Wednesday, August 06, 2014

Tropical Storm Bertha: August 5, Update A

Ahh... ice cream. The current favourite is Mud Pie. So delicious I might have to have another bowl to er... help me write.... :-)

Tropical Storm Bertha is now pretty weak with winds of 50mph (TS range: 39 - 74mph), central pressure 1007mb. She is officially centered at 37.5N, 68.1W heading NE at 23mph, but it is difficult to identify an actual center.

She's not really a Tropical Storm anymore even if she is bringing a bit of wet and windy weather with her...

Apart from not being able to see much of a circulation in the satellite imagery, we can also check the vorticity maps (I'm sure you memorized every brilliant word I wrote on this yesterday! ;-)) to get an idea of her structural integrity. Near the surface (850mb) she no longer has a self-contained red 'splodge' (don't be fooled, this is still a highly technical term ;-)) but is attached to another red splodge (splodges unite!) (ok, I admit it, I just like saying the word 'splodge' ;-))...

Same for the next level up (700mb) except the colors are a little weaker ...

And there's really very little going on in the middle troposphere (500mb)...

These all show that her structure is not really circular like a storm, but elongated like a front with two areas of stronger activity, which we can also see in a larger satellite image of the Atlantic:

The vorticity maps also show that she doesn't extend high into the atmosphere, so she is, indeed, a fairly weak system compared to a hurricane. But as a front, she can still bring some wet and windy weather... and it looks like she will to those in the UK area! Best put the deck chairs away!

<Technical Alert!> If you want to look at these maps for yourselves, go to the University of Wisconsin website for the Atlantic winds:

This will show you the map at 850mb. To look at the maps at the other levels, along the top are a number of tabs. Click on the level you want - 700mb, 500mb, 200mb.

These maps get updated every 3 hours, although you have to refresh the page each time. You can even go back to the map from 3 hours ago by using the tabs on the upper left. You can see a time stamp at the bottom, in the black border of the image.

There are a few more tabs at the top. Wind shear shows wind shear (are you surprised? ;-)). Wind shear tendency shows the direction the wind shear is heading in - so low tendency (dark blues) means that wind shear will not strengthen, and high tendency (reds and oranges) means that wind shear is likely to increase.

I'll go into upper level divergence and lower level convergence the next time we have a storm! (unless you have a super-amazing memory and really remember everything I ever wrote, in which case it is probably in an entry from last year :-)). <End Technical Alert!>

Meanwhile, over in the Pacific, we have TS Julio which has winds of 65mph and is still heading for the Hawaii region for the weekend, just a couple of days after Hurricane Iselle ges there (she has weakened to a cat 2 with winds of 100mph... I'm sure that's a relief to those on the islands!)...

(And in the western Pacific, Typhoon Halong is now down to a cat 1 with winds of 90mph, heading for Japan on Friday).

If Bertha is not downgraded tomorrow, I'll be back with another update - although it will be a bit late in the day because I'll be watching that scientifically accurate upcoming movie, Into the Storm (and then recovering from it). ;-) Otherwise, I'll back for the next storm (next name in the Atlantic is Cristobal) but I'll be tweeting about the other basin storms as usual in between.

Night night!

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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