Intensity Forecasting EXperiment 2006
(IFEX06)

IFEX/NASA brief

NOAA's Hurricane Research Division, part of the Atlantic Oceanographic and Meteorological Laboratories located in Miami, FL, will begin a multi-year experiment this summer with the NOAA Aircraft Operations Center (AOC) called the Intensity Forecasting Experiment (IFEX). Developed in partnership with NOAA's Environmental Modeling Center (EMC) and its Tropical Predition Center, IFEX is intended to improve our understanding and prediction of hurricane intensity change by collecting observations that will aid in the improvement of current operational models and the development of the next-generation operational hurricane model, the Hurricane Weather Research and Forecasting model (HWRF). Observations will be collected in a variety of hurricanes at different stages in their lifecycle, from formation and early organization to peak intensity and subsequent landfall or decay over open water.

There are several unique aspects of IFEX in 2006 that will help improve our understanding and prediction of hurricane intensity change:

• Hurricane genesis experiment (GenEx) - This experiment, flown with a single NOAA P-3 aircraft is intended to improve our understanding of how a tropical disturbance becomes a hurricane. Very few aircraft measurements have been made in tropical disturbances over the past 25 years, largely because it is so difficult to collect data in these systems.

• Impact of Saharan air on intensity forecast models (SALEX) - Recent research has shown that very dry air originating from the African continent, called the Saharan Air Layer (SAL), may be an important factor in hurricane intensity change in the North Atlantic and Caribbean Sea. The SAL feature may play an important role in the ability of operational models to predict hurricane intensity, since the presence of dry air can significantly impact the strength and longevity of the vigorous convection that drives hurricanes. These studies suggest that providing accurate measurements of humidity for incorporation into hurricane models could produce better tropical cyclone intensity forecasts and also suggests that further research is needed to understand how the SAL affects tropical cyclone intensity. High-quality moisture data provided by GPS dropsondes deployed by the NOAA G-IV jet will provide these observations to better prescribe the initial conditions in the operational global model.

• Mapping of the center wind field from airborne tail Doppler radar and its transmission to EMC and TPC in real-time - Scientists onboard the NOAA P-3 will test a method for sending radar-derived wind measurements of a hurricane's inner-core to EMC in real-time. These measurements will ultimately be used in the development of techniques for incorporating data into models that can be applied to storms at all stages of their lifecycle. These measurements will also be sent to TPC, where they will be evaluated for the potential of being routinely provided to the hurricane specialists during the hurricane season.

• Aerosonde project - While the capabilities and utilization of the WP-3D Orion and Gulfstream 4 aircraft have made NOAA a global leader in hurricane aircraft surveillance and reconnaissance, detailed observations of the near-surface hurricane environment (sea level to 500 meters) have been elusive due to the severe safety risks associated with low level manned flights. A successful deployment the unique low flying unmanned Aerosondes will accurately document and improve our understanding of the rarely-observed near surface hurricane environment. An important (and immediate) additional benefit would be the real-time transmission of hurricane surface conditions directly to the OAR. In addition, detailed comparisons between in-situ and satellite-derived observations will also be possible.

• Hurricane landfall and Inland Decay experiment - The lifecycle of a tropical cyclone often ends when it makes landfall and decays as it moves inland. Research has shown that the rate of decay is a function of the storm intensity at lanfall. During landfalling situations efforts will be made to collect SFMR, Doppler radar, GPS dropsonde, SRA, IWRAP, and flight level wind data to accurately depict the storm's strength to improve decay forecasts and provide validation for the HWRF model.

• Hurricane Eye Mixing Module - Eyewall mesovorticies have been hypothesized to mix high entropy air from the eye into the eyewall, thus increasing the amount of energy available to the hurricane. Observations within the eye below the inversion can allow for the study of the dynamic and thermodynamic structures of these mesovorticies and improve our knowledge of intensity changes in strong hurricanes.
  During the course of other experiments scientists will attempt to carry out a detailed examination of the mixing layer within the eye of a mature hurricane. It is necessary for this module that the eye be at least 25 nmi in diameter and the hurricane at least Category 4.

During this year, IFEX will be operating in partnership with several other experiments:

• African Monsoon Multidisciplinary Analysis (AMMA) - An international research project and field campaign scheduled for Spring and Summer in the eastern Atlantic and western Africa. HRD and AOC will look to schedule follow on flights in the western Atlantic of systems investigated by AMMA.

• NASA African Monsoon Multidisciplinary Analyses (NAMMA) Experiment - Based in the Cape Verde islands, starting in August 2006, the NASA DC-8 will serve as the primary research tool as the aircraft will carry out in situ and remote sensing investigations of disturbances coming off the African coast, in coordination with the AMMA expedition (see above).
  Jason Dunion's news brief with NASA scientists

• NOAA Ocean Winds Experiment - The goal of the Ocean Winds experiment is to further our understanding of wind direction and speed retrievals at the ocean surface level from microwave remote-sensing measurements in high wind conditions and in the presence of rain. Measurements taken from the Ocean Winds experiment in mature storms will aid in the understanding and improvement of satellite remotely-sensed wind measurements which are currently used operationally by marine forecates and in numerical weather prediction models.

References:
Rogers, R., et al. "The Intensity Forecasting Experiment: A NOAA Multiyear Field Program for Improving Tropical Cyclone Intensity Forecasts", 2006, Bulletin of the American Meteorological Society, (v.87)n.11, p.1523-1537

Rogers, R., et al. "NOAA's Hurricane Intensity Forecasting Experiment: A Progress Report", 2013, Bulletin of the American Meteorological Society, (v.94)n.6, p.859-882