Storm2K Hurricane Ivan Update and Model Analysis - 8PM

[MWatkins]

Storm2K Hurricane Ivan Update and Analysis
8:00PM EDT 9/05/2004

CURRENT INTENSITY AND MOVEMENT

Satellite imagery indicates that Ivan has become the 4th major hurricane of the 2004 Atlantic season...and the strongest hurricane on record for a system this far south in the tropical Atlantic by a large margin. At 8:00PM AST this evening...the eye of powerful hurricane Ivan was located near 10.6 north...48.5 west...or about 765 miles east of the Windward Islands.

It must be stressed that Ivan is nothing like Frances in terms of track and forward motion. Unlike Frances...Ivan will continue to move rapidly across the Atlantic and could reach the Windward Islands in less than two days.
Maximum sustained winds in Ivan are now 135MPH. Ivan is a dangerous Category 4 hurricane and should remain intense upon it's arrival into the Caribbean sea.

5 DAY FORECAST MOTION AND MODEL ANALYSIS

Today's 12Z model runs are in very good agreement on a track throughout the 5 day period...with one exception. The 12Z NOGAPS...the 12Z European...12Z UKMET and most recently the 18Z GFDL...all present the same general scenario. Ivan will begin bending more to the WNW tomorrow and travel around the periphery of the Atlantic ridge. Late in the forecast period...Ivan should move more to the northwest as the western extent of the Atlantic ridge weakens some. This is the reason for the track close to the Dominican Republic and into the southern Bahamas. The official forecast from the NHC closely follows this track and is in good agreement with the model consensus. The only outlier...once again...is the 12Z GFS which appears to be too weak with the initialization of Ivan...and hence takes it too far to the west in a weaker steering layer.

The 18Z GFS also ultimately fails to handle the hurricane well...and develops a spurious-looking weakness in the 500MB flow in the central Atlantic well after the hurricane passes through. Needless to say...the GFS solution is being discounted for now...and the 18Z GFDL is being used as a representation for the GFS model for now.

There are no indications that there will be anything to weaken the Atlantic ridge in the next 3 or 4 days. Overall...this remains a fairly predictable pattern.

FORECAST INTENSITY

Ivan is expected to remain a dangerous category 4 hurricane throughout the next few days...and could approach Category 5 intensity. Minor differences in track may determine if the hurricane weakens due to land interaction...and there are some indications that upper-level winds may not be as favorable as the current environment toward the end of the forecast period. However...little is known about changes in hurricane intensity...especially in the long range.

The hurricane will weaken some once it crosses the DR. However...the environment should be somewhat favorable for re-intensification once the hurricane exits the island.

EXTENDED MOTION

In the longer term...if Frances is slow to exit...and it is not forecast to be at this time...then the Ivan may find a weakness left in the ridge. If not...there is some concern that Ivan could end up as a threat to some portion of the southeast US. It is far too early to determine which location would be threatened...if any at all. Much depends on the angle the hurricane takes out of the Caribbean. It could cut to the south of Florida or turn in front of the peninsula. There is not currently as good agreement in the extended period among the models on these details...but the overall pattern continues to look ominous for residents of the southeast US.

MISC QUESTIONS

Q: What should residents of the Eastern Caribbean be doing right now...including Puerto Rico?
A: Residents should review their hurricane plan and understand that a hurricane watch could be posted for their area in the next day or two...and begin to make preliminary preparations for this hurricane at this time.

Q: I live in (ANY CITY) and our meteorologist thinks the system is coming here...what should I do?
A: This far out...landfall points are guesswork. We have plenty of time to watch this system...you should go ahead and do everything you should have done at the beginning of the year...including getting your hurricane plan and supplies together. From there...no additional action is needed before a Hurricane Watch is issued for your area...unless there are things you should have already done still left to do.

Q:When will this impact the US if it does at all?
A:It still appears this could be another 6 to 7 days from the US coast.

Q:Oh no...Ivan is heading straight for Florida too?
A:Although the current track of Ivan looks somewhat scary...there is no indication that this system is targeting any specific location. There is plenty of time to watch the progress of Ivan...it could still miss the US all together...so there is no need to worry about this hurricane. Florida residents should simply monitor it's progress like all residents of the hurricane region should be doing.

We will update or replace this update around 12PM tomorrow. Of course...other Storm2K forecasters may tack on to this update as well.

MW

[Stormsfury]

One of the things that may play with Ivan's intensity in the short-term are of course, ERC's (eyewall replacement cycles), and currently, Ivan's eye is like looking through a pin needle ... very, very small ...

also, the FWD speed of Ivan continues to be faster than the TUTT-type low that's been carved out by the outflow wake of Frances by some 5 MPH ... currently, the conditions over Ivan are almost perfect ... however, should Ivan continue at its FWD clip and outrace the trough out ahead, those enhancing outflow winds will become more hostile winds and serve to hinder its continued development today and tonight ... which MIGHT spare the Islands a little (emphasis on the word, a little)

Frances is NOT expected now to go as far west as originally progged with a dramatic shift in the guidance towards the right which has HUGE implications on GA, and the Western Appalachians in NC ... and could POSSIBLY carve out a trough in its wake as it moves NE in the MR and becomes extratropical ... and the trough left in the wake will have some bearing on just how much (if any, poleward motion) Ivan can take ...

In the MR, the ECMWF on day 7, the 500mb pattern shows quite a large trough over the Western States, and two large domes of high pressures ... however, a weakness in between the ridges over the Mississippi Valley does show up ... The EC wants to place Ivan in the Florida Straits on Day 7, with a slowing on the Day 8-10 3 day avg .. (slowly over Florida).

SF

[MWatkins]

One of the things that may play with Ivan's intensity in the short-term are of course, ERC's (eyewall replacement cycles), and currently, Ivan's eye is like looking through a pin needle ... very, very small ...

also, the FWD speed of Ivan continues to be faster than the TUTT-type low that's been carved out by the outflow wake of Frances by some 5 MPH ... currently, the conditions over Ivan are almost perfect ... however, should Ivan continue at its FWD clip and outrace the trough out ahead, those enhancing outflow winds will become more hostile winds and serve to hinder its continued development today and tonight ... which MIGHT spare the Islands a little (emphasis on the word, a little)

Frances is NOT expected now to go as far west as originally progged with a dramatic shift in the guidance towards the right which has HUGE implications on GA, and the Western Appalachians in NC ... and could POSSIBLY carve out a trough in its wake as it moves NE in the MR and becomes extratropical ... and the trough left in the wake will have some bearing on just how much (if any, poleward motion) Ivan can take ...

In the MR, the ECMWF on day 7, the 500mb pattern shows quite a large trough over the Western States, and two large domes of high pressures ... however, a weakness in between the ridges over the Mississippi Valley does show up ... The EC wants to place Ivan in the Florida Straits on Day 7, with a slowing on the Day 8-10 3 day avg .. (slowly over Florida).

SF

Great analysis SF...of course...I hope your final note about the euro is off base some...

MW

[Ground_Zero_92]

Great analysis SF...of course...I hope your final note about the euro is off base some...

MW

I hope so too. I don't think I could take another stalled storm by Florida. Is the EC showing a very strong system at that point?

[Stormsfury]

0z ECMWF looks a little better for Florida, but not so good for the Bahamas on Day 7 ... and bad for the Carolinas later ... actually, almost looks like a Hugo scenario ...

0z ECMWF Day 3 to 7 loop - 850mb level

0z ECMWF Day 3 to 7 loop - 500mb level