102nd Anniversary of Bob Simpson’s birth

Bob Simpson with his daughter Peggy.

Bob Simpson with his daughter Lynne.

Today we send congratulations to Dr. Bob Simpson on his 102nd birthday.  Bob was the first director of the National Hurricane Research Project (NHRP) which eventually became the Hurricane Research Division of the Atlantic Oceanographic and Atmospheric Laboratory.  In addition to being a pioneer in the field of tropical cyclone research, he and his late wife Joanne were invaluable mentors to scores of meteorologists around the world.

Paper on the rapid intensification of Hurricane Earl released online in Monthly Weather Review

Hurricanes sometimes change intensity very quickly, and if this happens when they approach land, it can suddenly cause a lot of damage or kill many people. This so-called Rapid Intensification (RI) is very hard to forecast. For the first time, the Hurricane Weather Research and Forecast (HWRF) model that NOAA uses to forecast where a hurricane will go and how strong it will be, was used to help understand RI. During RI, the HWRF forecasts matched information from aircraft in hurricanes.Screen Shot 2014-11-13 at 3.45.14 PM

Important conclusions:

  • Sometimes, the position of the hurricane eye changes with height. It was thought that this change needed to disappear before RI began, but, in this case, it does not disappear until a few hours after RI begins.
  • Hurricane eyes are warm in the middle and upper parts of the atmosphere, and the amount of warmth is tied to intensity. The eyewall is the ring of strong thunderstorms surrounding the eye that fuel the hurricane winds. When the thunderstorms get especially strong in a special part of the eyewall, they can help to transfer more warm air into the eye and lead to further intensification.

The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-14-0097.1.

Paper on corrected surface wind-speed measurements from reconnaissance published in the Journal of Atmospheric and Oceanic Technology

The Stepped-Frequency Microwave Radiometer (SFMR) measures surface wind speed and rainfall from aircraft.  Using a large database of surface wind-speed measurements from the SFMR and dropwindsondes, the SFMR wind speeds are shown to be too high at low wind speeds and in heavy rain. The measurements are corrected using other rainfall measurements. Though the wind-speed measurements are still a little bit too high at the lowest wind speeds and in heavy rain, the bias is reduced in all conditions.

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The full paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/JTECH-D-14-00028.1.

Paper on using aircraft data in hurricane models to improve forecasts released online in Monthly Weather Review

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NOAA and U. S. Air Force aircraft have been gathering wind, temperature, humidity and pressure information inside hurricanes for more than 30 years. The NOAA aircraft have been fitted with Doppler radars that can see the entire hurricane’s rain and wind from near the ground to the top of the clouds. All the information is sent from the aircraft to the National Hurricane Center so they can see what the hurricane looks like. However, until now, we have not yet had the computer power to get the information into the models that are used to forecast where the hurricane will go and how strong the wind and rain will be. This study marks the first time that this information has been used in NOAA’s Hurricane Weather Research and Forecast (HWRF) model. It shows that there is hope for making better forecasts using the information from flights into hurricanes.

Important conclusions:

  1. Forecasts of where the hurricane will go using the information from the aircraft are about 10% better than those that do not use it.

  2. Forecasts of the fastest wind speed in the hurricane using the aircraft data are up to 23% better than those that do not use it.

  3. Forecasts of the winds surrounding the hurricane center are also better when they use the information from the flights.

15th Anniversary of the Odisha Cyclone

Odisha cyclone makes landfall (METEOSAT-5)

Odisha cyclone makes landfall (METEOSAT-5)

On October 29, 1999, a Super Cyclonic Storm struck near the city of Bhubaneswar in the Indian state of Odisha.  The day before it had become the strongest cyclone on record in the North Indian Ocean when its maximum sustained winds peaked at 140 kt (260 km/hr).  It also became the deadliest Indian cyclone since the Bhola cyclone 29 years before.

The storm began as a disturbance in the West Pacific, but did not organize into a depression until it moved over the Malay peninsula into the Bay of Bengal.  There, it steadily strengthened as it moved on a northwest course across the Bay.  It rapidly intensified to its peak a day before landfall, but its winds slightly decreased to 135 kt (250 km/hr) as it came ashore.  It brought a 26 foot (8 m) storm surge to the Odisha coast and dumped torrential rains on the area as the cyclone stalled shortly after landfall.  This caused the greatest flooding to the area seen in the last century. A blocking high-pressure ridge to the north forced the storm back over the Bay where it finally dissipated.

Track of Odisha cyclone (Wikipedia)

Track of Odisha cyclone (Wikipedia)

Despite the evacuation of tens of thousands of families from the shore, over 9,800 people died in this cyclone.  Many drowned in the storm, but substantial numbers were lost to disease and starvation in the aftermath.  Crops throughout the province were destroyed, 405,000 livestock animals perished,  and millions of trees were uprooted.  275,000 homes were damaged and over a million and a half people were left homeless. Total financial damage is estimated to be US$4.5 billion.

Paper on the rapid intensification of Hurricane Earl in 2010 released online in Monthly Weather Review

The paper discusses changes to the structure of Hurricane Earl (2010) as it rapidly intensified.   It found

  • Earl tilted with height before it intensified, but was upright during the intensification.
  • Strong thunderstorms played a significant role in the rapid intensification of Hurricane Earl.
  • Thunderstorms located on the inside of the eyewall are a condition favorable for intensification.
  • It is important to learn why thunderstorms form where they do to improve forecasts.
  • It is also important to observe the structure of the hurricane to better represent where these thunderstorms may occur in forecast models and improve hurricane forecasts.

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The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-14-00175.1.

Paper on a dataset of dropwindsonde observations in tropical cyclones released online by the Bulletin of the American Meteorological Society

A long-term (1996–2012), high-quality, high vertical resolution (∼5–15 m) GPS dropsonde dataset is created from NOAA Hurricane flights and consists of 13,681 atmospheric profiles for 120 tropical cyclones.

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The paper can be accessed at http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00203.1.