Guest Post by Ric Werme
The CSU Klotzbach/Gray Sep 1-14 hurricane forecast (PDF) is out. This period is the peak of the hurricane season and average conditions are pretty active:
“Climatology” is just the average weather, and “We expect that the next two weeks will be characterized by amounts of activity near (70 to 130 percent of) climatology.”
“Only” average, given that all eyes are on Earl, and a few more on Fiona? While Earl is racking up Accumulated Cyclone Energy (ACE) points now thanks to it being a category 4 storm, the NHC isn’t expecting new storm development, citing a high pressure system and dry Saharan air in the eastern Atlantic. Global models have no more storms in their forecasts.
This is not to say Earl and Fiona are it for the next two weeks, the total ACE expected from them is 15 units, but the forecast range is for between 20 and 37 units.
Another factor in tropical storm development is the Madden-Julian Oscillation, a band of enhanced and suppressed precipitation areas. Currently the oscillation is weak, as it was for the past two week period, so it will have little impact on storm development.
Overall, the expectations for an active season are balancing out the near term outlook:
The most recent seasonal forecast calls for a well above-average season. We utilize the seasonal forecast as a baseline for our two-week forecasts. Since the MJO is predicted to be weak over the next two weeks, and forecast models are not calling for much additional storm development over the next two weeks, we believe the next two weeks should have activity at near-average levels.
Finally, the two week period just ending came in at 250% of average. Klotzbach and Gray are only forecasting three ranges during the season, and they forecast activity would be “high,” or > 130% of the average. They credit the activity to low wind shear in the Main Development Region, but note that’s expected with warm Atlantic water and moderate La Niña conditions.
Thanks Ric for the explanations.
Tenuc says:
September 1, 2010 at 3:07 pm
Reply; In this particular case, the best guess would be the coupling between the Earth and Mercury with the fields of the sun riding on the solar wind, follow the action from this viewpoint:
http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=399&vbody=10&month=9&day=1&year=2010&hour=01&minute=25&fovmul=1&rfov=45&bfov=30&porbs=1&brite=1&showsc=1
See it this gives you answers, past examples I have followed seen to indicate CMEs are magnetic flux ropes that just come out of the surface of the sun where ever they can (weak spots? or concentrations already?).
This ‘dry air’ drum that keeps getting beat –
See my post under ‘Trio’ regarding this ‘dry air’ business; I contend the WV (Water Vapor) imagery depicts WV in the troposphere topping out at about 20,000 feet give or take …
At what (altitude) level do the T-storms in a hurricane draw atmosphere (containing warm, moist air) – 5,000 ft? 10,000 ft? 20,000 feet?
I ask the question rhetorically …
.
Per Ric’s post:
Vindication; ‘moist’ air (as indicated on WV imagery) to altitudes of only 18 – 20 k feet …
Apparently this is sufficient to ‘keep the beast fed’ …
.
_Jim says:
September 1, 2010 at 6:57 pm
Apparently this is sufficient to ‘keep the beast fed’ …
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Your instincts have been correct, _Jim. And Earl has become downright scary.
Chris
Norfolk, VA, USA
Here is an interesting discussion and way to analyze hurricanes that you don’t hear much about, but should.
This measurement accurately predicted when Ike, a Cat 2 on the Saffir-Simpson scale, would cause catastrophic and Cat 4+ storm surge damage on the Bolivar Peninsula in Texas in 2008.
The IKE as it is called, by the way, is an acronym, and has nothing to do with the name of the storm.
From Dr. Jeff Master’s I give you this quote:
Earl is a large hurricane, which gives it a higher potential for storm surge damage than a smaller hurricane with the same top winds. One measure of a storm’s power, useful for gauging storm surge threat, is to measure the speed of the winds and multiply by the area over which those winds blow. This total is called the Integrated Kinetic Energy (IKE). Based on the storm’s IKE, one can come up with a scale from 0 – 6 rating the storm’s destructive power from its storm surge. A separate rating can be given to the destructive potential of the storm’s winds. The IKE value of 112 Terrajoules for Earl, at 3:30pm EDT today, gives its storm surge a destructive power of 5.0 on a scale of 0 – 6. Earl’s winds have a lower destructive power, 3.4 on a scale of 0 – 6. Let’s hope the right front quadrant of Earl, where the main storm surge would occur, stays offshore! For comparison, the small Category 5 Hurricane Camille of 1969 had an IKE of 80 Terrajoules, and the very large Category 2 Hurricane Ike of 2008 had an IKE of 116 Terrajoules–similar to Category 3 Earl’s. –Dr. Jeff Masters
Chris
Norfolk, VA, USA
_Jim says:
September 1, 2010 at 6:57 pm
The beast is feasting quite well! Maybe next time I’ll look for a cold front associated with the dry air, that will have dry air at low levels. Check out http://twister.sbs.ohio-state.edu/surface/dewpoint.gif for old-fashioned surface dewpoint temps – the dry air is in Canada. And the Great Basin – it’s amazing how quickly things dry in hot, dry air like that.
Earl is a big enough storm so that it may be able to saturate the dry air by the time it gets to the eye.
If Earl had stayed at cat 3 or declined to cat 2, I could excuse that with notes about dry air affecting the strongest storms the most, but I gotta give Earl credit for shrugging off that dry slot. Remind me to get out of its way, and let’s hope it stays off shore.
PaulM says:
September 1, 2010 at 5:42 am
> These are the same charlatans experts who wrote in June, “We foresee a very active hurricane season in 2010″, and got it completely wrong,
Do keep in mind that the peak date for storm formation is Sept 10, and that’s before the 50% of the storm making days – the fall off from the peak is slower than the rise to the peak. Calling any seasonal hurricane forecast completely wrong before it’s half over is a bit of a reach. I would have said they have some catching up to do, and that seems to be happening!
Now this is the type of article I wish all the talking heads would do! Easy to understand and follow, without the hype. We can supply the hype ourselves.
Update and verification on the temp drop post hurricane transit, someone mentioned up stream, this data from the same buoy 41046 Earl rolled over earlier. Shows a delta of 6 degrees but the slope is also telling.
http://img52.imageshack.us/img52/3028/watertemp.png