Will Fewer Balloon Weather Observations Mean Reduced Forecast Skill?

 Due to retirements and hiring suspensions, the number of launches of balloon-launched weather balloons (called radiosondes) has been reduced by about 10% in the U.S.  

Specifically, of the 92 U.S. radiosonde locations, about ten have reduced launches either totally or partially.

Several media sources have suggested this reduction could seriously degrade U.S. weather prediction (see samples below).   

But is this true?   As discussed below, there are several reasons to expect that the impacts will be very small, not the least because balloon-launched weather observations now play a much, much smaller role in the modern observing network.

Why upper air data matters

The atmosphere is fully three-dimensional, and predicting the weather requires understanding the 3D distribution of temperature, wind, and humidity.

Such three-dimensional data is the starting point of the key technology of weather forecasting: numerical weather prediction (NWP), in which meteorologists simulate the evolution of the atmosphere by solving the equations describing atmospheric physics on the largest computers available.

Such forecasts start with a three-dimensional description of the atmosphere, called the initialization.

During the early years of NWP (1950-1970), radiosondes were the only source of weather information above the surface.  Absolutely critical.

The number of radiosondes has declined modestly over the years, with the current global network shown below.  

Lots over the U.S., Europe, and Southeast Asia.  You will notice a major issue with the radiosonde distribution:  there are few over the oceans and the polar regions, which encompass about 70% of the planet!

The current U.S. radiosonde network is displayed below, with red circles indicating radiosonde sites that are either suspended or only launched once per day.  Keep in mind that at most sites, these observations are only made twice per day.

Is there any objective evidence that forecasts have declined with fewer U.S. radiosonde observations?

As far as I can tell, the answer is no.  

I have gone through all the objective verification scores and could not find any degradation in National Weather Service forecast skill.  For example, the 5-day precipitation scores over the U.S. in March 2025 are better than March 2024.

I could show you a dozen more like this.  

But we have to be careful here.  Perhaps 2025 was an easier year to forecast.  

To do this right, we need to do OSSEs...observing system simulation experiments... in which we run identical periods we different amounts of radiosonde data.

However, there are powerful arguments about why the radiosondes are no longer as important to weather prediction, and particularly whether the temporary loss of a few of them would make much of a difference.

Today, three-dimensional satellite observations are dominant--in fact, approximately 99% of the weather data used today in numerical weather prediction is from satellites.    For example, we can determine the winds by tracking features in the infrared part of the spectrum.

 Or we can use satellites to measure how humidity varies with height.

Other satellites measure temperature and humidity with height by noting how GPS signals are bent by the Earth's atmosphere.

I have hardly warmed up.  There are dozens of other examples of how satellites provide detailed, three-dimensional weather data over the entire planet...over most of which there are no radiosondes.

But there is more.   Many aircraft take continuous observations in flight and provide vertical profiles of the atmosphere (called soundings) are they take off and land at airports (see below).   Such soundings are very much like the radiosonde data, but are taken at more locations and at more times.

The bottom line of all this is that balloon-launched weather instruments (radiosondes) are now only a very, very small proportion of the atmospheric weather data used by meteorologists for weather prediction.   

As a result, a loss of a few observations over a portion of one country probably has very little impact.

Thus, the headlines of gloom and doom are probably wrong.    

Let me be clear....I think we should restore the U.S. radiosonde network and then complete careful experiments to determine how many of them are really needed for calibrating the satellite data and other uses.  From what I have learned, restoration of the missing radiosondes will occur over the next few months, with the National Weather Service now hiring again.

Below-Normal Wildfire Year so Far

Announcement:

 I will be teaching ATMS 101 this autumn at the UW, so if anyone is interested in securing a basic understanding of weather and climate (UW students, non-students), you can check it out here.

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Even with a relatively dry spring,  cumulative wildfire acreage in Washington State is currently below normal.  

You read that right, below normal.

Interestingly, the dry condition may have even contributed to the modest wildfire totals so far this year.

To start, consider the Washington State Department of Natural Resources (DNR) acres burned statistics for Washington State (below).  This year is very low...the second lowest since 2015.

Currently, there are only two significant wildfires burning in Washington right now, and both are relatively small:  the Pomas and Barstow Road fires (see map below).

While the wildfire season has been restrained so far, spring precipitation has been below normal, and temperatures have been above normal (see plots below).  

Western Washington has been particularly dry, with the Columbia basin modestly below normal.

So, how could the wildfire area be less with warmer and drier conditions?

Because wildfire generation is more complicated than communicated in the media, such as the Seattle Times.

To get a wildfire, you need ignition, sufficient fuels, dry fuels, and supportive meteorological conditions, with wind being the most important.

Precipitation during late winter and spring is important for producing bountiful light fuels, such as grasses and range-type vegetation.

Rainfall deficit has resulted in normal to lower than normal amounts of annual vegetation over much of the region, something shown by the USDA Fuelcast site (see graphic below).

Last weekend, I explored the situation in the hills north of Teanaway, WA on the eastern side of the Cascades.  Grass productivity was less than I have seen in recent years, and much of it was still green in forested areas (see pictures below).

So we start with a light to normal fuel load over much of the region.

What about ignitions?  

 Many utility companies are stating they will be more aggressive with strategic power shut-offs, which should help.   But what about lightning-initiated fires, which are often in remote areas and difficult to extinguish?

The extended precipitation forecast this summer is for drier than normal conditions (see below).  Since thunderstorms are the big precipitation producers for much of the summer (particularly east of the Cascade crest), this implies fewer thunderstorms.

Which means fewer lightning starts and fewer ignitions.  This implies less wildfire activity.

August and September are generally our big wildfire months.   The European Center's prediction of precipitation anomaly (difference from normal) is near normal for August (except north of the border) and perhaps wetter than normal over western Washington in September (see below).   Not very threatening.

All in all, I don't think there is much reason to expect an above-normal wildfire season over Washington, even with the teeth gnashing in a certain local paper.

David Horsey, Seattle Times