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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233. 4Gaia
12:30 AM GMT on June 07, 2007
Forget about it FL. After Katrina, I was sent pictures of a "sixteen foot alligator" that was captured in the french quarter. The "gator" was actually a croc, and was being loaded into a vintage military vehicle by people in African garb and the tags on the vehicles weren't even in our alphabet I dont know why people forward fakes after an event, But yours looked legit.
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231. Patrap
7:20 PM CDT on June 06, 2007
Latest MIMIC showing Gonu 's impact on Oman.Link
Member Since: July 3, 2005 Posts: 434 Comments: 133270
229. KoritheMan
12:16 AM GMT on June 07, 2007
Eh...? That thing in the GoM could develop if shear just abaits to about 20-30 knots. We saw what Barry did in the face of 20-40 knot shear. It's not something we can just turn our eyes off and ignore, even if the models aren't forecasting tropical cyclone development.
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228. Fl30258713
12:09 AM GMT on June 07, 2007
Here is latest Quikscat.

24N 87W
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225. Fl30258713
12:03 AM GMT on June 07, 2007
It was a Cat 5, it caught that dry air. Those folks don't know how lucky they are with those 90+ SST's.
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223. sullivanweather
12:02 AM GMT on June 07, 2007
For all the hype of the unprecedented about to occur it sure didn't pan out.
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222. Fl30258713
12:00 AM GMT on June 07, 2007
Yep, you might have to fall on your sword for fake pics. :-)
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220. hurricane23
8:00 PM EDT on June 06, 2007
For those intrested in looking at some hurricane videos now that things are quite feel free to check out my youtube page.
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218. Fl30258713
11:58 PM GMT on June 06, 2007
I'm just looking at what the clouds are doing. If it doesn't develope,great.
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217. sullivanweather
11:55 PM GMT on June 06, 2007
Well well well.

It looks like Gonu didn't make landfall at hurricane strength after all...
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216. hurricane23
7:52 PM EDT on June 06, 2007
Folks there will be no development of any kind across the gulf tonight or tommorow.Maybe some slight chances during the middle of next week as some models are indicateing windshear will drop some which might allow some development but even that is questionable at the moment.

Windshear values presently are running anywere from 40-60kts across the gulf.Adrian
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214. Fl30258713
11:49 PM GMT on June 06, 2007
I'm very interested to see the next QuikSCAT image for GOM

Here is the visible loop for GOM http://www.ssd.noaa.gov/goes/east/gmex/loop-vis.html

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213. Fl30258713
11:47 PM GMT on June 06, 2007
looks like a low may be developing at 24N 87W


24N 87W
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212. EllistonVA
11:45 PM GMT on June 06, 2007
Lots of local info on what's happening on the ground with Gonu: GulfNews.com
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211. 1900hurricane
6:39 PM CDT on June 06, 2007
That's got to be at least a 10 foot surge!
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210. 1900hurricane
6:38 PM CDT on June 06, 2007
Wow! Oman is really gettin' it bad!
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207. Patrap
6:31 PM CDT on June 06, 2007
Surge,..the storm surge is the thing one has to avoid. Especially in an area where it never happens. Remarkable scene.
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206. MZT
11:30 PM GMT on June 06, 2007
Flooding in Oman

Qurum flood
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205. RL3AO
6:25 PM CDT on June 06, 2007
Storms are starting to pick up in South Dakota.
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203. Vanagew
11:04 PM GMT on June 06, 2007
Posted By: Littleninjagrl at 11:03 PM GMT on June 06, 2007.


Posted By: Vanagew at 10:59 PM GMT on June 06, 2007.

The shear is predicted to be highly favourable for development in 48 hours time.

So how come this says no develop ment is likely on 48 hrs? http://www.wunderground.com/tropical/ABNT20.RAW.html Just asking cuz now i'm confused.


Because there are no storms over the concerned regions. Just because shear is low doesn't mean that a disturbance will form.
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202. JGreco
11:11 PM GMT on June 06, 2007
"So how come this says no develop ment is likely on 48 hrs? http://www.wunderground.com/tropical/ABNT20.RAW.html Just asking cuz now i'm confused."

After the 48hr period of no development the situation changes is what he is implying.
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201. FormerFloridian
7:04 PM EDT on June 06, 2007
Posted By: Littleninjagrl at 7:03 PM EDT on June 06, 2007.


Posted By: Vanagew at 10:59 PM GMT on June 06, 2007.

The shear is predicted to be highly favourable for development in 48 hours time.

So how come this says no develop ment is likely on 48 hrs? http://www.wunderground.com/tropical/ABNT20.RAW.html Just asking cuz now i'm confused.


Because nothing is going to develop.
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200. Littleninjagrl
11:00 PM GMT on June 06, 2007

Posted By: Vanagew at 10:59 PM GMT on June 06, 2007.

The shear is predicted to be highly favourable for development in 48 hours time.


So how come this says no develop ment is likely on 48 hrs? http://www.wunderground.com/tropical/ABNT20.RAW.html Just asking cuz now i'm confused.
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199. Stormy2day
10:59 PM GMT on June 06, 2007
Groundsman - if you are still lurking, I saw your post explaining your "handle" - very cool. Sounds like an important and rewarding job. Don't be offended by me saying that I hope I never need your services.
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198. FormerFloridian
6:57 PM EDT on June 06, 2007
Posted By: SLU at 5:34 PM EDT on June 06, 2007.

Nice words about St. Lucia


SLU,

I assume you live there by your username. We've had a great time there everytime we have gone. The people are wonderful and the scenery is beautiful. Can't wait to get back there in the next couple of years. Hope you guys have a safe hurricane season.
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196. Hellsniper223
10:27 PM GMT on June 06, 2007
Does anyone have any pressure maps from 05 or 04?
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195. Patrap
5:22 PM CDT on June 06, 2007
4-panel WV Zoom to La..Link
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194. IKE
5:14 PM CDT on June 06, 2007
I'm not saying anythings gonna form now SK...I was just noticing the shear tendency maps on WU.

I predicted 18 storms for 2007 in the Atlantic...already had 2...seems about right.
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193. GainesvilleGator
10:02 PM GMT on June 06, 2007
Hey Stormkat, June is traditionally a slow month for hurricane activity. It picks up a little bit in July. If no tropical storms form in June it isn't s predictor for a slow hurricane season. It is also hard to see beyond 2 weeks as far as wind shear is concerned. I wouldn't rule anything out towards the end of June - you just have to wait & see.
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192. ClearH2OFla
6:11 PM EDT on June 06, 2007
Ike i live in clearwater Fla gulf coast and i say lets rock and roll
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191. stormkat
10:09 PM GMT on June 06, 2007
no way ike they have a short wave impulse coming down from canada for the weekend....that will keep the shear way up no way anything will develop in the gulf this weekend or next weekend...StormKat
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190. Hellsniper223
10:11 PM GMT on June 06, 2007
SK, do you think that maybe between Pulses the shear may weaken enough for a small system to form?
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189. IKE
5:08 PM CDT on June 06, 2007
According to the shear maps on WU...by Saturday..it will be favorable from Louisiana all the way east around Florida and up to the Carolinas.

I did notice...looking at the GFS..that the high is positioning itself differently then it did in 2006...with it stretching further west.

If that holds up..this could really be a bad year.
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188. Hellsniper223
10:08 PM GMT on June 06, 2007
Alright. =D
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187. stormkat
10:02 PM GMT on June 06, 2007
hell im looking at the short wave impulses that are still rocking down from canada....as long as that continues the shear will stay very strong in the gulf and caribbean..this looks good for the gulfcoast and the caribbean sea....i think our main hurricane season will be the cape verde which begins in august...that looks to firing up this season and im kind of concerned where the azores has set up this year its the same place it was in 2005...not good news...well we will see what happens to that weak lanina in the next 2 months...this will be a big factor in our season....StormKat
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186. Hellsniper223
10:04 PM GMT on June 06, 2007
There ya go IKE. ;)
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185. IKE
5:03 PM CDT on June 06, 2007
And the shear forecast for the GOM...especially the central and eastern GOM is predicted to become favorable by this weekend. The Caribbean looks mostly favorable...according to the shear maps on WU.
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184. IKE
5:01 PM CDT on June 06, 2007
There's already been a storm(Barry), in June....SK.
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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