Eye of the Storm

backup for http://radio.weblogs.com/0131089/

Saturday, September 10, 2005

Back at home

With my laptop now repaired, return to primary site: http://radio.weblogs.com/0131089

Tuesday, September 06, 2005



Saturday, September 03, 2005

Tropics Watch 03 SEP

Tropical Storm Maria continues to spin harmlessly in the mid-Atlantic and will probably become a hurricane by tomorrow.

A few of the global computer models are suggesting that an area of disturbed weather that is currently east of the Bahamas will become organized over the next few days and head to the northwest and north such that there would be a tropical cyclone in the vicinity of the Carolinas in five or six days. NHC will be watching this carefully over the next couple of days to see whether the models' forecasts verify.

The low that's moving west on the northern fringe of the ITCZ and had been considered a candidate for tropical cyclone formation continues to show no signs of development. It is of no concern for the next couple of days.

Friday, September 02, 2005

Tropics Watch 02 Sep

Tropical Depression Fourteen was upgraded to Tropical Storm Maria with the 11 AM advisory package. 880 miles east-northeast of the northern Leeward Islands, it is not a threat to land as it is forecast to turn to the northwest and pass well east of Bermuda.

The last advisory on Tropical Depression Lee was released at 11 PM last night. Shear killed off the former tropical storm that was in the mid-Atlantic.

The low pressure center mentioned yesterday(that is in the general vicinity of where the tropical depression that became Ivan formed a year ago today) has looked progressively worse over the past 24 hours. It is not expected to develop any time soon, if it all.

Thursday, September 01, 2005

Tropics Watch Sep 01

The Hydrometeorological Prediction Center released its last advisory on Katrina last night, stating that her remnants had been absorbed into a frontal boundary in southeastern Canada.

In the mid-Atlantic, Tropical Depression Lee is spinning, but is not a threat to land and is barely an annoyance to ships. The streak of earliest named storms came to an end as it formed one day later than the earliest twelfth named storm on record (Hurricane Luis of 1995).

Tropical Depression Fourteen has formed about 1000 miles west of the Leeward Islands. Given how north it is relative to its longitude (18.8 North at 45.5 West), it is very unlikely to be a threat to the U.S. National Hurricane Center advisory packages will commence at 11 AM EDT.

Much further south and east, a low near the Intertropical Convergence Zone has the potential to become a Tropical Depression during the next couple of days. While it is often difficult for such low-running storms to develop, this will have to be watched carefully since Ivan of last year was such a storm.

Tuesday, August 30, 2005

Pre-landfall forecast verifications for NHC

Thought I would follow up on my comments from Sunday (on the 12 and 24 hour pre-landfall forecast positions from Charley and Ivan) with how the forecasts fared this time around. 24 hours out, the forecast position for 12Z (7 AM CDT) was 29.1 North 89.6 West. 12 hours out, the forecast was 29.2 N 89.7 W. Actual position was 29.5 North 89.6 West., yielding errors of 24 and 23 nautical miles, respectively.

With the caveat that this certainly may not be representative of overall performance (since it only covers a quarter of the forecasts made over the five days before landfall, here's the rundown for forecasts from 12 to 120 hours before landfall.

12 hours - 29.1N 89.6W 23 nm
24 hours - 29.2N 89.7W 24 nm
36 hours - 29.0N 89.8W 44 nm
48 hours - 28.6N 89.9W 70 nm
72 hours - 29.5N 86.3W 173 nm
96 hours - 30.5N 84.5W 328 nm
120 hours - 29.0N 86.0W 213 nm

And no, there is are no typos in that, the 96 hour forecast really was 54% worse than the 120 hour forecast. Mostly because the 120 hour forecast was 'uncertain' so the track of the extended forecast was just a straight line to the west-northwest. The next day, there was a higher confidence in the scenario of the storm curving to the north-east, and the forecast featured that. Of course, while the general idea was right, the timing of it was way off.

The Katrina graphics archive shows how the forecast track shifted over the life of Katrina.

Personal post

For about as long as I've followed hurricanes, I've always had a bit of an odd feeling after landfall. Something on the order of 'Well, it's out of our hands now', as if forecasters somehow controlled or dropped responsibility for the storm the moment of the center of the eye crossed land. Such was my feeling today.

As I expected, it was a very long drive home (slightly longer than usual time-wise owing to some heavy rain encountered, but otherwise long in the sense that my mind was heavily burdened). When I pulled onto I-10, I saw in my rear-view mirror the site all too familiar from last year, a large convoy of the trucks used to aid workers in restoring electricity to storm-stricken areas bound for their staging area.

Had dinner at a friend's apartment and then drove to my own. Too impatient and tired to properly navigate the close confines of my complex's parking lot, I rounded my car into the rear bumper of a truck, putting a nice dent just behind the passenger door.

Didn't care to watch any of the media coverage of landfall. I'm not sure of a major landfall that the full scope of damage was comprehensively covered in the first few hours after. This goes back as far as Andrew and as recently as Dennis. The bigger the storm, the more inaccurate the initial read.

At the moment, the death toll from Katrina is the greatest U.S. death toll from a hurricane since Agnes of '72, which claimed 117 lives, almost all of them lost in epic flooding that occurred after the remants of the storm sat over Pennsylvania for more than a day. The deadliest prior to that was Camille, which caused 256 deaths. Nearly half of those (113) were from flooding caused by remnants.

Sunday, August 28, 2005

Katrina continues to intensify

Last post from Orlando. Next will be from Tallahassee in a few hours, pending computer availability. Brendan Loy should be up and blogging again soon.

Pressure is now down to 902 millibars.

Model guidance for intensity is not encouraging. Latest SHIPS output is for 180 mph winds in 12 hours with no indication of weakening before landfall (note that DSHP is the SHIPS output with the dissipative effects of land taken into account.)

The 12Z runs of GFS, GFDL and NOGAPS models do not provide much hope for New Orleans .

I have a feeling that regardless of traffic, the drive to Tallahassee is going to be the longest ever for me. Work has helped me somewhat in keeping my thoughts off the imminent catastrophe, but I won't have any such distraction on the road.

Katrina's winds now at 175 mph


At 10 AM CDT, the center of category five Hurricane Katrina was at 26.0 North 88.1 West, 225 miles south-southeast of the mouth of the Mississippi River. Maximum sustained winds are 175 mph and minimum central pressure is 907 millibars (26.78"). Hurricane force winds extend up to 105 miles from the center.

Hurricane Katrina Advisory Number 23

"Katrina is comparable in intensity to Hurricane Camille of 1969 only bigger." Fluctuations in strength are likely, however, "we see no obvious large-scale effects to cause a substantial weakening (of) the system and it is expected that the hurricane will be of category 4 or 5 intensity when it reaches the coast".

There is no change in the track forecast, which is in the center of model guidance. Due to the average errors in a 24 hour forecast, Katrina could strike anywhere from southeastern Louisana to the Missippi coast. Destructive weather extends well beyond the eye, so focusing on the exact point of landfall is not necessarily productive.

Hurricane force winds are expected to last for up to 150 nautical miles (172.5 statute miles inland)

Hurricane Katrina Discussion Number 23

Official track forecast with warning areas

Alternate view of track forecast


A couple of days ago, I wrote about the average track error in the NHC's forecasts last year. I went back and looked at the forecasts for the two hurricanes last year that featured a synoptic situation roughly similar to this, namely Charley and Ivan.

In the case of Charely, the forecast that took place 24 hours before landfall was off by about 40 nautical miles and the forecast 12 hours before was off by 29 nautical miles. Both were too far to the left, meaning that Charley turned harder than forecast.

For Ivan, the error at 24 hours out was 42 nautical miles, and the 12 hour error was 26 nm. Again, the forecast was too far left as it hit further east than forecast.

If a similar error to occur in this case, then the resulting landfall position would be comparable to that of Camille. However, due to the greater size of Katrina, effects in New Orleans would be worse than they were for Camille.

No guarantees however, as if we will see a repeat of this type of error. After all, it is quite possible that the forecaster has already factored it into his forecast (i.e. shifted it say, 20 miles to the right of where he normally placed it).

The Gulfstram-IV jet flew this morning to feed upper-air data from the Gulf of Mexico to the 12Z global models, which just started crunching the numbers. Forecasts will be coming out from them over the next two hours, and any changes in their tracks would affect a change in the 5 PM advisory package.

Intensity forecasting at this stage is nothing more than speculation with regards to whether Katrina will maintain her strength. It is fairly certain however, that if she were to weaken some, the bottom would probably be at the high end of the category four range (i.e. 145-155 mph winds).

If you are under evacuation orders now is the time to leave. Time for preparations to secure property is expiring. Remaining in your present location longer reduces your chances of making it to a shelter or other refuge in a safe manner. Conditions will quickly detoriate this evening.

Is Katrina an annular hurricane?

One thing frequently mentioned in discussion from the NHC about intense hurricanes is that they are prone to fluctuations in intensity such that category five strength is not held for a long period of time. The exception to this is a special classification called an anular hurricane. Such hurricanes do not fluctuate as rapidly. The most recent case was Ivan, which retained category five status for 30 consecutive hours.

The tell-tale sign of an annular hurricane is that the convection is uniform, making a perfect circle, i.e. there are no spiraling bands, just a donut. That is almost exactly the case with Katrina, as one can see from infrared satellite. Another feature is a larger than average eye (average being 14 miles). The message from the recon plane shown in my last full update shows that Katrina's eye is 25 nautical miles in diameter, so it is well above average. As far as conditions associated with annular hurricanes go, some of the conditions are most certainly there. Average Sea Surface Temperatures associated with them are 26.9° C. Katrina is certainly on the more favorable side of that (ref). Weak vertical wind shear is another key factor. That is certainly the case in the immdiate vicinity of Katrina(ref)

For a technical paper on annular hurricanes, see the paper 'Annular Hurricanes' (PDF) by John Knaff, James Kossin and Mark DeMaria (Demaria, by the way developed the Statistical Hurricane Intensity Prediction Scheme (SHIPS) that has been mentioned so much with regards to the potential intensity of storms.

It will be over the head of most people, but it is worth checking out to compare the satellite imagery of known annular hurricanes with that of Katrina.


So enough of the theory, what does this mean practically?

It means that the situation has gotten even worse. If Katrina is indeed annular, then the chances of her retreating down to say category three status are nil. If we make the somewhat unlikely presumption that she has reached her maximum strength (and again if she is annular), then the averages of such hurricanes suggest that she would only weaken to 145 mph at landfall. That would be a storm with Charley-like intensity, but on a much larger scale as Charley was puny compared to the present size of Katrina.

I do hate repeating myself when it comes to evacuating, but the only way I've been thinking of not repeating myself involves a very salty string of compound-complex expletives that would not be appropriate for this family publication.

If you are on the coast, or in a low-lying area, or otherwise in a structure of dubious integrity, and are in the cone of uncertainty, you need to leave now. Otherwise, you will become a statistic.

One last thing to share: In my high school earth science class, my teacher stated 'There is only one tool needed for disaster recovery from a category five hurricane: A bulldozer".

Category Five Katrina

WTNT62 KNHC 281117



Hurricane Katrina Update 280400 CDT

At 4 AM CDT, the center of extremely dangerous Hurricane Katrina was at 25.4 North 87.4 West, 275 miles south-southeast of the mouth of the Mississippi River and moving to the west-northwest at 10 mph with a turn to the northwest. Winds are up to 145 mph and minimum central pressure is 935 millibars (27.61")

Hurricane Katrina Advisory Number 21

Katrina continues to both strengthen and grow in size. While the official forecast does not call for a further increase in size, it is possible. The Statisical Hurricane Intensity Prediction Scheme does call for Katrina to make category five before landfall, however the official forecast goes just short of that (155 mph) due to the unpredictable nature of structural changes of the eye that would weaken Katrina temporarily. While the specifics are unknown exactly, it is clear that Katrina will be a very dangerous hurricane at landfall.

Katrina is moving along as forecast. Models are in tight agreement and their consensus has barely shifted from their past run. As such, the track forecast is merely an update of the previous one (i.e. the only thing that changed was the initial position).

Hurricane Katrina Discussion Number 21

Official forecast track with watches and warnings


Here is the model guidance, which is nearly unaminous in putting New Orleans in the bullseye. The only deviator being the North American Model (NAM, labeled ETA1 in this graphic); it is a hemispheric model that does not exhibit much skill in tropical cyclone forecasting.

So, those who went to bed thinking that the storm would either not strengthen or would deviate from forecast 'like it always does' are facing reality this morning. An extremely dangerous hurricane is taking the worst possible path.

If you are in New Orleans, you should leave now. Going west is the preferable option, with north being a viable one as well. Note that it doesn't have to be particularly far west as the worst effects of the storm are on the eastern side of it. People in coastal areas east of the center line should head inland by proceeding north.

In New Orleans, traffic is liable to be bad enough to justify leaving now, rather than spending time to secure property. In any event conditions will start to rapidly detoriate tonight, so the absolute latest one could plausibly hit the road in a safe manner would be early afternoon.

One note on the possibility of Katrina weakening due to an eyewall replacement cycle. Weakening is a relative term. If we were talking about a category three storm, then weakening from an ERC does reduce the hurricane's winds to those that are not particularly damaging. However, when we are talking about a category five or a strong category four as we are with Katrina, an ERC is only going to knock her down to category three. Category threes are still dangerous and destructive storms. It would not create catostrophic damage in New Orleans, but damage would still be major.

Looking at the Tropical Cyclone Heat Potential chart, I notice that Katrina is yet made her way across the hot spot yet.

Cutting this short and here's why:

URNT12 KNHC 281120
A. 28/11:04:10Z
B. 25 deg 39 min N 087 deg 32 min W
C. 700 mb 2310 m
D. NA kt
E. deg nm
F. 141 deg 153 kt
G. 046 deg 018 nm
H. 910 mb
I. 10 C/ 3056 m
J. 25 C/ 3057 m
M. C25
N. 12345/ 7
O. 1 / 1 nm
P. AF302 1712A KATRINA OB 10MAX FL WIND 153 KT NE QUAD 10:58:50 Z

That is a report from the recon plane. Pressure has plummeted. Katrina has gone category five.

Hurricane Katrina Update 0100 CDT

At 1 AM CDT , the center of extremely dangerous Hurricane Katrina was at 25.1 North 86.8 West, 310 miles south-southeast of the Mississippi River and moving to the west-northwest at 8 mph with a turn to the northwest expected later today. Maximum sustained winds are up to 145 mph, which makes Katrina a category four on the Saffir Simpson-scale. Minimum central pressure has fallen to 935 millibars (27.61"). Hurricane force winds extend up to 70 miles from the center and rains from the storm will start to affect the gulf coast on Sunday evening.

Hurricane Katrina Special Advisory Number 20


Hurricane Katrina Special Discussion Number 20

Bedtime. Up at 5 (EDT).