How strong was Monica?

By: Dr. Jeff Masters , 4:48 AM GMT on April 25, 2006

Cyclone Monica has come and gone. Fortunately, the storm hit a very sparsely populated area. There no reports of deaths or injuries, and damage was light. Darwin, the capital of the Northern Territory, received just tropical storm-force winds. With Monica's departure, we are left puzzling over an important question--how strong was she? The Navy Research Lab, using a satellite intensity estimation technique called the "Dvorak Technique", rated Monica as the strongest cyclone ever recorded in the Southern Hemisphere, with a central pressure of 879 mb and 180 mph sustained winds. However, the Australian Bureau of Meteorology (BOM) rated Monica a much weaker storm, with a central pressure of 915 mb at that time. Curiously, the BOM give Monica a 905 mb pressure 12 hours earlier, at a time when the Navy Research Lab had her much weaker--892 mb.

Figure 1. Cyclone Monica at peak intensity at 0130 GMT April 24, 2006, the strongest storm in Southern Hemisphere history--180 mph sustatined winds, and a 879 mb pressure. Or was she 915 mb?? Image credit: Navy Research Lab.

So who's right? Well, today I was in the right place to find out! I am attending the American Meteorological Society's 27th annual conference on hurricanes in Monterey, California all week, and I had the opportunity to talk to an Australian hurricane expert. Bruce Harper of Systems Engineering Australia Pty Ltd in Brisbane, Australia, gave a talk titled, "On the importance of reviewing historical tropical cyclone intensities," and I had the opportunity after his talk to ask him about Monica. He told me that hurricane forecasters in eastern Australia, the North Pacific, and Atlantic all use a uniform technique for estimating pressure of tropical cyclones from satellite imagery, but the western Australian forecasters use a different set of equations for that ocean region. These region-specific equations were developed to better model the small and intense cyclones that typically affect the area, such as Tropical Cyclone Tracy of 1974. The equations were not developed with much data from large and intense Category 5 storms, and so the 915 mb pressure estimate for Monica is suspect.

In reality, we will never know just how strong Monica was. There are no hurricane hunter airplanes anywhere but the Atlantic. Satellite estimation techniques are getting better each year, but are still subject to large errors. Scientists who are researching the link between hurricanes and global warming are free to use either intensity estimate for Monica's lowest pressure. This underscores the difficulty of assigning much credence to the reported 80% increase in Category 4 and 5 hurricanes globally since 1970 reported by Peter Webster and Greg Holland last year in their controversial article in Science. While I do believe there has been some increase in these storms, the estimation of maximum cyclone intensities is so fraught with uncertainties that I do not believe a reliable estimate of how significant this increase can be done until a full re-analysis of all historical tropical cyclones is completed. Even then, I think we need at least another ten years of data, since our data set covers such a short period of time.

Jeff Masters

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131. cycloone
1:46 AM GMT on November 15, 2008
Monica was stronger than Tip
Member Since: March 2, 2003 Posts: 65 Comments: 1009
130. CybrTeddy
11:41 AM GMT on October 12, 2006
2006APR24 003300 8.0 868.5/ +10.5 /170.0 8.0 8.0 8.0 8.0 NO LIMIT OFF 9.75 -80.54 EYE/C 20 IR -11.46 -135.07 COMBO
Member Since: July 8, 2005 Posts: 259 Comments: 26100
129. Inyo
3:51 AM GMT on April 27, 2006
Lightning10, when i was driving home from work on the 210 around La Canada Flintridge i saw one massive lightning bold splatter across the sky and apparently hit the ground a few miles in front of me. I didn't see any other lightning, although it did rain a bit.. big drops, wouldnt be surprised if someone got hail. Perhaps we will get more tonight but it doesnt look immediate.
Member Since: September 3, 2002 Posts: 42 Comments: 932
128. Scotth
3:19 AM GMT on April 27, 2006
Are we having an effect on the environment? You betcha we are. Is it going to "ruin" our world?...I don't think so. Hey, who to say these changes...if they ever Do come...won't result in great technological advances....or new species, since all the doomsayers have significant species dying off. Significant species have been dying off since this world began. And new species have always taken their place. Cycles...its what this Earth is all about.

Rule #1 - The Lord giveth...and the Lord taketh away.

Rule #2 - WE are not going to change rule #1.

Member Since: August 4, 2004 Posts: 0 Comments: 23
127. Scotth
3:09 AM GMT on April 27, 2006
I don't know windsurfer. I have spent the week in Madison, WI and, for the end of April, its awfully chilly. It was 31 degrees last night! As for your twins (may God bless them both), what severe consequences do you think they will be facing? Who's to say they will suffer from this. No one knows what these "changes", if that's what they are, will change things for the worse. I also think that we tend to look at our little part of the world and disregard the other parts of the world that have seen incredible cold this past winter. Of course, with that comment comes everyone out of the woodwork to say that the Earth has seen a 1 degree temperature change! WOW! A whole degree. Why do we think that is such a big deal? The hurricanes?...cyclic. And we are in the active cycle. seems to me that our hurricane count WOULD go up if we're in the active phase.
Member Since: August 4, 2004 Posts: 0 Comments: 23
126. grayingwindsurfer
2:45 AM GMT on April 27, 2006
Regarding global warming:
The earth has been warming, more or less, since the end of the last ice age ~10,000 years ago. It is difficult to prove that the arctic melting, earlier springtimes, etc. are anthropegenic. Also, because there is naturally large variability in weather from year to year, the relatively small increases in average temperature (1 degree F)are hard to definitively link to human-induced climate change.
I think the data show the RATE of warming has increased and global, not local, averages appear to be rising. I am personally confident that we are very significantly altering climate and my 5-year-old twins will suffer severe consequences throughout their lifetimes, worsened by slow reaction to a long-awaited threat. I am also confident that some portions of the ecosystem will thrive and that people will use technology to adapt, but not without perhaps significant problems.
Member Since: December 11, 2002 Posts: 1 Comments: 24
125. RL3AO
2:43 AM GMT on April 27, 2006
wow, 138,000 dead...
123. grayingwindsurfer
2:32 AM GMT on April 27, 2006
Is the appearance of a tropical cyclone in the North Indian Ocean in April unusual? Is this the 2nd tropical cyclone of the season in that basin? Thanks for any info.
Member Since: December 11, 2002 Posts: 1 Comments: 24
122. lightning10
2:24 AM GMT on April 27, 2006
Wow we just had a very nice Thunderstorm pass over the area. I didnt get pictures but it was very nice. Several Cloud to groud lightning strikes. I live in Whittier, CA

Scattered thunderstorms...some with brief heavy rain and possible small hail...will affect the Los Angeles County coast...and the San Fernando and San Gabriel valleys through 900 PM. As of 700 PM...Doppler weather radars indicated a thunderstorm near Burbank...and another one near Whittier. These thunderstorms were moving west at 30 mph. Additional showers and thunderstorms are possible through early this evening.
Member Since: November 24, 2005 Posts: 41 Comments: 630
121. ForecasterColby
2:10 AM GMT on April 27, 2006
Hmm - Sargasso Sea way colder, rest of atl similar, Gulf on FIRE...
120. Levi32
1:19 AM GMT on April 27, 2006
Snowfire here is the SST Anomaly and archives back to 1996. Link
Member Since: November 24, 2005 Posts: 635 Comments: 26780
119. ForecasterColby
12:27 AM GMT on April 27, 2006
Gippig, probably the closest thing to a subhurricane (that's what I'd call them) would be a warm-cored blizzard. It happens sometimes when they move NE over the Gulf Stream, though it's usually brief.

Epsilon wasn't really totally tropical, nor was Vince, so you might consider them subhurricanes.
118. Snowfire
9:55 PM GMT on April 26, 2006
Some comments about the latest SST anomalies:

-The Sargasso Sea is still cooler than normal. If this trend continues, it could be unexpected good news for the East Coast. Oddly, a thin ribbon of inshore water from about Jacksonville to the Chesapeake is much cooler than normal. More good news?

-Unless I misinterpret what I see, reports of La Niña's demise may be exaggerated. The area of cold water off equatorial South America seems to be expanding westward, if anything.

-The Caribbean is only slightly above normal, so far.

-The Gulf of Mexico has some real hot spots up by the coast, but most of the rest of it looks only slightly above normal.

I don't know how to find last year's map for comparison purposes.
Member Since: June 29, 2005 Posts: 24 Comments: 315
116. Mysticdog
9:32 PM GMT on April 26, 2006
Primez sez: "Here are my thoughts on the link between Global Warming and Atlantic Hurricanes: There isn't one.

It's impossible. Global Warming would be like an El Nino on a global scale. Wouldn't that mean that wind shear would increase in the Atlantic, DECREASING the number of storms, let alone intense hurricanes? The wind shear would rip them apart!"

Absolute temps and pressures don't make wind, relative temps and pressures make wind. Same with ocean currents. Its the differences between two places that drives mass.

Pressure differences and temperature differences go towards larger numbers as energy increases in a system.

We don't know what a Carribean or Gulf weather pattern will look like when its 5 degrees warmer in the water. They could set up a semi-permanent high. They could set up a greater variability in highs and lows, making stronger winds and stronger "regular" storms. The could shift around based on what land and water around them does, or whether big polar masses penetrate further south (again because the difference between high and low pressure systems is greater).

You can bet that the effects of global warming will first be seen at the extremes of our climates and weather, because changes at the bounds of systems are almost always the most visible. You can see that now in the loss of cold habitats, and the growth of hot habitats, the deeper penetrations of artic air south, the reciprocal penetrations of warm air into the articm, and the stronger storms.

Global warming naysayers remind me of Bagdad Bob. I imagine them hunkering in their home with 160 mph winds ripping the roof off screaming above the storm "There is no evidence this storm is any stronger than storms 40 years ago! This is a lie perpetrated by fatcat meteorologists trying to dig up more taxpayer money!"
115. Levi32
9:19 PM GMT on April 26, 2006
gippig you can visit the developer's blog and tell Aaron your suggestion on the reporting problem. He is the one that makes changes and upgrades on this site.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
113. Trouper415
9:14 PM GMT on April 26, 2006
I wonder what the SSTs were like during the dust bowls when temps as far north as North Dakota were 120 degrees at their peak.

Member Since: September 22, 2005 Posts: 5 Comments: 725
112. gippgig
9:10 PM GMT on April 26, 2006
There are subtropical depressions and subtropical storms. Are subtropical hurricanes possible? If not, why not? If so, have there been any?

I have seen a couple mentions of someone accidentally reporting as spam etc. Clicking on spam etc. should give an option of cancelling or going ahead with the report to avoid this problem.
Member Since: December 5, 2005 Posts: 0 Comments: 86
111. sayhuh
9:07 PM GMT on April 26, 2006
So its safe to say that since this is the first I have seen the blue..that the vorticity in this frame is likely stronger than I have seen in the past, or is it due to the proximity of the other vorticity nearby causing a sinking effect?
110. Levi32
9:04 PM GMT on April 26, 2006
sayhuh I am not sure but I think that hurricanes don't create a negative void because they are not baraclonic storms. They don't run on the same dynamics and they are uniform, that is, there is the most vorticity in the center of the storm and it doesn't need a negative to balance.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
109. sayhuh
9:01 PM GMT on April 26, 2006
Levi...I will have to research what that actually means..but thank you. I am curious to why I never saw that when looking at canes..seems the vorticity would be enough to create a negative void?
107. Levi32
8:55 PM GMT on April 26, 2006
sayhuh that blue represents the strong positive vorticity balancing the strong negative area of vorticity to its west.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
105. Levi32
8:53 PM GMT on April 26, 2006
Michael the maximum says 30.40 degrees Celsius. That is only just over 86 degrees F.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
104. sayhuh
8:52 PM GMT on April 26, 2006
Quick question all. In looking at this at the 72 hr frame, I notice blue shadings on the map near Oklahoma. I don't think I have ever seen blue on this map. What does it mean?
102. Levi32
8:42 PM GMT on April 26, 2006
Trouper I have that SST site already but thank you. I was asking which SST loop Colby was referring to.
Member Since: November 24, 2005 Posts: 635 Comments: 26780
101. Trouper415
8:31 PM GMT on April 26, 2006
Heres a link to the SSTs:

Image comparing 2006 SST to average:

Nice satellite image of Monica:
Member Since: September 22, 2005 Posts: 5 Comments: 725
99. Levi32
8:25 PM GMT on April 26, 2006
Colby could you post a link to the SST loop you are reffering too?
Member Since: November 24, 2005 Posts: 635 Comments: 26780
98. TampaSteve
8:23 PM GMT on April 26, 2006
Randyman wrote:
"Hopefully, this will provide you with a direct link...some good examples of what a hurricane is capable of doing..."

Yeah...that's a cool site...I have that video of Charley dismantling a gas station in Port Charlotte...160+ MPH winds...awesome!
Member Since: July 8, 2005 Posts: 1 Comments: 97
97. RL3AO
8:20 PM GMT on April 26, 2006
Hurricane Katrina, which tore onto the Louisiana and Mississippi coasts on August 29, was the deadliest Atlantic hurricane in 77 years and the costliest ever, with property damages estimated at $75 billion.

I think they forgot Hurricane Mitch; it should say "the deadliest U.S. hurricane in 77 years".

Your definatly right. Sadly, there's a storm in the Atlantic that kills more than Katrina ever 2 or 3 years it seems.

And it was mentioned above, but that doesn't look like a 879mb storm.

Another thing, I looked at some of the tracking maps from the 1880's and 1890's, and it seemed like alot of the storms were Cape Verde storms. Not many in the Caribbiean.
96. ForecasterColby
6:50 PM GMT on April 26, 2006
Check out the SST loop...really boiling now.
92. Trouper415
6:13 PM GMT on April 26, 2006
I have 4 questions. Thanks in advance for the answer.

How many hurricane does Australia average in a year?

How many hurricanes does the US average in a year?

What was the ratio of Atlantic catagory 4-5 hurricanes to the number of hurricanes this year?

What was the ratio of Australian catagory 4-5 hurricanes to the number of hurricanes this year?

Member Since: September 22, 2005 Posts: 5 Comments: 725
91. gcain
6:09 PM GMT on April 26, 2006
I would agree that "we can't kill the earth..." but we can alter the enviornment enough decrease our comfort level...For example, gas prices, insurance rates, building costs, immigration, food availability, etc. are all things that take resources out of our collective pocket. The supply of money is not limitless and each time of these factors cost us more, the money must come out of some other place...sooner or later life styles begin to erode. The erosion may not be as dramatic as "Final Days" or "Earthquake" or even "Storm Stories" but the standard of living for our children or grandchildren may be less because of what we do or don't do now...Is that the legacy that our generation wants..."They could have done something, but elected to do nothing because there was no absolute proof." That makes me uncomfortable.
90. swlaaggie
5:50 PM GMT on April 26, 2006
Hello everyone.

First time commenter but long time reader. This is a very educational site and one that I visit every day, especially living here in SW LA.

We are understandably a little nervous about the upcoming hurricane season given that many here are still repairing their properties from Rita.

I guess that I sense a bit of global warming frenzy/panic in many of the comments. I believe we are a bit early to make any finite conclusions other than to offer simple opinion. I will agree that the last few years have been extraordinary, especially 2005. Nevertheless, the good earth does tend to have a mind of her own and this isn't the first period of weather phenomena that illustrates her moodiness. It is only the latest and, unfortunately, it comes when the hot topic of debate is global warming and when we have a great deal more media coverage and hype.

As for me, I'll continue to ride the fence(at least the section I have left after last September) and hold my pro/con warming opinion while more data is acquired to truly support any of my future rhetoric.

Thanks for the opportunity to participate.
Member Since: April 26, 2006 Posts: 0 Comments: 1032
89. HurricaneMyles
5:05 PM GMT on April 26, 2006
Gotta love the media. They'll do anything to get themselves attention.

Also, if people are just now pandering the agenda of the major media angencies, then what have you been watching and reading? I haven't watched CNN, FOXNEWS, or MSNBC, or any of those in years because all they do is spout non-sense. They never have thier facts straight and always use a quick one liner for a story that makes the story itself seem absolutly abhorable. Then you realize that what the news agency meant by "WOMAN EATS KIDS" is that she ate goat kids(kid is the proper name for a goat baby)

Ok, so done with my rant about the media. There new story about the Global Warming link to the 2005 season is not surprising at all.
Member Since: January 12, 2006 Posts: 5 Comments: 827
88. SickOfDumbQuestions
1:24 PM GMT on April 26, 2006
I love this view presented by on their homepage as: "2005 hurricanes linked to global warming"

Wow... no real mention of the AMO or anything else, it panders to the agenda of the website as we can very well tell by reading the article. You have to love it.

86. Inyo
7:00 AM GMT on April 26, 2006
nah, the planet will be fine. some extinctions will occur, and the animals that suffer the greatest losses will be those highest on the food chain, such as humans. The roaches, coyotes, and rabbits will continue to run around.

That doesnt mean we should cause anthropomorphic greenhouse warming or other forms of pollution. It just means we can't 'kill the earth'
Member Since: September 3, 2002 Posts: 42 Comments: 932
84. Trouper415
6:30 AM GMT on April 26, 2006
Question about the coral. Pretty astonishing.

How good of track did we keep of coral before now? I'm wondering what the coral looked like after the last AMO cycle we had in the 1960s and if that as well killed of coral. Or is it the warming or the waters due to global warming that is the sole contributer to the killing of this specied?

Educate yourself on global warming and Educate your friends.

Member Since: September 22, 2005 Posts: 5 Comments: 725
83. Snowfire
12:41 AM GMT on April 26, 2006

Storms that pinhole dring their building stages, like Wilma most famously did, represent a special case. Such storms are typically evolving rapidly, and I find myself wondering whether the usual formulae relating pressure, flight-level winds, surface winds, and other such parameters are even valid in such cases, as they were calibrated with storms with larger eyes and in a more stable, slowly changing state (think Katrina, Rita, or Monica near peak intensity). Are we comparing apples and oranges?
Member Since: June 29, 2005 Posts: 24 Comments: 315
82. lightning10
12:18 AM GMT on April 26, 2006
Sigh I hope this isnt a preview of what we can expect for the Alantic Hurricane season.
Member Since: November 24, 2005 Posts: 41 Comments: 630
81. atmosweather
11:29 PM GMT on April 25, 2006
LOL FUMBLE. I would wait until the market slows down and then sell :)
Member Since: September 24, 2005 Posts: 33 Comments: 9265

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