Sea Dog Meet Sea Fog Day 8 (Jan 12, 2016)

Sea Dog Meet Sea Fog Day 8 (Jan 12, 2016)

At 0630 I heard sonobuoys (for the sunrise deployment) being shuffled in the aft deck crate. I must report, this is a truly effective alarm! A glancing appraisal of the day’s weather out our window, (my morning daily ritual), revealed we were in a fog bank-socked in, from every direction.

White Blanket. All around, a dense advection fog enveloped Whale Song.

A few minutes later Skipper and I were hitting the decks getting photos, since you never really know how long such a phenomenon like this, will last at sea. Sure enough, within half an hour it was all gone.

Fog in Our Fairlead. White and grey all over, the 100% relative humidity and other factors formed
sea fog!

A white, ghostly haze had shrouded Whale Song, like the sea fog we experienced in the Antarctic two summers ago.   A few things were different in each situation, including our latitude and longitude, (although both experiences were in the Southern Ocean) but my bare feet on the steel deck, really told me I was not at the ice-edge again!

This was a Tropical-Air Fog, which is a type of advection fog. Perhaps a little explanation of at least one feature of our weather observations is in order. Four times a day, Sam and I record the dry-bulb and wet-bulb temperatures. The comparison of these two readings indicates the Dew Point, which is “the temperature to which a parcel of air must be cooled at constant pressure and constant water vapour in order for saturation to occur”. Rather, the temperature at which the dry-bulb thermometer is wet and the wet-bulb is also wet is the point of saturation, which is when the temperatures are the same. This is the % relative humidity expressed as a division of the two temperatures and multiplied by 100. At my 0200 weather report, I had both dry and wet-bulb readings to be 20.0⁰ C, and thus 100% relative humidity. We have been reporting the weather for 2 years now and have had some 98% readings in the Kimberley, but this was my first 100%.

Sea Dog Meet Sea Fog. Another first for Mr. Skipper.

Several situations had conspired together to form the perfect conditions for advection fog this morning, such as the following:

1. 100% relative humidity recorded,
2. Light winds (3knots) present,
3. Whale Song being to the north of a high pressure system,
4. Warmer air (20.0 ⁰ C) moving over cooler water (18.3⁰ C) from lower to higher latitudes, and
5. Stable barometer readings over the previous 12 hours.

In a nut-shell – the cool water chills the warm air flowing over it, the water vapour of the air condenses on particles of salt, dust or smoke (forming smog), even before the relative humidity reaches 100%. The 2pm reading of 98% relative humidity was a huge clue, as well as the 2am 100% reading.

“But What Can I See?” Just white-white everywhere!

And viola-with all these things occurring, Whale Song became surrounded by fog!

The warming sun and a southeast breeze of 10-12 knots combined to burn it off as quickly as it arrived. Indeed, a phenomenon well-known and well-documented but very interesting to experience and understand the physical features that had occurred.

White Bow. As the fog began to clear a white bow was evident.

Two swells and wind made a soft ride but alas despite great sighting conditions we only heard a blue whale call around dinner… we are hopeful we will be in serious blue whale country tomorrow afternoon.

Here’s to hoping!