Dr. Jeff Masters' WunderBlog

Grading NHC's Tropical Weather Outlook
Posted by: Dr. Jeff Masters, 16:33 GMT le 06 juin 2007 +4
The National Hurricane Center's Tropical Weather Outlook (TWO) is a text-only product that rates the potential of disturbed areas of weather to turn into tropical depressions or tropical storms. The outlooks are issued four times daily, at 5am, 11am, 5pm, and 11pm EDT. I've found them to be an excellent guide to what to watch out for. But how accurate are these outlooks? To find out, Jamie Rhome and Dan Brown, who are two of the hurricane specialists that write the Tropical Weather Outlook, verified the accuracy of all the outlooks issued in 2005 and 2006. They used a three-tiered classification of threat based on the following language appearing in the TWO:

High: "A tropical depression could form tonight or the next day."

Medium: "Some slow development is possible."

Low: "Tropical storm formation is not expected."


These forecasts were then graded by looking at the "best track" database of Atlantic hurricanes and seeing if a tropical depression formed within 48 hours of each TWO issued. The results, shown below, reveal that for the Atlantic in the years 2005 and 2006:

-When the TWO said, "A tropical depression could form tonight of the next day," a depression formed within 48 hours 53% of the time.

-When the TWO said, "Some slow development is possible," a tropical depression formed within 48 hours about 20% of the time.

-When the TWO said, "Tropical storm formation is not expected," a tropical depression formed within 48 hours only 3% of the time.




Figure 1. Verification of the Atlantic and Eastern Pacific Tropical Weather Outlooks issued in 2005 and 2006. Image credit: Jamie Rhome and Dan Brown, National Hurricane Center.

Jeff Masters
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1751. Stormchaser2007 16:53 GMT le 10 juin 2007    
Any way...... the blob in the SW carib looks pretty depression like on this........



NONE
Member Since: 9 juin 2007 Posts: 4 Comments: 15248
1753. WPBHurricane05 16:54 GMT le 10 juin 2007    
Why isn't the East Atl system a depression?

Forgot to answer that question. Because it needs to be around for a certain amount of time to make sure that it will hold. As we look at the satellite images we can see its not doing that.
Member Since: 31 juillet 2006 Posts: 56 Comments: 7919
1756. 0741 16:58 GMT le 10 juin 2007    
Any who the blob in the SW carib looks pretty depression like on this what are you asking????
1757. Stormchaser2007 16:58 GMT le 10 juin 2007    
93L wont survive the night today.
Member Since: 9 juin 2007 Posts: 4 Comments: 15248
1759. Stormchaser2007 16:59 GMT le 10 juin 2007    
Any who the blob in the SW carib looks pretty depression like on this what are you asking????


Im not asking anyone or anything.
Member Since: 9 juin 2007 Posts: 4 Comments: 15248
1761. Stormchaser2007 17:02 GMT le 10 juin 2007    
yeah shes on the NAM 12Z run its got a pressure of 992mbs. LOL!!!
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1762. turtlehurricane 17:03 GMT le 10 juin 2007    
Theres no planes based in the Cape Verdes, there were some for SALEX last year but none right now.
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1764. Hellsniper223 17:05 GMT le 10 juin 2007    
Can anyone link the NAM please?
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1765. Stormchaser2007 17:06 GMT le 10 juin 2007    
Im not laughing at it Im laughing because of another thing! CHILL
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1766. Stormchaser2007 17:06 GMT le 10 juin 2007    
Yeah..... one sec
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1768. Stormchaser2007 17:07 GMT le 10 juin 2007    
Here you go....Link
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1769. seminolesfan 17:07 GMT le 10 juin 2007    
Jed-Sorry bro, but you and I both know you were being condescending about recognizing ground clutter.
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1770. Stormchaser2007 17:08 GMT le 10 juin 2007    
No I just nearly spilled coke on my brand new computer!!!!!
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1771. IKE 17:09 GMT le 10 juin 2007    
Actually the 12Z NAM only gets that Caribbean low down to 996mb from what I see.
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1773. WPBHurricane05 17:09 GMT le 10 juin 2007    
No I just nearly spilled coke on my brand new computer!!!!!

That is why you always place it 6-8 feet away from your computer. Learned that one the hard way.
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1774. BahaHurican 17:10 GMT le 10 juin 2007    
Interesting to note the entire WCar is in the purple zone. . ..

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1775. Stormchaser2007 17:10 GMT le 10 juin 2007    
LMAO!!!!!!!!!!!
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1776. weatherblog 17:10 GMT le 10 juin 2007    
Ok. So I see we have two areas of interests..the carribean blob and 93L.
What are your guys opinions on those two features? Do you think any of them are likely to become TD3 or Chantal...?

I personally am taking an interest to 93L seems to be a depression. But the NHC will most definately not name or declare this thing as a depression unless it survives a bit longer and mantains its convection. But currently that does not look very possible as it will be entering less-favorable conditions...shear and lower SST's. So, this thing will have to hold together to be Chantal.

-Justin~
Member Since: 10 juillet 2006 Posts: 27 Comments: 1623
1778. Stormchaser2007 17:11 GMT le 10 juin 2007    

That is why you always place it 6-8 feet away from your computer. Learned that one the hard way


Ouch!!!! BTW im gonna be in WPB in September.
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1779. Stormchaser2007 17:12 GMT le 10 juin 2007    
GTG BBL!
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1780. kmanislander 17:12 GMT le 10 juin 2007    
Stormw

Now you have me confused. 13N is not near the Southern tip of Cuba. The latter is near 20N
Member Since: 19 août 2006 Posts: 0 Comments: 14939
1781. WPBHurricane05 17:13 GMT le 10 juin 2007    
Ouch!!!! BTW im gonna be in WPB in September.

Hope you enjoy. August/September is normally when we start getting hit by hurricanes. Hurricane Frances and Jeanne hit us just 2 weeks apart in September.
Member Since: 31 juillet 2006 Posts: 56 Comments: 7919
1783. kmanislander 17:20 GMT le 10 juin 2007    
yes I understand that part Storm but when I made that post earleir today there was an area much further South near 13N that seemed interesting and I was wondering about your take on it. I was not referring to the weather right over Jamaica which has been pulled N from the S Caribbean by the ULL over W Cuba. Since I made the post the far S Caribbean has become much more disorganised
Member Since: 19 août 2006 Posts: 0 Comments: 14939
1784. kylejourdan2006 17:21 GMT le 10 juin 2007    
Caribbean is definitely an area to watch. Shear is decreasing in most spots. That combined with below normal surface pressures and very warm SSTs is basically asking for a tropical system to form there. I'm keeping my eyes peeled...


(SORRY kman)
Member Since: 18 juillet 2006 Posts: 32 Comments: 1521
1785. eye 17:22 GMT le 10 juin 2007    
yall, the wave is a fish, already above 10N, and much cooler SSTs(thus convection decreasing) Only chance for it to make it across would be to remain a wave with little to no convection, and get in the Carribean(assuming no shear exist there). If it strengthens any, it will recurve, and most likely will recurve anyways....and the shear will kill it in about 24hrs, will just be a low level swirl.
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1786. kmanislander 17:22 GMT le 10 juin 2007    
Kyle

You've done it again ! lol

Pls resize your post
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1789. kmanislander 17:24 GMT le 10 juin 2007    
No problem. Always appreciate your take on things
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1790. eye 17:25 GMT le 10 juin 2007    
Kyle, what happened to Hurricane Chantal and her pinhole eye?
Member Since: 21 août 2006 Posts: 0 Comments: 147
1791. kmanislander 17:25 GMT le 10 juin 2007    
Doing great Storm. The ULL was creating some thunder here last night but nothing yet today. May change with the daytime heating.

How about U ?
Member Since: 19 août 2006 Posts: 0 Comments: 14939
1796. kmanislander 17:30 GMT le 10 juin 2007    
Storm, this is a close up of the area I was referring to. Still seems like something trying to get going here

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

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