Hurricane Dean Live Thread Part III

Extremely dangerous Hurricane Dean is steaming toward the Yucatan Peninsula today, packing winds over 150 mph. The Hurricane Hunter aircraft aborted its mission Monday morning due to equipment problems. The storm is expected to attain catastrophic Category 5 status today. The Cayman Islands have been spared the brunt of the storm's winds as Dean passed 125 miles south of Grand Cayman.

Jamaica continues to assess damage to its infrastructure after Dean uprooted trees, knocked down power lines, stripped off roofs, and dumped up to 20 inches of rain, causing mudslides in the mountains. The government of Jamaica has declared a month-long state of emergency. Haiti has reported four fatalities. The Dominican Republic reported a 20ft storm surge. Martinique lost its banana crops. Additional details are scarce at this point due to extensive power outages.

Alcoa suspended aluminum production in Jamaica. Mexico evacuated thousands of workers from oil platforms. Texas mobilized the National Guard, opened emergency operations centers and moved inmates inland from three prisons in advance of the storm.

Space shuttle Endeavour is returning home Tuesday, a day early due to Hurricane Dean.

In other storm news, the remnants of Tropical Storm Erin caused massive rains and flooding in Oklahoma Sunday. Two people have drowned, and three are reported missing at this time.

Category	Wind Speed	Barometric Pressure	Storm Surge	Damage Potential
Tropical Depression	< 39 mph < 34 kts			Minimal
Tropical Storm	39 - 73 mph 34 - 63 kts			Minimal
Hurricane 1 (Weak)	74 - 95 mph 64 - 82 kts	28.94" or more 980.02 mb or more	4.0' - 5.0' 1.2 m - 1.5 m	Minimal damage to vegetation
Hurricane 2 (Moderate)	96 - 110 mph 83 - 95 kts	28.50" - 28.93" 965.12 mb - 979.68 mb	6.0' - 8.0' 1.8 m - 2.4 m	Moderate damage to houses
Hurricane 3 (Strong)	111 - 130 mph 96 - 112 kts	27.91" - 28.49" 945.14 mb - 964.78 mb	9.0' - 12.0' 2.7 m - 3.7 m	Extensive damage to small buildings
Hurricane 4 (Very strong)	131 - 155 mph 113 - 135 kts	27.17" - 27.90" 920.08 mb - 944.80 mb	13.0' - 18.0' 3.9 m - 5.5 m	Extreme structural damage
Hurricane 5 (Devastating)	Greater than 155 mph Greater than 135 kts	Less than 27.17" Less than 920.08 mb	Greater than 18.0' Greater than 5.5m	Catastrophic building failures possible

Category

Wind Speed

Barometric Pressure

Storm Surge

Damage Potential

Tropical
Depression

< 39 mph
< 34 kts

Minimal

Tropical
Storm

39 - 73 mph
34 - 63 kts

Minimal

Hurricane 1
(Weak)

74 - 95 mph
64 - 82 kts

28.94" or more
980.02 mb or more

4.0' - 5.0'
1.2 m - 1.5 m

Minimal damage to vegetation

Hurricane 2
(Moderate)

96 - 110 mph
83 - 95 kts

28.50" - 28.93"
965.12 mb - 979.68 mb

6.0' - 8.0'
1.8 m - 2.4 m

Moderate damage to houses

Hurricane 3
(Strong)

111 - 130 mph
96 - 112 kts

27.91" - 28.49"
945.14 mb - 964.78 mb

9.0' - 12.0'
2.7 m - 3.7 m

Extensive damage to small buildings

Hurricane 4
(Very strong)

131 - 155 mph
113 - 135 kts

27.17" - 27.90"
920.08 mb - 944.80 mb

13.0' - 18.0'
3.9 m - 5.5 m

Extreme structural damage

Hurricane 5
(Devastating)

Greater than 155 mph
Greater than 135 kts

Less than 27.17"
Less than 920.08 mb

Greater than 18.0'
Greater than 5.5m

Catastrophic building failures possible

Hurricane Dean Discussion Number 31

Statement as of 5:00 PM EDT on August 20, 2007

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.
 
 
Forecast positions and Max winds
 
initial      20/2100z 18.2n  84.2w   130 kt
 12hr VT     21/0600z 18.5n  86.7w   140 kt
 24hr VT     21/1800z 19.3n  90.2w    75 kt...inland
 36hr VT     22/0600z 20.2n  93.6w    85 kt
 48hr VT     22/1800z 21.0n  97.0w    95 kt
 72hr VT     23/1800z 21.5n 103.0w    30 kt...inland
 96hr VT     24/1800z...dissipated
 
$$
forecaster Franklin

Hurricane Dean Public Advisory Number 31

Statement as of 5:00 PM EDT on August 20, 2007

...Extremely dangerous Hurricane Dean expected to strike the Yucatan
tonight...could reach category five before landfall... 
At 5 PM EDT...2100 UTC...the government of Mexico has issued a
tropical storm watch from west of ciudad del Carmen to Veracruz.
 
At 5 PM EDT...all warnings in the Cayman Islands are discontinued.
 
A tropical storm watch remains in effect for the following provinces
of Cuba...Pinar del Rio...la Habana...and Isla de la Juventud.  At 5
PM EDT...all other watches and warnings in Cuba are discontinued.
 
A Hurricane Warning remains in effect for the entire coastline of
Belize...along the East Coast of the Yucatan Peninsula from the
Belize/Mexico border northward to Cancun...and along the West Coast
of the Yucatan Peninsula from south of Progresso southward to
ciudad del Carmen.  Preparations to protect life and property
should be rushed to completion.
 
A Tropical Storm Warning remains in effect on the Yucatan Peninsula
from north of Cancun to Progresso.
 
Interests elsewhere in the southern Gulf of Mexico should closely
monitor the progress of Dean.
 
For storm information specific to your area...including possible
inland watches and warnings...please monitor products issued
by your local weather office.
 
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.
 
Dean is moving toward the west near 20 mph...32 km/hr...and and a
westward or west-northwestward motion is expected over the next 24
hours.  On this track the center of the hurricane is expected to
make landfall on the Yucatan Peninsula very early Tuesday morning.
However...conditions will begin to deteriorate along the coastline
this evening.
 
Maximum sustained winds are near 150 mph...240 km/hr...with higher
gusts. Dean is an extremely dangerous category four hurricane on
the Saffir-Simpson scale.  Some strengthening is expected later
today...and Dean is likely to become a category five hurricane
prior to making landfall.
 
Hurricane force winds extend outward up to 60 miles...95 km...from
the center...and tropical storm force winds extend outward up to 175
miles...280 km.
 
The minimum central pressure reported by an Air Force Reserve unit
reconnaissance aircraft was 918 mb...27.11 inches.
 
Dean is expected to produce storm total rainfall of 5 to 10 inches
over the Yucatan Peninsula...Belize...Guatemala...and northern
Honduras...with maximum amounts of up to 20 inches.  These
rains could cause life-threatening flash floods and mud slides.
Coastal storm surge flooding of 5 to 7 feet above normal tide
levels...along with large and dangerous battering waves...is
possible in the Cayman Islands.  Storm surge flooding of 12 to 18
feet above normal tide levels is possible near and to the north of
where Dean makes landfall along the East Coast of the Yucatan
Peninsula.
 
Repeating the 500 PM EDT position...18.2 N...84.2 W.  Movement
toward...west near 20 mph.  Maximum sustained winds...150 mph.
Minimum central pressure...918 mb.
 
An intermediate advisory will be issued by the National Hurricane
Center at 800 PM EDT followed by the next complete advisory at 1100
PM EDT.
 
$$
Forecaster Franklin/Rhome

Meanwhile, out in the Atlantic:

Disturbance 92L needs to be watched

An area of disturbed weather associated with a tropical wave a few hundred miles northeast of the Lesser Antilles Islands, "Invest 92L", has changed little in organization today. Wind shear is about 5-10 knots in this region, and an upper-level anticyclone has formed over 92L. This is a very favorable environment for intensification, should 92L start to get organized. The disturbance has the potential to develop into a tropical depression by Wednesday. It is moving west to west-northwest at 15-20 mph, and will be near the central Bahamas by Wednesday, and the east coast of Florida by Friday. It does not appear that any troughs strong enough to recurve 92L will swing by until Saturday at the earliest.

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