Bob Henson ·

Above: A woman checks on her vehicle as Hurricane Michael passes through, after the hotel canopy had just collapsed, in Panama City Beach, Fla., Wednesday, Oct. 10, 2018. Image credit: AP Photo/Gerald Herbert.

Hours after making landfall—and making history—as one of the most powerful U.S. hurricanes on record, Hurricane Michael was still a serious threat as it moved across southen Georgia on Wednesday night. As of 8 pm EDT, Michael was about 20 miles southwest of Albany, Georgia, with Category 1 sustained winds of 90 mph. Michael entered the state's southwest corner as a Category 3 storm, making it the first major hurricane in Georgia since 1898.

Michael left a trail of destruction in its wake across the central Florida Panhandle, especially along and near the coastal stretch from Panama City to Apalachicola. One death had been reported as of Wednesday evening. Mexico Beach, which encountered the worst of Michael's dangerous right-hand-side eyewall, appears to have been particularly hard hit, as was Tyndall Air Force Base, which reported "extensive damage" in a Facebook post. For more on Michael's damage, see this weather.com roundup.

Flash floods and powerful winds will remain a threat from Michael as it accelerates northeastward Wednesday night and sweeps across the Carolinas on Thursday. Tornadoes will also be a threat, especially northeast of Michael's center on Thursday across the eastern Carolinas. A tropical storm warning extended north along the Atlantic coast on Wednesday night all the way from Fernandina Beach, FL, to Duck, NC, including Palmico and Albemarle sounds.

Michael will weaken steadily tonight, but it is expected to remain a tropical storm until it moves offshore from the Virginia/North Carolina coast into the Atlantic late Thursday or early Friday. At that point, it will restrengthen while evolving into a non-tropical cyclone. A final stripe of very heavy rain could develop from southern Virginia into the Delmarva area as Michael departs.

Figure 1. Visible satellite image of Hurricane Michael at 1738Z (1:38 pm EDT) Wednesday, October 10, 2018. Michael’s center had come ashore around 1 pm, but the eye was still impressively clear even at this point. Image credit: tropicaltidbits.com.

Storm surge and wind reports from Michael

At 2:12 pm EDT, the storm tide at Apalachicola, FL peaked at 7.72’ above high tide (Mean Higher High Water, or MHHW), which was the highest water level on record there (going back to 1967). Hurricane Dennis of 2005 (a 6.43’ storm tide) held the previous record. The highest storm surge at the site (height of the water above the normal tide) was 8.53'. NHC predicted a storm surge of 8 - 14 feet for this portion of the coast.

At 2:06 pm EDT, the storm tide at Panama City, FL peaked at 5.31’ above MHHW, which was the second highest water level on record. The record was 5.72’ above MHHW, set on October 4, 1995 during Hurricane Opal. The highest storm surge at the site (height of the water above the normal tide) was 5.62'. Records extend back to 1973 at the site.

At 2:54 pm EDT, the storm tide at Cedar Key, FL peaked at 4.05’ above MHHW, their 6th highest water level on record.

NOAA buoy 42039, located about 90 miles (145 km) south-southwest of Panama City, Florida, reported sustained winds of 60 mph (97 km/h) and a wind gust of 76 mph (122 km/h) at 5:50 am, before the buoy stopped transmitting data. The highest significant wave heights were 30.8 feet at 4:50 am EDT.

Tyndall Air Force Base, which got the western eyewall winds of Michael, reported sustained winds of 86 mph, gusting to 129 mph, at 12:19 EDT, five minutes before the station stopped sending data. This measurement was taken at 30 meters, so is higher than the winds that would be reported from the standard 10-meter measuring height.

According to NHC, a wind gust of 130 mph was reported between 1 - 2 pm EDT at a University of Florida/Weatherflow observing site near Tyndall Air Force Base before the instrument failed. A wind gust of 129 mph (207 km/h) was reported at the Panama City Airport.

The peak sustained winds of a hurricane (in the case of Michael, estimated at 155 mph) typically affect only a small area, and instruments may not be in place to capture those peak winds, so we shouldn't be surprised if the highest sustained wind reports from Michael near ground level end up being less than 155 mph. For more on how hurricane winds are assessed during and after a landfall, see our two-part report from earlier this year.

At Donalsonville, Georgia sustained winds of 45 mph, gusting to 56 mph, were measured at 3:15 pm EDT, fifteen minutes before the station stopped sending data.

At Albany, Georgia, sustained winds of 51 mph, gusting to 70 mph, were measured at 7:24 pm EDT, and the winds were still increasing.

A stunner of a storm

Even veteran meteorologists were astounded by Michael’s ultimate fury. The estimated sustained winds at landfall of 155 mph are at the very top end of Category 4 strength. Unlike most hurricanes, Michael continued to intensify right up until it made landfall just northwest of Mexico Beach around 1 pm EDT. Michael had struggled all day Tuesday to carve out a clear eye and a closed eyewall, yet the hurricane still managed to intensify.

Once the closed eyewall formed on Tuesday night, Michael’s strengthening really took off. The brief life of Michael’s closed eyewall meant that there wasn’t quite enough time for an eyewall replacement cycle to kick in, a process that could have weakened the storm’s top sustained winds by 20 – 30 mph. On the contrary, Michael’s inner structure was at its most impressive right when the storm made landfall: the hurricane’s eye was amazingly distinct on satellite even after it was completely onshore.

This viral Facebook video from Stefan Melendez shows what it was like to be on the ground Wednesday as Michael’s clear eye passed overhead and the sun shone. The tweeted video below gives a pilot’s-eye perspective of the same thing.

A pilot’s view of the eye wall of #HurricaneMichael from an Air Force Reserve Hurricane Hunter mission today. (U.S. Air Force photo by Lt. Col. Sean Cross, 53rd Weather Reconnaissance Squadron pilot.) pic.twitter.com/df6Ll3nLz0 — Hurricane Hunters (@53rdWRS) October 10, 2018

Michael’s place in hurricane history and how it got there

Michael’s central pressure at landfall was estimated by hurricane hunters at 919 mb, and the Univ. of Florida/Weatherflow station near Tyndall AFB measured a central surface pressure of 920 mb. The only two hurricanes in U.S. history known to make landfall with a lower central pressure were Mississippi’s Camille (1969, 900 mb) and Florida’s Labor Day Hurricane (1935, 892 mb). Both of these were Category 5 storms at landfall. The nation’s only other landfalling Cat 5 on record was Andrew (1992, 922 mb). Andrew was initially classified as a Category 4, then upgraded in 2004 after the storm was reanalyzed. It’s possible that the National Hurricane Center will find enough evidence to similarly promote Michael, but we’ll have to wait and see on that.

Another very close contemporary of Michael’s would be Hurricane Maria from 2017. Maria struck Puerto Rico with a central pressure of 920 mb and peak winds of 155 mph.

One important reason Michael got so strong is that very warm water (around 29°C or 84°F) extended to some depth across the Gulf and extended all the way up to the northern Gulf Coast, a rarity for mid-October. More typically, at least one or two cold fronts have chilled the waters just off the Florida Panhandle coast by this point. Florida just experienced the warmest September in its history, one measure of the overall atmospheric and oceanic warmth that’s prevailed across the region over the last few weeks.

As human-produced greenhouse gases continue to warm our climate, it’s reasonable to assume that waters warm enough to support an intense hurricane will be present over larger areas and over longer stretches of the season. Michael came ashore more than a month later in the season than all six of the previous strongest mainland hurricanes in U.S. history (as measured by central pressure at landfall). Many studies have shown that we can expect an increasing proportion of Earth’s hurricanes to reach intense levels as the climate warms. In addition, at least one study has found that hurricanes and other tropical cyclones have tended to intensify more rapidly over the last 30 years. See the Climate Signals website for more on the links between hurricanes and climate change.

Michael also developed at a pace very well suited for a powerful landfall, with upper-level conditions aligning at just the right time for Michael to strengthen. As noted above, the hurricane struggled to form a closed eyewall on Tuesday even as the central pressure steadily dropped and powerful thunderstorms (convection) pulsed throughout the storm’s central core. As noted by Philippe Papin (U.S. Naval Research Laboratory), a shallow layer of dry air injected into the southwest side of Michael’s circulation about 4 – 5 miles high may have interfered with the eyewall closure. Even so, it appears that the moisture and convection that congealed on Tuesday laid the groundwork to Michael to vault to its top-end Category 4 ranking once Michael's eyewall finally closed on Tuesday night and the moderate wind shear in place for most of Michael’s life briefly relaxed.

We can be grateful for at least one thing: had Michael reached its top strength a day or two sooner, or moved more slowly, the storm surge could have been even more intense than it was.

Figure 2. People arrive at a special needs shelter at Tallahassee’s Florida High School on Wednesday, October 10, 2018, as Hurricane Michael approaches. Image credit: Mark Wallheiser/Getty Images.

Portlight disaster relief charity responding to Hurricane Michael

The portlight.org disaster relief charity, founded and staffed by members of the wunderground community, is responding to Hurricane Michael. They need your help!! Experience shows that a disproportionate number of those who lose everything in the storm will be people with disabilities and older adults. Portlight’s Disaster Hotline (800-626-4959) has already assisted many people with disabilities. Portlight is rallying stakeholders, working to get people to safety, providing for any immediate needs for durable medical equipment and other assistive technology, and responding to evacuation and sheltering issues and problem-solving for a variety of immediate disability accessibility issues.

Despite laws requiring equal access to emergency services and programs, massive federal funding investments, and years of effort by disability organizations to compel communities to plan for the emergency- and disaster-related needs of 26% of the U.S. population, it is clear that evacuation and sheltering plans are falling short, placing individuals with disabilities and communities in jeopardy once again. We hope you'll consider supporting Portlight’s work with a donation.

Dr. Jeff Masters co-wrote this post.