![]() ![]() The National Hurricane Center is aware of the shortcomings in communicating uncertainty. They went with the track down the middle, but the cone underestimated the actual uncertainty.” Some models were predicting it landing in the Carolinas, some the Northeast U.S., and some out to sea. “But for Joaquin,” said Sobel, “the models were all over the place. If most models agree about the storm’s future, the certainty may actually be higher than what’s portrayed by the cone. The specific uncertainty for the storm comes from how differently the various weather models are forecasting it. Rather, it’s based on the accuracy of the NHC’s previous forecasts. ![]() The cone, however, does not represent uncertainty specific to that storm. The line in the middle of the cone is the forecasted track, with the cone around it representing uncertainty. In following up with Sobel on this point, he gave the example of the “cone forecasts” put out by the NHC (see image with Sandy and Joaquin forecasts at about three and five days out). They rely on the main messages and graphics put out by the National Hurricane Center (NHC), the Weather Channel, and their local weather stations. For ease of public understanding, the uncertainty is often not fully explained, though Sobel makes the point that the uncertainty information is there for those who look for it.īut, of course, many people can’t dedicate the time to delving through websites to find and interpret this technical information. When forecasters relay their predictions, they do so with varying explanations of how they arrived at them and what their uncertainty is. Sobel also explains how forecasters look at a variety of weather models and use their best judgment to predict how a storm will unfold. And, many of them are only from satellites, which tend to be less precise compared to land-based data.” In tropical areas, especially over water, we don’t have as many observations. we can get good observations from a variety of sources, including weather stations, satellite data, weather balloons and even commercial airplanes with weather instruments. David Stensrud, chair of the department of meteorology at Pennsylvania State University, said there is a kind of data inequality between the continental systems and the tropical areas where hurricanes originate. Forecasters use observations to initiate computer models, so the more accurate the initial data, the more accurate the final forecasts. “If the forecast of a low-pressure system is off by 100 miles, it may make little difference to the weather in particular places.”Īnother issue is the data on which forecasts are based. ![]() “If a forecast of where a hurricane will be in three days is off by 100 miles, it will make the difference between a particular place receiving high winds and heavy rains, or having a nice sunny day,” said Emanuel. These physical differences make accurate forecasting more difficult for hurricanes. The strong winds and heavy rains of a hurricane cover a path that is usually 100 miles or so across, and they can change in less than a day ordinary low-pressure systems can be thousands of miles across and only change over several days, said Emanuel. While both systems consist of spinning centers of low pressure, according to the Kerry Emanuel, professor of atmospheric science at the Massachusetts Institute of Technology, hurricanes and land-based systems “have completely different physics.” Evaporation of ocean water fuels hurricanes, while land-based low-pressure systems are driven by horizontal temperature changes over land. Lives, livelihoods, and wider economic costs make such forecasting a high-stakes endeavor, but hurricanes remain harder to predict than the land-based weather systems that track across continents producing rain, snow, wind, and severe weather. Hurricane Joaquin has been yet another example of the complexity of predicting a hurricane’s path and strength. ![]()
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