Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 3:26 PM GMT on September 12, 2008
Hurricane Ike is closing in on Texas, and stands poised to become one of the most damaging hurricanes of all time. Despite Ike's rated Category 2 strength, the hurricane is much larger and more powerful than Category 5 Katrina or Category 5 Rita. The storm surge from Ike could rival Katrina's, inundating a 200-mile stretch of coast from Galveston to Cameron, Louisiana with waters over 15 feet high. This massive storm surge is due to the exceptional size of Ike. According to the latest wind field estimate (Figure 1), the diameter of Ike's tropical storm and hurricane force winds are 550 and 240 miles, respectively. For comparison, Katrina numbers at landfall were 440 and 210 miles, respectively. As I discussed in yesterday's blog entry, a good measure of the storm surge potential is Integrated Kinetic Energy (IKE). Ike continues to grow larger and has intensified slightly since yesterday, and the hurricane's Integrated Kinetic Energy has increased from 134 to 149 Terajoules. This is 30% higher than Katrina's total energy at landfall. All this extra energy has gone into piling up a vast storm surge that will probably be higher than anything in recorded history along the Texas coast. Storm surge heights of 20-25 feet are possible from Galveston northwards to the Louisiana border. The Texas storm surge record is held by Hurricane Carla of 1961. Carla was a Category 4 hurricane with 145 mph winds at landfall, and drove a 10 foot or higher storm surge to a 180-mile stretch of Texas coast. A maximum storm surge of 22 feet was recorded at Port Lavaca, Texas.
Figure 1. Experimental wind field analysis for Ike at 9:30 am EDT 09/12/08. The area of hurricane force winds is inside the heavy black line where the yellow color begins (64 knots). The area of tropical storm force winds is inside the heavy black line at 35 knots (turquoise colors). The total Integrated Kinetic Energy was 149 Terajoules, which makes Ike's storm surge potential a 5.4 on a scale of 1 to 6. Image credit: NOAA Hurricane Research Division.
Ike's small inner eyewall has completely collapsed, leaving Ike with no eyewall. Creation of a new eyewall is being hampered by some dry air to the storm's west, and the presence of about 10 knots of wind shear. However, Ike is beginning to look better organized on satellite imagery, and may still intensify by 5-10 mph before landfall. Ike will not inflict extreme wind damage like Katrina's or Rita's. The big story with Ike will be the storm surge.
An oil rig in Ike's path measured sustained winds of 125 mph, at 6:45 am CDT. Lower winds of 105 mph were occurring at the surface, since the rig is at an elevation of 400 feet. The Hurricane Hunters are still reporting maximum winds of 105 mph over a large region of the surface.
Ike's storm surge
According to the NOAA tide gauges, storm tides along the Mississippi coast peaked at about 6 feet above normal yesterday, with a 7 foot storm tide observed on the east side of New Orleans at Shell Beach in Lake Borgne. At 10 am CDT, storm tides of 5-6 feet were being seen in western Louisiana, and were 5 feet at Freeport, Texas, and 5.5 feet at Galveston. According to the latest NWS forecast from the Galveston office, we can expect the following storm surges in Texas:
Gulf-facing coastline west of Sargent... 4 to 6 feet
Shoreline of Matagorda Bay... 2 to 5 feet
Gulf-facing coastline from Sargent to San Luis Pass... 12 to 15 feet
Gulf-facing coastline San Luis Pass to High Island including Galveston Island... ... 15 to 20 feet
Shoreline of Galveston Bay...15 to 25 feet
NOAA's experimental storm surge forecast is calling for a 10% chance that the storm tide from Ike will reach 27-30 feet on the south and east sides of Houston. The exact track of Ike is key in determining if Galveston's 17-foot sea wall gets overtopped, flooding the city. A slight wobble 30 miles to the north of Galveston would put the city into offshore winds from Ike, possibly saving it from inundation. The situation is grim for Port Arthur, Texas, on the Louisiana border. The expected storm surge of 15-20 feet will overtop the city's seawall by six feet, resulting in flooding of the city and a number of major oil refineries. Expect a significant tightening of gas supplies in coming months, due to extensive damage to the oil refineries in the Houston and Port Arthur area.
Ike's winds in Houston and inland
Winds in the Houston metro area will increase to tropical storm force--39 mph--by about 4 pm CDT today, and remain that strong for about 24 hours. Category 1 hurricane force winds of about 75-85 mph will affect the city for about an 8-hour period from midnight to 8 am on Saturday. People in well-built homes will suffer only minor damage, but mobile homes and homes not build to code will suffer significant damage. The extremely long duration of the hurricane force winds will cause much greater damage than is typical for a hurricane of this strength.
Winds and damage in Houston should will be slightly greater than was experienced during Hurricane Alicia of 1983. Alica had higher winds at landfall, but was a smaller storm that weakened relatively quickly inland. Ike's damage will cover a much wider area and spread farther inland, due to the large size of the storm. During Alicia, Houston Hobby Airport on the south side of the city recorded top winds of 89 mph, gusting to 99 mph. The strongest winds recorded at Houston International Airport, on the north side of the city, were 51 mph, gusting to 78 mph. Winds from Ike will probably be sustained at 85-90 mph at Houston Hobby, and 75-80 mph at Houston International Airport.
A good guess on what kind of winds inland areas will experience can be had by using the Inland Wind Model developed by NOAA scientists Mark DeMaria and John Kaplan. This simple model shows the expected winds inland from the coast for the five Category hurricanes moving at different speeds. Plotted below (Figure 2) is the inland wind model plot that best fits the type of winds I expect will penetrate inland from Ike. I think Ike will be a strong Category 2 hurricane moving at about 15 mph at landfall, but the hurricane's strongest winds will penetrate farther inland than is typical due to the huge size of the storm. Thus, I picked a slightly stronger storm with a higher forward speed to base my inland wind estimate on. I expect hurricane force winds of 74 mph will penetrate about 110 miles inland, near the cities of Huntsville and Livingston to the north of Galveston, and not quite reaching Lufkin. We can expect Ike to cause the largest and longest-lived power outage in Texas history, with power knocked out along a 200-mile wide swath in eastern Texas and extreme western Louisiana extending 300 miles inland to I-20. Dallas will be at the fringe of the region of widespread power outages, and should not suffer major power failures.
Figure 2. Inland penetration of tropical storm and hurricane force winds from a Category 3 hurricane with 120 mph winds moving perpendicular to the Gulf Coast at a forward speed of 17 mph. Image credit: NOAA.
Tornadoes from Ike
Texas hurricanes have a history of producing strong tornadoes. Hurricane Alica spawned 23 tornadoes when it hit, including one strong F2 tornado. Hurricane Carla of 1961 unleashed 26 tornadoes, including the only violent F4 tornado ever spawned by a hurricane. The tornado hit Galveston, killing between 6 and 12 people.
Heavy rain from Ike will be the least of Texas' concerns, since the hurricane is not expected to stall, and will move quickly northwards out of the state by Sunday. The latest NOAA/HPC rain forecast (Figure 3) predicts the swath of heaviest rains of six inches or more will cover an area about 100 miles square.
Figure 3. Predicted 5-day rainfall totals along the path of Ike, beginning at 8am EDT Friday September 12, 2008. Image credit: NOAA Hydrometeorological Prediction Center.
For more information
I recommend Texas residents consult NHC's wind probability product to determine their odds of getting hurricane force winds.
For storm surge evacuation zone information, consult the Texas Division of Emergency Management.
For storm surge heights, consult our Storm surge risk for the Texas coast page.
Links to follow
Galveston, TX weather
Port Arthur, TX weather
Houston, TX weather
Tide gauges along the Gulf Coast
Long-range radar out of Galveston, TX
wundermap of weather stations near Ike
Buoy observations near Ike from the National Data Buoy Center.
Tropical disturbance 91L north of Puerto Rico
An area of disturbed weather (91L) is located a few hundred miles north of the Dominican Republic. Satellite loops show that 91L's heavy thunderstorm has shown a modest increase this morning, but these thunderstorm are not well organized and cover a limited area. This morning's QuikSCAT pass missed 91L, but last night's pass showed no evidence of a surface circulation, and none is apparent on visible satellite imagery.
The disturbance is under about 10 knots of wind shear, and is also having trouble with some dry air to the west. There is an upper-level low pressure just to the west of 91L that is creating shear and pumping dry air into the system, similar to the situation Hanna had to deal with in its formative stages. Shear is expected to remain 10-20 knots though Monday, which may allow some gradual development. None of the models are developing 91L, but the Bahamas can expect heavy rain and strong gusty wind over the next three days as 91L tracks west-northwest towards the east coast of Florida. NHC is giving this disturbance a low (<20% chance) of developing into a tropical depression by Sunday.
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