM and will push this storm further south as it eneters the gulf more towards the central mexico area.
(Click on thumbnail below)
Questions: if the ULL stops weakening or gets stronger, am I right in thinking that the northwestern/central gulf coast might still be in danger? I don't think we should let our guard down until Monday AM...better to be on the safe side.
What factors can make a ULL strengthen?
but no worries Jamaica, I can assure you the large caribbean community in South Florida will send help and relief as soon as we can. I've already heard of efforts being made to send relief goods as soon as Dean makes it impact.
cold air
positive voticity advection
aplification between to high pressure ridge
merger with another upper low or upper trough
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