WPAC: HAIYAN - Post-Tropical

[Meow]

JTWC gave 895 hPa to Haiyan when it was at 170 knots, but that is from their new conversion table since 2007.

Based on the Koba table, JMA should have given 890 or 885 hPa to Haiyan, but JMA also gave 895 hPa. I guess the smaller radius made JMA estimate higher pressure.

[ozonepete]

how do you get an RMW of 25NM with a 17NM wide eye? The RMW occurs at the inner edge of the eye wall in a fully developed cane

Maximum winds do not occur solely at the inner edge of the eyewall at all. The zone of highest winds within the RMW has a thickness - it is not razor thin with a diameter of max winds of 1 or 2 miles. The eyewall is often 5-10 miles thick and max winds can occur anywhere in that zone.

[CrazyC83]

Interesting to note that pressure wise, it was NOT as intense as Megi at landfall. That said, this has a MUCH stronger ridge north of it. Thus, I am convinced that the peak winds were GREATER than Megi despite not being as intense of a low pressure system

I agree with you. 1015 is a very high OCI pressure for the WPAC (or even the Atlantic).

[Alyono]

how do you get an RMW of 25NM with a 17NM wide eye? The RMW occurs at the inner edge of the eye wall in a fully developed cane

The RMW does not occur solely at the inner edge of the eyewall at all. It has a thickness - it is not razor thin with a diameter of max winds of 1 or 2 miles. The eyewall is often 5-10 miles thick and max winds can occur anywhere in that zone.

Not in these well developed storms. I've seen an analysis on the T storms list, which had the eye striking 16NM south of Tacloman and the RMW 4NM south of Tacloman. That corresponded to the inner edge of the eye (which the radar showed numerous features that look like those dangerous mesovorts. That's where I got an eye diameter of 12NM and the RMW of 12NM. Not pulling the numbers out of thin air

[christchurchguy]

Are you using the city center location or the airport to count distance?

[CrazyC83]

Are you using the city center location or the airport to count distance?

I used an earlier report 10 mb lower than Tacloban (using 946 mb), a little over an hour before landfall, to count distance. There was no data after that.

[ozonepete]

how do you get an RMW of 25NM with a 17NM wide eye? The RMW occurs at the inner edge of the eye wall in a fully developed cane

The RMW does not occur solely at the inner edge of the eyewall at all. It has a thickness - it is not razor thin with a diameter of max winds of 1 or 2 miles. The eyewall is often 5-10 miles thick and max winds can occur anywhere in that zone.

Not in these well developed storms. I've seen an analysis on the T storms list, which had the eye striking 16NM south of Tacloman and the RMW 4NM south of Tacloman. That corresponded to the inner edge of the eye (which the radar showed numerous features that look like those dangerous mesovorts. That's where I got an eye diameter of 12NM and the RMW of 12NM. Not pulling the numbers out of thin air

Lol my friend I know you're not pulling numbers out of the air - you are making very intelligent proposals for what went on based on the little data we have so far. Just look at this radar from Dr. Masters' blog. Tacloban was clearly in the RMW and got the max winds possible at that point of the cyclone. You can see that even stronger storms were about to rotate into the city and it is clear that an extreme eyewall mesovortex was just about to rotate in over the city from the east.

You can calculate eye size, distances, RMWs, etc. in many ways, but you don't need anything more than this to see where Tacloban was in relation to max winds.

[EquusStorm]

You know... not to add fuel to the fire or beat a dead horse or anything... but if we had reconnaissance in particularly significant storms such as Haiyan, we wouldn't HAVE to guess and estimate and debate the minimum pressure. ;p

*dodges thrown rocks*

[Meteorcane]

Curious as to what people would estimate the 10m wind speeds that occurred over near-coastal areas (ie. shoreline exposure class) of Guiuan? I have yet to see enough damage photos from the region to make any good estimates, although based on crude conversions I think sustained winds may very well have been in the 150 area, gusting to near 180.

I also am curious why the pressure tends to be higher in low latitude cyclones for a given wind speed (ie. Sandy for example having very low pressure yet relatively low maximum winds)? Is it a size issue (ie. systems enlarge when they encounter the wind shear of the mid-latitudes decreasing the PGF. Or is it related to the force balance in the Navier Stokes equations (in particular I could see how a smaller Coriolis parameter in the equations of motions would require a higher wind velocity to balance the other forces (obviously a TC is in Geostrophic balance, or even Gradient Balance, but FV is a term that does appear, so a lower f would require V).

I also should add that I thought I had read that in a TC eyewall the Rossby number was quite high (generally higher the smaller the eye diameter), leading me to believe Cyclostrphic balance could be more appropriate which would eliminate the Coriolis force/parameter from the discussion

[TropicalAnalystwx13]

I'm not sure how credible this blog is (it doesn't look terrible to me), but it states that a handheld recorded a barometric pressure of 889mb at 5:01 am local time (that's the time the eye was passing over) in Guiuan. Taking into account that the pressure may have been slightly lower at the core, and also taking into account that the storm seemed to have peaked a few hours earlier, the best estimate...at least in my opinion...for the lowest pressure would be in the 880-885mb range. This matches well with NOAA's pressure estimate of 884mb.

One thing I think needs some discussing is the doppler radar on Guinuan. If you've not seen the picture (I'll post it below), the dome has been blown off. Depending on the model of the doppler radar, it takes anywhere from 150-200 mph to do such. Personally, I would assume that it's the one made to withstand 200 mph winds considering this is the Philippines (where they have to be durable), but we don't know for certain. At any rate, the flattening/stripping of trees on Guinan makes me believe they got the 190-200 mph sustained winds.

[phwxenthusiast]

for more info:

Time (local) Tacloban Dulag
5:00am 989.4 988.3
5:15am 987.8 986.2
5:30am 986.0 983.5
5:45am 982.7 979.8
6:00am 980.0 976.1
6:15am 977.1 969.1
6:30am 972.7 -
6:45am 965.6 -
7:00am 957.4 -
7:15am 955.6 -

Instruments go out after

[Meteorcane]

I'm not sure how credible this blog is (it doesn't look terrible to me), but it states that a handheld recorded a barometric pressure of 889mb at 5:01 am local time (that's the time the eye was passing over) in Guiuan. Taking into account that the pressure may have been slightly lower at the core, and also taking into account that the storm seemed to have peaked a few hours earlier, the best estimate...at least in my opinion...for the lowest pressure would be in the 880-885mb range. This matches well with NOAA's pressure estimate of 884mb.

One thing I think needs some discussing is the doppler radar on Guinuan. If you've not seen the picture (I'll post it below), the dome has been blown off. Depending on the model of the doppler radar, it takes anywhere from 150-200 mph to do such. Personally, I would assume that it's the one made to withstand 200 mph winds considering this is the Philippines (where they have to be durable), but we don't know for certain. At any rate, the flattening/stripping of trees on Guinan makes me believe they got the 190-200 mph sustained winds.

That would be an ideal location I would assume to guesstimate the top winds, as it seems fairly high/isolated the tree damage patterns look consistent with Cat.5 gusts, it would be great to know the exact specs of that radar dome (and assume it was installed correctly/tested accurately).

[Alyono]

Not debating the strong winds and I still contend max winds were either 180 or 185 KT at landfall.

Just saying Tacloman did not receive those extreme winds that Guiuan did

[ozonepete]

Not debating the strong winds and I still contend max winds were either 180 or 185 KT at landfall.

Just saying Tacloman did not receive those extreme winds that Guiuan did

Don't think you'll get an argument. And it's Tacloban with a B

[ozonepete]

Curious as to what people would estimate the 10m wind speeds that occurred over near-coastal areas (ie. shoreline exposure class) of Guiuan? I have yet to see enough damage photos from the region to make any good estimates, although based on crude conversions I think sustained winds may very well have been in the 150 area, gusting to near 180.

I also am curious why the pressure tends to be higher in low latitude cyclones for a given wind speed (ie. Sandy for example having very low pressure yet relatively low maximum winds)? Is it a size issue (ie. systems enlarge when they encounter the wind shear of the mid-latitudes decreasing the PGF. Or is it related to the force balance in the Navier Stokes equations (in particular I could see how a smaller Coriolis parameter in the equations of motions would require a higher wind velocity to balance the other forces (obviously a TC is in Geostrophic balance, or even Gradient Balance, but FV is a term that does appear, so a lower f would require V).

I also should add that I thought I had read that in a TC eyewall the Rossby number was quite high (generally higher the smaller the eye diameter), leading me to believe Cyclostrphic balance could be more appropriate which would eliminate the Coriolis force/parameter from the discussion

You hit it on the head when you said that a smaller Coriolis force requires a higher wind velocity to balance it with the other 2 forces. You will see many mid latitude cyclones with very close isobars and very low pressure that still don't have nearly the high winds that the same pressure would produce nearer the equator. It just goes to show how low pressure centers and their relation to wind speed is relative depending on the latitude.

Here's a blog entry from a former professor and friend who explains it pretty well.
http://www.wunderground.com/blog/24hourprof/the-bering-sea-a-puzzle-of-wind-speed

[Meteorcane]

Curious as to what people would estimate the 10m wind speeds that occurred over near-coastal areas (ie. shoreline exposure class) of Guiuan? I have yet to see enough damage photos from the region to make any good estimates, although based on crude conversions I think sustained winds may very well have been in the 150 area, gusting to near 180.

I also am curious why the pressure tends to be higher in low latitude cyclones for a given wind speed (ie. Sandy for example having very low pressure yet relatively low maximum winds)? Is it a size issue (ie. systems enlarge when they encounter the wind shear of the mid-latitudes decreasing the PGF. Or is it related to the force balance in the Navier Stokes equations (in particular I could see how a smaller Coriolis parameter in the equations of motions would require a higher wind velocity to balance the other forces (obviously a TC is in Geostrophic balance, or even Gradient Balance, but FV is a term that does appear, so a lower f would require V).

I also should add that I thought I had read that in a TC eyewall the Rossby number was quite high (generally higher the smaller the eye diameter), leading me to believe Cyclostrphic balance could be more appropriate which would eliminate the Coriolis force/parameter from the discussion

You hit it on the head when you said that a smaller Coriolis force requires a higher wind velocity to balance it with the other 2 forces. You will see many mid latitude cyclones with very close isobars and very low pressure that still don't have nearly the high winds that the same pressure would produce nearer the equator. It just goes to show how low pressure centers and their relation to wind speed is relative depending on the latitude.

Here's a blog entry from a former professor and friend who explains it pretty well.


Thank you very much.
http://www.wunderground.com/blog/24hourprof/the-bering-sea-a-puzzle-of-wind-speed

[supercane4867]

I'm not sure how credible this blog is (it doesn't look terrible to me), but it states that a handheld recorded a barometric pressure of 889mb at 5:01 am local time (that's the time the eye was passing over) in Guiuan.

It will be pleasant to see if there going to be any further confirmation of that reading, but for now I think chances are slim

[PaulR]

Interesting discussion (of the power / intensity of Haiyan). I found a couple more pics that demonstrate it in another way. I only went back a couple pages, so hopefully these have not already been posted.

From Fox News website:



And from shipwrecklog.com:



As for our relatives:

Our relatives on the island of Biliran have not been heard from. So that has us concerned. Hopefully they are ok, but simply unable to
get a message out because of the downed communications.

Other relatives lived in Ormoc and were able to get a message out: They lost their home, but at least for the present are physically ok and in a shelter that survived the storm. I also have read that apparently the city's deep wells are functional, so drinking water is available. Hopefully the situation there is not quite as bad as in Tacloban, where martial law may have to be declared.

In case anyone "new" to this story is reading this:

The Philippine Red Cross needs help, so if you can, forward a request for donations to anyone you can. They are a reputable group and the help is badly needed. Here is their website donation page address:

http://www.redcross.org.ph/donate

[ravyrn]

How much difference is there in eyewall readings compared to where the eye passes straight over?

[ozonepete]

How much difference is there in eyewall readings compared to where the eye passes straight over?

I assume you're talking about pressure. The places where the eye center passes directly overhead will always have the lowest pressure. The tighter wound up the storm is the greater the difference from the eyewall to the center of the eye so that in some storms there can be quite a difference. There is no standard way to measure it without calculating the size of the wind field, the latitude the storm is at and how large the area of core thunderstorms is. In terms of the discussion we've been having here, it's quite clear that the actual minimum pressure of Haiyan was quite lower than whatever was measured at Tacloban since the center did not pass over there and the storm was already weakening slightly when it did. I would love to see a validated pressure from an instrument in Guiuan since the eye passed very close to there at near peak intensity.