HURRICANE DEAN - Path/Landfall/Intensity Predictions

[tmariar]

An attempt to organize discussion early on in case Dean grows into a major threat and discussion topic. I thought it would be helpful to those seeking info to centralize discussion of the forecasts so that comments aren't scattered in response to individual posts in the forum created for the NHC updates (the format of which is dictated by the NHC feed). To get this topic going, here are some excerpts from Eric Berger's posts this morning:

Early: "Hurricane Dean has not strengthened overnight due to an encounter with some slightly dry air and a bit of wind shear. It remains a 100-mph hurricane and is just now crossing the Lesser Antilles. Forecasters anticipate Dean still will become a major hurricane.The overnight models have become more tightly clustered, and the news is not favorable for Texas, which now appears the target if Dean makes a U.S. landfall. . . . Nearly all call for some sort of strike on the Yucatan Peninsula by late Monday or early Tuesday, and the popular resorts of Cancun and Cozumel are likely to be affected by a major hurricane at that time. What happens after that remains a very close call. Given the geography of the Yucatan, if Dean spends more than 12 hours over land it will be significantly weakened, with positive consequences for a subsequent landfall in Texas or Mexico. If it just glances off the Yucatan, however, we're going to have a major hurricane entering the Gulf, likely aimed for our state."

Later: "At 10 a.m. Dean had begun slowly strengthening again, increasing its sustained winds to 105 mph. The official forecast now calls for an extremely intense 150-mph hurricane (strong Cat. 4) in three days time. Residents and vacationers in Mexico's Yucatan Peninsula should make plans accordingly. This morning's official forecast track also only grazes the Yucatan, weakening it to a Category 3 hurricane. Most of the morning model runs are unchanged, and I'll wait until this afternoon to see if there are any significant shifts. The official forecast also says there's considerable uncertainty as to where the storm will go once its past the Yucatan. They're right, of course."

And here is a computer models chart from earlier this morning:

And here is a link to the Saffir-Simpson intensity scale.

[tmariar]

1:30 Update on Eric Berger's info (I've found his site very informative):

"Dean has strengthened considerably today and is now a Category 3 hurricane with powerful 125-mph winds. A slight increase in wind speed would make Dean a Category 4 storm. This explosive growth is to be expected as Dean moves across the northern Caribbean where waters are both warm, and the warm water runs deep (meaning that as the system churns up the seas it is feeding itself additional warm water, rather than cooler water from the depths.) Just as interesting as this rapid intensification is what the models may be trying to tell us this afternoon. All of the models that were initialized at 7 a.m. Central this morning have completed their runs on supercomputers. The results are below:

What can we learn from the above? The GFS (purple) and NOGAPS (red) have both shifted slightly southward, and have now consistently forecasted tracks that make a final landfall into Mexico for a couple of days. For models, consistency is generally a positive. Significantly, a third dynamic model, the UKMET (gray) has made a large southward shift from around the Corpus Christ area into northern Mexico. Has this model picked up the trend? Too early to tell. Finally, the GFDL (blue) continues to jump all over the map, this time from a Galveston landfall to central Louisiana. This indicates one of two things: 1) the model has not properly initialized Dean and is rendering its path incorrectly, or 2) the model is detecting a trend in the upper atmosphere the other models have missed. Given its inconsistency I'd lead toward the former answer, but there's no way to know for sure. The new HWRF, which doesn't project far enough out to call a landfall, also appears to have moved further south in this latest run.

Which model is best? For all sorts of model-verification goodness, click this link. Here, according to National Hurricane Center data, are the average five-day errors for the models discussed above in 2006:

1. GFDL (234 miles)

2. GFS (250 miles)

3. NOGAPS (250 miles)

4. UKMET (294 miles)

And for the extremely active 2005 season, which had a lot more storms like Dean, the average five-day errors were:

1. UKMET (253 miles)

2. NOGAPS (275 miles)

3. GFDL (296 miles)

4. GFS (314 miles)

So this doesn't suggest the GFDL has been any better than the other models recently. And if you live in Houston, the fact that three major dynamic models now take the storm quite far to the south is good news. In the big picture it doesn't mean all that much because models often shift, but you'd rather have them moving away than toward you. The downside is that Mexico's chances of a landfall have increased. What now will be really intriguing is how the National Hurricane Center treats the new set of models. I'd bet on a shift southward. We'll find out at 4 p.m. and I'll update this entry then."

[editor]

If it hits the Yucatan, that's good news for Texas because it will lose some strength.

Of course, there's been more than one storm that's plowed through that corner of Mexico then turned right and made a run for the border.

[Jax]

Here is a good blog entry at Wunderground discussing the different models. It's similar to what tmariar already said, but additional info is always good.

[tmariar]

Here is a good blog entry at Wunderground discussing the different models. It's similar to what tmariar already said, but additional info is always good.

That's helpful info. Especially: "In conclusion, the official NHC forecast outperforms all the individual models, particularly at long ranges. Looking at the individual model plots can be helpful to determine the uncertainty in the forecast, but it's tough to beat the NHC. In the case of Dean, where one model is an outlier from the rest, it is usually better to believe the consensus of the other models."

It's good to keep that in mind. (Though I can't help wanting to see the underlying models, too, especially when the storm is still this far out.)

Scenarios that seem good for Houston (if not necessarily other places): Dean passes to the north of Jamaica (suggests to me landfall east of Houston), or Dean spends a lot of time over the Yucatan (as opposed to passing just to the north or passing quickly over the tip of the peninsula).

[jm1fd]

I predict it will make landfall at Cleveland TX as a category 6

[Trae]

One model has it blowing right into middle Louisiana. These thing usually take a jog to the east when they get towards land, so what if New Orleans gets hit with the east side of a strong hurricane instead of the weak left side? Could it be worse than Katrina?

[MidtownCoog]

We are all going to die.

[Guest danax]

We are all going to die.

I blame Bush.

[MidtownCoog]

Bush hates people.

[jm1fd]

Bush hates people.

Espesically black ones.....Or at least so sayeth Connie A. West.

[TheNiche]

One model has it blowing right into middle Louisiana. These thing usually take a jog to the east when they get towards land, so what if New Orleans gets hit with the east side of a strong hurricane instead of the weak left side? Could it be worse than Katrina?

No, the population numbers haven't recovered, and certainly not in those parts of the city below sea level. Between that and that every single local, state, and federal politician would be frantically trying to prepare an excess of rescue personel, vehicles, and supplies so as not to be portrayed negatively by the media, Katrina can't happen again.

Personally, if it has to hit the Gulf Coast as a major hurricane, I hope it wipes out NO again. Perhaps then politicians would be sufficiently discouraged from launching multi-billion dollar programs to rebuild places below sea level.

[EastEnd Susan]

Well, If it DOES come this way I am not going anywhere. I evacuated last time and it was worse than going through a hurricane. And yes I have been through 2 of them. Carla and Alicia. That was the biggest mess I have ever seen. I really hope it goes in somewhere thats not very populated. And yes, I blame Bush. lol

[Jax]

If I understand it correctly, they don't recommend you evacuate unless you're in one of the evacuation zones (near the coast) or in a really floor prone area. Why did so many people evacuate last time? I was not in Houston yet, but I heard it was a huge mess. I'm on the 3rd floor of a fairly strong building, so I'm thinking I'll most likely stay put. In the worst case, I'll go to the hurricane shelter at Rice.

[tmariar]

Why did so many people evacuate last time?

There were a number of factors, but I'd say the biggest was the recency of Katrina.

On the tracking front, this update from Eric Berger:

"4:10 p.m. UPDATE: The hurricane center's afternoon update appears to have nudged the five-day forecast only very slightly southward. As noted below, the models have made a more significant move south. What is happening here is that the hurricane center doesn't want to have its forecasts, in the wise words of Jeff Masters, have a "winshield-wiper-like" effect.

Therefore if this evening's model runs show a similiar southward movement, as this morning's did, I would expect a southward shift in the 10 p.m. forecast track.

Dean's winds are now 125 miles per hour, still a Category 3 storm. But the hurricane center says Dean's likely to be near Category 5 strength by Sunday, and Jamaica and the Yucatan Peninsula need to be preparing right now for an incredibly intense system.

The key feature here is an upper-level low pressure system ... that's moving to the west ahead of Dean. The GFDL model (the outlier at this point) handles the movement of this system differently than the other forecast models. I'll have more on this tomorrow morning if the models have not agreed upon how to handle the upper-level low, which could steer Dean into Texas or even Louisiana."

And new computer models:

And the 8 EST update upgraded it to a Category 4 storm.

[Jax]

That GFDL model sure likes to point near Houston...

[RedScare]

The National Hurrican Center reported an updated wind and pressure reading after the hurricane hunters returned. Dizzy Dean is now at 145 mph sustained winds, and pressure is at 936 mb....and headed straight for Jamaica.

[Trae]

If I understand it correctly, they don't recommend you evacuate unless you're in one of the evacuation zones (near the coast) or in a really floor prone area. Why did so many people evacuate last time? I was not in Houston yet, but I heard it was a huge mess. I'm on the 3rd floor of a fairly strong building, so I'm thinking I'll most likely stay put. In the worst case, I'll go to the hurricane shelter at Rice.

Well, tornadoes and wind gusts can still happen inland in areas like Cypress, Katy, or Spring. You don't want to be near tall pine trees when winds are gusting at 110 MPH.

[westguy]

GFDL has a Category 5 making landfall west of Houston. It's a good model, but it is not in consensus with the others. NHC has pointed that out, and they are the best warning center in the world.

[Guest Marty]

Well, tornadoes and wind gusts can still happen inland in areas like Cypress, Katy, or Spring. You don't want to be near tall pine trees when winds are gusting at 110 MPH.

To bad there's a pine tree in my neighbors yard about 15 feet from my bedroom, pine trees are bad about the tree's top breaking and falling like lawn darts.

My Magic 8 Ball says Corpus Christi.

[TheNiche]

The National Hurrican Center reported an updated wind and pressure reading after the hurricane hunters returned. Dizzy Dean is now at 145 mph sustained winds, and pressure is at 936 mb....and headed straight for Jamaica.

200 AM AST POSITION...15.0 N...66.7 W. MOVEMENT

TOWARD...WEST NEAR 18 MPH. MAXIMUM SUSTAINED WINDS...150 MPH.

MINIMUM CENTRAL PRESSURE...930 MB.

They expect for it to continue stengthening. Looks like we're going to have ourselves a Cat 5.

[Guest Marty]

I still doubt it will strike the Texas coast at a Cat 5 strength because of the shallow coastal shelf usually weakens them, but you never know.

[HtownWxBoy]

I still doubt it will strike the Texas coast at a Cat 5 strength because of the shallow coastal shelf usually weakens them, but you never know.

The OOz gfdl has it coming into Matagorda Bay as a Cat 5... of course that doesn't mean it's going to happen, it's just one model.

[TheNiche]

I still doubt it will strike the Texas coast at a Cat 5 strength because of the shallow coastal shelf usually weakens them, but you never know.

I'm not sure about the shelf...I'd think that shallower waters would be warmer waters with a less powerful convection to draw colder water to the surface. Does that make sense?

But I think that you'd be correct that it is unlikely to strike as a Cat 5 because by the time that Cat 5 winds got to land, the storm would've already weakened. ...but that doesn't mean that striking as a Cat 4 is better than a Cat 4 weakening and striking as a Cat 3, or something to that effect.

[Guest Marty]

Seems like I remember that the storm mixes up shallower water and it cools down quicker than deep water. I know I heard a couple of weather men talk about it in the past. It could be urban myth ect...

[TheNiche]

Seems like I remember that the storm mixes up shallower water and it cools down quicker than deep water. I know I heard a couple of weather men talk about it in the past. It could be urban myth ect...

I'm somewhat at a loss myself. I heard on one of those Discovery Channel made-for-TV movies that the frothy waters act as a feedback loop, adding continually more water vapor to the storm...but there are so many blatant errors in Discovery Channel programming that I just don't take it very seriously anymore.

[musicman]

My Magic 8 Ball says Corpus Christi.

what does it say about puma's hd dvd vs blu ray dilemma?

[tmariar]

"So why are the models now appearing to cluster? The key is understanding a low-pressure system in the upper atmosphere. These features, unlike low-pressure systems at the surface, don't generally form tropical storms. They can, but they're also a different animal. Here's a water vapor image from this morning showing the location of the upper-low in relation to Dean:

The upper-low is over south Florida, and moving west like Dean. This motion can be seen quite clearly in this water-vapor loop. As long as the low remains ahead of Dean, the hurricane will be steered by a ridge of high pressure to its north, which is also building westward. The GFS, UKMET and other models have forecast the upper-low to zip across the northern Gulf, allowing Dean to move almost due westward until reaching the Bay of Campeche. In contrast the GFDL has been much slower in its handling of the upper-low. How would Dean interact with the upper low if it catches it in the Gulf? Both systems circulate counterclockwise, and Dean would trace around the upper-low's right side (hence the earlier GFDL model solutions bringing the hurricane into Louisiana.) Things are more complex than this, however. If the upper low is strong at this time it could shear Dean; however if the low is weaker, and Dean is slightly below its maximum intensity (a possibility if it has just encountered the Yucatan) the upper-low could merge with Dean and enhance the system. See why forecasting the path and intensity of hurricanes is difficult?Anyway, for those looking on the bright side of things, Houston is now narrowly outside the hurricane center's "cone of uncertainty," meaning it's unlikely Dean will move this far north. That being said, hurricanes are unpredictable and anything can happen. My best guess is a landfall somewhere between Matagorda, Texas, and northern Mexico." Eric Berger 6:30a.m.

[westguy]

They still forecast Dean hitting around Cancun at Category 5 strength.

[ricco67]

Looks like Cancun is in for a fairly bad day.