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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As for the blob in the Carribean, Barry formed in the face of 20-40 knot shear, so why wouldn't this survive shear? Shear has died down about 10 knots, so if it keeps surviving, it may eventually acquire a circulation.
I have to agree here, no chance of development.
We cover all the basins here.
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN JUN 10 2007
LARGE TROPICAL WAVE LOCATED ABOUT 415 NM SSE OF THE CAPE VERDE
ISLANDS IS ALONG 21W S OF 14N. THE WAVE IS MOVING JUST N OF DUE
WEST NEAR 20 KT AND REMAINS WELL DEFINED FOR EARLY JUNE. A SFC
LOW IS ALONG THE WAVE AXIS NEAR 9N. ALTHOUGH CLIMATOLOGY IS NOT
ON ITS SIDE...SOME DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER
THE NEXT DAY OR SO BEFORE IT ENCOUNTERS UNFAVORABLE UPPER-LEVEL
WINDS AND COOLER WATER TEMPERATURES. THE DEEP CONVECTION
ASSOCIATED WITH THIS SYSTEM HAS DIMINISHED A BIT OVER THE LAST
SEVERAL HOURS...THOUGH SCATTERED MODERATE STILL EXISTS FROM
9N-11N BETWEEN 21W-24W...AND S OF THE LOW FROM 3N-7N BETWEEN
19W-25W.
Pressures in the West / Central Caribbean remain low and early vis images show what appears to be a "spin" near 15N 78W but without any recent Quikscat data I cannot tell if it is at the surface or in the mid/upper levels. The ULL that is pushing to SW near W Cuba is not allowing anything to develop for the time being
Looks like another round of rain and thunder for us today as the ULL pulls convection into our area from down South
So...if the East Atlantic invest stays weaker rather than gaining strength....is it likely to regain a more westward....rather than west-north westward track??
Basically its just way to early to worry about anything this far out in the eastern atlantic which usually does not get going till mid july and especially august.Having said that some impressive waves have been rolling of the african coast the past 2-3 weeks but very little chance of tropical cyclone formation out here.Adrian
That ULL has to push back to the Yucatan and beyond before the SW Caribbean stands any chance of seeing development. In the meantime the NW Caribbean will have very unsettled weather. Jamaica will likely see flash flooding today. Could be a dangerous situation over there later today. Hope they are paying attention to what is coming up from their South
Have a great day - will check back later and see what's going on. Right now, searching the personals trying to find a guy for my MOM. :)
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High pressure definitely in control here. First sun in days :o)
Taking a look at our two areas of interest this morning. I still say that E ATL system is showing lots of potential. It looks amazingly well structured for a simple tropical wave. It will be interesting to see if it persists.
I'm not so convinced by the disturbance in the SW Car. I think that will end up in the EPac before it makes something of itself.
the wave in the eastern atlantic is still holding on. but for how long. during the next 24-36hrs it should encounter hostile conditions which should preclude any futher development. now the area of cloudiness in the sw caribbeanis moving north towards jamaica. to the south of this cloud mass is an area near 13n 80w is showing some form of circulation. wonder whether something might be brewing there. pressures in the vicinty are relatively low. still an area of concern
However, it's really just a still shot.
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