Uncertainty and skill

I was reading about what the National Hurricane Center will be doing this year. It was quite interesting:
1. Watch lead time to 48 hours; warning lead time to 36 hours
2. The size of the cones will be based on 5 year running mean of 2/3 of track error.  The cone size radius varies in the Atlantic basin from 36 to 59 miles from 12 to 24 hours and grows about 35-40 miles per 24 hours thereafter.*

This means they have skill out to 48 hours in advance. They will be communicating actively their uncertainty via the graphical product (cones).

My foolish expectation would be to shy away from any sort of climatological cone of uncertainty and use ensemble guidance. This may not be the best option since it could provoke the so-called meteorological cancer i.e. over-dependence on models which have little value, not necessarily little skill. On the plus side it allows forecasts to be naturally consistent ... fairly certain in their ability to track where storms are, where they are going in the immediate future. To be fair the cone widens for a reason: tropical storms and hurricanes can encounter harsh or favorable environments quickly and these types of environments are hard to recognize over the ocean at longer lead times. Of course these environments can bring about changes to the inner workings of tropical storms in which case certain status quo forecasting rules may not work so well, and of course models also tend to not be spot on with hurricane intensity changes.

If nothing else, just seeing the products and how they are discussed should be interesting. It will be worth paying attention to see how the "public" reacts to be under "threat" for longer periods of time.

* I have not seen what this will look like but it will certainly be interesting!

Katrina - My look back

5 years ago I gave my Intro class an assignment. Forecast the landfall and intensity of Katrina.

It was a forecasting exercise. They weren't supposed to be justified or have reasoning of any kind. I gave them the National Hurricane Center link where they could follow it along. I was hoping they would loop satellite imagery, read forecast discussions, follow the projected track over the several day period.

I wanted them to take ownership of their forecast. That is, I wanted them to realize what they were doing more than what they were forecasting. They were making a projection of doom. A projection where people, actual real people, in their own country, maybe even in their own state, would act based on that forecast. If they watched the news they got to see what those forecasts brought about:

Mandatory Evacuation orders;
Descriptions of doom along the coastline;
the evacuation of countless people via clogged highway;
The media reports of people NOT leaving nor worrying.

Then the other night, NatGeo presented Witness: Katrina.

It showed the beer laden hurricane parties. People preparing with duct tape, candles, and supplies. people evacuating. Police doing city wide patrols. News media covering the storm. Stormchasers stormchasing. People trapped in the rafters watching the water rise. people hanging onto their front porch for two days. People being rescued by helicopter. Dead bodies floating in the water.

The very definition of destruction was accurately viewed through regular, everyday cameras from regular people.

I knew it was going to hit close to New Orleans and that the storm surge would be impressive. Upwards of 35 feet of water at the coast, which if I recall was a few feet above forecasts. The track of Katrina, her strength prior to landfall and the shape of the coastline made for the perfect surge event. The levies were an afterthought, especially s the media reports rolled in during that morning. I knew they would come, it was just a matter of when and where and how.

Not sure what those kids learned that week. But I am pretty sure a few of them will remember that exercise and the aftermath. I hope I made them appreciate the strength and unpredictability of severe weather hazards, and the predictability of shorter range forecasts. Perhaps even the predictability of unpredictability of the storm surge in Florida, Mississippi, and Alabama.

As far as my personal feelings go, it was a tragedy of course. On par with OKC and 9-11 but without the "we hate you" part added in. It was as disastrous as natural disasters can be. But that comes with an asterisk ...because it could have been worse. Had Katrina finished her eyewall cycle 9 hours earlier she would have been stronger, bigger, with more surge.

We really wont know Katrina's impact until the next big coastal city is threatened. Sure there have been a few already. But Katrina was the beginning since it was the biggest. They didnt make movies after Isabel wrecked southwest FL in a very small path of destruction. Nor did Ike inspire documentaries and tv shows. Only time will tell.

One thing is for certain. The hurricane research community responded rather well. Currently 3 field programs trying to better understand hurricane genesis, hurricane prediction, and hurricane processes this year. One was ongoing doing Katrina too. The results are flowing in, but there is still alot to understand ... including communicating with the public.

Little swirls

It is also neat to watch the various types of tropical storms that develop either in very favorable conditions, or sheared conditions.  Tropical Storm Colin was highly sheared and the convection that was over the low level center became displaced to the east exposing this low level center. One particular "hot tower" went up just as the low level center attempted to re-align with the mid level center, and as that tower collapsed a little whirl emerged. What I always find to be remarkable is how long it takes to spin up one of these little whirls: 1.5-2 hours. The animation is much more impressive as this little hot tower goes up, dissipates and out spins the little whirl.

Ike lied

rapid organization transpiring. eye to 40mi, winds right at cat 3 for the surface and cat 4 near 6500 feet. Radar imagery indicates mesovortices in the eyewall. 2 hours left before landfall.
water levels are rising rapidly, right around a foot per hour. This is outside of the eye, well tothe NE. This is with the winds blowing along the coast, once the winds turn southerly, watch out for the wall of water.

I want to be like Ike

Ike. Cat 2, insanely large wind field and yet uncharacteristically unorganized. I was almost angry that the wind max at flight level moved from 60 to 80 nmi away from the center. Then I read that the inner eyewall at 8 or 10 nmi still has not been removed.

I am blown away by the absolute lack of outflow on the east side. NHC insists there is no shear, but rather dry air. I need dropsonde proof.

I have noticed recurrent bouts of what appear to spiral bands emanating along the east side which produce brief outflow, but no channel forms aloft because the convection is short lived. But you can see these outflow bursts or waves or something. Fascinating. I recently skimmed Willoughby (2008) on inertia-bouyancy waves so I am thinking these bursts are waves or at least energy radiating away from Ike.

The 0315 satellite IR picture shows Ike transforming. The CDO has expanded eastward and the center still has deep convection (no classic eye). Notice the banded cold cloud tops encircling the center. This is probably the radius of maximum wind. Still the east side has not developed an outflow channel aloft. SIL and LCH at 00 UTC still had 20-30 kt NE winds , while TBW and EYW had 50 knots in the outflow channel. Perhaps they will launch 06 UTC soundings.

Power of Ike: Shown is from a buoy that Ike went by. 48 kt on the east side gusting to 62 kt. 60 kt on the west side gusting to 70. On the east side the wave heights were 30 feet. Notice that tropical storm force winds were experienced at this buoy for 27 hours so far.

Central pressure got as low as 947, but more recently is 956. Based on the sat image I think Ike will be cat 3 by morning. The storm is so large though, it will be hard for the wind maximum to contract enough to drop the pressure in the core for the hurricane to truly spin up 10-15 knots.
**********************************************
Update 0733: 20 nmi eyewall maybe forming.


Notice the huge cirrus blowoff over the texas coast. The soundings still didnt show an outflow channel to the north nor did the soundings have the cirrus layer though it appeared more towards 00 UTC (confusing since the flow agreed with both the high to the west and the outflow from the storm).

update 9-12: Eye wall at 50 nmi formed, broken to the east now but filling in prior to landfall. flight level winds stillcoming in around 107 kt, with the pressure holding at 953 hPa.

The surface wind field is changing rapidly with winds lessthan 90 kt focusing around the 50 nmi eyewall on the NE side (according to the 0130 HWIND analysis). This is one of the most confusing storms I have seen. Cant wait to see what research papers appear in the next 5 years. especially with all the research flights (2 planes simultanously sampling every 6 hours or so).

I expect surge to approach 20-25 ft east of landfall. unfortunalty a buoy has been unmoored 22 nmi out of Galveston Bay (42035). water levels at Galveston are at about 10 feet, though the pictures on TV indicate closer to 15 feet.

Lets address something controversial. Staying in Galveston. Good Luck. I would say to update your will, however it is likely your material possessions will be non-existent in a few hours. Hopefully the military will pull you out, so your greatest achievement will be to help make heroes even more heroic. Crude? Rude? yup.

Categorical strength misrepresents a hurricanes power. Wind speed, storm surge, rain, forwrad motion, angle to the coastline, and size determine a catostraphe. Andrew was small and a cat 5...I was there... it cleared some Florida areas pretty well. Gustav was bigger, weaker, but hit at the right angle and after the levy's already broke for Katrina (a weakening cat 3).

This is way too long, I will verify my gross speculation tomorrow when the damage reports come in.

Hurricanes

The hurricane season gets interesting:
NOLA needs to be worried if this track verifies. Like Katrina, a wall of water will approach and funnel into the area. Can the levy's hold? I hope so.

Much like Katrina, the fetch will be more important that the exact intensity. if the hurricane slows down in forward speed upon arrival, the water may well pile up along the SE coast of LA.

For a good chance at survival, the storm needs to make landfall in Texas. I don't see that quite happening now, but it is a distinct possibility.

In the Atlantic a few potential storms are also brewing. Keep an eye to the sky because something big is gonna happen this year.