Tropical Update: Harvey and Hurricane Safety

Hurricane Harvey, now 115 miles southeast of Corpus Christi Texas, has seen the maximum sustained winds increase to 110 this morning, just shy of major hurricane status. The minimum central pressure has dropped 947 Millibars. Harvey is expected to become a major hurricane today with winds increasing further to 120 mph. As of this 11 AM EDT, the following watches and warnings are in effect.

A Hurricane Warning is in effect from Port Mansfield to Sargent Texas. Hurricane conditions will be occurring in these areas within the next 12-24 hours.

A Tropical Storm Warning is in effect from south of Port Mansfield to the Mouth of the Rio Grande River and from North of Sargent to High Island Texas

A Tropical Storm Watch is in effect for South of the mouth of the Rio Grande to Boca de Catan Mexico

A Storm Surge Warning is in effect from Port Mansfield to High Island Texas. A Storm Surge Warning means there is a danger of life-threatening inundation from rising water moving inland from the coastline in the indicated locations. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch is in effect from south of Port Mansfield to the Mouth of the Rio Grande. A Storm Surge watch means there is a possibility of life-threatening inundation from rising water moving inland. Persons located within these areas should take all necessary actions to protect life and property and be on the look out for rising seas.

Forecast Information

Harvey

Hurricane Harvey continues to increase in strength this morning and is now approaching major hurricane status. Harvey is expected to be a category 3 storm when he moves ashore in Texas. Sustained winds are expected to be between 120 and 130 miles per hour with higher gusts. Harvey will be bringing life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast. Preparations to protect life and property should be completed this morning, as tropical storm force winds will first arrive in the hurricane and storm surge warning areas later today.

Life-threatening storm surge flooding could reach heights of 6 to 12 feet above ground level at the coast between the north entrance of the Padre Island National Seashore and Sargent. Devastating and life-threatening flooding is expected across the middle and upper Texas coast from heavy rainfall of 15 to 25 inches, with isolated amounts as high as 35 inches, from today through next
Wednesday.

Harvey will hug the coast after he moves inland, which could help prevent the quick weakening associated with land falling hurricanes. While Harvey will still weaken, it may be a slower process and he could maintain Tropical Storm strength longer than usual. Harvey is forecast to impact this area for several days.

Hurricane Harvey Hazards

Storm Surge and Storm Tide

Storm Surge and large waves are the greatest threats to life and property along the coast. A storm surge is an abnormal rise of water generated by a storm’s winds. Many will remember the surge from Hurrican Ike is 2008. Storm Surge with Harvey is expected to be as high as 12 feet in some locations (was 20 feet in Ike). Please check your local media sources for the exact surge totals expected for your area. Surge related flooding will be dependent on the exact timing and the tide and can vary greatly over short distances. Large waves will also be a factor at the coast. Based on the tide charts, Harvey should hit as tides are moving out and close to low tide, but onshore winds are possible during several tidal cycles.

Tornadoes

Hurricanes frequently produce tornadoes, usually in the embedded thunderstorms in the rain bands now beginning to hit the Texas coast line. They can also be associated with the eye wall. Tornadoes produced by these systems are usually weak and short lived, but they can be a threat to where they hit. A Tornado watch is expected to be posted for coastal areas of Texas and Louisiana later today.

Winds

It goes without saying that winds are a major issue with Hurricanes. Sustained winds with Harvey are expected to reach up to 120 mph with gusts reaching as high as 150 mph with some locally higher gusts. Harvey is forecast to be a major Hurricane at landfall.

Rainfall

Forecasts for Harvey have indicated significant rainfall is possible, with some models showing over 30 inches of rain. This will be a very long duration event and flooding and flash flooding will bea major issue for many areas.

Hurricane Safety

Evacuations

Many areas in Texas have had evacuation orders given, for those who are evacuating, you will need to determine a safe evacuation route inland. While evacuating, you’ll want to monitor the latest information to ensure that you will be evacuating to a location that is not also under a risk. Public services in these areas will already be strained and adding many evacuees will only cause more strain for everyone. Learning the location of official shelters will be helpful both in the event that you evacuate as well as for those who do not evacuate. Areas that are not under evacuation orders should also have shelters for the residents who end up in trouble due to hurricane hazards. Tornadoes, lightning, power outages, and property damage due to falling trees can force residents from their homes, even if a mass evacuation isn’t needed. The good news is that a quick check of traffic in this region doesn’t show any, so many heeded these orders in advance.

When evacuating, put together a go-bag. Include a disaster supply kit, including a flashlight, batteries, cash, first aid supplies, medications, and copies of your critical information if you need to evacuate. Snacks and stuff to drink will also be good for longer evacuations, especially with children. While you may stop for gas, many others are also evacuating with you so its possible that many supplies will be sold out along your route. If you haven’t already, fill up your gas tank in your local area, gas supplies may also be strained along your route. Cell phones should be charged before you leave. Have one member of your family turn their phone off while travelling together. This will ensure that if one phone does run out of battery, you will have another phone to turn on and use. All family members should have all numbers for your phones and know to call multiple numbers if they can’t get a hold of you.

You should also inform someone of your plans. If you fail to arrive at your destination due to a car accident, your contact can alert the authorities. Having them know the route you planned to take is essential in locating you.

Stay tuned to local news outlets as you travel. Conditions may change and areas you were heading to that were going to be safe may not be anymore. Harvey is brining a large area of rain to Texas and the location you were heading for may end up under a flood warning when it wasn’t before. Always ensure that the safety of your location is the top priority.

Staying at home

For those of you who are not leaving home, I would first implore you to heed local evacuations if you are under them. Evacuation orders are given for a reason. If you are under those orders it is absolutely not safe where you are. While I do realize that some properties remain even in massively damaged areas, you only put yourself and those who would need to rescue you in the event of an emergency in danger by taking that gamble. It is never just your survival on the line.

If you have not been ordered to evacuate, there are several things you should plan for. First, as I mentioned above, have a plan to be able to evacuate to a local shelter if your house if one of the unfortunate locations that falls victim to one of the more local hurricane hazards. Lighting occurs frequently within a hurricane and can strike even in areas where hurricane conditions are not occurring. You should also have a plan for any pets you may have. Not all shelters accept pets so ensure the one you may go to does.

What to bring to the shelter

You will need to make sure that you have everything you need at the shelter. While the shelter will have supplies, they don’t usually carry specific medications or your specific brand of baby food. Ensure that you have a first aid kit with all the medications taken by your family. If you are running low, see if your local pharmacy can give you more. Baby food and diapers will be needed. Your baby should be prepared for a multiple day stay at the shelter. Bring things to do as well. Books, games for children, headphones and a source of music (we all know some of you still have a Walkman) will all be desired. The shelter is not exactly a fun place to be. Bring your toiletries and blankets. The shelter will have some but we all prefer our own. Flashlights and batteries are good to have in case the power goes out at the shelter as well. Also ensure you bring identification, cash and credit cards as well as copies of your essential documentation like proof of insurance.

Protecting your home

Be aware that Hurricane winds can cause trees and branches to fall, so before a hurricane trim or remove damaged trees and limbs to keep you and your property safe.
Secure loose rain gutters and downspouts and clear any clogged areas or debris to prevent water damage to your property. When it comes to repairing your rain gutters, it’s as easy as checking out sites such as https://www.aluminiumwarehouse.co.uk/, finding the right materials and replacing your damaged/old gutters. This will help protect your property, which is what you need to consider, especially after weather conditions like thunderstorms and heavy rain. This can also help keep them lighter and not fall under the weight of all the rain. Reduce property damage by retrofitting to secure and reinforce the roof, windows and doors, including the garage doors. Plywood over windows or close storm shutters if your house has them, this can protect them from wind and debris. If you are construction inclined, hurricane clips can be installed in your attic to help secure your roof to the house. You may also want to get in touch with a home improvement service similar to Mastershield Atl that may be able to provide support for homeowners who are looking for a way to protect their roof from water damage. While it is certainly too late to hire a contractor to do this for Harvey, other storms will come along and this can be done for future storms. You can also brace your garage door and doors that lead outside with planks to keep it from blowing in. You should also close all interior doors to compartmentalize the house. This way, if a window does break in one area, the remaining areas will have protection against the elements coming in. Purchasing a portable generator or installing a generator for use during power outages is also a good idea. Remember to keep generators and other alternate power/heat sources outside, at least 20 feet away from windows and doors and protected from moisture. You should never try to power the house wiring by plugging a generator into a wall outlet. If power does go out, use a flashlight. Candles are a fire hazard.

Keeping food and water safe

The most important thing when it comes to food is to buy nonperishable goods and to store water. You do not need to buy multiple gallons of water for activities like brushing your teeth. Simply refill an old milk or water bottle with tap water and use it. You can do the same thing for bath water, pre-filling your tub is also recommended. Tap water storage can be done with any container from large pots used for cooking to old bottles and even any large plastic container. Always remember to keep using the tap water until it goes out, you don’t want to needlessly use up your supply and not be able to replenish it. For any cold food you do have, turn your refrigerator and freezer to their maximum cold settings and open them as little as possible. This will help keep things cold. Try to use up any chilled foods first so that keeping things cold becomes unnecessary and have a supply of ice on hand to keep things cold longer. While you can buy ice at the store, you can also just use ice cubes. Simply dump your tray into a plastic bag and refill the trays. Dump new ice cubes as they form and keep refilling the trays. You will be able to continue this process for as long as you have power or tap water. This also creates an emergency water supply should you run out of water. Simply melt the ice. You can also use rain water if you have a safe way to get a bucket outside to collect some. You should always try to keep a lid on your water supply. This will keep dust and bugs out of it.

After the Storm

It will be tempting to go outside after the storm has passed or during the calm period in the eye. This should be avoided. The eye is only temporary and hurricane conditions can start very quickly. After the storm, there will be a lot of damage in the region. Floods could still be occurring and the water could be contaminated. You also can’t see what’s in the water. Animals and hazards in the water could be potentially dangerous to your health. The water could even be electrically charged from downed power lines.

We here at Firsthand will do our utmost to keep you up to date with the latest information. Our thoughts go out to those in the areas affected by Harvey. Stay safe everyone.

Robert Millette

Incident Meteorologist

Braintree Emergency Management Agency

Harvey Likely To Drop Excessive Rainfall Along Texas/Louisiana Coasts

Quick note: This is a forecast that I wrote specifically for a tropical meteorology class that I’m taking, which is why the format is a bit different than what you’re used to seeing from me. However, I figured all of you would find this information beneficial.

Discussion on Harvey (August 24, 8 am CT update):

As expected, Harvey re-strengthened back into a tropical storm last night and now has sustained winds of 50 knots. Harvey has picked up some forward speed and is currently moving north- northwest at 9 knots. Convection is now much better focused around Harvey’s center, and he does not have the elongated look that he did just last evening. At this time, no modifications/updates need to be made to last night’s forecast (below).

Hurricane warnings have now been issued for parts of the Texas coastline. Excessive rainfall is still expected, and at this point, it is not unreasonable to say that parts of Texas could exceed 20 inches of rainfall over the next 5 to 7 days.

Harvey Projected Path

Figure 1: Tropical Storm Harvey’s latest projected path from the National Hurricane Center

Discussion on Harvey (August 23, 7:00 pm CT update):

As of 7:00 pm CT, Tropical Depression Harvey is currently to the west of the Yucatan Peninsula and is moving very slowly to the northwest at 2 knots. After weakening and losing its closed circulation earlier in the week, Harvey finally made its transition back into a depression and will likely strength into a tropical storm by tonight or tomorrow morning. At this point, hurricane status may eventually be reached before landfall.

An upper-level low has been positioned just to the south of the Texas/Louisiana border over the Gulf of Mexico, which has resulted in an elongated region of convection firing from Harvey’s center of circulation extending northward away from this center in an area of heightened upper- level divergence. Harvey’s circulation has been quite elongated thus far, but convection should eventually become more confined to Harvey’s center as the upper-level low dissipates.

With time, vertical wind shear should decrease ahead of Harvey, as the upper-level low dissipates. There is currently moderate to strong vertical wind shear that extends south of the Louisiana coast to the northeast Gulf of Mexico. The southern extent of this stronger shear has likely played a role in Harvey’s disorganized and asymmetrical look so far this week, but over time, this should no longer be a significant hindrance to Harvey’s intensification, especially as this tropical system moves northwest.

atlantic vertical wind shear

Figure 2: Locations of vertical wind shear across the Gulf of Mexico and western/central Atlantic from CIMSS

atlantic upper-level winds

Figure 3: Upper-levels wind across the Gulf of Mexico and western/central Atlantic from CIMSS

Sea surface temperatures are anomalously warm over much of the western Gulf with temperatures running around 30 to 31°C on average. Even more noteworthy, Harvey will be moving over a region of higher ocean heat content, so while some upwelling could occur due to Harvey’s slow forward motion, it appears that this system has plenty of warm, Gulf of Mexico water to enhance strengthening. In addition to warmer sea surface temperatures and a low-shear environment, there will be very little dry air to hinder further development.

gulf of mexico ocean heat content

Figure 4: Gulf of Mexico and western Caribbean ocean heat content map from CIMSS

GOES-16 Harvey water vapor

Figure 5: GOES-16 water vapor image from early morning, August 24, 2017

Aside from the fact that Harvey could quickly intensify as he moves towards the Texas coast, one major concern at the moment is the significant flooding situation that could unfold across Texas and Louisiana. A region of high pressure is expected to build over the eastern Gulf of Mexico by this weekend, while ridging is expected to amplify over the western United States around the same time. The mean flow will generally be from the north on the east side of the western ridge and from the south on the west side of the eastern Gulf high pressure system, putting Harvey is a region of weak steering flow. Unless one of these high pressure regions becomes more dominant than the other, Harvey will likely meander along or just inland over Texas for quite some time. Broad troughing over the eastern U.S. could eventually pull Harvey northeastward next week, but at this point, that remains uncertain. Due to the complexity of this pattern, model guidance has had a difficult time determining where Harvey will go once he moves closer to the Texas coast. Given the moisture-rich environment that will be present along the Texas and Louisiana coasts and the frontal boundary that will remain stalled across that region, rainfall totals over the next 5 to 7 days could reach 10 to 20+ inches across those locations. Reaching such totals will be highly dependent on the overall track of Harvey, which will be dependent on the strength and exact placement of the two high pressure features.

harvey rainfall totals

Figure 6: 7-day rainfall forecast from the WPC

Discussion on the rest of the Atlantic (August 23, 7:00 pm CT update):

Aside from Harvey, the rest of the Atlantic is relatively quiet. There is a trough of low pressure that is currently located near the Florida peninsula, which is bringing unsettled conditions south of a frontal boundary that will continue to makes its way southward.
In addition to sea surface temperatures being anomalously warm across the Gulf of Mexico, temperatures are also warm across the main development region. This will be extra fuel for any African easterly wave that moves across that region. It is worth noting that there is quite a bit of dust that is now moving over the eastern Atlantic from Africa, which for the time being, will likely hinder the development of any wave in that region.

global sea surface temperature anomalies

Figure 7: Weekly global sea surface temperature anomalies from NOAA

saharan air layer map

Figure 8: Saharan air layer map from NOAA

Discussion on the eastern and central Pacific (August 23, 7:00 pm CT update):

For now, the tropics in the eastern Pacific are quiet. Kenneth recently dissipated after moving northward into a region of lower sea surface temperatures. While sea surface temperatures are anomalously cool over the central and eastern equatorial Pacific, sea surface temperatures are above average north of that region, including near Hawaii. As the hurricane season continues, that region will bear watching.

central pacific sea surface temperature anomalies

Figure 9: Sea surface temperature anomalies across the central Pacific from Tropical Tidbits