Typhoon Haiyan hit the Philippines on November 7th.
It is estimated to be one of the strongest tropical systems on record.
But unlike Atlantic and East Pacific Ocean hurricanes, there are no Hurricane Hunter crews that fly into the storm.
Because of this, exact measurements of the winds from instruments inside the storm simply do not exist.
So how do we know it was one of the most powerful storms on record?
NASA Earth Observatory says "In the absence of direct wind speed measurements, one of the common methods used to estimate the intensity of tropical cyclones is the Dvorak technique. Developed four decades ago by American meteorologist Vernon Dvorak, the technique estimates maximum wind speeds by analyzing subtle differences in visible and infrared satellite imagery."
However, some scientist believe this method overestimates wind speed is some cases.
Scatterometers are also in use to measure wind speeds.
According to NASA Earth Observatory this is "a type of microwave radar, can also measure the strength of a storm's winds. The dual-beam rotating scatterometer on the Indian Space Research Organization's Oceansat-2 satellite, for instance, can be used to measure the strength of the winds at the ocean surface."
The image below shows scatterometer measurements of Typhoon Haiyan on the morning of November 7th.
The "arrows indicate wind direction and colors indicate wind speed, with darker shades of purple indicating stronger winds." according to NASA Earth Observatory.
Oceansat-2 dataOceansat-2 dataNASA's Jet Propulsion Laboratory (JPL) also analyzed Oceasat-2 data and estimated the winds peaked at 150 miles per hour.
That ranks the storm equivalent to a strong Category 4 hurricane.
The hurricane scale only goes to 5.
Because there are no direct measurements of Haiyan's true top winds speeds Jeffrey Halverson, a meteorologist at the University of Maryland at Baltimore County, says "The bottom line is that meteorologists are going to be debating what Haiyan's top wind speeds were for some time."