The year 2013 marked the 25th anniversary of 1988's Hurricane Gilbert--the most intense Atlantic hurricane ever measured up until that point, with a central pressure of 888 mb--a record has since been surpassed only by 2005's Hurricane Wilma. I was on the historic flight that caught Gilbert at its peak intensity, and below is my story of that flight, published here for the first time.

Jeff Masters


I awake early on September 13, 1988, not suspecting that I will be an eyewitness to meteorological history. I look out the window at the telltale bands of high cirrus clouds that curve across the Miami sky--far-flung outflow clouds streaming away from massive Hurricane Gilbert, centered over 500 miles to the southwest. Wow. This storm is huge. I turn on the news. The reports coming out of the Caribbean are shocking, heart-wrenching. Gilbert has ripped through Jamaica as a destructive Category 3 hurricane, delivering a crippling blow. At least 45 people are dead, and the island's infrastructure is devastated. Damage will be later estimated at $6.5 billion, making it Jamaica's costliest disaster of all-time. And the hurricane isn't done--Gilbert is now in the Western Caribbean, home of the Atlantic's deepest and warmest waters--rocket fuel for a Cape Verdes hurricane.


Figure 1. Hurricane Gilbert at peak intensity on September 13, 1988. Gilbert peaked at 175 mph winds and a central pressure of 888 mb.

Preflight Briefing
I am the flight director for today's 11:30 am hurricane hunter mission on NOAA's N43RF hurricane research aircraft, affectionately named "Miss Piggy". On my way to Miami International Airport, I stop at the National Hurricane Center in Coral Gables to get a pre-flight weather briefing. Fittingly, the briefing comes from Gilbert Clark, the senior hurricane specialist on duty. Gil is the longest-serving and most knowledgeable hurricane forecaster working at NHC, and it is only fitting that his namesake storm will get its name retired the same year that he is retiring. Amidst the media zoo at NHC, Gil briefs me that the 8 am center fix from the Air Force reconnaissance aircraft in Gilbert shows Category 4 winds of 145 mph, and a central pressure of 934 mb. "The bottom's dropping out of this thing," he tells me, "and you just might be looking at a Cat 5 by the time you get there." I gulp down a bit of nervousness as I look at the imposing spiral of Gilbert's clouds, sprawled out over the entire Western Caribbean. The strongest hurricane I had flown through in two prior years with the Hurricane Hunters was a Category 3--1987's Hurricane Emily. After repeated penetrations into the eyewall of Emily, where the G-forces steadily rose until they hit three times the force of gravity, we finally had to abort the mission when a dangerous aerodynamic flutter developed in the wings. Hurricane Gilbert is far larger and more powerful than Emily was. Am I in for an even more dangerous ride?


Figure 2. An island of calm in a sea of chaos: NHC director Bob Sheets tries to get work done during the media zoo at NHC on September 14, 1988. Image credit: Jeff Masters.

Preflight Preparations
I arrive at NOAA's Office of Aircraft Operations at Miami International Airport for preflight preparations. The energy at the office is electric. A film crew from the PBS show, "NOVA" is here. CNN is here, as are camera crews and reporters from half-a-dozen other media outlets. Three graduate students performing hurricane research for Dr. Bill Gray have just flown in this morning from Colorado to go on the flight. There isn't room for all of them. In the end, the grad students, the PBS NOVA crew, and the CNN crew get to go, but some of the media get left behind. "We've got plenty of media on board, and we'll do more good for the future of hurricane science by have these grad students go on the flight," my boss, Jim McFadden argues. Twenty-one people wind up on the flight, three more than the maximum we usually allow. The flight engineers are concerned about the aircraft's weight and balance, with such a large passenger list, but in the end they give the thumbs up to go, and we are on our way south towards the great storm.


Figure 3. Track of Hurricane Gilbert.

Takeoff
As we fly south over the Miami Beach, I look down on angry, white-capped waters. Here, 500 miles away from the eye, gale-force winds blow--an astoundingly large radius of strong winds for a hurricane. We chop through our first outer spiral band over the Florida Keys, and place a call to Cuba's Air Traffic Control center to get clearance to fly over the island. In those days, the Cuban government sometimes did not allow us to fly over the island, but for this storm, they give us immediate clearance. By the time we cross over Cuba 45 minutes later, we are plunging in and out of big cumulonimbus clouds with light turbulence and heavy rain showers. As we reach the south side of Cuba, Gilbert's eye comes clearly into view on the lower fuselage radar. The eye is very tight, ten miles in diameter, surrounded by an imposing swirl of reds and yellows on the radar screen. Lead scientist Hugh Willoughby and I have a critical decision to make--do we play it safe and penetrate the eye at 10,000 feet, where turbulence should be lighter? Or should we go in at 5,000 feet, where we will collect better data, but possibly risk hitting extreme turbulence? With the experience of last year's risky flight into Hurricane Emily fresh in my mind, I lobby for 10,000 feet, and Hugh goes along with this plan.

Pentration
"Set Condition One!" crackles the voice of aircraft commander Dave Turner, as we begin our descent from our ferry altitude of 15,000 feet to our penetration altitude of 10,000 feet. I check the security of my heavy duty seat belt and shoulder harness, stow away my flight bag and clipboard, and prepare to meet the worst Gilbert has to offer. My heart beats faster, and an inner voice questions the wisdom of challenging one of nature's most fearsome storms in a mere mechanical creation. The formidable wall of dark clouds of Gilbert's eyewall lies just ahead. Darkness falls. The big plane lurches as turbulent winds grip us. Rain hammers down on the fuselage and streaks the windows. Flight-level winds jump from 90 mph to 115 mph. I watch the winds and radar carefully, and issue a request to Dave Turner for a slight course correction to keep us headed towards the eye. One minute in, two minutes to go. No significant turbulence yet. The eye, a remarkably small oasis of blue in a sea of angry reds and oranges on the radar, beckons. Two minutes in. The clouds grow thicker. The tip of the bouncing wing is hard to see through torrential rain, and the winds increase to 160 mph. A rough jolt hits us, as a 10 mph updraft gives way to a 3 mph downdraft in four short seconds. The plane skids forwards into a far more powerful updraft, which steadily increases to 10 mph, then 20 mph, and finally 35 mph. For a full minute this amazingly smooth updraft carries us higher into Gilbert's eyewall, even as the flight level winds crank up to a furious 185 mph. Category Five! The sky suddenly brightens as the updraft ejects us into the fearsome eye of monstrous Hurricane Gilbert.


Figure 4. Eye of Hurricane Gilbert taken from 10,000 feet from NOAA hurricane hunter aircraft N43RF at 5pm EDT September 13, 1988, when it was at peak strength as a Category 5 hurricane with a central pressure of 888 mb and 185 mph winds. Photo by Jeff Masters.

The Eye
The eye is awesome, supernatural, intense. We are at the edge of a stadium of majestic, towering cumulonimbus clouds that rise up high above us to a small circle of blue sky. The sun lights up a brilliant ring of whiteness along the top of the clouds. Beneath us is a white-capped ocean filled with chaotic, colliding waves up to 50 feet tall. Beneath the ragged bottom edge of the eyewall clouds, Gilbert's 175 mph surface winds whip the ocean surface into a greenish-white blur. I have little time to take in the spectacle, though, as I track the winds to make sure we penetrate to the exact center of the eye. I order one minor course correction, and then we have it--the winds drop to 4 mph, and we see a calm spot on the ocean below. "Let's mark it there!" I say. "Central pressure, 903 millibars." I pull out my VORTEX message form, and begin coding in the readings for transmission to the National Hurricane Center over our HF radio link. Within a minute, I have to stop, as we have arrived at the opposite west end of the eye, and a new eyewall penetration begins.


Figure 5. PBS's NOVA series videographer captures an image of Hurricane Gilbert from NOAA hurricane hunter aircraft N43RF on September 13, 1988. Image credit: Jeff Masters.

Rough Penetration
This time, the ride is rougher. Though the horizontal winds are weaker--165 mph--we hit a powerful 30 mph downdraft that leaves us nearly weightless at zero Gs. Commander Turner fights off the downdraft, keeping us at 10,000 feet. We pop out of the eyewall on Gilbert's west side, and begin a long trek to the south of the storm to do another penetration of the eye from south to north. I finish filling out my VORTEX report, unbuckle myself, and head back to the radio station to hand the report to our radio operator for transmission to NHC. The NOVA and CNN film crews are happy, busily taking footage of the crew at work. The scientists from NOAA's Hurricane Research Division are excitedly poring over the data we've collected. There's only been one storm stronger than this that they've flown into, Hurricane Allen of 1980. In another hour, that will no longer be true. The excitement we feel at being a part of meteorological history, though, is tempered by the somber realization that this storm is headed right for the Mexican resort areas of Cozumel and Cancun, which will undoubtedly suffer a catastrophic blow.


Figure 6. The VORTEX message I filed after penetrating through Hurricane Gilbert on September 13, 1988 and finding the lowest pressure ever measured in an Atlantic hurricane. A surface pressure reading was actually not filed at the time, since NHC told the crew that the pressures they were measuring were too low to be believable. The value shown here was added later after a research effort led by Hugh Willoughby determined 888 mb to be the actual pressure (myself and Chris Landsea, who was also on the flight, were co-authors on the paper documenting the new record.)

A New Record Low Pressure
We line up for our south-to-north penetration, and the crew takes their seats as the eyewall comes into sight. This time the winds are stronger--185 mph at flight level, gusting to 199 mph. We hit another huge updraft, 30 mph, but the ride is surprisingly smooth. As we pop into the eye, it is clear that Gilbert has intensified in the hour and half we've been way. The eye has shrunk to nine miles in diameter, and the central pressure has fallen to an astonishing 894 millibars--a spectacular nine millibar drop in just 90 minutes. Now, only the great Labor Day Hurricane of 1935 (892 mb central pressure) stands in the way of Hurricane Gilbert's run at all-time greatness. But there is controversy. Through an unfortunate oversight, we are not carrying any dropsondes, which we usually launch into the eye. Dropsondes fall to the surface on parachutes, and radio back the surface pressure. Instead, we have to estimate the surface pressure based on flight level measurements, which must be carefully calibrated. After sending in my VORTEX report with the 894 mb surface pressure from our second penetration, NHC radios back that they don't believe our surface pressures, and we are stop transmitting them for the VORTEX messages from our three final penetrations. The scientists and I protest this. Our instruments and our eyes show what NHC cannot see--we are witnessing meteorological history. Gilbert is clearly on its way to becoming the most intense hurricane of all-time.

After another long trek around the periphery of Gilbert, we punch through the eyewall an hour and a half later. This time, the eye is even more impressive, and the surface pressure has fallen another fifteen millibars, to an unbelievable 879 mb. (It turns out that NHC was right to question our pressure readings, as a later research effort led by Hugh Willoughby determined that 888 mb was the actual lowest pressure in Gilbert.) Our fourth penetration also measures 879 mb--Gilbert has finally finished intensifying. During our fifth and final penetration, we measure 883 mb, then head home. We arrive back in Miami nine hours after we took off. But, there is no rest for the weary: at 10 pm I am back at the frenzied media circus at NHC for a live remote interview with CNN's Larry King Live--my first-ever TV interview.

For more photos and eyewitness accounts of this amazing flight, check out the Gilbert Photo Gallery put together by Neal Dorst of NOAA's Hurricane Research Division. See also this remarkable video from Playa del Carmen, Mexico, as Gilbert made landfall on September 14, 1988, as a Category 5 hurricane.

My flight though Gilbert was one of two flights I did through a Category 5 hurricane. The story of my other Cat 5 flight, through Hurricane Hugo in 1989, is here. The story of that flight has been made into a 1-hour show that is scheduled to air on "Air Crash Investigation" (AKA "Mayday" outside the U.S.) on the National Geographic Channel in 2014, the 25th anniversary of Hurricane Hugo. Myself and six other veterans of the flight were interviewed for the show, which features a recreation of the near-fatal penetration into Hugo's eyewall, complete with actors playing the roles of the crew, and CGI sequences of stuff flying around the inside of the aircraft as we hit 5.7 Gs of acceleration.


Video 1. Nine-minute clip of the September 14, 1988 hurricane hunter mission into Hurricane Gilbert, as aired on the 1988 PBS NOVA show, "Hurricane."

I'll be back on January 6, 2014, with a new post. Have a Happy New Year, Everyone!

Jeff Masters