Fog

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UngaWunga

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UngaWunga
What's a good way to predict fog? Living on the seacoast of NH, we've had some pretty thick fog roll in during the mornings and evenings. It didn't show up on any of the forecasting tools I was using, include the NOAA GFA tool. Are there other things I can look at to try to predict when fog might roll in?

Been trying to fly out to see some local baseball in the evenings, and weather really hasn't cooperated recently.
 
Temp / DP spread, local knowledge

Last summer we had some scud that would show up around 8:30 then dissipate by 9:30. It often wrecked an 8-10am lesson.
 
Can you be more specific about temp/ dew point spread? Local knowledge, been living here for 15 years, so....
 
UngaWunga said:
Can you be more specific about temp/ dew point spread? Local knowledge, been living here for 15 years, so....
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As you know, the closer the ambient temperature is to the dew point, the likelihood for fog increases. So if the temp and dew point spread are only a couple degrees from each other, expect fog.
 
UngaWunga said:
What's a good way to predict fog? Living on the seacoast of NH, we've had some pretty thick fog roll in during the mornings and evenings. It didn't show up on any of the forecasting tools I was using, include the NOAA GFA tool. Are there other things I can look at to try to predict when fog might roll in?

Been trying to fly out to see some local baseball in the evenings, and weather really hasn't cooperated recently.
Click to expand...

It's easy. Take a look at a map. If you are operating anywhere in the northeast / New England, you can expect fog.
 
Skew t, you need to study to learn to use those, satellite images, close dew point spread, wind direction. I'm about 35 miles inland from the MA/NH coast and it happens. Yesterday was pretty bad in parts of NH, forecast to burn off at 8, it stuck around until 9:30 inland.
 
Not sure if it is correct but I was taught...If the temp dew point spread are within 4 degrees there will be some sort of obscuring phenomenon.
 
DFH65 said:
Not sure if it is correct but I was taught...If the temp dew point spread are within 4 degrees there will be some sort of obscuring phenomenon.
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I was taught 2 or less, but it could happen at 4, it depends on what's going on.

I'm going to sound like a schill for Scott D., but I'm not. He has been doing weekly facebook live sessions on weather, mainly to expose people to his Ezwxbrief weather flight planning site. But the info on weather, how to use charts and the various forecasting tools is priceless imo. His last one, which is on Facebook now, should be on youtube soon, talks about "evolution of mesoscale convective systems". If you want to learn about weather, check out his videos.

avwxworkshops - YouTube
 
also look at trends... is the spread getting smaller (e.g., https://w1.weather.gov/data/obhistory/KPSM.html)? And pay attention to fronts and prevailing wind.

I suppose the best way to view a local baseball game in the evening in the NH area is do it on a day that has severe clear in the afternoon... which makes evening fog less likely. Yes, I know, we get very few of those in July.
 
PaulS said:
I was taught 2 or less, but it could happen at 4, it depends on what's going on.

I'm going to sound like a schill for Scott D., but I'm not. He has been doing weekly facebook live sessions on weather, mainly to expose people to his Ezwxbrief weather flight planning site. But the info on weather, how to use charts and the various forecasting tools is priceless imo. His last one, which is on Facebook now, should be on youtube soon, talks about "evolution of mesoscale convective systems". If you want to learn about weather, check out his videos.

avwxworkshops - YouTube
Click to expand...
You may have been taught the same thing, one in F and the other in C
 
Not that another reply is necessary, a lot of good accurate info above. But also keep in mind the fact that air mass over land can change (ie heat up) more quickly than the air mass over a body of water. This warmer, moist air will mix with the cooler air near the coast, dropping closer to the dew point as many have said. The result is an advection fog phenomenon.
 
Using a combo of aviation weather and local weather products. The dew point at Portsmouth is 21.1C this afternoon, the low tonight is forecast 19.4C and the winds after 0000z are variable at 3 knots.
 
SkewTLogPro as an app the will be of great help once you learn to read the graphs. It will also tell you about cloud tops.
 
Rgbeard said:
((??)). A mighty Skyhawk can still climb through a cloud layer to on-top. Especially nice to know how thick the layer is sometimes.
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Yeah, especially fog layers…. They can be very thin sometimes…. Love that view when you takeoff in a fog layer and pop out right above it. Sometimes buildings and skyscrapers are penetrating the fog layer. Pretty neat.
 
There are several good weather books tailored for aviation available plus the previously mentioned resources.
 
UngaWunga said:
Can you be more specific about temp/ dew point spread? Local knowledge, been living here for 15 years, so....
Click to expand...
Many years ago I learned to pay close attention to the temp/dewpoint spread. Not only to get an idea of the carb icing risk, but to see if fog was likely. I noticed that if we had had rain overnight and the ground was wet, and the morning was nice and clear but the temp and dewpoint were close together, watch out. I would tell the students that "we'll have fog by 9 AM" and they'd say "how do you know?" Well, wet ground and minimal temp/dewpoint spread meant that as soon as the sun got a little higher and started boiling that moisture off the ground we'd have a sudden fog as the dewpoint rose faster than the temp did. I didn't want to send low-time PPL students off for circuits on a morning like that. They'd be stuck up there until the fog burned off. No cross-country experience yet. No maps aboard, either.

And if you're taking off late in the afternoon and the temp/dewpoint are really close, you could expect fog as the sun descends. Saw that in flight on an early cross-country nearly 50 years ago, flying through the mountains with cloud forming all around us.
 
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