First Category 5 storm of the year is Choi-Wan

By: Dr. Jeff Masters , 1:38 PM GMT on September 16, 2009

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The remains of Hurricane Fred continue to generate sporadic bursts of heavy thunderstorm activity over the middle Atlantic Ocean. These thunderstorms were generating winds up to 30 mph, according to this morning's QuikSCAT pass. However, QuikSCAT also showed that the remains no longer have a surface circulation. Water vapor satellite loops show that ex-Fred has moved beneath an upper-level low pressure system. This low features dry air on all sides, and this dry air will interfere with any redevelopment of Fred. While wind shear is now moderate, 10 - 15 knots, and is expected to remain in the moderate range for the next five days, the presence of so much dry air will require at least three days for the remains of Fred to overcome and regenerate a surface circulation. Only the HWRF model redevelops Fred, predicting it will develop on Sunday as it approaches the Bahama Islands. NHC is giving ex-Fred a low (less than 30% chance) of developing into a tropical depression by Friday. Fred's remains will be near the Bahamas on Sunday, and near Florida on Monday night. It is possible that a strong trough of low pressure expected to develop over the eastern U.S. early next week will turn Fred's remains northwards into South Carolina/North Carolina on Monday/Tuesday.

This morning's QuikSCAT pass shows a surface circulation near 13N 32, with a small region of heavy thunderstorms to the north. This region is about 450 miles west of the Cape Verdes Islands, and is headed west at about 10 mph. Satellite imagery shows a decrease in the amount of heavy thunderstorm activity this morning, and high wind shear of 20 knots is interfering with development. A band of high wind shear lies just to the north of the disturbance, and will continue to interfere with the system's development over the next three days. NHC is giving the system a low (less than 30% chance) of developing into a tropical depression by Friday.

The GFS model is predicting development of a new tropical wave coming off the coast of Africa early next week.


Figure 1. The remains of Hurricane Fred (left) keep on chugging across the Atlantic. A tropical wave is 450 miles west of the Cape Verdes Islands (right). The thunderstorms of the Inter-Tropical Convergence Zone (ITCZ) are far to the south, off the coast of Africa.

Super Typhoon Choi-Wan hits Category 5 strength
This year's first Category 5 tropical cyclone is Super Typhoon Choi-Wan, which intensified into a Category 5 storm with 160 mph sustained winds yesterday afternoon. Choi-Wan is over the open ocean south of Japan, and is not expected to impact any land areas. It is unusual to have to the globe's first Category 5 storm form this late in the year. Indeed, global tropical cyclone activity as measured by the ACE index, which measures destructive potential, has been near historic lows over the past two years. Only one Category 5 storm was recorded in 2008--Super Typhoon Jangmi, which attained winds of 165 mph at 06 GMT on September 27, as it approached the north coast of Taiwan. The last time so few Category 5 storms were recorded globally was in 1974, when there were none.

We got a rare treat yesterday when the Cloudsat satellite caught a perfect cross section through Choi-Wan when it was a Category 4 super-typhoon with 150 mph winds (Figure 2). The CloudSat satellite, launched in 2006, carries the first satellite-based millimeter wavelength cloud radar. It is the world's most sensitive cloud-profiling radar, more than 1000 times more sensitive than current weather radars. It collects data about the vertical structure of clouds, including the quantities of liquid water and ice, and how clouds affect the amount of sunlight and terrestrial radiation that passes through the atmosphere. The satellite has a narrow field of view, so can image only a small portion of the planet each day. About once per year, CloudSat happens to slice through the eye of an Atlantic hurricane. This happened last month, when Cloudsat caught a remarkable view of Hurricane Bill.


Figure 2. Top: conventional visible satellite image of Super Typhoon Choi-Wan at 3:57 UTC Tuesday, 9/15/09 from Japan's MTSAT. Bottom: cross section through Choi-Wan's eye taken at the same time, from the CloudSat cloud radar instrument. The CloudSat pass occurs along the red line in the top image. The CloudSat pass runs from south (left side of CloudSat image) to north (right side of CloudSat image). At the time of the image, Choi-Wan was strengthening into a Category 4 Super Typhoon (150 mph winds, 928 mb pressure), and reached Category 5 strength fourteen hours after this image was taken. In the CloudSat image, one can see 6+ isolated towers, marking the positions of spiral bands on the south side of the center. The eye is remarkably well-defined, with symmetric "hot towers" extending up to 55,000 feet, sloping outward with height. The thin solid grey line at 5 km marks the 0°C temperature line. Ice particles falling inside the hurricane melt at an altitude just below the 0°C line, creating a "bright band" of orange echoes throughout most of the hurricane. This is one a few inner eye images CloudSat has captured of an Category 4/5 tropical cyclone. Image credit: NASA/Colorado State University/Navy Research Lab, Monterey.

Twenty years ago today
On September 16, 1989, Hurricane Hugo weakened slightly as it underwent an eyewall replacement cycle. The tight inner eyewall that we had flown through the previous day had contracted to the point where it became unstable and collapsed. A new eyewall formed out of an outer spiral band, and Hugo's highest winds dropped to 140 mph--Category 4 strength. As this was occurring, the storm began a more northwesterly path and slowed down, in response to a region of low pressure north of Puerto Rico. By midnight, Hugo was only an hour away from its first encounter with land--the Lesser Antilles island of Guadeloupe.

Back on Barbados, our one undamaged P-3 Orion Hurricane Hunter aircraft flew a mission into Hugo, while the crew of the damaged aircraft remained on the ground. Our plane was grounded until a team of experts from the mainland could fly out and perform a detailed x-ray analysis of the wings to determine if the high g-forces we endured had caused structural damage. This might take a week, so the plan was to fly us back to Miami on a commercial jet. However, Hugo had forced the cancellation of virtually every commercial flight in the eastern Caribbean that day, so we were stuck on the island. Most of us spent a frustrated day touring the island on rented mopeds, getting a look at Hugo from the ground. We got thoroughly drenched by one of Hugo's outermost spiral bands, but the hurricane was too far away to bring any winds more than 20 mph to the island.

That night, our already jangled nerves got a new jolt--a tropical depression had formed due east of Barbados, and was headed right for us. In two days time, it seemed likely that Tropical Storm Iris would be paying us a visit.


Figure 3. AVHRR visible satellite image of Hurricane Hugo taken on September 16, 1989. Image credit: Google Earth rendition of the NOAA HURSAT data base.

Jeff Masters

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Morning Everyone...checking in and it seems as though things have been pretty quiet so far.

Relatively warm out here today - thought perhaps we were having a Santa Ana yesterday since the winds were blowing pretty steady. No fires down this way though.
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159. JRRP
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Quoting Floodman:


You keep on asking and let them be upset...not really our problem if they have a board up their a$$, is it?

druseljic just posted a great link on the MJO; that should prertty much explain it to you...


Yeah I went to it and started reading it and just checked back here gonna go back and finish reading it. I wanted to say thanks to Druseljic i do appreciate it. Some of you all are very nice folks. That's why I love the WU Family.

Sheri
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Quoting nrtiwlnvragn:


You can keep up to date by reading the NCEP Synergy Meeting Highlights
Now you're scaring me. I read that already today, too.

Edit: Nope I take that back. That one's new to me. :) The one I read was the 08 summary.
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156. Skyepony (Mod)
jeffs~ Choi-wan looks like the best annular candidate we've seen in a while. Started off a little lopsided. Guess we'll have to see how he handles shear & cooler waters. Huge eye..
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Quoting AussieStorm:
Good Evening all.
Just wondering about Dr. Jeff Masters' Wunder Blog Title.....First Category 5 storm of the year is Choi-Wan. What about Severe Tropical Cyclone Hamish, Intensity: 215 km/h (130 mph) (10-min), 925 hPa (mbar)




Wasn't Hamish the 1st Cat 5 of the year????


Hamish was a CAT 4 and is now the 3rd strongest cyclone of the year behind Choi-Wan and Jimena
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Quoting P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.




I couldn't agree more but the problem is you have those on here who consider themselves self absorbed weather big shots who don't like persons having a different opinion then theirs so they have to give them such a name. Good luck trying to change that, they're pretty set in their ways!
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Good Evening all.
Just wondering about Dr. Jeff Masters' Wunder Blog Title.....First Category 5 storm of the year is Choi-Wan. What about Severe Tropical Cyclone Hamish, Intensity: 215 km/h (130 mph) (10-min), 925 hPa (mbar)




Wasn't Hamish the 1st Cat 5 of the year????

Note: In June 2009, Severe Tropical Cyclone Hamish was retired by the Bureau of Meteorology
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Quoting catastropheadjuster:


Thanks Flood, I try not to ask to many ?'s cause some get upset. But hey I am still learning. And yes I like your Funny.LOL

Sheri


You keep on asking and let them be upset...not really our problem if they have a board up their a$$, is it?

druseljic just posted a great link on the MJO; that should prertty much explain it to you...
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Quoting seminolesfan:
Thanks for chiming in nrti!
I looked at that page and didn't see it scheduled, but didn't post the link. Glad to know I wasn't too far off base and that I wasn't misremembering the anticipated update.


You can keep up to date by reading the NCEP Synergy Meeting Highlights
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150. Skyepony (Mod)
Quoting StormChaser81:
The AOI near PR might be working its way to the surface, you can see the vorticity on the 200 mb map.


It does show up well at 200mb.. That is the far upper levels. Is beginning to get some midlevel vorticity at 500mb.
500mb


Long ways to go in the lower levels.
850mb
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Quoting catastropheadjuster:
I'd like to ask a question and don't mean to sound dumb. But here we go What does the upward MJO mean? I mean what does it do to help develop anything or does it even do that?

Sheri


-

Here is a blog post from a while back that does a nice job of explaining the MJO
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Quoting BurnedAfterPosting:


vorticity has increased at the 500mb level, most of the vorticity is still in the upper levels, but I do see some indications that the ULL could slowly work to the surface


We'll have to watch in the 700mb range
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Quoting Floodman:


Sheri, darlin', you never sound stupid for asking a question...it sounds stupid when you ask the same question over and over again...just remember: Upward MJO can be a big mess, Downward MJO considerably less...hey, I made a funny! LOL


Thanks Flood, I try not to ask to many ?'s cause some get upset. But hey I am still learning. And yes I like your Funny.LOL

Sheri
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Quoting Skyepony:
I wish they did the Annular Hurricane index for the WPAC basin.. I don't think we've seen eyewall replacement one with Choi-wan.


I agree. I noticed how Choi-Wan's eye looked abnormally large for his overall size, and how circular his CDO looks...
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Quoting catastropheadjuster:


Hey Flood, Thanks Like i said a minute ago I couldn't figure it out. So how's your side of the world going? It's been so rainy here. Where leaving to go to Gainstown,Al Friday morning to go fishing in the bass club tournament, I hope it's not going to rain very much at least this weekend. It's only about 80 miles from the house but it's the first time in a while we been able to do something. The shop is very slow and we have been saving money well like in a peeny jar. LOL Have bologna sandwhiches and stuff like that. You know what I mean..

Sheri



Been pretty rainy here too, darlin'...and I know all about bologna sammiches...have fun fishin'!
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Quoting SQUAWK:
Sheri, stop making excuses for asking a question. Just ask the question. We already know you are not dumb.




Excuse me,I did ask the question.
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Quoting jipmg:


there is some weak vortocity at 700mb


Yes. Thereby the "really." ;)
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Present at 500 mb


Not so present at 700 mb
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141. jipmg
Quoting Seastep:


That's upper level. No real signs of working its way down atm. Only vorticity, really, is at 500-200mb. Nothing lower.


there is some weak vortocity at 700mb
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140. 789
Quoting StormW:
TROPICAL WEATHER SYNOPSIS SEPTEMBER 16, 2009 ISSUED 11:00 A.M. EDT
nice blog your going to be busy monitoring all that thanks again
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Quoting Floodman:


200mb is rather high in the atmosphere...waht you're looking at there is a ULL. If it were extending down to say 500 I would think it were trying to drop (or had the potential)


vorticity has increased at the 500mb level, most of the vorticity is still in the upper levels, but I do see some indications that the ULL could slowly work to the surface
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Quoting Grothar:


It should have read the most annoying and persistant. However, using a superlative in that context, would simply be acceptable by most teachers, since it was not meant to be a technical phrase contained in a dissertation. It is a double superlative using "most" preceding the "est" form of the adjective, which is never acceptable.

Grammar aside, I still like reed's blogs. If we were to correct each other's English, we would never get to discuss the weather.

Too bad most people do not understand when sentences are preceded with words like "might" and "could". It would prevent a lot of unnecessary arguments. They are modals auxiliary words intended to express possibility, not fact.


Wow, someone who understands the mechanics of our language! Welcome, friend!
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137. jipmg
Quoting Floodman:


200mb is rather high in the atmosphere...waht you're looking at there is a ULL. If it were extending down to say 500 I would think it were trying to drop (or had the potential)


well..

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8vor2.html
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Quoting nrtiwlnvragn:


HWRF update is 3rd in line and has not been scheduled yet.

2009 - CHANGES TO NCEP MODELS

It is after the RTOFS.
Thanks for chiming in nrti!
I looked at that page and didn't see it scheduled, but didn't post the link. Glad to know I wasn't too far off base and that I wasn't misremembering the anticipated update.
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Quoting StormChaser81:
The AOI near PR might be working its way to the surface, you can see the vorticity on the 200 mb map.


That's upper level. No real signs of working its way down atm. Only vorticity, really, is at 500-200mb. Nothing lower.
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Quoting Floodman:
\

An upward MJO (Madden-Julian Oscillation) is indicative of more energy and moisture in the atmosphere as well as more potential for distubances. It creates a more favorable environment for the development of tropical systems


Hey Flood, Thanks Like i said a minute ago I couldn't figure it out. So how's your side of the world going? It's been so rainy here. Where leaving to go to Gainstown,Al Friday morning to go fishing in the bass club tournament, I hope it's not going to rain very much at least this weekend. It's only about 80 miles from the house but it's the first time in a while we been able to do something. The shop is very slow and we have been saving money well like in a peeny jar. LOL Have bologna sandwhiches and stuff like that. You know what I mean..

Sheri

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Quoting StormChaser81:
The AOI near PR might be working its way to the surface, you can see the vorticity on the 200 mb map.


200mb is rather high in the atmosphere...what you're looking at there is a ULL. If it were extending down to say 500 I would think it were trying to drop (or had the potential)
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Quoting catastropheadjuster:


Thanks for answering my question. I couldn't figure it out and didn't want to sound stupid by asking.

Sheri


Sheri, darlin', you never sound stupid for asking a question...it sounds stupid when you ask the same question over and over again...just remember: Upward MJO can be a big mess, Downward MJO considerably less...hey, I made a funny! LOL
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Quoting StormChaser81:

Could there be development in the carribean?
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Quoting rwdobson:


Not sure...maybe someone more in tune with the models can tell us.

All i know is, the model has been intensifying everything this year...


HWRF update is 3rd in line and has not been scheduled yet.

2009 - CHANGES TO NCEP MODELS

It is after the RTOFS.
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The AOI near PR might be working its way to the surface, you can see the vorticity on the 200 mb map.
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Sheri, stop making excuses for asking a question. Just ask the question. We already know you are not dumb.


Quoting catastropheadjuster:
I'd like to ask a question and don't mean to sound dumb. But here we go What does the upward MJO mean? I mean what does it do to help develop anything or does it even do that?

Sheri
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127. Skyepony (Mod)
I wish they did the Annular Hurricane index for the WPAC basin.. I don't think we've seen eyewall replacement one with Choi-wan.

Storm off NC looks too frontal & weak to be declared tropical at the moment.

Phase analysis looks interesting though. Completes the transition up by Greenland..


Fredex has hit a rough patch tangling with the ULL. AS it moves off & fredex gets to warmer waters & moisture air we may see his tenacious self pull a reprise. I'll go outside chance (15%) of a TS for FL on Monday.
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Quoting jeffs713:

Yep. Upward MJO is over the CPAC right now, and its neutral in the EPAC. The ATL basin should be getting upward MJO over the next week or so.

Not a good setup with the high SSTs we have in the ATL, Caribbean, and GOM right now.


Yep...the potential there is for a big mess, if shear values and trofs cooperate...
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200mb Vorticity
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Quoting BurnedAfterPosting:


the upward phase of the MJO helps to generate convection just like the downward phase of the MJO supresses convection


Thanks for answering my question. I couldn't figure it out and didn't want to sound stupid by asking.

Sheri
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Quoting catastropheadjuster:
I'd like to ask a question and don't mean to sound dumb. But here we go What does the upward MJO mean? I mean what does it do to help develop anything or does it even do that?

Sheri
\

An upward MJO (Madden-Julian Oscillation) is indicative of more energy and moisture in the atmosphere as well as more potential for distubances. It creates a more favorable environment for the development of tropical systems
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Does anyone have a link to Large cloudsat images like the one that Dr M posted? If so could you WU mail me (at work and dont have much time before business hits)

Thanks in advance!
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Quoting P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.




Needed to be said. Congrats. Also, some are relentless in their criticism, ever notice that, as well?
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this hurricane season is 100% lol

I was 100% right

told ya

fred was rip

O____________O
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Quoting rwdobson:


Not sure...maybe someone more in tune with the models can tell us.

All i know is, the model has been intensifying everything this year...
No argument from me. Pretty much universally off the charts on deepening just about anything. The GFDL has been a little touchy too.
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Quoting P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.




Lots of stupid people out there ---- that is the answer.
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Quoting Patrap:
00 Z FredEx Dynamic Models (More sophisticated models)



Hey Patrap. Just how "sophisticated" is "this "model. How are you, my friend?
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I predict Fred will strike S/N Carolina as a minimal Cat 1 storm 9 days out. No scientific back up, just my gut.
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steering west pac for choi wan

500-850 hPa steering layers in front of Super Typhoon Choi Wan
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Quoting Magical:


Most longest??????


It should have read the most annoying and persistant. However, using a superlative in that context, would simply be acceptable by most teachers, since it was not meant to be a technical phrase contained in a dissertation. It is a double superlative using "most" preceding the "est" form of the adjective, which is never acceptable.

Grammar aside, I still like reed's blogs. If we were to correct each other's English, we would never get to discuss the weather.

Too bad most people do not understand when sentences are preceded with words like "might" and "could". It would prevent a lot of unnecessary arguments. They are modals auxiliary words intended to express possibility, not fact.
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111. Skyepony (Mod)
1900hurricane~ Nice, even same time of day..
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Quoting P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.





amen
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.