Differences in wind speed between v02 and v03

[Grant, Hazel]

Firstly, thanks so much for the work you do to create and maintain the IBTrACS data, we rely on it greatly for identifying cyclonic and non-cyclonic distributions for metocean criteria. We are still in the process of updating our scripts to deal fully with the v3 data and I have a few questions. We use the extended csv data for all stations (rather than just the WMO sanctioned ones) and are interested in trying to make the wind speeds more consistent between stations for plotting and comparison with model data.

 

1. Regarding Latitude and Longitude, what are the different sources for Latitude (deg_north), Longitude (deg_east) versus Latitude_for_mapping (degrees_north), Longitude_for_mapping (degrees_east)? Looking back at v02 data, the previous lat/lon correspond to the mapping versions. I thought one might be the average of all stations and the other the average of only the WMO-sanctioned but this doesn't seem to be the case.

 

2. Under the FAQ of 'Why does IBTrACS differ from HURDAT (or data from other agencies)?' for v02r01 and earlier, it is stated that JTWC provides data as 1-minute and (for v02) winds were converted to 10-min using a factor of 0.88. Is it right however that the MSW is  calculated from 10-min means, but the individual agency data provided is not corrected to 10-min means? For example, comparing v02 and v03 data for JTWC_SH for storm INGRID in March 2005 shows that the wind speeds are the same, even though the v03 winds should be 1-min means, therefore v02 winds for JTWC_SH are also 1-min means.

Also it states that the IBTrACS maximum sustained winds (MSW) is an average from all available agencies, but surely MSW_max is the maximum of all available agencies? This is what it appears to be (and if so, we will calculate something similar from the v03 data once we do some corrections).

 

3. Are the winds in ds824.1 presented as 1-min means? I couldn't find this information on the IBTrACS website or elsewhere. Also what about the Neumann dataset, ATCF, mlc_natl (not sure what this is anyway?), NCDC's DSI-9635 and DSI-9636?

 

4. More data is occasionally available for some cyclones at <6hr resolution (i.e. on the 3-hrly intervals). However there is lat and lon and WMO max wind, there doesn't seem to be any information from any of the centers, even WMO ones! For example INGRID has a record 06-Mar-2005 03:00 with a Wind(WMO) of 45kts but nothing in the subsequent columns. Why is this, and where do the numbers come from for lat/lon and Wind(WMO)?

 

Sorry for all the questions! But it will be extremely helpful in knowing the difference in what we were plotting previously and what we want to plot with the v03 data.

Many thanks.

 

Kind Regards,

Fugro GEOS Ltd.

 

Dr Hazel Grant

Senior Oceanographer

 

T +44 (0)1491 820533 | F +44 (0)1491 820599

h.g...@fugro.com | www.fugro.com

Fugro House, Hithercroft Road, Wallingford, OX10 9RB, UK

Company Registration No. 2985431 | VAT No. GB 655 4756 06

 

[hazyda...@gmail.com]

Hi,

I wonder if it would be possible to get an answer to this particular questions as it is most vital:

What are the original wind averages of the following datasets:

The Neumann dataset, ds824.1 , ATCF, and NCDC's DSI-9635 and DSI-9636.

We are also very interested in the following, but it's not so vital:

Regarding Latitude and Longitude, what are the different sources for Latitude (deg_north), Longitude (deg_east) versus Latitude_for_mapping (degrees_north), Longitude_for_mapping (degrees_east)?

Many thanks

Hazel

[Ken Knapp - NOAA Federal]

Hi

Please see my responses below.

On Fri, Jul 1, 2016 at 6:54 AM, <hazyda...@gmail.com> wrote: 

What are the original wind averages of the following datasets:

The Neumann dataset, ds824.1 , ATCF, and NCDC's DSI-9635 and DSI-9636.

Neumann - As far as I know, he converted observations to 1 min.

ds824.1 - 1 min.

ATCF - 1 minute (only source is NOAA, which is 1 minute)

NCDC's 9635 - 1-min. (only source of this data was from JTWC data, so is 1-min)

DSI 9636 - This is interesting. From the documentation: The value is "Estimated highest wind speed in knots at the time indicated by the ID. This field is used only for data from the N Atlantic (about 1899 onward), N Pacific (1945 onward) and Australian region (1956 onward). These estimates are necessarily subjective and must be interpreted with caution."

So it appears that 9636 are a mix of values since they have various sources for intensity, but those listed (N Atl, N Pac) are 1 min and the Australian region are 10-min.

Also, another interesting comment from the documentation: "It must be emphasized that for all early periods, no matter the source, many of the positions and intensities were deduced through estimates and compromise among various reports using synoptic and climatological judgment."

However, these data are so old, that I agree with the documentation, use intensities from 9636 with caution.

 

We are also very interested in the following, but it's not so vital:

Regarding Latitude and Longitude, what are the different sources for Latitude (deg_north), Longitude (deg_east) versus Latitude_for_mapping (degrees_north), Longitude_for_mapping (degrees_east)?

Lat/Long are usually from one agency - in most cases, the WMO responsible agency (e.g., the Hurricane Center for the north Atlantic). This can be "missing" when the WMO responsible agency doesn't report on a storm.

The lat/long_for_mapping are a mean position of the system from all available agencies reporting the system. This value will never be listed as "missing" since a position from at least one agency will always be possible.

Hope this helps-

-Ken

--

Ken Knapp, Ph.D.

Meteorologist, Center for Weather and Climate

NOAA National Centers for Environmental Information

formerly NOAA’s National Climatic Data Center

E/NE31

151 Patton Ave
Asheville, NC 28801
828-271-4339 (voice) 828-271-4328 (fax)
http://www.cyclonecenter.org/ where your clicks count!

"Leave this world a little better than you found it."
                             ---Baden-Powell's Last Message (1945)

Disclaimer:
The opinions expressed in this email are those of the author. They do not necessarily reflect the official views or policies of NOAA, Department of Commerce, or the US Government.