Grading NHC's Tropical Weather Outlook

By: Dr. Jeff Masters , 4:33 PM GMT on June 06, 2007

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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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33. miamihurricane12
5:22 PM GMT on June 06, 2007
If the shear dies down to 10 knots or less across much of the central atlantic in the coming weeks then we can see some serious action out there b/c those waves are poppin off almost every 2 to 3 days now.
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31. Jedkins
5:22 PM GMT on June 06, 2007
Posted By: stampapaul at 5:17 PM GMT on June 06, 2007.

Posted By: Jedkins at 5:10 PM GMT on June 06, 2007.

"ya well before Dr. Masters hopes that it will, you might want to remind him we need those bermuda highs to hold in place so we can get some drenching rains in Florida, I'd rather have a hurrican ravage the state then more drought, hurricanes are a natural part of Florida too."


JED...your kidding right...I don't really know of too many people who would like to see their state ravaged by any storm


You don't live here, you have NO IDEA how bad our drought here has been, remember its only a risk that we will be raveged by a hurricane, its a risk worth willing to take to get rid of this drought.

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30. StoryOfTheCane
5:19 PM GMT on June 06, 2007
yeah they're gettin up there round 12-13, pretty unusual for June
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29. miamihurricane12
5:15 PM GMT on June 06, 2007
story those waves coming off africa have gained alot of latitude in the recent weeks. That new wave is probably around at least 15 N right?
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28. stampapaul
5:13 PM GMT on June 06, 2007
Posted By: Jedkins at 5:10 PM GMT on June 06, 2007.

"ya well before Dr. Masters hopes that it will, you might want to remind him we need those bermuda highs to hold in place so we can get some drenching rains in Florida, I'd rather have a hurrican ravage the state then more drought, hurricanes are a natural part of Florida too."


JED...your kidding right...I don't really know of too many people who would like to see their state ravaged by any storm.
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27. StoryOfTheCane
5:13 PM GMT on June 06, 2007
June 27th
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25. StormHype
5:09 PM GMT on June 06, 2007
Ok. So when is Chantal expected to come ashore in SW Florida?
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24. Jedkins
5:05 PM GMT on June 06, 2007
ya well before Dr. Masters hopes that it will, you might want to remind him we need those bermuda highs to hold in place so we can get some drenching rains in Florida, I'd rather have a hurrican ravage the state then more drought, hurricanes are a natural part of Florida too.


Yes if the bermuda high holds in place the hurricane risk is higher buts its a risk I'm glad to accept for the sake of normal heavy rain in Florida.

Here in pinnelas county where I live, last year rain around the area was normal, about 60 inches. but most of Florida is had slightly below normal rain, and after very dry conditions last dry season, most Floridians didn't get enough rain in the "safe" hurricane pattern.
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23. StoryOfTheCane
5:08 PM GMT on June 06, 2007
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22. Boatofacar
5:10 PM GMT on June 06, 2007
Barry just didnt produce for us here in lake county...just about an inch here at the house...maybe we will get some training rain action here today...
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20. WPBHurricane05
1:06 PM EDT on June 06, 2007
Local met. in West Palm says today will be the last chance of rain until Tuesday.
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19. cenzo6969
5:04 PM GMT on June 06, 2007
we sure could use the rain here in lake county FL where im at Barry managed to drop barely over an inch and thats it
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18. miamihurricane12
5:05 PM GMT on June 06, 2007
Jedkins we will have to wait and see...last year each time the high woud set up it would be weak and it would be pushed around by the fronts dipping down. Dr. Masters was hoping that the setup we previously had would hold, but your right...The summer pattern is setting in.

The past 2 mornings here in miami I woke up, went outside for the paper and I could feel the moisture in the air, it is so humid right now! summer is here, the afternoon storms are starting to fire
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16. Boatofacar
4:57 PM GMT on June 06, 2007
I was thinkng the same as you Jedkins when i saw how cloudy is was, but rising air across our area (im in Clermont) will kick off some decent storms today...however i could be wrong
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15. Jedkins
4:53 PM GMT on June 06, 2007
Posted By: Boatofacar at 4:51 PM GMT on June 06, 2007.

Central Florida will have rain and storms today.....



Don't be so sure, its possible, but the chances are lower, these kind of conditions and the airmass in place supports numerous thunderstorms with heavy rain amounts, things are severely deing limited due to high cloud deck, and we may not get as many storms going today as expected its a shame really.

Although it is still possible considerg the potential is still there, although my confidence isn't as high as before thats all, I'm just not gonna buy it till it actually happens but we could still get some good action today.
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14. Jedkins
4:50 PM GMT on June 06, 2007
Posted By: miamihurricane12 at 4:48 PM GMT on June 06, 2007.

the shear is 30 to 40 knots across the entire gulf of mexico currently...not the most favorable environment

but what is interesting, since barry I have noticed that the east coast high has moved on and the azores or bermuda high has taken complete control of the atlantic. This could just be temporary but it will be interesting to see how long the high stays put b/c this could be a sign of things to come


Ya forecasters are still talking that they aren't buying the bermuda high bilding in yet till they see it and are going with the drier solution with subsidence across the area friday through monday and not letting up till mid widweek next week.

Thing is, I think they might be overdoing it, looks like the summer pattern is trying to take shape to me, still can't buy it 100% for sure just yet but looks better then not.
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13. leelee75k
4:46 PM GMT on June 06, 2007
sorry about this off topic question, but it still hurricane related

how or where do you store propane gas tanks during a hurricane? (the type used for bbq grills)
Also what about those little green tanks, is there a shelf life on those things.

i've been researching hurricane preparedness and can't seem to find a suitable answer to that question.
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12. Boatofacar
4:50 PM GMT on June 06, 2007
Central Florida will have rain and storms today.....
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11. Jedkins
4:45 PM GMT on June 06, 2007
Stupid convecrion in the gulf is keeping us dryt in xentral Florida todat, moisture and instability is very high and favorable for numerous thunderstorms.

But the problem is with no significant forcing mechinism these storms need daytime heating and seabreeze collisions to produce that upward ascent which we normally get this time of year, but thanks to stubborn sheard convection in the gulf its spreading a very thick canopy of high clouds over central Florida and inhibiting thunderstorm formation.

That convection is not helping out Florida at all, its only limiting development, its doing nothing but bad.
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10. miamihurricane12
4:44 PM GMT on June 06, 2007
the shear is 30 to 40 knots across the entire gulf of mexico currently...not the most favorable environment

but what is interesting, since barry I have noticed that the east coast high has moved on and the azores or bermuda high has taken complete control of the atlantic. This could just be temporary but it will be interesting to see how long the high stays put b/c this could be a sign of things to come
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8. ciclonson
4:45 PM GMT on June 06, 2007
MrCold, the only honest answer anyone can give is ZERO.
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7. MrCold
4:39 PM GMT on June 06, 2007
So, if there is only a 53% chance that we can predict a tropical depression forming within 48 hours, what degree of certainty do we have that we can predict detrimental global warming 100 years from now?
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6. Tazmanian
9:43 AM PDT on June 06, 2007
thanks for updating aron
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5. Jedkins
4:40 PM GMT on June 06, 2007
Posted By: cajunkid at 4:08 PM GMT on June 06, 2007.

Last night on Deadliest Catch they said that winds in the Bering Sea get up to 200kts often.

Is that true? anyone...



its not, thats just seaman folk lore, the strogest winds in the world occurr in hurricanes outside of very high mountain tops where the jet stream on rare occasions digs incredibly low and the peak jet stream winds move to the mountain level brifely and also tornados.

Winds never get to 200 kts in the bering sea thats scientifically impossible, at least in the planet we live on, unless some major climate changes occurr thats impossible.
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1. TheCaneWhisperer
4:35 PM GMT on June 06, 2007

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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.

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