Hurricane Fred: September 10 Update A

Well apparently there are more Scooby Doo fans out there than Fred
Astaire! Yes, yesterdays Famous Fred quote was from Fred in Scooby Doo,
Fred Jones (thanks D.P. for telling me his surname... saved me having to
look it up). :) Todays quote is at the end of this update.

Hurricane Fred is a Cat 1 now, with winds of 90mph (cat 1 range: 74-95mph)
and central pressure of 975mb. He's currently at 17.3N, 35.1W, casually
sauntering northwards at 5mph. The track forecast has him turning WNW in a
couple of days. I don't have enough data, so I'll go along with this. He
has slowed down, and looks like he might slow down even further in the
next few hours. As I have mentioned before, things become trickier to
forecast when storms slow down or stall because conditions around them can
still change. But as expected, he is now in greater wind shear from the
southwest and is looking very lopsided, with convection mainly in the
northeast quadrant. He may not even survive in such conditions.

<science alert> why would a storm stall? This goes back to the large scale
atmospheric pressure fields I was waffling on about a couple of days ago.
Imagine the storm is a ball. If the path ahead of it is low pressure (in
meteorological jargon you may hear "trough" or other such words), it's
like a downhill gradient and the ball will happily keep on rolling. But if
the path in front of it has high pressure, it's like an uphill gradient.
If it is 'uphill', the ball will slow down, or maybe move in a different
direction until it finds an easier path. But if it is in a 'dip',
surrounded by high pressure, then it's difficult for the storm to move in
any direction, so it will stop until the pressure fields around it change.
Of course, as pressure fields change, the forecast track will change even
though the storm may not have moved far. So not only do forecasters need
to predict the track of the storm, but they need to predict the entire
surrounding pressure field and how it will change before the storm moves
again. That's where the computer models really kick in. <end of science
alert>.

Famous Fred quote of the day: "I always knew I was a star, and now the
rest of the world seems to agree with me." Which Fred? :)

Have fun!
Tally ho,
J.

Disclaimer: read previous entries.