Hurricane Forecasts Rely on Modeling the Past

Could the first tropical storm of the Atlantic hurricane season break the 10-year “hurricane drought” record?It has been a decade since the last major hurricane, Category 3 or higher, has made landfall in the United States. This is the longest period of time for the United States to avoid a major hurricane since reliable records began in 1850. According to a NASA study, a 10-year gap comes along only every 270 years. The National Hurricane Center calls any Category 3 or more intense hurricane a “major” storm. It should be noted that hurricanes making landfall as less than Category 3 can still cause extreme damage, with heavy rains and coastal storm surges. Such was the case with Hurricane Sandy in 2012.Timothy Hall, a research scientist who studies hurricanes at NASA’s Goddard Institute for Space Studies, New York and colleague Kelly Hereid, who works for ACE Tempest Re, a reinsurance firm based in Connecticut, ran a statistical hurricane model based on a record of Atlantic tropical cyclones from 1950 to 2012 and sea surface temperature data. The researchers ran 1,000 computer simulations of the period from 1950-2012 – in effect simulating 63,000 separate Atlantic hurricane seasons. They also found that there is approximately a 40% chance that a major hurricane will make landfall in the United States every year. These visualizations show hurricane tracks from 1980 through 2015. Green tracks are storms that did not make landfall in the U.S.; yellow tracks are storms that made landfall but were not Category 3 or higher; and red tracks are Category 3 or higher hurricanes that did make landfall.Research: The frequency and duration of U.S. hurricane droughtsJournal: Geophysical Research Letters, May 5, 2015 Complete transcript available.Watch this video on the NASA Goddard YouTube channel.Music credits: Climb the Ladder by Kurt Oldman in the KillerTracks Catalog Hurricane tracks from 1980 through 2015. Green tracks did not make landfall in US; yellow tracks made landfall but were not Category 3 or higher hurricanes at landfall; red tracks made landfall and were Category 3 or higher. A corresponding chart on the right accumulates the number and types of storms for each year. Tracks layer with alpha channel. Dates layer wih alpha channel. Table layer with alpha channel. Accumulated tracks from 2006 through 2015 with alpha channel. A background Earth layer. For More InformationSee [http://www.nasa.gov/feature/goddard/no-major-us-hurricane-landfalls-in-nine-years-luck](http://www.nasa.gov/feature/goddard/no-major-us-hurricane-landfalls-in-nine-years-luck)

Not all raindrops are created equal. The size of falling raindrops depends on several factors, including where the cloud producing the drops is located on the globe and where the drops originate in the cloud. For the first time, scientists have three-dimensional snapshots of raindrops and snowflakes around the world from space, thanks to the joint NASA and Japan Aerospace Exploration Agency Global Precipitation Measurement (GPM) mission. With the new global data on raindrop and snowflake sizes this mission provides, scientists can improve rainfall estimates from satellite data and in numerical weather forecast models, helping us better understand and prepare for extreme weather events.Watch this video on the NASA Goddard YouTube Channel. Complete transcript available. This is a conceptual animation showing how the size and distribution of raindrops varies within a storm. The animation travels from the top to the bottom of a storm. Blues and greens represent small raindrops that are 0.5-3mm in size. Yellows, oranges, and reds represent larger raindrops that are 4-6mm in size. A storm with a higher ratio of yellows, oranges, and reds will contain more water than a storm with a higher ratio of blues and greens. Credit: NASA s GPM satellite is measuring the size and distribution of raindrops globally. A GIF optimized for posting on Twitter.With GPM’s three-dimensional snapshots of drop size distribution, scientists can gain insight into the structure of a storm and how it will behave. A GIF optimized for posting on Twitter.In the mid-latitudes, raindrops can originate from snowflakes, allowing them to melt into bigger raindrops compared to the tropics. For More InformationSee [NASA.gov Article](http://www.nasa.gov/feature/goddard/2016/size-matters-nasa-measures-raindrop-sizes-from-space-to-understand-storms)

LEAD: Science and computer advances over the past ten years since Katrina are giving meteorologists clearer pictures of hurricanes. 1. A NASA weather and climate model now (2015) has a resolution of 4 miles, and updates the dynamic state of the atmosphere every 5 seconds and physical processes every 5 minutes. 2. Katrina s wind speed is shown on the left, water vapor on the right. 3. Abundant water vapor was one factor that helped to intensify Katrina to a Category 5 storm, with sustained wind speeds of 175 mph. 4. But, 18 hours later Katrina made landfall over Louisiana as a Category 3 storm, with winds of 125 mph. TAG: Detailed computer models will help meteorologists understand these quick wind changes and make better forecasts about hurricane strength at landfall. For More InformationSee [http://www.nhc.noaa.gov/data/tcr/AL122005_Katrina.pdf](http://www.nhc.noaa.gov/data/tcr/AL122005_Katrina.pdf)