Grading NHC's Tropical Weather Outlook
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
Reader Comments
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However I refuse to believe that it will develop because afterall it's June 9th.
Only 2 tropical cyclones have formed in June in this part of the basin since 1886. Hurricane #1 in 1933 and TS Anna in 1979. So the odds are against it inspite of the "seemingly" favorable conditions ahead of it.
Do you mean in June??
Good point.... wont be surprised if we see 93L today or tomorrow.
Only 2 tropical cyclones have formed in this part of the basin since 1886
Do you mean in June??
Yeah sorry, in June.
There is nothing in the tropics that show any signs of development.
Little aggressive are we now..... but still possible.
Although there is an area around Panama. This is most likely thunderstorms and shear is around 15-25 knots.
Link
http://manati.orbit.nesdis.noaa.gov/cgi-bin/qscat_storm.pl
I haven't been able to access it for two days.
Come on now people, get a grip...LOL
For the Full Tropical Outlook, including data, several images, and an extremely close-up look via satellite at the blob, please visit my forums :Tropics Forum
So I think the estimated guess of 20% possibility for the Panama Blob should be down-casted to more like 3% at the most.
OF AFRICA ALONG 14W/15W S OF 13N ESTIMATED TO BE MOVING W 15-20
KT. THERE IS NOT MUCH DEBATE ABOUT THE EXISTENCE OR PSN OF THIS
WAVE WITH A LARGE AREA...ABOUT 10-12 DEGREES OF LONGITUDE...OF
WELL DEFINED LOW TO MID LEVEL CYCLONIC TURNING EVIDENT ON
SATELLITE IMAGES AND TO SOME DEGREE IN QSCAT DATA. THERE IS ALSO
A POSSIBLE LOW ALONG THE WAVE NEAR 7N WHICH MAY BE ADDED TO THE
18Z ANALYSIS. SFC OBS...MOSTLY STATIONS OVER AFRICA...CLEARLY
INDICATE THIS FEATURE WITH 24-H PRES DROPS IN THE 2-4 MB RANGE
IN DAKAR AND SURROUNDING CITIES. CONVECTION HAS DECREASED SOME
OVER THE PAST SEVERAL HOURS BUT SCATTERED MODERATE STILL EXISTS
FROM 4N-8N BETWEEN 13W-19W.
As noted by the NHC this wave has very nice mid-level circulation with it but iam also noticing a decrease in convection the past couple of hours.
Here is a very recent visible image...
I agree.....freak things happen though but aren't the norm.....
GOES-East, METEOSAT-8, & MTSAT
Atlantic Region
Link
Oh and BTW, systems have trouble forming when they are at a low latitude because the coriolis force is weaker...
850 hPa Vorticity
North Atlantic
Link
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