Grading NHC's Tropical Weather Outlook

By: Dr. Jeff Masters , 16:33 GMT le 06 juin 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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2184. HCW
20:18 GMT le 12 juin 2007
Latest GFS . Still looks good for a TS this week :)

Link
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2183. Patrap
17:25 GMT le 11 juin 2007
Meteosat-8 Split window with SAL...Link
Member Since: 3 juillet 2005 Posts: 414 Comments: 125605
2182. IKE
13:38 GMT le 11 juin 2007
NEW BLOG!
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
2181. emagirl
13:37 GMT le 11 juin 2007
so any guesses on when the next storm may form??
2180. stoormfury
13:37 GMT le 11 juin 2007
good morning to all.

the western caribbean is really unsettled at the moment. the ULL although showing signs OF WEAKENING IS STILL ENHANCING THE TROPICAL WAVE IN THE REGION. THE AREA WILLHAVE DIFFICULTY IN ORGANISATION because of high wind shear.
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2179. kmanislander
13:20 GMT le 11 juin 2007
New QS pass. No surface low in the NW Caribbean at this time but there are some very strong winds
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2178. Fl30258713
13:16 GMT le 11 juin 2007
It will interesting to watch too see if it follows that wave.

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2177. seminolesfan
13:08 GMT le 11 juin 2007
The remarkable fact, and the generator of so much met interest in 93L was the intensity and presence of dual low pressure centers, identifiable by ground stations, before it even left the coast of Africa. The winds flowing into these low pressure areas pulled additional dust from the upper continent into and behind the wave that was tagged as invest 93L. It therefore stands to reason that this dust will follow the wave as it moves into the East Atl.

In the EUMETSAT pic you posted you can see the intensity of dry air/dust is more intense near 93L and towards the next wave leaving the coast now. After the wave still over the continental center, a marked difference is noted in the dry air presence.

I'm sorry to disagree w/ your opinion, but IMHO the dust will continue to not be at the forefront of inhibiting factors for CV storms.
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2176. Fl30258713
13:07 GMT le 11 juin 2007
I hadn't thought about in a while, are there still a bunch of folks that come in here with dial up connection, where images end up taking for ever too load?
Member Since: 24 juillet 2006 Posts: 1 Comments: 981
2175. emagirl
12:58 GMT le 11 juin 2007
good morning everyone...well i see i missed alot this weekend...it seems it might be a busy week..
2174. Fl30258713
12:56 GMT le 11 juin 2007
Here's the EUMSAT dry air



SAL

http://www.eumetsat.int/Home/Main/Image_Gallery/Derived_Product_Imagery/index.htm?l=en
Member Since: 24 juillet 2006 Posts: 1 Comments: 981
2173. Fl30258713
12:52 GMT le 11 juin 2007
ok, it is thick enough to effect SST's
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2172. seminolesfan
12:50 GMT le 11 juin 2007
FL302-I'm not trying to be argumentative...sorry if I came off as preachy. :(

Just trying to let ya know that dust is just a real light layer, unlike last yrs thick blanket.
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2171. Fl30258713
12:48 GMT le 11 juin 2007
seminolesfan, true, but it is considerably more SAL than last week.

Everything coming off Africa now has to punch trough that dry air. 93L didn't have to.
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2170. seminolesfan
12:47 GMT le 11 juin 2007
Sorry...where are my manners?



Morning Everyone!!!
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2169. seminolesfan
12:46 GMT le 11 juin 2007
Posted By: Fl30258713 at 12:25 PM GMT on June 11, 2007.
SAL has really spread south in the East Atl


Actually, if ya look at the scale/legend at the bottom of yer pic; the yellow represents the weakest the SAL can be while still being analyzed on that map.

So actually, the SAL is diluted across the entire E. Atl. Meaning it's not nearly as much of an inhibiting factor as in 06.
Member Since: 14 juin 2006 Posts: 0 Comments: 2106
2168. Fl30258713
12:46 GMT le 11 juin 2007
None of the bouy's in the area reflect low pressure
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2167. IKE
12:44 GMT le 11 juin 2007
I'm in Defuniak Springs. It's been around 100 each afternoon since about Friday.
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2166. Fl30258713
12:43 GMT le 11 juin 2007
I'm in Pensacola, it did seem a bit warm yesterday.
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2165. Fl30258713
12:40 GMT le 11 juin 2007
Looks like that GFS model will end the drought problem around Florida south of Georgia and South Georgia
Member Since: 24 juillet 2006 Posts: 1 Comments: 981
2164. IKE
12:40 GMT le 11 juin 2007
Posted By: Fl30258713 at 7:35 AM CDT on June 11, 2007.
Chart are showing a 1011 Low in the North Central GOM, I don't see it.


Maybe it's a heat low...like they get in the desert SW. Temps have been near 100 for the last 3-4 days here in the inland Florida panhandle.
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2163. IKE
12:36 GMT le 11 juin 2007
Latest GFS....

Link
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2162. Fl30258713
12:35 GMT le 11 juin 2007
Chart are showing a 1011 Low in the North Central GOM, I don't see it.

This little bit coming of the Yucatan Pennisula looks interesting on Satelite loop.

GOM

Loop http://www.ssd.noaa.gov/goes/east/gmex/loop-avn.html
Member Since: 24 juillet 2006 Posts: 1 Comments: 981
2161. IKE
12:33 GMT le 11 juin 2007
Posted By: chessrascal at 7:29 AM CDT on June 11, 2007.
that blob in the Carribean is going to be something to watch. That is near the spot where Barry formed.


You're right...it is...

The GFS takes it into the central GOM by this weekend.
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
2160. nash28
12:32 GMT le 11 juin 2007
Yeah... The Carribean blob could be our next invest.
Member Since: 11 juillet 2005 Posts: 190 Comments: 16972
2159. CrucianCrip
12:31 GMT le 11 juin 2007
Thanks, nash...
2158. chessrascal
12:29 GMT le 11 juin 2007
that blob in the Carribean is going to be something to watch. That is near the spot where Barry formed.
2157. nash28
12:26 GMT le 11 juin 2007
Dr. Masters is on vacation with his family.
Member Since: 11 juillet 2005 Posts: 190 Comments: 16972
2156. Fl30258713
12:25 GMT le 11 juin 2007
SAL has really spread south in the East Atl

Saharan Air Layer

http://cimss.ssec.wisc.edu/tropic/real-time/wavetrak/sal.html
Member Since: 24 juillet 2006 Posts: 1 Comments: 981
2155. CrucianCrip
12:23 GMT le 11 juin 2007
Greetings, All...

Am a bit surprised to se how long it's been since Dr. Masters has done an update. Dos anyone know if he's away, or just isn't there that much on which to comment so early in the season?

Would be happy if it's the latter...as a Virgin Islander, I don't share your excitement about things brewing or perking up in the Caribbean...
2154. nash28
12:17 GMT le 11 juin 2007
Good morning all. 93L is history. Carribean looks to be brewing this morning. All falls in line for what to expect this time of year. Something tells me that come late July/early August, we may have a conveyor belt of storms coming off of the coast of Africa.
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2153. weathersp
12:03 GMT le 11 juin 2007
I think it's pretty dead to me... Image 1hr ago.

Image
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2152. Patrap
11:57 GMT le 11 juin 2007
93 L ,no convection this am...Link
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2151. IKE
11:55 GMT le 11 juin 2007
Not really and good morning.
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2150. kmanislander
11:54 GMT le 11 juin 2007
Off to work but will check in later
Have a good day all
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2149. kmanislander
11:52 GMT le 11 juin 2007
Hi Ike

No surprise there.
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2148. IKE
11:51 GMT le 11 juin 2007
I guess 93L is about history...

"Statement as of 5:30 am EDT on June 11, 2007

For the North Atlantic...Caribbean Sea and the Gulf of Mexico...

Tropical cyclone formation is not expected during the next 48 hours.

$$
Forecaster Blake"

Member Since: 9 juin 2005 Posts: 23 Comments: 37858
2147. kmanislander
11:46 GMT le 11 juin 2007
The ULL almost seems to be moving more W to WNW now but at barely a crawl. In the WV loop you can see the moisture filling in to its S which would not happen if it was still moving WSW
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2146. IKE
11:46 GMT le 11 juin 2007
From Key West extended...

"The third regime will begin around Friday...and will be characterized
by episodes of weak large-scale ascent east of developing cyclonic
flow over the Gulf of Mexico. Lower-tropospheric flow will likely
become southerly with further increases in low-level moisture. Rain
chances have been increased to slightly above climatology...and sky
cover may be higher and more variable as well from Friday-Sunday."
Member Since: 9 juin 2005 Posts: 23 Comments: 37858
2145. IKE
11:42 GMT le 11 juin 2007
That ULL does appear to be undergoing some changes.
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2144. IKE
11:41 GMT le 11 juin 2007
This from the Tallahassee,Fl. extended...

"Long term...the GFS is now trying to make things interesting over
the Gulf of Mexico by the weekend...as it gradually spins down a surface
low into the central Gulf from the old upper low which is now near
the Yucatan Channel. Will be monitoring the other global models for
any similar indications...but for now...the old 12 UTC Euro run is
still negative."
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2143. Patrap
11:41 GMT le 11 juin 2007
GOES WV Loop of Tropical Basin
Link
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2142. kmanislander
11:40 GMT le 11 juin 2007
early vis shot

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2141. IKE
11:27 GMT le 11 juin 2007
Posted By: seminolesfan at 12:45 AM CDT on June 11, 2007.
And oh my, the Carr. Blob is dead too.


I don't think so.
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2139. kmanislander
11:10 GMT le 11 juin 2007
Surface pressures are high for now

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2138. kmanislander
11:06 GMT le 11 juin 2007
good morning all
The sky is quite dark to the S of us and it looks like there is a new flare up in the NW Caribbean to watch. Pressures are not particularly low ( 1012.9 ) and winds are calm here. Lets see what happens throughout the day

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2137. WPBHurricane05
11:00 GMT le 11 juin 2007
aroughleague-Did you sleep last night?????
Member Since: 31 juillet 2006 Posts: 56 Comments: 8112
2135. SCwxwatch
10:45 GMT le 11 juin 2007
Hope the DR. puts up a new post today.
2134. Thundercloud01221991
10:11 GMT le 11 juin 2007
ok
Member Since: 1 août 2006 Posts: 28 Comments: 3716

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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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