Hurricane Gustav Discussion

Hurricane Gustav is currently, per the NHC, a 980 mb hurricane with 75 mph winds to the northwest of Jamaica. The hurricane hunters have found winds up to 90 mph just 24 miles from the center of circulation, which tells me it is within the storms strengthening eyewall. I expect the NHC to up the winds at the 5 pm advisory. Even if they don't, however, this report helps to show that the storm is quickly strengthening and should be near category 2 status as it reaches the Cayman islands.




Gustav is situated in a very favorable environment for strengthening. The system is over the warmest sea surface temperature and tropical cyclone heat potential (TCHP) water in the entire tropical Atlantic. TCHP helps to indicate when rapid, or explosive, strengthening is possible. The waters around Gustav now, and until it reaches the center of the Gulf of Mexico, support rapid strengthening. Upper-level winds are also conducive, with little shear (near 5 knots) and an upper-level anti-cyclone developing over the system. The ridge to the northeast is steering Gustav towards the northwest.



The image above shows the GFS 700 mb forecast 60 hours into the future from the 12Z model run. The red area indicates the ridge that is currently situated through the United States and out into the Atlantic. The purple line indicates a trough that will be digging off of the eastern United States. All of the yellow circles show tropical waves or storms that are forecasted by the GFS model. Gustav is located in the Gulf of Mexico, Hanna off of the Florida coast, and then three more waves are shown in the Atlantic.



The ridge shown in this image is what should steer Gustav to the northwest until Monday. At that time, some of the models then forecast the ridge to build in stronger than the GFS forecast to the north of Gustav as it approaches Louisiana. This would cause Gustav to stall or push towards the west. Below are the models, with the European in red bold, UKMET in yellow bold (which should go a bit further west), and the HWRF in purple bold. As you can see, model trends are starting to indicate that a more western track is looking more likely. However, these models do not develop as deep a system as the GFS or GFDL, which forecast a more eastern landfall in central Louisiana towards New Orleans. A stronger system is much more likely to bust through a developing ridge than a weak system. Thus, the stronger Gustav becomes, the more likely it will make landfall in central Louisiana. However, all I said was more likely, not guaranteed. A stall could occur just as Gustav approaches Louisiana and the storm could move towards the LA/TX border.



Right now I am going to put my forecast track into the area just east (Creole, LA) of the LA/TX border as a Category 3 Hurricane. We should see rapid strengthening as Gustav moves over the Caribbean waters until it reaches Cuba, possibly reaching strong Cat 3 strength. Cuba should weaken the system a bit, and then weak shear should inhibit rapid strengthening over the Gulf of Mexico. The storm may increase back to a strong Cat 3 in the Gulf of Mexico before weakening slightly as it approaches the coast. A Cat 4 is possible either just before Cuba or after, but I do not expect it to hold that strength as it approaches the coast because TCHP waters are not quite as strong in the northern Gulf. We should also see a few eyewall replacement cycles along the way, which could cause strength fluctuations.

Hurricane Gustav Once Again

The Hurricane Hunters have now found surface pressure of 978.4 mb, indicating the pressure has dropped another 5 mb in the last 2 hours. The HH also found surface winds of 80-90 mph, but only in one small area. The NHC has decided to go with 75 mph, at least upgrading the system. The latest votrex message said 980 mb with 90 mph winds! We will likely see stronger winds at the 5 pm advisory, if not updated again before.

Hurricane Hunters and Gustav

The Hurricane Hunters just found a surface pressure of 983 mb and winds of 64 knots, one knot short of hurricane strength. The NHC could go with a 70 mph storm or 75 mph hurricane at the next advisory, depending on what they think is best. I think they will likely go with Hurricane Gustav so the wording sounds more ominous considering the storm will definitely be a hurricane by the time it reaches the Caymans. The Caymans better be ready for a strong Cat 1 at least by the time this storm reaches the islands. The storm has dropped 5 mb in the last 6 hours.

Another update will come later.

Gustav and Hanna.....

I don't like the look of either of these storms right now. The tracks are so ominous, so scary that the thought of what could occur over the next week is not good at all. We are likely to see two major hurricanes traverse through the Gulf over the next week! Think of Ivan and Katrina...and you are fairly close to what is going to occur. Move Ivan a bit west and Katrina a bit east...voila! Not good at all!

I am sorry about the lack of updates, but I had a surprise lengthy visit from a friend from out of town which kept me busy. I will be updating for the next five days continuously until my next 'weekend' Wed-Thurs when I will be going to North Dakota and away from a computer. This might be the best time to take a break considering Gustav should have already made landfall and Hanna will be busy drifting about in the Atlantic near the Bahamas. A quick 5-10 minute update on Gustav and Hanna. A more detailed analysis will come later today.

GUSTAV

Tropical Storm Gustav, which used to be Hurricane Gustav as it plowed into Haiti with 90 mph winds (much stronger than forecasted), is currently moving off of the western edge of Jamaica. Yes, Gustav went northwest into Haiti, took a sharp left turn and move down towards Jamaica and is now moving towards the west or westnorthwest. If we remember back to the models, this type of track was closest to the BAMS as the storm formed. The BAMS was even further south with the future track, but has since corrected and is now in line with all of the other models. Actually, model consistency is VERY good right now for a 5 day track. The models take Gustav westnorthwest through the Caribbean and then turn it northwest into the Gulf over the western edge of Cuba. They then go northwest to about the gulf coast of Louisiana, where they they move west towards Houston over land (take that turn a bit earlier...and Houston is under the gun). Watch out, the models have trended further west with time. This may end up being a Texas storm rather than Louisiana!

Basically the ridge that built over the Bahamas is guiding Gustav on this track. As this ridge breaks down (as Hanna develops into the Bahamas as well) the track of Gustav should move more and more closer to north. However, a second ridge will build in over the south-central US towards just north of the Bahamas in about 5 days. This will begin the push of Gustav back towards the west. The strength of Gustav will generally be determined by the strength of southwesterly shear in the Gulf, which doesn't look to be too much of a destructive factor at the moment. Add 5 knots and a major hurricane could be avoided, but right now I think its a good bet. High sea surface temperatures and tropical cyclone heat potential waters are ahead of the system until it reaches the central Gulf. My guess is we might see the storm go through explosive cyclogenesis, close to a Katrina or Rita development, as it moves over a heat eddy in the Gulf. Hopefully I am wrong, but I wouldn't be surprised. However, the storm should weaken as it moves towards the Gulf coast as TCHP waters decrease. This is NOT a storm to fool around with!

HANNA

Let me state this again....This is NOT a storm to fool around with. Hanna is currently just north-northeast of Puerto Rico, moving northwest. Models have it moving northwest for a day or two and then turning west towards Florida. The storm then looks to stall out as the steering currents subside with the ridge deteriorating in 3-5 days. A second ridge will build in, pushing Hanna southward towards Cuba and the Bahamas. As the ridge strengthens, it will then steer Hanna westward towards southern Florida, possibly right through the straight (European and GFS both go with this solution). Basically, this is a worst case scenario for the Gulf coast, as this track often results in a major hurricane. Right now the European drills this storm into New Orleans....but with this being over a week out, anything is possible. If Hanna takes this track, however, the entire Gulf coast is going to have to be on guard again just a few days after dealing with Gustav. One lucky scenario would be that Gustav uses up a lot of the TCHP waters in the Gulf, thus eliminating the strengthening potential of Hanna. Only problem...the models forecast Hanna to already be a major before it even reaches the Gulf. It is going to be a crazy week to two weeks in the western Tropical Atlantic. And this doesn't even count the eastern Atlantic where we could see another 1-2 storms develop before the Hanna makes landfall.

Note: A few models do pull Hanna out to sea after its stall near the Bahamas. However, I don't think that scenario is as likely because of the strengthening ridge which should push it back westward after the stall.

Tropical Storm Gustav

Ok, its not official yet from the NHC, but it will be in about 15 minutes. The hurricane hunters just found 995.6 mb in the center of the storm, with winds to 59 mph around the center. In my opinion, the NHC will go 995 mb and winds to 55 mph at 2 pm. This storm is wrapping up quickly, and I wouldn't be surprised to see hurricane watches issued for Cuba or even Haiti.


Make that 996 mb at 60 mph! A hurricane before it makes landfall in Haiti seems very possible now, hurricane watches coming.

TD7

TD7 has been officially designated. The track brings it over western Haiti and then along the northern coast of Cuba towards the Keys, close to what I was thinking. The forecast was, of course, low confidence for the NHC. I earlier posted the 6Z model runs with their high divergence...thinking they might get better by 12Z...nope, they got worse. We are going to need another 12-24 hours to really get a handle on where this storm will go in the long term. This may be one of those times when the NHC gets the track completely wrong, but don't blame them. This is an unusual situation.

However, they did go close to the CMC, GFDL, and HWRF which are all reasonably reliable track models. The GFS does not develop the system, so that model can not be used for track. The NOGAPS and European bring the storm north and then northeast, which seems the least likely at this point. However, the European was the first storm to notice that Fay would cross Florida into the Atlantic and then turn back towards the west....so we shouldn't ignore it. This storm will be a good learning experience.

Where Will 94L Go?

That is for you to decide today. I already have my idea, but I would like to hear some of your opinions, and why. Here are the current model tracks:





If you can tell me who is right, you win a cookie! The divergence in the models is amazing, some seeing a weakness which pulls 94L to the north, some seeing a building high which holds 94L south and moves it westward. I wouldn't want to be the NHC right now trying to come up with a forecast when they designate this system a TD/TS later today. The system is looking very well structures right now, and I am not fully sure why it is not a TD. I understand the low level circulation has not completely closed, but it is very strong in all of the quadrants except the southwest. Strong, meaning Tropical Storm winds. I, personally, think they should call it a Tropical Depression right now, keep it as such until it closes off the low, and then bump it to a Tropical Storm, unless wind speeds in it warrant a Tropical Storm classification earlier (for instance, 60 mph winds). But, that's just my opinion. I think 94L will jump TD status (for the 5th time this year!) and become Gustav later today or tonight. Where it goes....you get to tell me. (I will update later today with what I am thinking.)





Fay



Quickly, thought I would post this image from the National Weather Service which Dr. Masters posted on his blog on Weather Underground. It shows how much rain Fay dumped on Florida...amazing!

Addition: Of course, just after I finish this, the Navy says we have TD7. So, I guess it will be called a TD before a TS. However, I don't think it will be long until we have TS Gustav. Because the NHC is going to put out a forecast soon, I thought I would let you know what I am thinking. I think the storm will continue its northwest movement for the next day or two, bringing it very close to mainland Cuba. The weakness created by Fay and the trough moving through the eastern US should allow TD7 to move towards the Keys. After this, it really is a flip-the-coin type of situation. A ridge builds over the gulf/southeast, which will reduce the steering and make it very difficult to pinpoint a track. I wouldn't be surprised to see the NHC track go over Cuba towards the Keys. But with strong model divergence, I expect the NHC to say that it is a low confidence forecast, for both track and strength. Land interaction is going to be a major player.