WPAC: HAIYAN - Post-Tropical

[CrazyC83]

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 35 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/35) = e^(-0.7143) = 0.4895

Using the calculator to try to find Po, I find the best fit for the central pressure to be 901mb.

[Ptarmigan]

pressure data from Tacloban indicate that the pressure at landfall was nowhere near as low as was Tip. May not have been sub 900.

However, lets remeber that low latitude storms have higher pressures for extreme winds. See the Felix 160+ SFMR at 930mb

What this does say, it is high time to blow up the WPAC pressure to wind relation. For starters, the data used to derive that relation is so highly suspect as I believe it is based upon ESTIMATES from recon and not mesured winds. This and Megi have showed that the extreme wind speeds often occur with pressures similar to those found in Atlantic hurricanes

I notice storms at low latitude are smaller. The further north or south (Southern Hemisphere), they get larger.

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 35 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/35) = e^(-0.7143) = 0.4895

Using the calculator to try to find Po, I find the best fit for the central pressure to be 901mb.

Looking at Haiyan, it was quite a tightly wounded storm, more so than Katrina. I see those type of storms more in the West Pacific, where the typhoon is almost a perfect circle. How did you figure out RMW?

[phwxenthusiast]

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 40 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/40) = e^(-0.625) = 0.536

Using the calculator to try to find Po, I find the best fit for the central pressure to be 890mb.

PAGASA's Tacloban Station recorded 955.63hPa at 7:15am local time... the other station in Dulag gave up an hour before Tacloban did and it was already running 10hPa lower than Tacloba's readings...

[CrazyC83]

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 40 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/40) = e^(-0.625) = 0.536

Using the calculator to try to find Po, I find the best fit for the central pressure to be 890mb.

PAGASA's Tacloban Station recorded 955.63hPa at 7:15am local time... the other station in Dulag gave up an hour before Tacloban did and it was already running 10hPa lower than Tacloba's readings...

I'll try to adjust based on that. Will change the equation again, using a 946mb peripheral pressure at 2215, center about 30 nm away.

[CrazyC83]

Using the Schloemer equation from Dulag:

At 2215 UTC (landfall was at 0000 UTC, center was about 30 nm away), the pressure was recorded at 946mb in Dulag.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(946 - Po) / (1015 - Po) = e^(-25/30) = e^(-0.8333) = 0.4346

Using the calculator to try to find Po, I find the best fit for the central pressure to be 891mb.

[CrazyC83]

Given that calculation and the factors I considered, the pressure at about 2200 UTC was likely about 891mb. It likely peaked around 1800 UTC, and was a bit stronger then - so the minimum central pressure was likely around 888mb.

[phwxenthusiast]

Given that calculation and the factors I considered, the pressure at about 2200 UTC was likely about 891mb. It likely peaked around 1800 UTC, and was a bit stronger then - so the minimum central pressure was likely around 888mb.

Thank you for the calculation! You learn something new everyday around here...

[Alyono]

You sure the eye was 35 NM south of Tecloman? The RMW also was not 10NM from Tecloman, it was closer to 5 NM. Think your numbers are a little off, which can lead to a major change in the output of your equation (you're assuming a 50NM wide eye and it was NOT close to a full degree wide)

Did you get km and NM mixed up?

[cycloneye]

The final epilog for what was an historic cyclone named Haiyan (Yolanda) as JTWC issues the final warning.

[CrazyC83]

You sure the eye was 35 NM south of Tecloman? The RMW also was not 10NM from Tecloman, it was closer to 5 NM. Think your numbers are a little off, which can lead to a major change in the output of your equation (you're assuming a 50NM wide eye and it was NOT close to a full degree wide)

Did you get km and NM mixed up?

Those were used at the time of the measurements (in that case, the eye was well to the east-southeast) - and in the case of Dulag, the measurement was about 1 hour and 30 minutes before landfall, while at Tacloban, it was about 45 minutes before landfall.

[CrazyC83]

pressure data from Tacloban indicate that the pressure at landfall was nowhere near as low as was Tip. May not have been sub 900.

However, lets remeber that low latitude storms have higher pressures for extreme winds. See the Felix 160+ SFMR at 930mb

What this does say, it is high time to blow up the WPAC pressure to wind relation. For starters, the data used to derive that relation is so highly suspect as I believe it is based upon ESTIMATES from recon and not mesured winds. This and Megi have showed that the extreme wind speeds often occur with pressures similar to those found in Atlantic hurricanes

I notice storms at low latitude are smaller. The further north or south (Southern Hemisphere), they get larger.

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 35 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/35) = e^(-0.7143) = 0.4895

Using the calculator to try to find Po, I find the best fit for the central pressure to be 901mb.

Looking at Haiyan, it was quite a tightly wounded storm, more so than Katrina. I see those type of storms more in the West Pacific, where the typhoon is almost a perfect circle. How did you figure out RMW?

The eye looked to be about 35 miles wide and then added the eyewall to result in my estimate of a 25 nautical mile RMW. (Katrina had a larger RMW, about 35 nautical miles.)

[Ptarmigan]

The eye looked to be about 35 miles wide and then added the eyewall to result in my estimate of a 25 nautical mile RMW. (Katrina had a larger RMW, about 35 nautical miles.)

I would guess the RMW is related to size of the eye.

[CrazyC83]

1015 is quite high for an outermost closed isobar, especially in the Pacific, but I went with a higher number due to the ridge nearby.

If 891 was used as a central pressure at 2200 UTC, using Atlantic pressure-wind relationships, the Brown et. al. relationships are 165 kt and 162 kt for a strengthening storm and a steady-state storm at low latitudes, respectively (164 kt as a blend of the data). Adding 5 kt for a fast translational speed results in an estimate of 169 kt - estimated intensity at that time would be 170 kt, well in line with the Dvorak estimates (it was likely slightly stronger earlier).

[Alyono]

pressure data from Tacloban indicate that the pressure at landfall was nowhere near as low as was Tip. May not have been sub 900.

However, lets remeber that low latitude storms have higher pressures for extreme winds. See the Felix 160+ SFMR at 930mb

What this does say, it is high time to blow up the WPAC pressure to wind relation. For starters, the data used to derive that relation is so highly suspect as I believe it is based upon ESTIMATES from recon and not mesured winds. This and Megi have showed that the extreme wind speeds often occur with pressures similar to those found in Atlantic hurricanes

I notice storms at low latitude are smaller. The further north or south (Southern Hemisphere), they get larger.

Using the Schloemer equation:

At 2300 UTC (landfall was at 0000 UTC well to the south, center was about 35 nm away), the pressure was unofficially recorded at 957mb in Tacloban.

The RMW appeared to be 25 nm in size and the OCI pressure I am going to estimate at 1015mb (due to the ridge to the north). That leads to the following:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(957 - Po) / (1015 - Po) = e^(-25/35) = e^(-0.7143) = 0.4895

Using the calculator to try to find Po, I find the best fit for the central pressure to be 901mb.

Looking at Haiyan, it was quite a tightly wounded storm, more so than Katrina. I see those type of storms more in the West Pacific, where the typhoon is almost a perfect circle. How did you figure out RMW?

The eye looked to be about 35 miles wide and then added the eyewall to result in my estimate of a 25 nautical mile RMW. (Katrina had a larger RMW, about 35 nautical miles.)

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

[CrazyC83]

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[/quote]

I thought the eye was larger? I could try some other calculations to get a more reliable estimate. I'll use 10 nm and 15 nm to try to create additional estimates.

[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

I thought the eye was larger? I could try some other calculations to get a more reliable estimate. I'll use 10 nm and 15 nm to try to create additional estimates.[/quote]

I'd use 12NM and 12 NM (however, shouldn't those be in terms of KM in the equation?)

[CrazyC83]

I will try with those numbers (12 and 12). Using 30 and 10 or 15 creates an insanely low pressure.

[CrazyC83]

Using the recommended numbers by Alyono:

(PR - Po) / (Pn - Po) = e^(-RMW/R)

(946 - Po) / (1015 - Po) = e^(-12/12) = e^(-1.000) = 0.3679

Using those numbers, my estimated pressure at 2200 UTC is 906mb, which seems more reasonable than the numbers I was getting with greater distances. All things considered, it was probably close to 900 (on either side) given the error margins. Clearly nowhere near Tip's record.

[Alyono]

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

[gigabite]

New moon eclipse Nov 3 2013 12 h 50m utc same date for the initiation for this, just a coincidence.