Using Wind Direction to Predict Weather

[Glflegolas]

Good day folks,

Are any of you weather weenies like me? Yes? Well, let me give you a quick meteorological lesson...

Since Great Bear Island is set in Northern Canada, it is in the Northern Hemisphere. Therefore, high-pressure cells (which bring fair weather) rotate clockwise, and low pressure (bringing poor weather) turns counterclockwise. If you face into the wind, the high pressure system will be to your left, and the low to your right. Keeping in mind that weather usually moves from west to east, wind direction can help you make fairly decent forecasts.

From my experience at home, here's some weather you can expect during the winter when winds come from certain directions. Note: wind velocity is very often highest around mid-afternoon,

Northwest:

• If it is snowing, it will generally stop within 6 hours, clear out (aside from a risk of the occasional flurry), and the temperature will fall. Winds will likely remain strong and from this direction for 1-3 days.
• If it is clear: Cold but clear weather is likely to continue for at least another day or so, especially if the wind does not die out by evening.

North:

• Generally means a low-pressure system is on the way out, and conditions will improve in the next 6-12 hours.

Northeast:

• If it's clear: The day ahead will be cool but clear, with generally light winds. Snow and cooler temperatures are likely within 36 hours, however.
• If it's already cloudy: A snowstorm is likely to start very soon.

East:

• If it is clear: Temperatures will likely rise and the day will be sunny, but rain (winds shifting towards the SE) or snow (winds gradually turning towards the NE) will arrive in 24-48 hours.
• If it's cloudy: A steady wind from this direction can mean an extended period of freezing rain.

Southeast:

• If it is clear: Temperatures will likely rise and the day will be sunny, but rain is on the way within 24-48 hours.
• If cirrostratus clouds are visible: Rain or snow, starting within 12-18 hours. Temperatures will likely rise. Winds are likely going to intensify.

South:

• If it is clear: Mild and fair weather for the next 12-24 hours, but a cold front, bringing rain, wind, and much colder temperatures behind it, is on the way.
• If it is raining: A cold front is moving through very soon. Expect heavy showers (possible thunderstorms) and strong, gusty winds. After the front, the wind will shift towards the west and temperatures will fall.

Southwest:

• If it is clear: fair weather will continue for the next 12-24 hours, with moderately cold temperatures.
• If it's raining/snowing: expect off-and-on showers/flurries to continue for the next 12 hours or so, followed by clearing.

West:

• Usually means a continuation of fair weather. It will likely be cold, but less so than with a NW wind.

No wind at all:

• If it's evening and there's no clouds: Expect a particularly cold night.

[ajb1978]

I used to have a cardstock weather forecasting kit back in the 80's. You select an insert based on where you are in the North America, then look at the pictures that match the current cloud pattern in the sky. Then you move the insert so the black marker aligns with the current wind direction, and it would give you a brief little 2 sentence forecast. And damn if that thing wasn't accurate as hell!!

[Glflegolas]

As a fellow weather nerd, I have to say: that's amazing! Now I wonder if I can get one of these for myself... do you have any pictures of it?

[Glflegolas]

Here's a photo of an extratropical cyclone (from TropicalTidbits.com, annotated by me). This is an example of a cyclone that is still relatively early in its lifespan. The wind direction at the surface is shown using the orange arrows. In this case, the highest absolute velocities will be found along the warm front (from the E or SE) and just ahead of the cold front (from the S). With a central pressure of 993 mbar, if this cyclone was to come to Great Bear, it might produce moderate snow (if it tracked to the south of the island), but it wouldn't likely be a blizzard. Where I live (in Nova Scotia) temperatures in the warm sector may reach upwards of 10C, even in the middle of winter!

Edited June 12, 2021 by Glflegolas

[Glflegolas]

Here's another, stronger, extratropical cyclone -- it's a classic nor'easter that's undergone occlusion, as seen by the warm seclusion (a pocket of warm air trapped within the cold sector). In this case, the heaviest snow will fall just to the west of the centre, possibly including thundersnow. The highest winds will be around the centre, either from the north or from the southwest (depending on the jetstream), and can reach the velocity of a weak hurricane, and cold temperatures, especially just after the storm has passed. A storm like this on Great Bear would mean: hunker down.

[ajb1978]

4 hours ago, Glflegolas said:

As a fellow weather nerd, I have to say: that's amazing! Now I wonder if I can get one of these for myself... do you have any pictures of it?

Sadly I do not, it disappeared at some point. It was called "Pocket Weather Trends", although a brief Internet search hasn't turned up any hits that match the thing I had. It may be one of those things lost to antiquity.

[Guest jeffpeng]

This stuff is fascinating.

[Glflegolas]

Speaking of weather, I wonder why there's no thundersnow in the strongest blizzards in TLD. Even if its effects were only aesthetic (very dark even during daylight, occasional lightning flashes), it would be cool. Of course, adding a risk of being struck by lightning during blizzards would only make Interloper harder and more fun, no? Throw in a risk of hail (causing rapid condition loss) and staying the blazes home becomes very important during a blizzard.

Another weather phenomenon that would be at home in TLD would be freezing rain. Other than soaking the player very fast and increasing the likelihood of sprains, though, I'm not sure what adding this would add to gameplay.

[Stinky socks]

Fascinating weather talk. Very interesting, thank you!

I agree about adding more weather phenomena to TLD; it would make game quite exciting!

[Glflegolas]

Given that the snow on the ground in TLD doesn't accumulate, there's no reason that real (non-freezing) rain not to fall from time to time. A max high of 5-8C during rain events isn't unreasonable. Aside from quickly soaking clothing (both outside and in buildings with leaky roofs) it could also make ice nearly impossible to stand on, resulting in a very high likelihood of sprains.

One of the classic winter weather events where I live is the "Nova Scotia mix" which progresses as follows:

Few flurries -> light, fluffy snow ->heavy, wet snow -> ice pellets -> freezing rain -> heavy rain (possibly including thundershowers) -> few showers -> clearing -> falling temperatures.

Not sure how/if this could be added to the game, but it would be interesting to experience. Dwarf Fortress has some very complex weather, and even includes its own dynamic in-game weather model. I doubt something like this could be added to TLD, but adding learnable patterns to the weather on Great Bear would make things a lot less frustrating, especially for veteran players.

One final thing I forgot to mention is sea-effect snow. This can occur anytime there's a strong cold wind blowing over relatively warm, open water. On Great Bear, this is unlikely, because Coastal Highway, Bleak Inlet, and Desolation Point have the ocean on their south and east sides, and southerly/easterly winds are generally relatively warm in the winter, so sea-effect snow would be rather uncommon.

[Glflegolas]

On 6/4/2021 at 10:02 PM, Glflegolas said:

Good day folks,

Are any of you weather weenies like me? Yes? Well, let me give you a quick meteorological lesson...

Since Great Bear Island is set in Northern Canada, it is in the Northern Hemisphere. Therefore, high-pressure cells (which bring fair weather) rotate clockwise, and low pressure (bringing poor weather) turns counterclockwise. If you face into the wind, the high pressure system will be to your left, and the low to your right. Keeping in mind that weather usually moves from west to east, wind direction can help you make fairly decent forecasts.

From my experience at home, here's some weather you can expect during the winter when winds come from certain directions. Note: wind velocity is very often highest around mid-afternoon,

Northwest:

• If it is snowing, it will generally stop within 6 hours, clear out (aside from a risk of the occasional flurry), and the temperature will fall. Winds will likely remain strong and from this direction for 1-3 days.
• If it is clear: Cold but clear weather is likely to continue for at least another day or so, especially if the wind does not die out by evening.

North:

• Generally means a low-pressure system is on the way out, and conditions will improve in the next 6-12 hours.

Northeast:

• If it's clear: The day ahead will be cool but clear, with generally light winds. Snow and cooler temperatures are likely within 36 hours, however.
• If it's already cloudy: A snowstorm is likely to start very soon.

East:

• If it is clear: Temperatures will likely rise and the day will be sunny, but rain (winds shifting towards the SE) or snow (winds gradually turning towards the NE) will arrive in 24-48 hours.
• If it's cloudy: A steady wind from this direction can mean an extended period of freezing rain.

Southeast:

• If it is clear: Temperatures will likely rise and the day will be sunny, but rain is on the way within 24-48 hours.
• If cirrostratus clouds are visible: Rain or snow, starting within 12-18 hours. Temperatures will likely rise. Winds are likely going to intensify.

South:

• If it is clear: Mild and fair weather for the next 12-24 hours, but a cold front, bringing rain, wind, and much colder temperatures behind it, is on the way.
• If it is raining: A cold front is moving through very soon. Expect heavy showers (possible thunderstorms) and strong, gusty winds. After the front, the wind will shift towards the west and temperatures will fall.

Southwest:

• If it is clear: fair weather will continue for the next 12-24 hours, with moderately cold temperatures.
• If it's raining/snowing: expect off-and-on showers/flurries to continue for the next 12 hours or so, followed by clearing.

West:

• Usually means a continuation of fair weather. It will likely be cold, but less so than with a NW wind.

No wind at all:

• If it's evening and there's no clouds: Expect a particularly cold night.

Although these wind/weather trends are generally true, there's always the exception that proves the rule. Case in point: Hurricane Fiona. On Thursday night, the storm was preceded by a normal cold front, where moderate winds blew from the southwest accompanied by moderately heavy rain snowers. As the front passed through Friday morning, the winds diminished and switched to the north, with the rain started to taper to showers. So far, things seemed to be normal, and, without satellite imagery, it would be safe to assume the rain would be over by Friday night, with a cooler, dryer airmass moving in, accompanied by northwesterly winds.

But by Friday afternoon, the winds went back to the northeast, and the rain never fully stopped. Early evening brought blustery winds with moderate rainshowers, and every hour, the winds and rain intensified. Gradually the winds turned northerly, and reached their maximum around midnight, gusting to around 160 km/h, accompanied by heavy bursts of rain. As morning broke, the winds went northwesterly and gradually diminished, as the skies cleared off.

Fiona's winds didn't follow the usual direction because the storm didn't move from west to east. Instead, it moved from south to north, which is quite unusual in the mid-latitudes.

[ajb1978]

On 6/11/2021 at 6:47 PM, Glflegolas said:

As a fellow weather nerd, I have to say: that's amazing! Now I wonder if I can get one of these for myself... do you have any pictures of it?

Looks like it pops up in an Amazon search now, but it's long since out of print. https://www.amazon.com/Pocket-Weather-Trends/dp/0812009576

Still, first time I've laid eyes on the cover in decades though!