Severe Tropical Cyclone Monica

[Mark Farnik]

Wow, and I was just guesstimating Monica's track given her previous movements! :blink: How weird is that? Right now Monica is as strong as Hurricane Katrina was at her strongest, with central pressure of 905 mb. With that recent flare of convection around the eyewall I wouldn't be surpised if Monica's sustained winds are in the 150-155 knot range. If Monica continues on her forecast path and maintains her forecast intensity, she should pass directly over or just south of Darwin as a 130 knot strong Cat 4 (US) cyclone with gusts to 160 knots. This could be a very dangerous and devastating situation for Darwin. I wouldn't be suprised to see destruction on a similar level of that caused by infamous Cyclone Tracy which devasted that city on Christmas Eve 1974 if the front right quadrant of Monica's core passes directly over the city (which it very well may do) and Darwin is considerably bigger now that it was in 1974 (only 43,500 in 1974 versus 109,438 today) so there is a lot more real estate for Monica to destroy and a lot more lives at risk. Also Monica is a MUCH larger storm than Tracy. Tracy was the smallest tropical cyclone on record with gale force winds only extending out 48 km(30 miles) from the center. Monica absolutely dwarfs Tracy in size. Gale force winds extend out 120 nm from the center! :blink: About the only good news is that after Tracy Darwin revised its building codes significantly, so at least the buildings that have been built since Tracy have been built with cyclone survivability in mind.
I think they need to issue an evacuation order for low lying areas and tell residents to either head east out of the path of the storm or move into shelters in substantial structures for those who don't want to or can't evacuate. Monica is a very dangerous storm and I hope the Darwin BoM and the Australian goverment take proper measures to ensure that the residents are either out of harms way or can seek safety in shelters.

 

[Josh Morgerman]

Mark, you have some kind of magical skill at track prediction.

Re: the threat to Darwin... The latest JTWC track (below) shows the center passing close to Darwin in less than 48 hours with winds of 130 kt-- really quite extreme! It's odd, though, that this forecast does not show any weakening during the 12 hours between a fourth landfall near Point Stuart (00Z 04.25) and its closest approach to Darwin (12Z 04.25). Since the center would be over land during this time, I don't quite understand that. I am no pro meteorologist, but I would be surprised to see a system maintain 130-kt winds during a 12-hour trek over land. Odd!

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Re: Cyclone Tracy 1974... What a curious little storm it was! The landfall pressure of 950 mb was hardly record-breaking, but I believe the freakishly small size of the system (that Mark mentioned above) made for an extremely tight pressure gradient that caused the ferocious winds that destroyed 70% of the city. The satellite photo shows how small Tracy was; the other pic illustrates the spectacular wind damage in Darwin.

(Tracy reminds me a bit of Charley 2004 at its Florida landfall. It, too, was a very small system that caused surprisingly high winds (130 kt) for its landfall pressure (941 mb).)

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[MClarkson]

without aircraft recon, there is no way to know what the central pressure is. the sat estimates could be off either way. Regardless, this is a very impressive cat 5.

EDIT: I would also expect signficant weakening as it crosses land before reaching darwin. however assuming the pressure is somewhere below 890mb... it can weaken a lot and still be strong.

 

[Josh Morgerman]

Interesting, check out the flare in intensity as viewed from CIMMS microwave imaging:
http://cimss.ssec.wisc.edu/tropic/real-tim...fsBy12hr_08.gif
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Wow, Scott, that loop is a great find. That eyewall almost doesn't look real-- it's so perfect, it looks machine-generated.

That flare-up is very interesting. Given the timing of it, I wonder if interaction with the Wessel Islands had anything to do with it-- since the convection deepens just as the center is crossing the island chain.

Those islands must have gotten raked!

 

[Scott Olson]

I've seen some flare-ups before but not many that showed what appeared to be almost a 2x increase in forward motion. The eye shows fast warming and cloud brightness goes signfiicantly up. As for the Dvorak AODT from CIMMS (which isn't as accurate as the two non-public versions) I've seen it under-estimate more often than it has over-estimated, at least in the Atlantic Basin. It doesn't do well in any rapid fluctuations but it usually is within 20mb or 30kts of the offical estimates from Recon (sometimes alot more and sometimes less). For contrast here is Hurricane Wilma during it's peak strength vs. Monica using the AODT Dvorak anaylsis site.


WILMA: 6CI 927mb 115kts Eye temp: 15.88C Cloud Temp: -64C
MONICA: 8CI 868mb 170kts Eye Temp: 19.8C Cloud Temp: -81.2C

Obviously it did pretty bad with Wilma, which is not suprising because of the incredible rate that Wilma deepend. Even with all that said the Dvorak IR/ VIS appearance is exactly what you would expect from a violent Hurricane. I can't remember seeing the CI max out for so long.

Here is a picture of Monica taken sometime today that I have enhanced a bit:

 

[Andy Wehrle]

Geez, I thought it was just the U.S. Gulf Coast that Nature had it out for. What’d you Aussies do to get on her bad side? :blink:

 

[Josh Morgerman]

INTENSITY
As usual, there are slightly conflicting signals between JTWC and BoM, probably due simply to the fact that JTWC only updates every 12 hours. The JTWC intensity has edged up, but the BoM intensity (based on central pressure) has simply held steady after filling a little since yesterday. JTWC currently indicates a spectacular 155 kt 1-min sustained wind! BoM indicates 915 mb and 350 km/hr (189 kt/218 mph) max gusts. Both agencies indicate a solid Cat 5 (AUS/USA) storm.

Both forecast tracks bring the center generally WSW to near Darwin as a weakened-- but still substantial-- cyclone in about 24 hours. The JTWC has the storm at 100 kt at its closest approach to Darwin; the Australian BoM has the storm as a Cat 3 AUS (high-end Cat 1/Cat 2 USA).

The precise intensity as the inner core approaches Darwin will depend largely on land interaction-- which in turn depends on the track.

TRACK
The JTWC track (below) has the cyclone making landfall around Maningrida as a 140-kt system and staying inland all the way to Darwin-- about 18 hours later. The BoM has the track curving poleward more gradually, and therefore reemerging over the Van Diemen Gulf before approaching the Darwin area. I think this track would be more threatening, as the reemergence over water will help the cyclone maintain its intensity as the inner core approaches the city.

CONCLUSION
Given that there will be significant land interaction before the system reaches Darwin, my gut feeling is that the BoM's more conservative forecast for the Darwin-area intensity seems more realistic.

Note: This image will dynamically update and will no longer reflect the above commentary when the next warning graphic is issued.

 

[Josh Morgerman]

Judging from the latest satellite imagery, Monica seems to be making its third landfall somewhere between Junction Bay and Maningrida. Maningrida is just left of the center-- on the stronger side-- and is most certainly experiencing extremely severe conditions right now. This landfall point is a little sooner and a little further E than previously forecast-- cetainly some good news for Darwin.

The very latest JTWC warning still estimates intensity at an amazing 155 kt, with the center just offshore the Arnhem Land.

The new projected track curves even more abruptly poleward, meaning 1) the system does not come as near to Darwin and 2) it has more time over land before its point of closest approach to the city. Additionally, this track keeps Darwin outside of the intense inner core and on the weaker side of the system, which-- according to this-- should have winds somewhere between 115 kt and 90 kt at its point of closest approach. Inland towns such as Adelaide River and Pine Creek are more directly threatened.

Note: This image will dynamically update and will no longer reflect the above commentary when the next warning graphic is issued.

 

[Michael Thompson]

You should be able to read some first hand accounts in about 12 hours on this board

http://www.weatherzone.com.au/cgi-bin/ulti...?ubb=forum;f=12

Just a warning there is a lot of noise and chatter, but some good stuff in between the junk.

We have a few enthusiasts in Darwin so there should be pictures with luck.

Michael

 

[Josh Morgerman]

You should be able to read some first hand accounts in about 12 hours on this board

http://www.weatherzone.com.au/cgi-bin/ulti...?ubb=forum;f=12

Just a warning there is a lot of noise and chatter, but some good stuff in between the junk.

We have a few enthusiasts in Darwin so there should be pictures with luck.

Michael
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Hey, thanks, Michael! I did find some interesting stuff in there, including a link to the observations from Maningrida Airport, which appeared-- based on visible satellite imagery-- to be extremely close to the center as it came ashore.

http://www.bom.gov.au/products/IDD60701/IDD60701.95142.shtml

Monica's wind field must have been very tight, because the highest 10-min wind on this table is only 51 kt and the highest gust 80 kt-- at about the time of the lowest pressure (986 mb)! Data such as these suggest Maningrida was clearly outside of the eyewall-- although I was so sure it was getting mega-raked when I looked on the visible satellite shots. Puzzling!

THE LATEST
Monica made landfall several hours ago and is moving WSW over the Arnhem Land toward the general Darwin area.

As of 10 pm (local time), the central pressure is 935 mb and max gusts are way down to 260 km/hr (140 kt/162 mph)-- now a Cat 4 AUS. The system has filled a bit and will continue to do do-- however, the BoM indicates it could be a Cat 3 AUS (high-end Cat 1/Cat 2 USA) when it reaches the Darwin area, where max gusts of 175 km/hr (95 kt/109 mph) are expected.

Darwin will not experience another Tracy-- but it may experience some significant effects.

 

[Josh Morgerman]

Monica has unraveled as quickly and dramatically as it spun up!

The JTWC has it at 40 kt and disintegrating over the Arnhem Land... The BoM is more charitable, calling it a Cat 2 cyclone (AUS) with max gusts of 125 km/hr (68 kt/78 mph) and a pressure of 980 mb. By USA standards, it's definitely not a hurricane anymore.

A truly spectacular demise-- like watching the Wicked Witch melt away!

 

[Josh Morgerman]

This is like the cheap horror flick, when the supposedly slain murderer leaps up to begin one last round of mayhem:

Overnight, Monica unraveled to a mere tropical low. However, it also turned more WNW and is now reemerging over the Timor Sea near Darwin. The BoM calls for reintensification as it moves SW toward the Kimberley coast for a fourth landfall.

P.S. The BoM is not predicting any explosive deepening-- right now suggesting that gusts could possibly reach 150 km/hr (81 kt/93 mph) along the Kimberley coast tomorrow-- Cat 2 AUS. I just wanted to add that to nip any weenie rumors in the bud.

 

[Josh Morgerman]

The Australian BoM in Darwin has published an initial estimate Re: Severe Tropical Cyclone Monica's landfall intensity in the Northern Territory. They say Monica was the strongest tropical cyclone on record to affect the Northern Territory, with higher winds than Tracy 1974.

The following data refers specifically to landfall No. 3. Note that all estimates are preliminary and subject to change:

Time: 8 pm 24 April
Location: Junction Bay, 37 km WNW of Maningrida
Category: 5
Central Pressure: 905 mb
Sustained Wind: 250 km/hr (135 kt/155 mph)
Max Gusts: 350 km/hr (189 kt/218 mph)

Keep in mind that the Aussies use a 10-min averaging period to express a sustained wind. Using a standard conversion factor of 1.15, their 10-min wind of 135 kt equals a 1-min wind of 155 kt-- which, if correct, makes Monica a solid Cat 5 on the USA scale at the time of this landfall. This is higher than Andrew 1992's estimated 145 kt at its Florida landfall.

They don't mention landfall No. 2, when the center crossed over the Wessel Islands. Monica was stronger during this landfall, so hopefully they'll provide an intensity estimate for this at a later date.

Also, they don't yet address the storm's maximum intensity over water, which-- as you'll remember-- was the subject of some controversy, as satellite intensity estimates suggested (probably erroneously) that Monica's pressure dipped lower than Super Typhoon Tip's 870 mb (1979).

You can see the brief memo, along with the official track, here: http://www.bom.gov.au/announcements/sevwx/...c20060417.shtml