HOW TO FORECAST THE NORTHERN LIGHTS IN NORTHERN NORWAY. MEN OF SEA GUIDE – NORTHERN NORWAY GUIDE – PART 1
HOW TO FORECAST THE NORTHERN LIGHTS IN NORTHERN NORWAY
Northern Lights forecast – what really matters?
People planning a winter trip to Tromsø or Northern Norway often ask one question:
Will there be Northern Lights tonight?
The answer is not as simple as it may seem. There is no single indicator and no single app that can tell us with 100% certainty that the Aurora Borealis will appear at a specific time.
Forecasting the Northern Lights means combining several types of information: solar activity, solar wind parameters, the Earth’s magnetic field, the position of the auroral oval and local weather conditions.
And in Northern Norway, particularly around Tromsø, Kvænangen and Spildra, one factor is often more important than all the others: cloud cover.
Tromsø lies within the auroral zone, which means that the Northern Lights can be visible even during relatively low geomagnetic activity.
Is the Kp index the most important factor?
No. This is one of the most common mistakes made by beginners hunting the Northern Lights.
The Kp index shows the overall level of geomagnetic activity on a scale from 0 to 9. The higher the Kp value, the farther south the aurora may become visible. But for someone in Tromsø or Kvænangen, the situation is very different from that of an observer in Poland, Germany or farther south. We are already beneath the auroral oval.
That is why even Kp 0–2 may be enough to see the Northern Lights in Northern Norway. Yr even indicates that for latitudes between approximately 66° and 74°N, the Kp threshold for aurora visibility can be as low as 0. In practice, this means that a low Kp value should not be a reason to stay indoors.
If the sky is clear, go outside.
Bz – one of the most important aurora parameters
If we want to forecast the Northern Lights more intelligently, one of the most important parameters to understand is Bz. Bz describes the north-south component of the interplanetary magnetic field carried by the solar wind.
The most interesting situation for aurora hunters is when: Bz is negative – or southward.
When this happens, the magnetic field carried by the solar wind can connect more efficiently with the Earth’s magnetosphere, allowing more energy to enter the geomagnetic system. The more negative Bz becomes, and the longer it remains negative, the better the potential conditions for active Northern Lights.
In Northern Norway, however, extreme values are not always necessary. Sometimes a moderately negative Bz is enough for the auroral oval to become clearly more active.
What does Bt mean?
Another important parameter is Bt. Bt represents the total strength of the interplanetary magnetic field.
In simple terms: the higher the Bt value, the greater the potential for geomagnetic activity – provided that Bz is also favourable.
SpaceWeatherLive describes values above roughly 10 nT as moderately strong and values above 20 nT as strong. However, a high Bt value by itself does not guarantee a good aurora display.
That is why we always look at: Bt + Bz together.
Solar wind speed
Another useful parameter is solar wind speed. Typical quiet solar wind values are often around 300–400 km/s.
When the solar wind accelerates to around: 500–600 km/s conditions may become more interesting.
At 700 km/s or more, we are dealing with a very fast solar wind stream, although speed alone still does not guarantee a strong aurora.
The direction of the magnetic field carried by the solar wind remains critical.
Solar wind density
It is also worth monitoring solar wind density. A sudden increase in density may indicate that a disturbance is arriving, for example the front of a solar wind stream or a coronal mass ejection – CME.
Density alone does not tell us whether we will see the Northern Lights.
However, when it appears together with an increase in: solar wind speed, Bt and favourable Bz
it may signal increasing geomagnetic activity.
What is the auroral oval?
One of the most useful tools for Northern Lights forecasting is the auroral oval map. It shows where aurora activity is currently concentrated around the polar regions.
The auroral oval continuously changes its:
- position,
- width,
- intensity.
The more active the magnetosphere becomes, the more the oval may expand.
For someone in Northern Norway, the most important question is simply: is the active part of the auroral oval above us?
NOAA provides an Aurora 30-Minute Forecast, showing the expected position and intensity of the aurora over the short term.
This kind of nowcast is much more useful when deciding: “Should we go outside now?” than a Kp forecast several days in advance.
Hemispheric Power
Another parameter often shown by aurora forecast services is Hemispheric Power. It is expressed in gigawatts and estimates the total energy associated with auroral activity over one hemisphere.
Generally, a higher value means greater overall auroral activity. However, Hemispheric Power should not be treated as a standalone indicator.
For someone standing on Spildra, a much more useful question is: is the active auroral oval above Kvænangen and is the sky clear?
Why is cloud cover so important?
We can have: Kp 6, strongly negative Bz, fast solar wind, and a very active auroral oval.
But if there is a thick layer of cloud above us: we will see nothing.
The Northern Lights form high in the atmosphere, usually tens or hundreds of kilometres above the Earth. Clouds are much lower. They do not stop the aurora from forming. They simply block our view of it.
That is why, during aurora hunting in Northern Norway, we pay very close attention to: low, medium and high cloud cover, as well as the direction in which the clouds are moving.
In our experience, a clear or at least partly clear sky is the single most important practical condition for seeing the Northern Lights.
If we do not have time to analyse anything else, this is the first thing we check. If at least part of the sky is clear, there is a good chance of seeing the aurora.
Low clouds are the worst
Not every cloud layer behaves in the same way. Thin, high clouds can sometimes allow part of the aurora’s light to remain visible. But low, dense clouds can completely block the sky.
High clouds may be partly transparent, while low clouds are usually a much greater obstacle. That is why a forecast showing simply “80% cloud cover” does not tell the whole story.
It is worth checking: what altitude the clouds are at.
The best aurora forecast is a short-term forecast
Solar activity can be monitored several days in advance. We may know that a coronal mass ejection is travelling towards Earth. We may also know the expected Kp level.
But one of the most important parameters – Bz – cannot be forecast precisely far in advance.
Its actual value becomes known only when the solar wind structure reaches the measurement point ahead of Earth.
These measurements usually provide around: 30–60 minutes of warning depending on the solar wind speed.
That is why good Northern Lights hunting works like this: a few days beforehand, we check the overall potential; a few hours beforehand, we analyse the weather; and once we are on location, we watch real-time data.
How do we forecast the Northern Lights?
During our expeditions, we do not rely on a single app. First, we check: weather and cloud cover.
If there is a chance of clear sky, we then look at: Bz, Bt, solar wind speed, solar wind density and the current auroral oval.
Only after that do we look at Kp.
This may sound like the reverse of what many simple aurora apps show.
But around Tromsø and Kvænangen, it is a very practical approach. Kp may be low. And the Northern Lights may still be beautiful.
Which websites and apps should you use?
Yr
For us, Yr is one of the most important weather apps in Norway. It provides local weather, cloud cover and its own Aurora Borealis forecast.
Yr offers an aurora forecast for up to three days and a short-term nowcast of around 30–90 minutes.
However, during Northern Lights hunting, the most valuable part of Yr is often simply: the local cloud forecast.
Windy
Based on our own experience, Windy is generally less precise than Yr for very short-term local weather forecasts. However, Windy has an important advantage: it allows us to analyse the structure of: low, medium and high clouds.
We also use Windy for longer-range forecasts to identify broader weather trends. For short-term forecasts, we usually start with Yr and then use Windy to add more detail.
NOAA Space Weather Prediction Center
NOAA is one of the main professional sources of space-weather information. It is useful for monitoring:
- auroral oval,
- solar wind,
- geomagnetic activity,
- short-term forecasts.
The Aurora 30-Minute Forecast is particularly useful.
SpaceWeatherLive
SpaceWeatherLive is a very convenient and easy-to-read tool for people who want to analyse aurora conditions themselves.
In one place, you can see: Kp, Bz, Bt, solar wind speed, density, the auroral oval and Hemispheric Power.
For more advanced aurora hunting, it is one of the most practical websites.
How to read a Northern Lights forecast – a simple method
For people who do not want to analyse ten different charts, we recommend this simple order:
- Is the sky clear?
If not, check whether there may be a break in the cloud cover in the next hour or two. - Is the active auroral oval above Northern Norway?
If yes, there is potential. - What is Bz doing?
If Bz is negative and remains negative for some time, conditions are more favourable. - Is Bt elevated?
A higher Bt value increases the potential for geomagnetic activity. - How fast is the solar wind?
Higher solar wind speed may strengthen the effect. - Only then look at Kp.
In Tromsø and Kvænangen, we do not need a high Kp value to see the Northern Lights.
The app shows 20% – should you still go outside?
Yes. Giving up because of a low percentage is a common mistake. The percentage shown in an app is simply the output of a particular model.
It does not mean: “there is a 20% chance that you will see the Northern Lights.”
If you are beneath the auroral oval and the sky is clear, it is worth watching the sky even when the forecast does not look especially impressive. This is exactly why experience matters.
Can you forecast the exact time of the Northern Lights?
No. It is not possible to reliably say: “the Northern Lights will start at exactly 22:15 tonight.”
We can identify periods of increased potential. We can monitor incoming solar wind. We can watch whether Bz is becoming increasingly negative.
And we can follow the development of the auroral oval. But the Northern Lights are a dynamic natural phenomenon.
SpaceWeatherLive also points out that only measurements taken upstream of Earth provide a useful assessment of conditions roughly an hour in advance.
That is why one thing is essential: patience.
And now we will reveal another of our secrets for checking whether there is an aurora above us: go outside and look at the sky. It is a surprisingly effective method.
Why is Spildra a good place for Northern Lights hunting?
During our Northern Lights and Whales expeditions, we stay on the small island of Spildra in Kvænangen.
That gives us a major advantage. There is very little artificial light on the island. We do not have to drive out of a large town every evening. We only need to walk a short distance from the harbour.
Around us we have: dark skies, sea, high mountains and a fjord.
This allows us to react very quickly when conditions change. If the apps show that a clear window is opening in the clouds, we do not need to organise a long journey. We can simply go outside.
Northern Lights forecasting and photography
Good forecasting is useful not only for seeing the aurora. It also helps us choose the best place for Northern Lights photography.
If we see that the aurora is beginning to develop, we can prepare our cameras and compositions in advance.
On Spildra, there are many possibilities: the Northern Lights above mountains, above the sea, above the fjord, above a snow-covered coastline, reflected in the water, or above our yacht Azimuth.
As photographers, we help participants not only find the Northern Lights, but also: take a good photograph of them.
The most important rule of Northern Lights hunting
You can know every indicator. You can analyse: Bz, Bt, Kp, solar wind, and the auroral oval.
But there is one rule more important than all the others: you have to go outside.
In Northern Norway, the aurora can appear even at low Kp. It can suddenly brighten for just a few minutes. It may become visible through a gap in the clouds.
And it can begin even when an app looks rather unpromising.
That is why the best Northern Lights forecasting tools remain: knowledge, experience, patience and looking at the sky.
FAQ – Northern Lights forecast
What Kp is needed to see the Northern Lights in Tromsø?
Tromsø lies within the auroral zone, so the Northern Lights can be visible even at very low Kp. A high Kp value is much more important for observers located farther south.
What is more important: Kp or Bz?
For real-time assessment, Bz is extremely important, particularly when it remains negative. Kp gives a broader indication of geomagnetic activity but reacts more slowly and does not precisely describe what is happening above one specific location.
What Bz is good for the Northern Lights?
In general, a negative Bz, meaning southward orientation, is favourable. The more negative it becomes and the longer it remains negative, the greater the potential for increasing geomagnetic activity.
Does a high Kp guarantee the Northern Lights?
No. Geomagnetic activity may be very high, but if the sky is completely covered by clouds, the aurora will remain invisible.
How far in advance can the Northern Lights be accurately forecast?
Long-range forecasts only indicate potential. The most useful real-time solar wind data usually provide around 30–60 minutes of lead time.
What is the best Northern Lights app in Norway?
There is no single best app. Yr is very useful for local weather and a simple nowcast.
NOAA is excellent for professional space-weather data.
SpaceWeatherLive is convenient for monitoring Bz, Bt, solar wind and the auroral oval.
Is cloud cover more important than aurora activity?
For an observer standing on the ground, very often yes. The aurora may be extremely active, but if you are beneath a thick layer of cloud, you will not see it.