Current Sea Surface Temperatures and the Sinking of the Titanic

 There are many similarities between the sea surface temperatures and atmospheric structure during the past week and those observed during the sinking of the Titanic on April 14-15, 1912.  

Should marine traffic today be worried about icebergs?   The answer is revealed below!

Examining the sea surface temperatures (SSTs) today (below), you will notice cool water (around 50F) off our coast, dropping into the forties to our north.   Temperatures slowly warm to our south, only hitting about 60°F in San Diego.  Not very exciting or unusual.

But if you want dramatic sea surface temperature contrasts, head to the East Coast. 

East of New England, ocean temperatures are in the upper 30s and 40s and are even colder near Newfoundland.

There is a huge increase in temperature south in a zone east of Maryland/Delaware.  This warmth is associated with the northern extension of the Gulf Stream moving along the southeast coast.

Below is an expanded view of the above:  amazing sea surface temperature changes over tens of miles.  

 As you can imagine, there are similarly large near-surface air temperature contrasts.  To illustrate, consider the air temperature at 2 meters above the surface this morning (below).  Air temperatures range from below freezing near Newfoundland to around 70°F over a few hundred miles to the south.   

As we will see, there are real dangers associated with this pattern....dangers that may well have destroyed the Titanic.

Let us go back to April 14, 1912.  Below is the near-surface (1000 hPa pressure) air temperature analysis for that date.  

Very similar to today's pattern: very cold east of northern New England and eastern Canada, with rapid warming to the south.

How could this weather pattern have led to the demise of one of the largest passenger ships of the air, with an experienced captain and crew?

As all of you know, the Titanic was sunk by a collision with a large iceberg, which was not seen as it approached.

It appears that the iceberg was not seen because of a mirage phenomenon:  a superior mirage caused by cold air near the surface and warmer air aloft.

When there is a large temperature increase with height, the atmosphere acts as a lens, causing objects to be elevated higher than they really are (see schematic below).

Courtesy: Ludovica Lorenzelli, DensityDesign Research Lab"

We see such superior mirages all the time here over Puget Sound, when warm air spreads over the cold water (see example below).  Not how the land is elevated upwards.

So, how does this explain the inability of the crew of the Titanic to see the approaching iceberg?

With cold air near the surface and warm air just to the south, one can get warm air riding over the cold air if southerly (from the south) winds develop (which happens very frequently)

Courtesy:  Charles Floyd

This configuration of cold air overtopped with warm air creates a lens that creates a superior mirage in which the image of the ocean surface is elevated, obscuring the approaching iceberg, with tragic results.

Courtesy:  Charles Floyd

A very similar situation happened today.  Examining the vertical temperature structure today at a point near the Titanic tragedy (red dot, solid lines are sea level pressure, first figure), the dangerous situation was evident.

There is a plot of temperature with height at the point.   It's there.  Cold near the surface, with rapid warming just above.

And there WERE icebergs out there today!  On the figure below, the blue dot shows the position of the sinking of the Titanic, the red line shows the boundary of the iceberg fields, and the numbers show how many icebergs were in each box.

But today, there is little issue with safety.  Satellites give us the ability to track icebergs, and ships have highly capable radars that can spot them far ahead.

Worry about icebergs in our area?  Although there are many occurrences of warm air over cold water in Northwest waters, there are no icebergs in our waters.😊

The Day of No Weather and SuperBlue Skies

When I get up in the morning, one of the first things I do is check the latest satellite image.

Today's imagery (below) was stunning: not a single cloud in the sky

Nearly all my blogs are about some interesting weather feature...the more severe the better.  

But what to talk about on the most boring weather day in years?

When I got to the UW this morning, I took pictures of the sky ..the most perfect blue skies I could remember.

Viewed from the Seattle PanoCam this am, the light from the blue sky on Puget Sound gave the water a super-blue tint.

So why was the sky so clear?

The upper-level (500 hPa, about 18,000 ft) weather map at 11 AM  explaines a lot.   There was a strong ridge or high offshore, and such features have powerful downward motion on their eastern side...which prevents cloud formation.

Sinking air causes warming by compression and relative humidity to drop (since warm air can "hold" more water vapor than cooler air).  This prevents cloud formation.

The predicted relative humidity at around 10,000 ft (700 hPa pressure) was extraordinarily dry, with dark blue colors indicating relative humidities below 30%.

The solar radiation today was unimpeded, resulting in the variation over the day being almost a perfect cosine shape (the values at Snohomish are shown below).

Why is the sky blue on clear days?

Light from the sun has all wavelengths of visible light.   Atmospheric molecules scatter short wavelengths (like blue) more than longer wavelengths (like orange and red).  As shown in the image below, this preferential scattering of blue light makes the sky look blue.

Water droplets and particles (such as from wildfire smoke) scatter all wavelengths similarly, giving the sky a whitest cast.

As you can imagine, small particle concentrations were very low today, as shown by the PM2.5 numbers (concentrations of particles of 2.5 microns or less) around Seattle (below).  With clear skies, low relative humidity, and clean air, no wonder our skies were amazingly blue.

Enjoy the blue skies....clouds move in over the weekend.