Menu Sign In Contact FAQ
Banner
Welcome to our forums

Why is fog so hard to forecast?

Interesting flying on Saturday! I left Felthorpe in the Chipmunk at around 11.15 for a short(ish) flight to the coast. On turning at Southwold I was asked by Norwich Radar if I intended to return soon! When informed them I was making my way back they told me that Felthorpe was fogged in! I headed back to the south of the city just south of the CTR when I was invited to give it a try but that they thought it unlikely I would get in. They cleared me direct. To the north of the city was a grey wall like a vicious storm. It soon became apparent that I would not get in as the fog was thick. I turned south to try Old Buckenham but that too was already covered. I turned east and made Seething in a few minutes, still bathed in sunshine. After me some four or five aircraft arrived who had similarly diverted. One failed to get into Tibenham, only a few miles to the west. The last one flew a low level circuit and a very tight turn onto final for 27 as the temperature noticeably dropped and the fog came in. Within about 5 mins the trees the other side of the field had all but disappeared.

After waiting some time, I eventually had to get another member more experienced than me to fly it back as I had an urgent appointment. Even if I had not I am not sure I would have chanced a flight given the conditions. The risk of departing and not getting in anywhere was too great for me. As it was, he got back to the field at around 15.35, with sunset around 15.48 at Norwich.

All in all a very interesting experience. At one point I was toying with the idea of asking Norwich for an SRA onto 27, despite the fact I have not done one for three years, as the options were getting a bit narrow. It would have been interesting in a Chipmunk!! It does have a set of basic instruments but not a full AI. In retrospecta bit risky as at one point the cloud base was 100 feet. I was lucky to be flying in my local area and therefore had a good knowledge of places I could put down without fumbling for charts and frequencies.

Hi Justiciar.

Interesting post. I saw an account elsewhere where someone described trying to get the weather from ATC for a number of airfields as the fog apparently just sweeped the country in a blanket of fog. He talked about seeing a SAR helicopter popping in and out of the clouds trying to find an aircraft which may have had an incident.

Was the weather forecast on the TAF?

I was planning to fly Saturday but had something else come up, so I never kept an eye on the weather. I wondered if it was a PROB30 or something and maybe people assumed it wouldnt happen.

PiperArcher

Fog is horrid stuff.

Nobody can forecast it with anything one could call "reliability".

You can "forecast" it when you see it forming e.g. over the sea, on a visible (not IR) satellite image and you have local metars of fog but otherwise clear skies, so you can see the patch on the image has to be the reported fog (rather than cloud), but hey anybody can do that

The only solution is carrying enough fuel.

I remember getting out of Caernarvon once, just in time, as a wall of fog was sweeping down the runway. We rotated and .... instant IMC. 20 secs later, blue skies and 100nm vis.

Administrator
Shoreham EGKA, United Kingdom

These are the relevant ones:

EGSH 081450Z 27006KT 7000 FEW012 04/02 Q1023 NOSIG

EGSH 081420Z 27007KT 6000 FEW009 04/03 Q1023 NOSIG

EGSH 081350Z 26006KT 6000 FEW008 04/03 Q1023 NOSIG

EGSH 081320Z 24006KT 4000 BR SCT002 BKN009 03/03 Q1023 BECMG CAVOK

EGSH 081250Z 26006KT 2500 HZ SCT001 03/02 Q1023 BECMG CAVOK

EGSH 081220Z 28008KT 1600 HZ SCT001 BKN004 03/02 Q1023 BECMG CAVOK

EGSH 081150Z 27008KT 8000 FEW008 04/02 Q1023

EGSH 081120Z 26006KT CAVOK 05/02 Q1023 NOSIG

I started up around 1110 and you can see what happened in the 50 or so minutes I was airborn! As you can alo see the return was a bit marginal and although doable there is always the question of local conditions, with 04/03 temp and dewpoint, plus by 1450 we are under an hour from official sunset and with a landing into sun (though there would have been a cross wind runway available, to be fair). It was an extraordinary day with areas to the west of Norwich CAVOK yet Seething in fog, so reliance of the TAF was a bit of a leap of faith. On other forums there is talk of the fog outpacing the speed of the aircraft!!

Thank god I still had about 1.20 hrs fuel

Justiciar - do you have the TAF for the period as well? I am always intersted to analyse whether I would have flown based on that TAF and others in the surrounding areas.

I can see why people were caught out. Normally fog moves and disperses very slowly, and when there is fog, there is sometimes relatively low wind, and it hangs around for ages.

I agree that fuel is part of the solution. For that reason, unless W&B reasons dont allow for it, I generally always take off with full tanks. Additionally I attach paper plates for every airfield near my route to my kneeboard, a spare copy of the Pooleys spiral bound book behind the P1 seat, and the frequencies for all local ATS services. I go on the basis that if something like this happened, then (hopefully) I have as much useful infomation close to hand, freeing me up to talk to ATC and finding a place that one can land at, and just being able to fly the plane.

An SRA on to R27 at Norwich may not have been of much use in fog, particularly since the days of half mile SRAs seem to be long gone.

Egnm, United Kingdom

TAF EGSH 081403Z 0815/0823 27004KT 9999 FEW045 PROB30 0815/0816 8000 BECMG 0818/0821 27014KT PROB30 TEMPO 0818/0823 27017G27KT 8000 -RA BKN010=

TAF AMD EGSH 081324Z 0813/0821 26004KT 4000 BR SCT002 BKN009 BECMG 0813/0815 CAVOK BECMG 0818/0821 26014KT PROB30 TEMPO 0818/0821 27017G27KT=

TAF AMD EGSH 081146Z 0812/0821 27004KT 9999 FEW045 PROB40 0812/0813 0500 FG BKN001 PROB40 0813/0815 4000 BR BECMG 0818/0821 27014KT PROB30 TEMPO 0818/0821 27017G27KT=

TAF EGSH 081103Z 0812/0821 27004KT 9999 FEW045 BECMG 0818/0821 27014KT PROB30 TEMPO 0818/0821 27017G27KT=

I think you can see the problem, between 1103 and 1146 amended!!

Assuming I was flying to or from Norwich, and I was only armed with the 081103Z TAF, and assuming I wasnt going to land at night when there was a PROB30 of gusting winds - then I too would have gone for it.

Had I been sitting in the cockpit of my plane with the engine running and I saw the amended TAF (I always refresh the Aeroweather app before I line up), then it would be a return to the parking spot I think. I would have accepted the 4K viz later on, so it depends on what time I intended to be in the area.

Had I been flying along and then managed to get the updated TAF on a marginal cellphone signal, I can imagine I would be a little worried.

I can see why people were caught out. What interest me is that between 081103Z and the AMD 081146Z TAF 43 minutes later, something must have caught the eye of a forecaster that they hadnt seen before and required to them to issue that TAF (maybe that satelite IR imagery Peter mentions).

Glad you were safe, and you got some good help from Norwich ATC.

Glad you were safe, and you got some good help from Norwich ATC

Thanks PiperArcher. I must admit that once in the aircraft I don't further check - my last was just after the walk-round and before ringing ATC to book out. By the amended TAF I was in the air over Southwold where there was no hint of the problem to come. Once the problems started Radar were great and vectored me to Seething without being asked.

See fog can be lethal. Earlier this year a C172 crashed in an area hampered with fog near Rotterdam. While the accident is still under investigation, it was most probably caused by inadvertent flight from VFR to IMC.

This incident triggered me to start doing the IR.

Len

47 Posts
Sign in to add your message

Back to Top