Thursday, May 30, 2013

Hurricane Season Begins!

Hurricane season officially starts on June 1st. The National Hurricane Center updated their hurricane season forecast. It continues to highlight above average activity. Here is this year's forecast with comparisons to average and last year:

Why the increase?  First, no El Nino this year.  El Nino's lead to stronger steering current with act to shear apart storms as they develop. 1997 was a great example!

This year, the upper level winds will be more favorable for storms. 

Second, since the mid 1990s, the Atlantic Ocean has been in a "warm mode".  This warm mode is part of a cycle called the AMO or Atlantic Multi-decadal Oscillation. This oscillation switches every (20-40 years).

When its positive or warm, the storms make landfall along the US coast more frequently.

The other more short-term variable is the current water temperatures in the Gulf of Mexico and atlantic ocean. Notice how warm these waters are running this early in the season. This favors early season storm development along the Gulf Coast and Florida.

In fact, the GFS is showing some development in the Gulf of Mexico by the middle of next week. Something to watch for sure!

Tuesday, May 28, 2013

Why Can't We Handle Probability in Weather Forecasts?

Our minds don't easily handle probability. Complex systems like the global economy, the financial sector, ecosystems or quantum mechanics are riddled with counter-intuitive randomness. We can visualize the movement of an electron as a point particle flying around a nucleus of an atom. Yet the real picture is filled with uncertainty. The electron's existence is a hazy cloud of probability. Its nature is not just a particle but BOTH a particle AND a wave! Say what? 

Much of our human experience is filled with such truths. We especially hate probabilities in our weather forecasts. Why? For our minds to grasp probabilities, we need to be able to handle multiple possible outcomes at once. Just our luck, weather has many, many outcomes over a large area over a significant period of time. Change the initial weather conditions (humidity, wind flow, frontal position, upper level energy, etc) and you create more uncertainty. Factor in time and the probability becomes significantly higher.

Typically, our brains work much better with a theme that is linear: A story that has a beginning, middle and an end. We want to visualize a line of showers that moves in at a specific time, stays for a select amount of time and then moves out without fanfare. Unfortunately, rain events rarely behave in this manner.

Here is a quick radar loop from May 28, 2013. Notice the disjointed nature of the rain/storm clusters and how they evolve. Some smaller cell develop independently of the main cluster. I guarantee that by the time they made it to Ohio, they looked nothing like what you are seeing here.

The radar loop above is an excellent example of why—much to the chagrin of the general public—probabilities are the only way to tell the weather story. We use 90% chance of rain, 40% chance of rain, etc. Yet if it doesn't rain over their house when the probability is 90% chance of rain, the forecaster is wrong even if the rest of the area was hit with a good downpour. We want to know if it will rain or not; a black and white scenario without caveats. Yet the behavior of some small scale weather events like warm frontal rain/storms can behave semi-independently of the overall large scale pattern. I’ve tried multiple times to convey this idea on the air. The explanation of small scale rain clusters as behaving somewhat “on their own” falls on deaf ears.

It all goes back to basic human nature. A good weather narrative (a feel-good forecast with some folklore) is desired versus something data/science driven. Nebulous weather data and science makes most of us feel uncomfortable even if the on-air meteorologist has the best of intentions. We have created some sophisticated models of the weather that can make some very good “probabilistic” outcomes for weather events and situations. Yet a level of uncertainty still remains and we humans don’t like it!  We try to rationalize the irrational. Our biases quickly dismiss the probabilistic science as irrelevant or at the very worst, an excuse.

Instead, we favor more simplified stories even though that story might gloss over important details. Our minds involuntarily cherry-pick elements of the story so that it fits our biases. Think of a time when someone told you a weather fact or forecast which you didn’t believe. You felt uneasy. Your mind shrugged it aside only to be replaced by a story, forecast or explanation that made you feel better…accuracy be damned.

A great financial blog called The Big Picture written by Barry Ritholtz explains the narrative vs data idea succinctly: (I inserted the weather components)

* Narratives (straight forward simple weather forecasts) are about hitting emotional buttons making the reader feel good by focusing on less qualitative aspects (weather science and probability) of an issue.

* Narratives (weather forecast) are/is about the outcome not the process (explanation of the science and probability)

* The process (weather science) is important in developing solid results

 So remember the psychology. How you react when you hear a weather forecast?  Do you dismiss the science? How do you handle probability?  Do you like hearing an explanation to why the weather does what it does? Do you overly simplify the weather? Are you aware of your biases?

The science of the atmosphere is never as straight forward as we'd like it to be…and never will.