Monday, August 29, 2011

Wind Speed Discrepancy Hurricane Irene

Hurricane Irene brushes Atlantic Coast 
Wind Speed Controversy.

We observed, along with many others, a substantial discrepancy between wind speed readings reported by ground based weather stations and speeds attributed to NOAA as seen on TV News.

As a regular user out here in Palm Springs CA, I can confirm viewing many ground based Atlantic Coast weather stations on Sunday August 28. What I saw was:  wind speeds reported by hundreds of automated ground based stations. The speeds were in the 10-35mph range. None of those I checked had 60-80mph readings. 

The wind direction indicators followed the swirling cloud cover.  I was very surprised at such low wind speed readings from weather stations in the heart of a reported hurricane. Hurricanes would be expected to generate at least 60mph-90mph wind speed readings. 

The next surprise came when I listened to TV news reporting of 60-80mph winds (and higher) at the same time and place I was looking at weather station readings of 10-30mph.  BTW "rapid fire" automated weather stations update readings in real time, so we were not looking at old data. 

This huge discrepancy is a serious problem. 
Was the wind speed actually 10-30mph or 60-80mph or 80-90 mph?? 

NOAA must respond to this problem, they owe the public an explanation. 

Further support for the low wind speed readings comes from video reports on the ground.  Anecdotal evidence from live TV video did not look like 60-90mph wind conditions. More like 10-30mph winds and often reporters commented that the winds were not very strong. Live video did show high surf and some flooding, but  high wind conditions were not at all evident. 

We have no explanation of this apparent discrepancy between ground based stations and the NOAA reports from TV News.  

This is a serious issue for observational meteorology. Why are the NOAA figures 30-40mph higher than the data from ground based weather stations?  So far we have no satisfactory explanation. Please comment if you have any relevant information.  

How do you use

To use weatherunderground, go to the site:
Enter any US city and state. When the city page comes up, scroll to the bottom for a list of weather stations. You can see local variations in wind speed, wind direction, temperature, etc. Or click on wundermap for a google maps overlay showing stations as icons having wind direction and wind speed in "flag format" 3 stripes = 30mph wind speed. The wind direction is indicated by the direction the "flagpole" points.

Here are some screen shots showing radar images of IRENE as she came ashore in North Carolina August 27th. Ground based weather stations are also displayed.  Wind speeds are 30mph, just count the flags on the icon.  We also viewed real time data in numerical format on the same website. Go to the link below and scroll down to get to the images. 
Link to some images from

Check out here:
Link to Weatherunderground page for Manhattan NYC.
Just type in your city and state on the site home page and bring up a local map and station readings in your area. Click "wundermap" for an overlay on google maps and real time display of radar images.

So far we have no explanation for this substantial discrepancy.

Comments welcome -  

1 comment:

  1. Fast forward 6 years to today. I watched the weather channel report that hurricane Harvey here in Texas went from cat 1 to cat 2. Then it supposedly grew to cat 3 and finally to cat 4. But actual wind readings showed Harvey making cat 1.Then, just before landfall wind gusts reached cat2 levels. But then Harvey dropped back to cat 1 status - barely, according to actual wind speeds. I want to know why there is such discrepancy.