ALERT: Hurricane Isidore forecasted to have at least 150 MPH winds within 72 hours

[newsperson999]

Statement as of 5:00 PM EDT on September 21, 2002

Air Force recon data indicate major Hurricane Isidore has continued to rapidly strengthen and the central pressure has dropped 21 mb in the past 13 hours. A pressure of 946 mb generally corresponds to a maximum wind of about 117 kt. However...the eye is open to the west and there may be a lag in the wind field. Also...dropsonde data indicated about 105 kt surface winds...but winds just a few hundred above the surface have been as high as 130 kt. The three satellite agencies reported a Dvorak satellite intensity estimate of t6.0...or 115 kt...while the 3-hour objective Dvorak T-number was also t6.0. Based on this information...the initial intensity was increased to 110 kt.

The initial motion estimate is 270/3. Recon fix positons since about 12z indicate Isidore has actually remained nearly stationary the past 6 hours...but right over some of the hottest water in the Atlantic Basin. Steering currents remain weak and are forecast by all of the global to remain weak or even get weaker. Isidore remains caught between a mid- to upper-level low east of Florida and one to the west over the Bay of Campeche. A weak and narrow low- to mid-level ridge extends across the northern Gulf of Mexico coast from Florida westward to Texas. Given the relative weakness of this ridge...only 5880 meters at 500 mb...it would not take much of a shortwave trough to erode it and allow Isidore to drift slowly poleward. All of the NHC model guidance...except LBAR...keeps Isidore moving on a slow west or west-southwest track through the forecast period. The AVN and GFDL are very similar in hooking Isidore to the southwest around the western Yucatan Peninsula in 36 to 48 hours. This may be some artifact of terrain interaction which I have ignored for this advisory package since all of the global models show no significant ridging north of isiodre to push the system to southwest. The forecast calls for a slow...less than 6 kt...motion throughout the forecast period with a slight west-northwestward motion after 48 hours as a strong shortwave trough drops down the west side of the broad longwave trough...which is expected to erode the weak ridge over Texas and the northwest Gulf of Mexico and allow Isidore to gain some latitude. However... the slower Isidore moves during the next 36 to 48 hours will determine just how far north and the cyclone will move in the longer time periods beyond 72 hours. The good news is that it appears that Isidore is not going to go anywhere fast. The bad news is that it will remain over very hot water.

The central pressure has dropped 21 mb in the past 13 hours. A typical rapid intensification period. This trend would normally continue for another 12 hours or so...but radar and recon data indicate that the eye is open to the west and that an eyewall replacement cycle may be starting. As such...the official intensity forecast is held below the ships intensity model which brings Isidore to 135 kt in 36 hours and 140 kt in 60 hours. This type of intensification is certainly possible given the low shear...less than 6 kt...and high SSTs...about 30c/86f. However...predicting internal convective changes is nealry impossible so there could be flucuations by as much 10 kt either way from the offical intensity forecast. Some coastal upwelling may weaken the hurricane slightly as it moves west of 88w longitude...but then some restrengtnening is forecast after 48 hours when Isidore is forecast to move back over warmer water.

Forecaster Stewart

forecast positions and Max winds

initial 21/2100z 21.9n 86.2w 110 kts
12hr VT 22/0600z 21.9n 87.0w 120 kts
24hr VT 22/1800z 21.9n 88.0w 125 kts
36hr VT 23/0600z 21.9n 89.2w 125 kts
48hr VT 23/1800z 22.0n 90.3w 125 kts
72hr VT 24/1800z 22.5n 92.5w 130 kts

[rwfromkansas]

Can you explain more where this concentric eyewall is? I have heard the term the past couple days, but never had a clue what the heck people were talking about...:)

[Nuke'm Glowing]

We won't. But it's the rest of the Atlantic that's getting churned up that has us concerned...not to mention the forecasters are still clueless about the final destination of this storm.

[dennis1x]

here is another good tropical link...lots of good stuff on their courtesy of Kauai,HI navy base (Kauai..by far the greatest Hawaiin Island).

http://www.nrlmry.navy.mil/tc-bin/tc_home

[eastforker]

My 2 cents worth Sam,A snowstorm os nothing like a tropical storm-hurricane.If you have never been through one it is hard to imagine.The Texas and LA coast is flat and when you get alot of rain,like tropical storm allison,you can have hundreds of millions in damage.Not to mention where the tornadoes are going to touch down.As weather forecasters will tell you,even with all the computer modules,no one realy knows what a hurricane is going to do next,only take an educated guess.Have you ever been in a hurricane Sam,have you?

[rwfromkansas]

That low in the BOC is heading south fast enough it may stop affecting it...perhaps that will be enough to let it do what it wants..or perhaps we will have to wait for the ridge to rebuild to the right of Isadore. I don't know..I am just an amateur. But I will say it is not taking as much of a depressed southerly track as it was earlier.

[rwfromkansas]

http://smn.cna.gob.mx/radares/rad-canc.jpg

It is the Cancun radar.

[dennis1x]

If you look at that Cancun radar pic that you posted you can see the innner eye, and then some precipitation, and then another open ring.

When a hurricane gets really strong it develops an outer eye in addition to the inner eye (called eye wall replacement). during this time the hurricane is not strengthening. as the outer wall contracts and if the hurricane is to strenghten the concentric structure wont be there. at its strongest there will be one and only one precipitation void with a solid eye wall (heavy precipitation around it.

[Dog Gone]

You really know how to stink up a thread.

[glock rocks]

[eastforker]

concentric means center ,like a concentric reducer in pipe,where as ecentric would have the eye to one side of the wall,in other words,if not mistaken,this is a very tight storm.

[dennis1x]

at least wait for a hurricane with 300mph winds, or a 10.0 earthquake, or at least something that HASNT HAPPENED SINCE THE BEGINNING OF TIME before posting end of the world doom bs.

[newsperson999]

Wow,
Latest inrared sot is a classic..the eye is becoming better defined.,in fact there is now a 'black hole" is the sea of cold white cloud tops(or blue depending on what sat you are looking at)

[dennis1x]

noticed that too, appears to have really gotten its act together in just the last 2 hours.

[Dog Gone]

Either the storm picks up speed, or it won't be anywhere nearly that far west in 72 hours.

[SamAdams76]

Have I ever been in a hurricane? Well supposedly I have - according to the local forecasters up here who spent days hyping them up. A couple I remember is Hurricane Belle from 1976 and Hurricane Gloria from 1985. There were a couple more but I don't remember the names.

You repeated what I already said in an earlier post. Even with the fancy computer models, nobody know what a hurricane is going to do next. I think that is why they originally used to name them after women until the PC crowd made them alternate the genders. So based on that, I believe both you and I can agree that it is far too early to get excited about this one. It will still be several more days until we have a better idea of where it might make landfall.

[glock rocks]

[ovrtaxt]

Here's a killer IR shot of Isidore:

http://hurricane.accuweather.com/adcbin/hurricane/satellite.asp?ocean=atlantic&thisreg=egul&type=&sattype=ei

[glock rocks]

[NautiNurse]

From Vortex Data Message Explanation

Hurricane Eye shapes are coded as follows: C-circular; CO-concentric; E-elliptical.

Orientation of major axis of ellipse is transmitted in tens of degrees, and all diameters are transmitted in nautical miles.

Example: E09/15/5 means elliptical eye oriented with major axis thru 90 degrees (and also 270 degrees), with length of major axis 15 nm, and length of minor axis 5 nm. CO8-14 means concentric eye with inner eye diameter 8 miles, and outer diameter 14 miles.

The "healthiest" hurricanes usually have a small, circular eye. A concentric eye (a ring inside a ring) is a relatively rare phenomenon that may signal a temporary weakening while the storm reorganizes.

An eye diameter that shrinks (compared to the previous vortex message) may signal strengthening: just as a twirling ice skater spins faster as she pulls in her arms, a hurricane may "spin" faster as its eye gets smaller. Eye diameters are usually 10-20 nautical miles, while we sometimes see them as small as 5 nm to as large as 60 nm.

[jpsb]

Me too, no way I could get out of my little coastal village, all the roads would be parking lots. Seen it before with Allen. At least I have a sail boat nearby, Drop the hook and hang on.