Prioritize...
Upon finishing this page, you should be familiar with major buoy deployment programs (such as the Global Drifter Program and TAO Buoys), and recognize why close encounters between ocean buoys and tropical cyclones are "lucky" encounters, especially over open ocean waters (away from coastal areas). You should also be able to interpret data summary plots from the TAO / Triton Buoy Array.
Read...
At 11 A.M. EDT on September 4, 2011, the National Hurricane Center upgraded Tropical Storm Katia to Hurricane Katia (see satellite image below) based on the observations of Buoy 41044 in the remote Atlantic Ocean (here's the 11 A.M. discussion, in which they reference the buoy data). Earlier, at 12Z on September 4, Buoy 41044 measured sustained wind speeds of 78 knots and a gust over 90 knots when the center of Katia passed very nearby. When coupled with other data, forecasters were convinced to upgrade Katia to a hurricane at 11 A.M.
In this particular case, several days of observations from Buoy 41044 provide some important insights about the storm. Indeed, this plot of sustained wind speeds (averaged over eight minutes), wind gusts, and sea-level pressure really demonstrates the drastic increase in wind speeds near the center of the storm along with the corresponding sharp drop in pressure around 12Z on September 4. In case you're interested, here's the 12Z station model from Buoy 41044 on September 4, 2011.
Encounters like the one that Hurricane Katia had with Buoy 41044 are, frankly, a bit "lucky," particularly when storms are located over remote ocean waters. Yes, sometimes we hit the jackpot and a tropical cyclone encounters a buoy or a ship (recall from previous studies that ships also provide weather observations over the ocean), but these observations miss many storms. To better see what I mean, check out the image below from the National Data Buoy Center, showing the locations of buoys (and oil-drilling platforms that collect observations) in the Gulf of Mexico, Caribbean Sea, and western Atlantic Ocean.
For the record, the buoys (or oil-drilling platforms) marked with yellow dots are stations that have recorded data recently. Meanwhile, stations marked by red dots hadn't reported data in at least eight hours at the time this image was produced. While the coastline of the United States and the central Gulf of Mexico are well sampled by buoys and observations from oil-drilling platforms, farther out over remote ocean waters, a tropical cyclone finding a buoy is akin to finding a needle in a haystack. The buoys over the Atlantic and other oceans around the world are widely spaced, leaving huge gaps between buoy observations.
The relative wealth of buoy observations along the coasts of the United States is augmented by the Coastal-Marine Automated Network (C-MAN), which was developed by the National Data Buoy Center in the early 1980s to better maintain weather observations near the coasts. C-MAN buoys provide crucial observations in coastal areas, particularly when tropical storms and hurricanes approach the East Coast and Gulf Coast states.
Besides C-MAN, other programs exist that supplement the data provided by the standard buoy network. One such program is the Global Drifter Program (GDP), under the auspice of the Atlantic Oceanographic and Meteorological Laboratory (AOML), which sometimes deploys drifting buoys in the paths of hurricanes. For example, on a mission into Hurricane Fabian in 2003, aircraft dropped 16 drifting buoys ahead of the storm, giving NHC forecasters crucial surface data.
The Global Drifter Program's Web site includes a wealth of data and interesting information, including an archive of deployments by year. You can actually look at the most current positions of drifting buoys in the Atlantic, but as a general rule, data from deployed drifter buoys are not regularly accessible. If you want to track buoy data around tropical cyclones, the resource discussed in the Explore Further section below might be your best bet.
Another special buoy program that you'll want to be aware of is the Tropical Atmosphere Ocean (TAO) project, which covers the equatorial Pacific (see image below). TAO buoys have since been combined with buoys from the Japanese TRITON (Triangle Trans Ocean Buoy Network) project to create the TAO / TRITON array, which contains roughly 70 buoys. As an aside, the TAO / TRITON array has a pretty interesting history, which you can read about in the Explore Further section below, if you would like. Data from the TAO / TRITON array are instrumental in detecting El Niño and La Niña conditions, which as you'll learn later, can have major impacts on global weather patterns.
On the TAO / TRITON Web site, you can access summary plots from individual buoys like this sample summary plot from the TAO buoy located at latitude 5 degrees South and longitude 155 degrees West. This summary, which spans from December, 2002 to December, 2003, represents a running five-day mean of wind speed and wind direction, elevation of sea level (not counting ocean waves) and temperatures from the sea surface to a depth of 300 meters. When you looked at the plot, you may have noticed that sea level in the vicinity of this buoy is not flat, nor does it correspond to an elevation of zero. We'll talk more about variations in sea-surface height in a later lesson.
One important note about the data on these graphs: You've learned that standard meteorological convention is to plot and express wind direction as the direction from which the wind blows. But, on the topmost graph of wind speed and wind direction, the red slashes extending outward point in the direction that the wind is blowing toward (exactly the opposite of the standard convention). So, for example, the winds from about October, 2002 to March, 2003 blew predominantly from the northeast (toward the southwest) at this buoy. By the way, the length of the red slash indicates the wind speed (in meters per second).
We'll return to data from the TAO / TRITON array later on when we cover El Niño and La Niña, but I wanted you to be aware of the TAO / TRITON project since it's an important component of the system of buoys that monitors tropical weather. Even with special buoy programs, however, the overall picture should be crystal clear to you by now -- ocean buoys simply can't cover the entirety of tropics, and they leave lots of gaping holes in our observing system. Therefore, forecasters must rely on other data sources to get a more complete picture of the state of the tropics. We'll start our investigation of those other sources by looking into the role that aircraft observations play in observing weather in the tropics (particularly when tropical cyclones are present). Read on.
Explore Further...
Data Resources on the Web
The Decoded Offshore Weather Data page hosted at coolwx.com is perhaps the best for accessing observations from ships and moored buoys in the vicinity of tropical cyclones. If you check-out "Tropical Cyclone/Hurricane Maps," you'll see the worldwide list of current or recent tropical cyclones. Simply click on the name of the tropical cyclone to access buoy and ship observations in the vicinity of the cyclone. The labels (two digits and a letter) used for unnamed storms follow the standards you learned about previously.
If you're interested in ship observations, you can keep an eye on with the NDBC site. Another sailing information site allows you to see the recent locations of ships around the world and generate plots of weather observations coming from ships, which some folks might find interesting.
The CIMSS tropical cyclones site also allows you to view buoy and ship observations in the vicinity of tropical cyclones. Just click on any particular active storm, and in the interface that pops up, select "buoy' and / or "ship" to view any nearby observations. We'll learn about many of the other available fields later in the course.
For History Buffs
As you just learned, the TAO / TRITON array provides critical monitoring that helps forecasters measure El Niño and La Niña, and predict their onset. The development of the program was motivated by the historic 1982-83 El Niño, which was the strongest on record at the time. And, at the time, forecasters didn't even know about the El Niño until it was near its peak! The impacts of El Niño that rippled through the atmosphere were far-reaching -- droughts and fires in Australia, Southern Africa, Central America, Indonesia, the Philippines, South America and India, as well as serious floods in the United States, Peru, Ecuador, Bolivia and Cuba. Globally, roughly 2,000 deaths were credited to weather events that were influenced by El Niño. We'll explore the connections between El Niño, La Niña, and global weather patterns in a later lesson.
The great devastation caused by the weather during the 1982-83 El Niño underscored the need for a real-time monitoring system for the tropical Pacific, to better detect and eventually predict the onset of El Niño and La Niña events. Thus, the foundation of what would become the TAO / TRITON array was laid in 1984 when a series of buoys was field tested along 110 degrees West longitude in the equatorial Pacific, and the rest is history. More recently, the project has fallen on some hard times because of a lack of funding (you can read the details in this editorial in Nature from 2014). If you would like to read a more thorough account of the evolution of the project, check out the complete history of the array.