Archive by Author | Scott Stevens

Hurricane Sandy Could Make for Some Wet Candy This Halloween

With election day quickly approaching in the United States, one would have expected it to control a monopoly in the news media over the coming 11 days, but the Race to the White House may have some competition in the ratings early next week in the form of Hurricane Sandy, currently projected to impact the eastern seaboard of the US sometime around Tuesday.

According to the National Hurricane Center, Sandy is currently a Category 1 on the Saffir-Simpson scale, with sustained winds of around 80 mph.  Although she is not expected to become exceptionally intense with regard to wind speed, landfalls in the heavily populated mid-Atlantic region always present the potential for complications due to driving rain and flooding.  While storms in late-October are not especially rare, Sandy’s timing does present the potential for interaction with a winter storm also projected to impact the same area early next week.

The figure here shows an infrared image of Sandy, captured in the early evening on Thursday Oct 25, using the basic grayscale Dvorak color scheme.  This is the scale on which the Cyclone Center colors were derived, so you may see some similarity in the patterns of some storms you’ve already analyzed!  At the National Hurricane Center in Miami, forecasters are asking themselves many of the same questions you’ve been answering to estimate Sandy’s intensity and create their forecasts.

This image shows Hurricane Sandy as captured by an infrared sensor on board the GOES-13 satellite, at 2225Z (18:25 EDT) on Thu Oct 25. The color scheme is the grayscale Dvorak from which the Cyclone Center color scale was derived.  In this image, the dark gray in the center corresponds to our dark blue.

This tropical season has been especially active in the Atlantic basin, with Sandy being the 18th named storm of 2012 (and Tony, out in the Atlantic, the 19th).  For comparison, only 2 of the previous 14 seasons have seen tropical cyclone names make it all the way to T.

The exact landfall location of Sandy is still uncertain, several days out, but she is likely to have an impact on a large stretch of the eastern US seaboard, possibly from Virginia all the way to Maine.  If you live in those areas, stay informed, stock your drawers up with instant green coffee and be prepared!  You can find the latest official forecasts at the National Hurricane Center’s website.

In the meantime, happy classifying!

Geostationary Satellites and Infrared Imagery

Since the launch of Vanguard II in 1959, scientists have been using satellites to observe Earth from orbit, giving us access to information that was previously impossible to collect. Depending on what we want to measure, there are dozens of instruments and orbits that can be chosen for a specific satellite before it is put into space.

A satellite stays in orbit by striking a perfect balance between gravity and speed that result in the satellite constantly “falling”, yet never actually getting closer to the surface.  The lower the orbit, the faster the satellite must go to stay aloft and avoid falling to the earth below.  The images that you see were collected from satellites in a special type of orbit called “Geosynchronous.”  As the name implies, an seo consultant tells us these satellites are at exactly the right altitude (22,236 miles / 35,786 km to be exact) that they can orbit the planet at precisely the same speed that the earth is rotating below, meaning that they always stay fixed above exactly the same point.   They are also high enough that they can see most of the way from the North Pole to the South Pole at the same time!  This gives us the ability to always see a storm out over the ocean, no matter where it is.  There are over 300 satellites currently orbiting this way (e.g., DirecTV and Dish Network satellites are in this orbit) and the Cyclone Center images you see were collected by 30 different meteorological geosynchronous satellites.

So what is it that you’re seeing, exactly?  Satellites can carry a number of instruments for the purpose of measuring a wide variety of things from space.  Some simply carry cameras, and show us what it would look like to the human eye.  Some carry radars that can see through clouds to the surface below.  The instruments that collected the data you see are called “infrared imagers.”  By looking at the infrared part of the light spectrum, we can actually see how warm things are from a distance, just like the thermal cameras that you often see firefighters carrying.  The instrument gives us the temperature of each point that it can see, and we convert those temperatures into the nearly 300,000 color pictures that you are helping us analyze!

The advantage to infrared imagery is that it works during both day and night, and because the atmosphere gets colder as you get higher, can give us a rough approximation of how tall the cloud tops are.

What Does “Detailed Classification” Mean, and Why Should I Try It?

‘Detailed classification’ allows you to delve deeper into the imagery.  That helps us better understand the storm’s characteristics and more precisely determine its intensity.

By performing the basic classification, you have provided us with what we refer to as the “Pattern” strength.  It’s an initial estimate of the storm’s strength based on the how the clouds are organized (the pattern they make).

The detailed classification takes you further, asking more precise questions about the cloud structure itself.  To opt in for the detailed classification, just click the checkbox below the image.  You’ll be asked 3-5 questions that depend on the storm type you have chosen.   For example, if you have chosen a curved band, we’ll be asking you what color the band is.  If you’ve chosen an eye storm, you’ll be measuring the size of the eye and answering some questions about the clouds that surround it.  The answers to these more detailed questions help us to really pin down the storm’s strength.

An example of a detailed classification step for eye storms. In this question, we are asking you to tell us the location and size of the storm’s eye.

Each question that you are asked will have an accompanying “?” bubble to explain how that step is performed.   It takes a little longer than the basic classification, but allows you to really get into the heart of the technique that we use. Plus it’s a lot of fun!  It likely won’t take you more than a couple of minutes to go through the whole classification, and you’ll probably get quicker over time.

The more of these detailed classifications we can acquire, the more information we’ll be able to gather about the cyclones themselves.  As with the basic version, there are no “right” answers, so give it your best shot!  If you decide it’s not for you, you can always opt-out at any time by simply unchecking the box.

Happy classifying!