Friday, August 31, 2007


"Smurfs" Vs. Hurricane Dean

By David Axe

August 19, 2007 | 9:54:06 PM

Two years ago Hurricane Katrina kicked the U.S. government's ass. Now, as Hurricane Dean sweeps past Jamaica on its way to the U.S. Gulf Coast, FEMA, the Coast Guard and the other military services are poised to prove they can do better the second time around. The military response actually began days ago when the Air Force's WC-130J hurricane-hunting patrol planes deployed brand-new sensors to more accurately predict when and where Dean will hit and what kind of damage it will do, according to the service. The "Stepped-Frequency Microwave Radiometer," or "smurf,"

allows the Citizen Airmen of the Hurricane Hunters to constantly measure surface winds directly below the aircraft. The smurf can also determine rainfall rates within a storm system. This, in addition to wind speeds at flight level, provides structural detail of the storm. "The SFMR will be the biggest advance I can think of to improve hurricane intensity forecasts," said Max Mayfield, former director of the [National Hurrican Center].

The data collected by the Hurricane Hunters increase the accuracy of the NHC forecast by 30 percent, a rate which will undoubtedly increase with the use of the smurf. This data enables the NHC to more accurately predict the path of storms in order to save lives and narrow areas of evacuation, according to NHC forecasters.

U.S. Air Force Fact Sheet

SFMR Ready for 2007


The Stepped-Frequency Microwave Radiometer is a state-of-the-art instrument designed to continuously and accurately measure the winds at the ocean's surface directly below the aircraft. The SFMR, affectionately known as "smurf", is installed on the WC-130J within a pod attached to the aircraft's wing. As the plane flies through a storm, the SFMR senses microwave radiation naturally emitted from foam created on the sea by winds at the surface. Computers then determine wind speeds based on the levels of microwave radiation detected. Currently, winds are extrapolated from the winds at the aircraft's altitude or from a dropsonde released from the aircraft, however, the SFMR directly measures the surface winds and is not confined to a single point like the dropsonde. This constant measurement of surface winds gives the National Hurricane Center a more complete picture of the storm.

The SFMR can also determine rainfall rates within a storm system. This, in addition to wind speeds at flight level, provide structural detail of the storm.

Two Hurricane Hunter aircraft will be equipped with the SFMR by the end of June with one added each month until all 10 WC-130J aircraft are outfitted with the SFMR pod, the last to be equipped in March, 2008.

Hurricane Hunters fly year's first storm mission over Atlantic


Radiometer Type Hatch
Tuning bandwidth 4.6 -7.2 GHz
Number of channels Up to 8
Receiver Channel Bandwidth 50 MHz
Antenna Type Corrugated horn
Antenna Beamwidth (3 dB) 20-28 deg Polarization Linear
Measurement precision 0.17 K (1second averaging)
Electronics Power Requirements 28VDC, 2A
Thermal Control Power Requirements 28VDC, 4A (max)
Power 168 W
Operating Temperature -65°C to +40°C
Humidity 0 to 100%
Size (L x W x H) 24" x 11" x 13"
Weight 40 lbs.

WP-3D Stepped Frequency Microwave Radiometer (SFMR)

Measurement of the hurricane surface wind field, and in particular the estimation of wind maxima, has long been a requirement of the Tropical Prediction Center/OAR. The NOAA/Hurricane Research Division's Stepped-Frequency Microwave Radiometer (SFMR) is the prototype for a new generation of airborne remote sensing instruments designed for operational surface wind estimation in hurricanes.

The SFMR has a downward pointing antenna which passively reads the microwave radiation coming from the ocean surface. By making assumptions about the vertical structure of the atmosphere together with sea surface temperature measurements by a downward-looking airborne infrared radiometer, reasonable estimates of the ocean surface brightness temperature can be made at six frequencies between 4.6 and 7.2 GHz. Wind speeds are then calculated assuming linear increase in wind speed with these brightness temperatures. Since some of the frequencies are more attenuated by rainfall than others, an estimate of the rainfall rate below the airplane can also be made.

Project page for SFMR development
Report on SFMR in Katrina and Rita 2005

Weather Story:

Well we have Tropical Storm Gil and Tropical Depression ELEVEN E (RESOE EDIS) off the Pacific Coast that we are keeping an eye on. There are also a couple of interesting tropical waves forming off the African Coast (see Tropical Weather Outlook and Storm Watch-Carib interactive graphics- left side of page)!

Chicago Weather for the weekend? Just great! Have a wonderful Labor Day Weekend!