Monica. Who got it closest?

[Rod Hagen]

I've just been listening to a discussion on our national broadcaster, ABC, in which a Darwin pundit was claiming that the US Navy Research Labs got Monica right and the Australian BOM got it wrong, when it came to the track of Monica.

THis seems to be based on the fact that people who evacuated Darwin and headed south kept on being told to head further south by the Authoritrie because the cyclone was tracking well to the south of Darwin, as suggested by the Navy site. Apparently many people are now saying that they will use the Navy projections next time rather than trusting BOM projections. THis worries me, if another one hits.

I don't think the interpretation is correct. The cyclone, as far as I can see, actually tracked very close to the BOM projection , and well to the north of the suggestions from the Navy site.

THe difference was really that BOM projections suggested a significantly greater strength than the Navy, in their later projections. The navy got the strength right , but the track wrong. As far as the track went BOM were really much closer to the mark.

Thoughts?

Cheers

Rod

[Matt-hurricanewatcher]

Wrong the Jtwc got the turn more right...In shown the track going about where it went while the BOM still shown it tracking back over water between that darwin in that island. So the JTWC was more right. Forecasted the track right before the cyclone made landfall.

[Aslkahuna]

Depends upon what you were tracking as it appears that the low level center did track close to Darwin and actually moved back out over water while the mid level center tracked inland.

Steve

[SouthFloridawx]

Well come on... if the cyclone would have moved over darwin the people would be thanking the BOM right now. Sounds like a bunch of media bull crap. Sorry bout that comment. But, seriously you should always listen to your local Meteorological souce for the best coverage and know how of what to do. Please if the cyclone such as Monica is threatening an area probably the best thing to do is get the people out who are in a surge and hi wind prone area. All standard evac plans apply whether you get the storm or not. heh look at rita and all those people in houston evac and didn't see the worst. But, ya know what? Taking a chance and staying is probably what some of the people who passed away along the gulf coast during Katrina, would be saying is not a good thing to do. IMO

[CycloneCarl]

After coastal crossing Monica continued WSW in line with the BoM forecast before curving WNW to pass just NNE of the city of Darwin, having dropped below cyclone intensity shortly before arriving (winds were still around 40 knots when the remnant eye-wall passed over Humpty Doo, SE of Darwin), and the LLCC proceeded out over water before stalling to the WNW of Darwin.

Visit this page to see a full set of daily animations of TC Monica whilst it was in radar range, which illustrate the track of TC Monica quite well - note the track on Darwin Radar on the 24th and 25th.

Personally, I think the BoM should be congratulated for doing such an outstanding job of warning the public in circumstances where a slight deviation in track made such a huge difference to the outcome.

[Matt-hurricanewatcher]

I'm sorry but the JTWC blew the Bom out of the water with them forecasting the southern turn 12 to 18 hours earlier. If the Bom where to be right it would of went back over that gulf as at least a cat3 on the Aussie scale. Yes it did turn back to the west then west-northwest but it was a remant when doing so.

[DoctorHurricane2003]

Just keep in mind that 99% of the time, BOM is right down there and JTWC is wrong.

Just because the *one* time JTWC did it better just happened, doesn't mean you should ignore all the other times that the BOM got it right.

[CycloneCarl]

Have a look at the set of BoM maps I've added to the TC Monica page below the links to the radar loops.

You will notice that the "southern turn" was at it's greatest approaching SW, and the system remained a tropical cyclone almost all the way to Darwin. You will also notice that in most cases the actual track was within the grey shaded uncertainty error of previous forecasts.

If I remember correctly, the only bit JTWC got about right in one warning was the coastal crossing point, and even then they had it continuing to curve more south a long way from the actual track - if anyone saved any of the relevant JTWC forecast maps, please email them to me and I will add them to the page.

[CycloneCarl]

I've now added the last four JTWC maps to the TC Monica page so you can see for yourselves the relative accuracy of the BoM and JTWC forecasts.

[CycloneCarl]

Here is a comparison of the last four JTWC warnings with BoM warnings for the same times. The actual BoM positions at the appropiate times are used to find the forecast differences.

Code: Select all

JTWC  | Position    | 12 hr        Diff          | 24 hr        Diff          |
dd hh | Lat   Lon   | Lat   Lon    Lat  Lon  Err | Lat   Lon    Lat  Lon  Err |
23 12 | 11.3  136.8 | 11.3  135.2  0.1  0.0  0.1 | 11.6  133.5  0.4  0.2  0.4 |
24 00 | 11.4  135.2 | 11.9  133.6  0.1  0.1  0.1 | 12.5  132.0  0.1  0.6  0.6 |
24 06 | 11.7  134.5 | 12.3  133.1  0.4  0.4  0.6 | 13.0  131.8  0.7  1.1  1.2 |
24 18 | 12.8  133.0 | 14.0  132.0  1.7  1.3  2.1 |                                 

BoM   | Position    | 12 hr        Diff          | 24 hr        Diff          |
dd hh | Lat   Lon   | Lat  Lon     Lat  Lon  Err | Lat   Lon    Lat  Lon  Err |
23 12 | 11.3  136.7 | 11.3  134.9  0.1  0.3  0.3 | 11.7  133.2  0.3  0.5  0.6 |
24 00 | 11.4  135.2 | 11.7  133.4  0.3  0.3  0.4 | 12.2  131.6  0.4  0.2  0.4 |
24 06 | 11.7  134.4 | 12.0  132.6  0.7  0.1  0.7 | 12.6  131.0  0.3  0.3  0.4 |
24 18 | 12.7  132.7 | 13.2  131.4  0.9  0.7  1.1 |                             



As you can see, there is variation from warning to warning for both agencies, with JTWC doing a little better earlier the BoM doing better later.

Of course, this sample is too small to be meaningful, however I may do a comparison of the full track when I get some time, as that would be a better sample size.

[Audrey2Katrina]

As you can see, there is variation from warning to warning for both agencies, with JTWC doing a little better earlier the BoM doing better later.

Seems to accurately sum it up.

A2K

[Supercell Hunters]

I think Monica is our very first category 6 storm? Looks like over top of the scale?

[Jim Cantore]

I think Monica is our very first category 6 storm? Looks like over top of the scale?

if 190mph and 870mb isnt a cat 6 then neither is this

[Audrey2Katrina]

I think Monica is our very first category 6 storm? Looks like over top of the scale?

if 190mph and 870mb isnt a cat 6 then neither is this

Nope, Wilma was Cat 7

A2K

[CycloneCarl]

I've done the complete JTWC and BoM tracks for TC Monica, and selected from the more frequent BoM warnings the ones that correspond with the times of the JTWC warnings for comparison - all times are UTC.

The table below shows the agency forecast position comparison results, showing differences in Lat, Long, and total position Error rounded to the nearest 10th of a degree. Actual BoM positions for the forecast times were used as references for all calculations.

Code: Select all

-----------------------------------------------------------------
|       | JTWC Forecast Error       | BoM Forecast Error        |
|       | 12 hr         24 hr       | 12 hr         24 hr       |
| dd hh | Lat Lon Err   Lat Lon Err | Lat Lon Err   Lat Lon Err |
-----------------------------------------------------------------
| 17 00 | 1.0 1.2 1.6   0.8 1.8 2.0 | 0.4 1.7 1.7   0.5 1.1 1.2 |
| 17 12 | 0.4 1.6 1.6   0.1 0.6 0.6 | 0.4 0.2 0.4   0.6 0.2 0.6 |
| 18 00 | 0.2 1.7 1.7   0.5 0.2 0.5 | 0.1 0.4 0.4   0.2 0.5 0.5 |
| 18 12 | 0.3 1.8 1.8   0.2 0.3 0.4 | 0.1 0.7 0.7   0.6 0.3 0.7 |
| 19 00 | 0.2 1.6 1.6   0.4 0.4 0.6 | 0.5 1.0 1.1   0.5 0.8 0.9 |
| 19 12 | 0.3 0.1 0.3   0.1 0.2 0.2 | 0.3 0.4 0.5   0.2 0.3 0.4 |
| 20 00 | 0.2 1.0 1.0   0.3 0.5 0.6 | 0.3 0.4 0.5   0.2 0.4 0.4 |
| 20 12 | 0.3 0.8 0.9   0.0 1.6 1.6 | 0.1 0.2 0.2   0.1 0.4 0.4 |
| 21 00 | 0.4 0.7 0.8   0.1 0.8 0.8 | 0.1 0.2 0.2   0.1 1.0 1.0 |
| 21 12 | 0.3 0.3 0.4   0.4 0.0 0.4 | 0.3 0.3 0.4   0.6 0.3 0.7 |
| 22 00 | 0.2 1.0 1.0   0.8 0.9 1.2 | 0.4 0.1 0.4   1.0 0.6 1.2 |
| 22 12 | 0.4 1.1 1.2   0.1 0.2 0.2 | 0.3 0.4 0.5   0.2 0.6 0.6 |
| 23 00 | 0.5 1.2 1.3   0.6 0.1 0.6 | 0.0 0.3 0.3   0.0 0.8 0.8 |
| 23 12 | 0.0 1.5 1.5   0.4 0.2 0.4 | 0.1 0.3 0.3   0.3 0.5 0.6 |
| 24 00 | 0.5 1.6 1.7   0.1 0.6 0.6 | 0.3 0.3 0.4   0.4 0.2 0.4 |
| 24 06 | 0.6 1.3 1.4   0.7 1.1 1.3 | 0.7 0.1 0.7   0.3 0.3 0.4 |
| 24 18 | 1.3 0.7 1.5               | 0.9 0.7 1.1               |
|       |                           |                           |
| Min   | 0.0 0.1 0.3   0.0 0.0 0.2 | 0.0 0.1 0.2   0.0 0.2 0.4 |
| Max   | 1.3 1.8 1.8   0.8 1.8 2.0 | 0.9 1.7 1.7   1.0 1.1 1.2 |
|       |                           |                           |
| Av    | 0.4 1.1 1.2   0.3 0.6 0.7 | 0.3 0.5 0.5   0.4 0.5 0.6 |
-----------------------------------------------------------------


The results show that both agencies had considerable variations in the accuracy of their forecasts for any particular warning, whilst overall the BoM performed far better for 12 hr positions and maginally better for 24 hr positions.

It should be noted that the unusual track and the size of some errors reveals that TC Monica was a difficult cyclone for any agency to forecast.