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Current Watches and Warnings A Tropical Storm Warning is in effect from Port O’Connor to Sargent, Texas

Current Details from the National Hurricane Center (NHC) COORDINATES: 29.0° north, 97.4° west LOCATION: 35 miles (55 kilometers) west-northwest of Victoria, Texas MOVEMENT: south-southeast at 2 mph (4 kph) WINDS: 40 mph (65 kph) with gusts to 50 mph (80 mph) RADIUS OF TROPICAL STORM-FORCE WINDS: 175 miles (280 kilometers) MINIMUM CENTRAL PRESSURE: 1000 millibars SAFFIR-SIMPSON SCALE RANKING*: Tropical Storm LANDFALL LOCATION: near Rockport, Texas LANDFALL TIMEFRAME: approximately 10:00 PM CDT August 25 (03:00 UTC August 26) LANDFALL INTENSITY: 130 mph (215 mph) – Category 4 Hurricane 24-HOUR ECONOMIC AND INSURED LOSS POTENTIAL: HIGH

Latest Satellite Picture

Source: NOAA


Cat Alert: Hurricane Harvey 2

Meteorological Discussion Hurricane Harvey, located approximately 35 miles (55 kilometers) west-northwest of Victoria, Texas, is currently tracking south-southeast at 2 mph (4 kph). Harvey continues to meander over southeastern Texas, where it is producing catastrophic and life-threatening flooding rainfall. NWS radars show that bands of deep convection continue to develop over the northwestern Gulf of Mexico and train over portions of southeastern Texas, including the Houston/Galveston metropolitan area. Rainfall amounts greater than 20-25 inches have already been reported and flash flood emergencies and warnings have been issued by local National Weather Service offices for a large portion of southeastern Texas. Additional rainfall amounts of 15 to 25 inches are expected over the next several days, and the NOAA Weather Prediction Center is now forecasting isolated storm total amounts of 50 inches. These historic rainfall amounts will exacerbate the already dire and life-threatening situation.

Surface observations of winds 30-35 kt within a band of convection over the western Gulf of Mexico and along the coast of Texas support an initial intensity of 35 kt. The latest track guidance show Harvey moving slowly southeastward for the next 24 to 36 hours and the center is likely to move very close to the coast, or even offshore, between 24-48 hours. After that time, Harvey is expected to begin a northward motion which should take it inland over eastern Texas later in the period. Since a large portion of the circulation is expected to remain over water during the next several days, Harvey is maintained as a tropical storm through 72 hours. However, the strongest winds are likely to occur over the Gulf waters.

Key Messages from the National Hurricane Center

1. Ongoing catastrophic and life-threatening flooding will continue across southeastern Texas. Additional rainfall accumulations of 15 to 25 inches are expected, with isolated storm totals as high as 50 inches, through Friday. Please heed the advice of local officials. Do not attempt to travel if you are in a safe place, and do not drive into flooded roadways.

Additional Information from the National Hurricane Center

RAINFALL: Harvey is expected to produce additional rainfall accumulations of 15 to 25 inches through Friday over the middle and upper Texas coast, including the Houston/Galveston metropolitan area. Isolated storm totals may reach 50 inches in this region. These rains are currently producing catastrophic and life-threatening flooding, and flash flood emergencies are in effect for portions of southeastern Texas. DO NOT ATTEMPT TO TRAVEL IN THE AFFECTED AREA IF YOU ARE IN A SAFE PLACE. DO NOT DRIVE INTO FLOODED ROADWAYS.

Elsewhere, Harvey is expected to produce total rain accumulations of 5 to 15 inches farther south toward the lower Texas coast, farther west toward the Texas Hill Country, and farther east through southwest and central Louisiana.

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water is expected to reach the following heights above ground if the peak surge occurs at the time of high tide:

Port Aransas to High Island, including Galveston Bay: 1 to 3 feet High Island, TX to Morgan City, LA: 1 to 2 feet



The deepest water will occur along the immediate coast near the area of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances.

WIND: Tropical storm conditions are occurring in an area near the center and over portions of the tropical storm warning area along the coast. Tropical storm conditions are likely to persist in areas of onshore flow within the warning area during the next day or so.

SURF: Swells generated by Harvey are affecting the coasts of Texas and Louisiana. These swells are likely to cause life-threatening surf and rip current conditions.

TORNADOES: A few tornadoes are possible today and tonight near the middle and upper Texas coast into southwest Louisiana.



Event Discussion The current scale and magnitude of flooding in Houston is catastrophic. As seen in the graphic below, some areas of the Houston metropolitan region have received more than 20 inches (508 millimeters) in just the past 12 hours. Total peak rainfall in these same areas over the past 48 hours is in excess of 27 inches (686 millimeters). This has led to widespread and extremely significant flash flooding throughout Harris County, including downtown Houston. More than 2,000 people have already been evacuated from their homes and more than 1,000 others are stranded in their homes and awaiting rescue. Most people are stranded given a high percentage of roadways that are currently under many feet (meters) of water. The National Weather Service has deemed this a “historic” event.

In a Civil Emergency Message released at 6:10 AM CT August 27 (12:10 UTC), the following message was transmitted at the request of the city of Houston:

“Emergency management officials have requested that people escaping flood waters as a last resort do not stay in the attic. If highest floor of your home becomes dangerous… get on the roof.”

The scale of damage is not quantifiable at this time. The Weather Prediction Center reported this morning that total event rainfall could already reach 35 inches (889 millimeters) in some parts of southeastern Harris County by Sunday afternoon local time, and the rains are not likely to subside in the Houston metro region until later this week given Harvey’s very slow motion. Total event rainfall may reach 50 inches (1,270 millimeters) in isolated areas around Houston and Galveston by the end of the week. The agency already believes the volume of water that has fallen in Houston has already matched that of 2001’s Tropical Storm Allison – which was previously considered the worst flood event in Houston’s recorded history. That event cost an estimated USD11.9 billion in economic damage (2017 USD). Less than half of that cost (USD5.0 billion, 2017 USD) was covered by insurance.

Dangerous flooding has also been recorded in parts of Bastrop, Grimes, Montgomery, San Jacinto, Galveston, Chambers, Liberty, Polk, and Walker counties.



Additional Comment It is worth noting that less than one-sixth of homes in Harris County, Texas currently have active National Flood Insurance Policies (NFIP) in place as per April 2017 NFIP policy data. Based on 2016 US Census Bureau data, there were nearly 1.8 million housing units in Harris County; which is home to Houston. Similar take-up rates are found in neighboring counties, though the rate drops off the further inland from the immediate coastline. Based on these statistics, it is expected that a large portion of the overall economic damage caused by flooding will not be covered by insurance.

Below is a partial list of projected record river, creek, and bayou crest heights in the greater Houston metro region as provided by NOAA. The data is from 8:30 AM CDT August 27 (14:30 UTC).

Location Projected Height (ft) Current Record (ft) Year Cypress Creek (Hockley), TX 163.9 163.40 1994 Cypress Creek (Cypress), TX 128.8 127.60 1994 Cypress Creek (Westfield), TX 102.3 94.34 1949 Buffalo Bayou (West Point Drive), TX 70.7 68.37 1983 Buffalo Bayou (Piney Point Village), TX 68.3 61.23 1992 San Bernard River (Boling), TX 45.2 42.4 1960 Navidad River (Sublime), TX 36.6 34.0 2004 San Bernard River (Sweeny), TX 33.6 23.9 1998 Clear Creek (Friendswood), TX 22.5 20.46 2001



To put the rainfall focus into greater context, the 50-inch (1,270-millimeter) forecast through Friday, September 1 would set the United States record for most rainfall ever registered by a tropical cyclone since data records began in 1950.

Bottom line: A historic event is currently unfolding in Texas. It will take weeks until the full scope and magnitude of the damage is realized, but the reality is the economic impact will be catastrophic and likely well into the multi-billion-dollar range. As mentioned previously, the relative lack of NFIP coverage in some of the hardest-hit areas will mean that an abnormally high portion of economic damage caused by flooding will not be covered by insurance.



National Hurricane Center Forecast



National Hurricane Center (NHC): Wind Speed Probabilities

Tropical Storm-Force Wind Probabilities (≥40 mph (65 kph))



Wind Probabilities (≥60 mph (95 kph))



Weather Prediction Center: Rainfall Potential



Current ‘Spaghetti’ Model Output Data

Source: NHC/Tropical Atlantic

Additional Information and Update Schedule Wind intensity forecasts and forecast track information can be found via the National Hurricane Center at www.nhc.noaa.gov

NEXT CAT ALERT: This will be the final Cat Alert regarding Harvey’s current meteorological information, though these may be re-initiated if the storm enters the Gulf of Mexico and regenerates. A special Cat Alert further detailing the storm’s ongoing impacts will be sent on Monday, August 28.

http://www.nhc.noaa.gov/



*Tropical Cyclone Intensity Classifications for Global Basins WIND SPEED BASINS AND MONITORING BUREAU

KTS1 MPH1 KPH1

NE Pacific, Atlantic

NW Pacific

NW Pacific

SW Pacific Australia SW

Indian North Indian

National Hurricane

Center (NHC)

Joint Typhoon Warning

Center (JTWC)

Japan Meteorological Agency (JMA)

Fiji Meteorological Service (FMS)

Bureau Of Meteorology

(BOM) Meteo-France

(MF)

India Meteorological

Department (IMD)

30 35 55 Tropical Depression

Tropical Depression

Tropical Depression

Tropical Depression

Tropical Low

Tropical Depression

Deep Depression

35 40 65

Tropical Storm

Tropical Storm

Tropical Storm

Cat. 1 Tropical Cyclone


Moderate Tropical Storm

Cyclonic Storm 40 45 75

45 50 85

50 60 95 Severe Tropical Storm



Severe Tropical Storm

Severe Cyclonic Storm

55 65 100

60 70 110

65 75 120

Cat. 1 Hurricane

Typhoon

Typhoon

Cat. 3 Severe Tropical Cyclone


Tropical Cyclone

Very Severe

Cyclonic Storm

70 80 130

75 85 140

80 90 150

85 100 160

Cat. 2 Hurricane 90 105 170


Cat. 4 Severe Tropical Cyclone Intense

Tropical Cyclone

95 110 175

100 115 185

Cat. 3 Major

Hurricane

105 120 195

110 125 205



115 130 210

120 140 220

Cat. 4 Major

Hurricane Very Intense Tropical Cyclone

Super Cyclonic Storm

125 145 230

130 150 240

Super Typhoon

135 155 250

140 160 260 Cat. 5 Major

Hurricane >140 >160 >260



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Aon Benfield, a division of Aon plc (NYSE: AON), is the world’s leading reinsurance intermediary and full-service capital advisor. We empower our clients to better understand, manage and transfer risk through innovative solutions and personalized access to all forms of global reinsurance capital across treaty, facultative and capital markets. As a trusted advocate, we deliver local reach to the world’s markets, an unparalleled investment in innovative analytics, including catastrophe management, actuarial and rating agency advisory. Through our professionals’ expertise and experience, we advise clients in making optimal capital choices that will empower results and improve operational effectiveness for their business. With more than 80 offices in 50 countries, our worldwide client base has access to the broadest portfolio of integrated capital solutions and services. To learn how Aon Benfield helps empower results, please visit aonbenfield.com. Copyright © by Impact Forecasting® No claim to original government works. The text and graphics of this publication are provided for informational purposes only. While Impact Forecasting® has tried to provide accurate and timely information, inadvertent technical inaccuracies and typographical errors may exist, and Impact Forecasting® does not warrant that the information is accurate, complete or current. The data presented at this site is intended to convey only general information on current natural perils and must not be used to make life-or-death decisions or decisions relating to the protection of property, as the data may not be accurate. Please listen to official information sources for current storm information. This data has no official status and should not be used for emergency response decision-making under any circumstances. Cat Alerts use publicly available data from the internet and other sources. Impact Forecasting® summarizes this publicly available information for the convenience of those individuals who have contacted Impact Forecasting® and expressed an interest in natural catastrophes of various types. To find out more about Impact Forecasting or to sign up for the Cat Reports, visit Impact Forecasting’s webpage at impactforecasting.com. Copyright © by Aon plc.

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