Dr. Jeff Masters' WunderBlog

Grading NHC's Tropical Weather Outlook
Posted by: Dr. Jeff Masters, 4:33 PM GMT on June 06, 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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501. stormhank 12:39 AM GMT on June 08, 2007    
Hurricane 23 u got mail.
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503. AndyN 12:47 AM GMT on June 08, 2007    
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507. sporteguy03 1:09 AM GMT on June 08, 2007    
That system out over the East Coast of FL any Quikskat on that?
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508. hurricane23 1:10 AM GMT on June 08, 2007    
Hey guys what i got from watson at the university of florida this evening and there models is that they said that this year will be very similar to 2004 for florida.

University of central florida 07 outlook
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509. StormJunkie 1:14 AM GMT on June 08, 2007    
Quickscat seems to be down right now...
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510. sporteguy03 1:17 AM GMT on June 08, 2007    
The models recognize its there but don't have anything else?
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511. StormJunkie 1:23 AM GMT on June 08, 2007    
Could be interesting with the shear dropping off sg....SSTs in the area look to be around 25-27. I think the upper level feature is what would keep it from developing, but it does seem to be holding it's own right now.

Anyone know what is up with the Quickscat?
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512. sporteguy03 1:41 AM GMT on June 08, 2007    
A Ship out there is posting a pressure drop near 26 80
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515. hurricane23 1:49 AM GMT on June 08, 2007    
I would like to see convection persist more in the bahamas vicinity also there's nothing at the surface presently and just appears to be in the mid levels.
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519. StormJunkie 2:08 AM GMT on June 08, 2007    
Looks like the Carib blob may be trying to fire up some new convection...

23, if it is in the mid-levels, it has a much better chance of working in to the lower levels then if it was in the upper levels.

Evening SW

Night all

ps, I think that he was talking about 26N 80W, but that is like in the port of Miami or something...

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522. weatherboykris 2:16 AM GMT on June 08, 2007    
Hey guys....did some research.Look at these maps.They show the 500mb(15000ft) height anomalies for May for selected years.
















Looks most similar to '04 to me...
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524. weatherboykris 2:19 AM GMT on June 08, 2007    
'07...looks like '04.
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525. weatherboykris 2:20 AM GMT on June 08, 2007    
The top map is May '07,next down is '06,followed by '05 then '04,then '99,and finally '95 and '92.And they are all for the May's of those respective years.
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526. weatherboykris 2:21 AM GMT on June 08, 2007    
The year for each map is right above that maps scale,along with the month of the year.
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529. weatherboykris 2:30 AM GMT on June 08, 2007    
Well,for one,I think IWIC was moronic to forecast a repeat of 1995.But more to the point,I meant to reinforce the link Adrian posted above.Things are shaping up like '04.
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530. weatherboykris 2:32 AM GMT on June 08, 2007    
Of course,things can and do change,so no particular area could be called safe in June,LOL.
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533. SavannahStorm 2:49 AM GMT on June 08, 2007    
1992 and 1999 also bear a resemblance to this year.
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534. Jedkins 2:53 AM GMT on June 08, 2007    
very heavy much needed rain over interior Florida today in many spots that missed out From Barry.
535. seminolesfan 2:54 AM GMT on June 08, 2007    
kris-by the same reasoning then 05 & 06 are very similar too.

So what meaningful parallels can be drawn from this data?
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536. homegirl 2:59 AM GMT on June 08, 2007    
Anyone take a look at the last couple infrared images on goes? I'm newbie but it looks like convection wraping just east of bahamas.
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537. sporteguy03 3:01 AM GMT on June 08, 2007    
JP,
That was a Ship report I posted on the Buoy Site not pressure reading those were the coordinates of the ship near GBI
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538. seminolesfan 3:04 AM GMT on June 08, 2007    
homegirl-that rotation is in the mid/upper atmosphere. If it was a llc the rotation would reflect down to 850mb.

500 mb Vorticity Link

850 mb Vorticity Link
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539. homegirl 3:08 AM GMT on June 08, 2007    
thanks, so we need persistant convection and lower shear for a llc to develop?
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540. sporteguy03 3:09 AM GMT on June 08, 2007    
Thats weird because the 850 Vorticity on the GFS shows a closed system crossing Florida?
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541. MTJax 3:09 AM GMT on June 08, 2007    

Atlantic Tropical Weather Outlook
--------------------------------------------------------------------------------


000
ABNT20 KNHC 080158
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1030 PM EDT THU JUN 7 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER PASCH



542. seminolesfan 3:10 AM GMT on June 08, 2007    
sporteguy-Do any other models show the same solution or just the GFS?

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543. MTJax 3:10 AM GMT on June 08, 2007    
Oh, I forgot to tell you... there will be a system in GOM on the 20th
544. sporteguy03 3:11 AM GMT on June 08, 2007    
The CMC does also
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545. fldoughboy 3:12 AM GMT on June 08, 2007    
Just a bit of trivia:A depression, tropical storm, or hurricane has never formed East of 55 degree latitude in the month of June.
546. homegirl 3:13 AM GMT on June 08, 2007    
when will the new vorticity report come out? that one is from 0000utc, the infrared images are from 0200 to 0245utc? could a surface low have formed?
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547. Jedkins 3:15 AM GMT on June 08, 2007    
the CMC destroyed the other models showing barry forming becoming a TC and heading for central Florida before the other models even showed a surface reflection.

So I'll give the CMC some credit, if it performs bad this time around then its just a flip floper like John Carry( Or should I say 90% of politicians LOL)
548. seminolesfan 3:18 AM GMT on June 08, 2007    
The 12Z CMC shows a low but def. not a closed low with a surface reflection. More of an ULL/type solution, IMHO.
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549. seminolesfan 3:19 AM GMT on June 08, 2007    
CIMSS releases data analysis every 3 hrs.
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550. seminolesfan 3:24 AM GMT on June 08, 2007    
homegirl-Sure...it could have, It has seemed to be creeping down into lower levels most of the afternoon.
It just takes so long for upper level lows to work all the way down to the surface for any kind of meaningful tropical organization to have a chance to get fired up. Usually two to three days.
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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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