Alternative Intensity Scale

[jasons2k]

Been debated beforte, but here is an article with the latest news on this:

http://blogs.chron.com/sciguy/archives/ ... st_63.html

[vbhoutex]

There are definitely changes needed. Some of that change has got to be education of:
1. OEM and Municipal leaders that life and limb are NO. 1 and it doesn't matter if you order an evacuation and it ends up not being needed. I am a weather weenie to say the least. I have known for years that exits off of Galveston Island and other such areas go under water early. Why don't the local leaders and/or general public know and/or understand this? I even think the media needs to be educatied along these lines.
2. Education, over and over, of the general public that the worst damage in a Hurricane, at least along the immediate coast, is usually from surge, not necessarily the wind. And I do mean over and over-it takes time for it to sink in unless you have been directly affected by it. There is NEVER "only a CAT2(or CAT1) hurricane which won't cause much damage/problems. Houston found this out all too well in 2001 thanks to a little TS called Allison.
I could go on and on about people living on barrier islands, but this will not change, so education and evacuation are the alternatives.

[tolakram]

We need a better magic number, something that when it shows up on the TV set or is uttered on the radio people know what it means and what to do. Anything more complex is not going to get the job done, and that's not meant as an insult to coastal residents.

[wxman57]

The Hurricane Severity Index is just part of a suite of tools that businesses can use to objectively trigger their phased hurricane response plans. It is not meant for use by the general public for deciding when to evacuate. Those of you near the coast need to listen to your public officials for guidance when a hurricane threatens. Unfortunately, some of those officials may not offer the best guidance at times (as with the Galveston mayor prior to Ike's impact). I've always said, if you're in a zone that could be impacted by ANY storm surge, then you need to evacuate for EVERY hurricane, even a strong TS can become a very dangerous surge producer in the 2-3 days prior to impact when evacuations would have to be carried out.

It's interesting that Ike's HSI score at landfall (30) was higher than Rita's (29) and not far from Katrina's (36) landfall at Buras. Knowing a hurricane's size is quite important when calculating its potential storm surge.

[Chacor]

I've noticed the NHC uses "dangerous", "very dangerous" and "extremely dangerous" (and sometimes "potentially catastrophic") to describe Category 3, 4 and 5 hurricanes respectively in their public advisories. I don't know, but doesn't this give one the impression anything less isn't "dangerous"?

[vbhoutex]

I've noticed the NHC uses "dangerous", "very dangerous" and "extremely dangerous" (and sometimes "potentially catastrophic") to describe Category 3, 4 and 5 hurricanes respectively in their public advisories. I don't know, but doesn't this give one the impression anything less isn't "dangerous"?

I'm not sure I agree with that, but I can see how some might interpret it as "less dangerous". It does give me an idea that they need to address surge or surge potential as extremely dangerous etc, along with a possible time frame for onset of surge and run up.

[Jason Foster]

......I have known for years that exits off of Galveston Island and other such areas go under water early. Why don't the local leaders and/or general public know and/or understand this? I even think the media needs to be educatied along these lines.

Just speaking of the water covered exits, I thought that evacuations were handed out early enough. I thought that officials did know about the roads being flooded much earlier in the storm. They certainly had plenty of road blocks Around Freeport and Galveston. I chased Hurricane Ike and did manage to access the island for the storm, but it was clear that conditions were going to get bad well ahead of the storm.

Speaking of the Intensity scale issue. I feel that the rating system wasn't designed with the public in mind, but more of a scientific frame of reference. I don't believe that a intensity scale is the important part in regards to the public. I think that it is important to deciminate the proper instructions and warnings for the residences and businesses to respond accordingly to the threat. There are many dynamics to hurricanes that are not going to fit neatly into a small group of catagories. Hurricanes hitting different areas are going to have different affects, even if the storm itself is the same as another.

[jinftl]

Just a thought....when a tornado warning is issued, the recommended course of action for those in its path is the same...regardless if it is an F0 tornado or an F5. Granted, because of the short-lead time and inability to accurately assess a tornado's strength as it is taking place, such a determination is practically impossible to make 'real time'.

But, it you know a tornado is coming, you should get into a storm cellar, interior room, etc....regardless of intensity, because it is, after all, a tornado. By definition, that is dangerous and destructive. Along the same lines, a hurricane by definition is dangerous and destructive, regardless of category. Houston with Ike and South Florida with Wilma can attest to what even Cat 1 and Cat 2 winds can do...not to mention the Cat 4 surge with Ike.

A hurricane is a hurricane....when one is heading towards you, preparations must be made, regardless of category. There is absolutely a risk of overpreparing and having the nuisance and expense of preparing a larger area than may be necessary. Such is the burden of survival. Better to prepare your home and leave for a day or 2 than to drown in a storm surge.

With tornado warnings, not everyone in a storm cellar is actually going to experience their home being ripped apart above them. With hurricane warnings, not everyone is going to see the worst that storm has to offer. Inconvenience? Perhaps. Lucky? For sure!

[vbhoutex]

......I have known for years that exits off of Galveston Island and other such areas go under water early. Why don't the local leaders and/or general public know and/or understand this? I even think the media needs to be educatied along these lines.

Just speaking of the water covered exits, I thought that evacuations were handed out early enough. I thought that officials did know about the roads being flooded much earlier in the storm. They certainly had plenty of road blocks Around Freeport and Galveston. I chased Hurricane Ike and did manage to access the island for the storm, but it was clear that conditions were going to get bad well ahead of the storm.

Speaking of the Intensity scale issue. I feel that the rating system wasn't designed with the public in mind, but more of a scientific frame of reference. I don't believe that a intensity scale is the important part in regards to the public. I think that it is important to deciminate the proper instructions and warnings for the residences and businesses to respond accordingly to the threat. There are many dynamics to hurricanes that are not going to fit neatly into a small group of catagories. Hurricanes hitting different areas are going to have different affects, even if the storm itself is the same as another.

That is the biggest problem with the SS scale. The warnings, while needing to be concise and to the point also need to fully explain(for lack of better words)the impacts expected including those prior to landfall.

The Galveston mayor was a full 1/2 day late in issuing the mandatory evac order based on previously published data concerning the times needed to fully evacuate Galveston Island.

[wxman57]

The general public should not use any hurricane scale to judge whether to prepare for a hurricane or evacuate. The public should heed warnings/guidance from local officials when a hurricane threatens. But as we saw with the Galveston mayor, local officials may make the wrong decisions, so you can't always rely on the government to protect you. If you live in an area defined as a surge zone, then you should seriously consider evacuating for any storm with the potential for becoming a hurricane when it's 2-3 days from landfall. If you have to cross any low-lying roads, you should be aware that these roads could be flooded days in advance of a slow-moving tropical storm, and you should be prepared to leave days before the actual center of the storm arrives.

One of the issues with NHC watches/warnings is that they're issued so close to impact that you can't wait for a warning to be issued before evacuating. By definition, watches are issued when hurricane is within 36 hours of possibly impacting a location, warnings within 24 hours. But evacuations need to be carried out 2-3 days prior to impact. Looking back at Ike, a hurricane watch was issued at 4PM CDT Wednesday, Sept. 10th. Hurricane force winds were not expected until early Saturday morning, about 54 hours from the time the watch was issued. So the NHC issued the watch long before that 36 hour mark. The hurricane warning was issued at 10AM CDT Thursday, Sept. 10th, about 38-40 hours prior to the projected arrival of hurricane force winds. This is way ahead of that 24 hour period. I've heard that the NHC will be moving their watch issuance to 48 hours prior to ETA in the future, with warnings going out at 36 hours. But the watches/warnings for Ike were issued even earlier than that. Still, it was too late for many.

Public officials are very reluctant to act without a hurricane warning in effect. We were yelling at the Galveston mayor on the TV in ops on Wednesday, Sept. 10th to get the people off the island! It was clear to us as meteorologists that Galveston was facing its biggest threat in decades. With Rita, the island was already being evacuated the Wednesday before Rita hit (same time - early morning Saturday). I'm sure the Galveston mayor was hoping Ike would turn away so she failed to act. Public officials need to err on the side of caution, but they need to be prepared to be wrong much of the time.

[Ed Mahmoud]

There was one NHC forecast 4 or 5 days prior to landfall where the line of landfall was near Baffin Bay, and the HOU area was barely in the cone, and I have heard that used as an excuse for the slow issuance of evac orders for GLS.


ETA
This was the discussion from the forecast package that supposedly led GLS area leaders to tarry with issuing evacs.

HURRICANE IKE DISCUSSION NUMBER 33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008
500 AM EDT TUE SEP 09 2008

SURFACE OBSERVATIONS AND DATA FROM A RECONNAISSANCE PLANE INDICATE
THAT IKE HAS A LARGE AREA OF TROPICAL STORM FORCE WINDS BUT THE
INNER CORE OR EYE IS VERY SMALL BUT WELL DEFINED...ABOUT 6 TO 8 NM.
THE EYE CAN BE SEEN FROM CUBAN AND KEY WEST RADARS. ALTHOUGH THE
MINIMUM PRESSURE HAS BEEN AROUND 963-965 MB...THE MAXIMUM
FLIGHT LEVEL WINDS MEASURED SO FAR WERE ONLY 69 KNOTS. THE INITIAL
INTENSITY IS KEPT AT 70 KNOTS ASSUMING THAT THE PLANE HAS NOT
SAMPLED THE ENTIRE CIRCULATION...BUT THIS VALUE APPEARS QUITE
GENEROUS AT THIS TIME. ON THE OTHER HAND...GIVEN THE WELL DEFINED
STRUCTURE ON RADAR AND SATELLITE AND THE FACT THAT IKE HAS SEVERAL
MORE HOURS OVER THE VERY WARM WATERS SOUTH OF CUBA...THE WINDS
WINDS COULD INCREASE SOME NEAR THE CORE BEFORE MOVING OVER WESTERN
CUBA. ONCE OVER THE GULF OF MEXICO IN ABOUT 24 HOURS...IKE WILL
HAVE PLENTY OF OPPORTUNITY TO STRENGTHEN SINCE THE ENVIRONMENT IS
CONDUCIVE...AND THE HURRICANE WILL LIKELY MOVE OVER SEVERAL AREAS
OF HIGH HEAT CONTENT. THE OFFICIAL FORECAST MAKES IKE A CATEGORY 3
HURRICANE AND THIS VALUE IS IN BETWEEN THE DYNAMICAL AND
STATISTICAL MODELS.

FIXES FROM CUBAN AND KEY WEST RADARS AS WILL AS PENETRATIONS FROM A
RECONNAISSANCE PLANE INDICATE THAT THE SMALL EYE OF IKE IS MOVING
WESTWARD OR 280 DEGREES AT 10 KNOTS...VERY CLOSE TO THE ZAPATA
PENINSULA ON THE SOUTH COAST OF WESTERN CUBA. A GENERAL WESTWARD TO
WEST-NORTHWESTWARD TRACK BETWEEN THE ISLE OF YOUTH AND THE SOUTH
COAST OF HAVANA PROVINCE SHOULD CONTINUE DURING THE NEXT SEVERAL
HOURS. THEN...THE CENTER SHOULD CROSS WESTERN CUBA LATER TODAY.
UNFORTUNATELY... IKE IS EXPECTED TO MOVE VERY NEAR TO WHERE
HURRICANE GUSTAV CROSSED CUBA A WEEK OR SO AGO. THE STEERING PATTERN
IN THE GULF OF MEXICO HAS CHANGED LITTLE AND IKE IS EXPECTED TO TURN
MORE TO THE NORTHWEST DURING THE NEXT 2 DAYS OR SO AS THE RIDGE
WEAKENS DUE TO THE PASSAGE OF A SHORT WAVE. THEREAFTER...THE RIDGE
IS FORECAST TO RESTRENGTHEN AND SHOULD FORCE IKE ON A MORE WESTWARD
TRACK. IN FACT...UNANIMOUSLY...GUIDANCE SHIFTED SOUTHWARD AND ONCE
AGAIN THE OFFICIAL FORECAST WAS ADJUSTED TO THE LEFT AND STILL IS
ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE.

IT CANNOT BE OVEREMPHASIZED THAT ONE SHOULD NOT FOCUS ON 4 AND 5 DAY
FORECAST POINTS SINCE THESE CAN BE SUBJECT TO SUBSTANTIAL ERRORS.
DO NOT FORGET THAT FEW DAYS AGO...THE GUIDANCE UNANIMOUSLY HAD IKE
NEAR SOUTH FLORIDA AND THEN GRADUALLY SHIFTED THE DANGER TOWARD
WESTERN CUBA AND THE GULF OF MEXICO.


FORECAST POSITIONS AND MAX WINDS

INITIAL 09/0900Z 22.0N 82.1W 70 KT
12HR VT 09/1800Z 22.7N 83.5W 80 KT...INLAND
24HR VT 10/0600Z 23.5N 85.3W 85 KT
36HR VT 10/1800Z 24.2N 86.8W 90 KT
48HR VT 11/0600Z 25.0N 88.5W 95 KT
72HR VT 12/0600Z 25.5N 93.0W 100 KT
96HR VT 13/0600Z 27.0N 97.5W 100 KT...INLAND
120HR VT 14/0600Z 28.0N 100.5W 40 KT...INLAND

$$
FORECASTER AVILA

[vbhoutex]

There was one NHC forecast 4 or 5 days prior to landfall where the line of landfall was near Baffin Bay, and the HOU area was barely in the cone, and I have heard that used as an excuse for the slow issuance of evac orders for GLS.

If this is the case then there is something REALLY REALLY WRONG in Galveston since those muuniciapal leaders and EOM personnel were all in on the conference calls with NHC.

[Tampa Bay Hurricane]

A hurricane is a hurricane. If you are under a hurricane watch/warning,
evacuate and prepare. Any category is capable of serious life-threatening
damage. A strong tropical storm is also deadly especially if
flying debris hits you, or the storm surge drowns your low
lying area.

[MiamiensisWx]

Personally, I believe the hazards presented by large waves are often overlooked, but they warrant more attention. Many (well built) structures can survive sustained winds of Category 3 intensity or greater. Examples include layouts that reduce obstacle flow, stucco structures, structures with sloping "hip" roofs, proper roof attachments, etc. Newer (post-Andrew) structures in southern Florida would not collapse because of the effects of wind. Additionally, the maximum sustained winds of a hurricane are restricted to a very narrow swath in the inner core. However, a large tropical cyclone would produce significant waves, which would induce significant erosion. Many structures would collapse, including structures of various sizes and multifarious uses. On the Gulf Coast, large waves (superimposed on Katrina's storm surge) resulted in the complete removal of structures. Floating debris also devastated structures along the coast.

If you truly consider the hazards, the non-surge facets of water are worse than wind in many aspects. An exceptionally large storm did not impact many "high risk" areas in the 1990s, unlike recent years (2000s). Ivan, Katrina, and Ike provided a taste of the destruction inflicted by high waves and debris. These storms produced these effects in relatively populated areas. The impacts of a large storm would be significant in the Miami/Fort Lauderdale/West Palm Beach region, the Mid-Atlantic/Northeast, and other regions, regardless of intensity. However, the angle of approach would determine the effects of the storm. Hurricane Wilma's angle of approach reduced the effects of large waves on the Atlantic coastline of southeastern Florida. A large and intense hurricane (approaching from the Atlantic Ocean), traveling on a perpendicular angle to the coast, has not occurred in the MIA/FLL/PBI region since the 1960s. However, you can estimate the effects of a repeat of several past cases.

Examples of large/intense south FL TCs moving on perpendicular angles to the coast

1888 #3 (125 mph/945 mb)
1926 #6 (145 mph/933 mb)
1928 #4 (145 mph/929 mb)
1947 #4 (135 mph/940 mb)*
1965 Betsy (125 mph/954 mb)

*Actual landfall intensity (based on research) was likely near 120-125 mph/945 mb

These TCs caused significant beach erosion, large waves, and tides along the coastline. The 1926, 1928, and 1947 hurricanes resulted in the collapse of structures (via erosion) on the barrier islands. The depth of the offshore water magnified the height of the waves. As an aside, Hurricane Carla (1961) also produced significant coastal effects via large waves and high storm surge values in Texas.

[MGC]

The Florida coastline will be a total wreck if and when the next 1928 type hurricane hits. Sure the surge is bad, but the wave riding the surge will destroy just about everything in the way. Observed this after Katrina with only a few structures on the beach that were left standing. Those that did remain standing were washed through....MGC