Posted on 09/21/2002 3:05:23 PM PDT by 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
LOL! Amen.
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
The smell of death, am I?
2Co 2:15 For we are unto God a sweet savour of Christ, in them that are saved, and in them that perish:
16 To the one we are the savour of death unto death; and to the other the savour of life unto life. And who is sufficient for these things?
It is best to take up discussions with the Author of the message ("Repent"), not to shoot the messenger.
Correction about Gilbert. Those were not major trofs. They were minor. Also...they never materialized. The models of the day kept showing them...but they were what we call minor short waves. They heat tranport from Gilbert warmed the environment enough to the north to create a small thin ridge by which it traveled. Again...David is a perfect example of a very big, strong storm that recurved. If the trof is strong enough and deep enough...you could put SuperTyphoon Tip up next to it and it is recurving.
For starters, wind force on a surface, as expressed in pounds per square inch, varies as the square of the difference in wind velocity. So a wall, or a window, or a roof is subjected to four times as much force if the wind speed merely doubles.
And, of course, once structures, trees, and so on begin failing, the problem is hugely increased. A window might be able to withstand a 100-mph wind, but not a branch flung into it at 100 mph. And as more windows, roofs, treees and so on become airborne debris, the problem feeds upon itself.
My guess is that a 150-mph hurricane might cause ten times the damage, or more, of a 75-mph hurricane of similar size and duration. And that's without addressing the storm surge, which is also exponentially worse in stronger storms.
This one could get ugly.
I read an interesting study 2-3 years ago that indicated that category 5 hurricanes were fairly routine until about 1,100 years ago and then they just fell off to what we know today. I expect that data is out on the inter-net if anyone wants to do a search.
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