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
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Thats what I was trying to tell him (see my 7PM EDT post)......
Why goes 200 miles when you can go 20
That is a good thing. Are you HurriAndrewFury or whatever his name was? Your from Dallas, and you want land falling storms.
BBL
NAVY NOGAPS MODEL...Link
Need a password to get in.
The NOGAPS model was not designed specifically to predict the motion of tropical cyclones. Rather it is the Navy's operational global atmospheric prediction system. The NOGAPS model is run four times daily every day of the year, producing forecasts out to 144 hours.
In 2002 the resolution of the NOGAPS model was increased from T150L24 to T239L30 (239 waves, which is about 55 km horizontal resolution with 30 vertical levels). In September 2003, the NOGAPS optimal interpolation data assimilation system was upgraded to the NRL Atmospheric Variational Data Assimilation System, a three-dimension variational system. Additionally, in November 2003, NOGAPS implemented the use of terrain fields from USGS Global Land One-kilometer Base Elevation database and changed the gravity wave drag scheme. The result of these changes has been an average increase in verification scores and fewer bad forecasts. The accompanying table provides a summary and relevant references for the NOGAPS model.
The NOGAPS model initializes the tropical cyclone using synthetic soundings based on the National Hurricane Center's estimates of storm location and intensity. These soundings are automatically inserted into the model in the vicinity of the tropical storm. The artificial atmospheric soundings are constructed at the storm center and at radii of two, four and six degrees from the storm The winds are derived from a specified vortex which has a radius of maximum winds of 50 km. Due to the horizontal spatial resolution of the NOGAPS model the maximum wind speeds inserted into the model are 60-80% of those observed.
Link
Hi everyone, Did you have a great weekend???
gams
Baha- Trade winds converge at the Equator. Where they converge, air is forced aloft and thus resulting in water vapor rising and condensing into your typical thunderstorm. This is why the ITCZ is there. It is, essentially, a band of thunderstorms around the Equator that is the result of converging trade winds which is associated with the Coriolis Effect. Northwestern trade winds converge with Southwestern trade winds at the Equator. The resulting deflection is what causes storms to rotate counter-clockwise and clockwise in the Northern Hemisphere and the Southern Hemisphere, respectively. This is the Coriolis Effect. The concepts of the ITCZ, Trade Winds, and the Coriolis Effect all are directly and closely related. However, the Coriolis Effect does not cause storms to move in any given direction, It merely dictates the way they rotate. If the Coriolis Effect was strong enough to force storms in a certain direction, then we would see every single Tropical System move the same direction. Because it does not do that, All storms are highly unpredictable as we all know. A Tropical System's direction is the result of prevailing wind currents in that area. This is why most storms tend to move in a generally westward path when near the Equator. That's the direction of the trade winds near the Equator. However, once storms become Influenced by other systems, such as High Pressure Systems, mainly, the Bermuda High.. They begin to deviate from the typical east to west path.
Summarily, Tropical Systems are not "steered" by the Coriolis Effect, The Coriolis Effect is simply the Force that causes their rotation. Tropical systems are "steered" by what ever the Prevailing Wind Currents of its area are at that moment in time.
Sorry, couldn't resist! :-)
Link
ALONG 25W/26W S OF 14N. THE WAVE IS MOVING WEST NEAR 25 KT. A
WEAK 1012 SFC LOW IS ALONG THE WAVE AXIS NEAR 10N. ASSOCIATED
SHOWER AND THUNDERSTORM ACTIVITY HAS DIMINISHED. UNFAVORABLE
UPPER-LEVEL WINDS...COOLER WATER TEMPERATURES...AFRICAN
DUST...AND A FAST MOVEMENT WILL HAMPER FURTHER DEVELOPMENT.
8:00pm discussion...
A TROPICAL WAVE IS IN THE WESTERN CARIBBEAN ALONG 81W S OF 16N
MOVING W NEAR 15 KT. ABUNDANT DEEP LAYER MOISTURE AND CLOUDINESS
OVER THE SW CARIBBEAN IS MAKING IT DIFFICULT TO DEPICT LOW CLOUD
MOTIONS NEAR THE WAVE. A CLUSTER OF MODERATE TO STRONG
CONVECTION IS BETWEEN THE WAVE AXIS AN THE EAST COAST OF
NICARAGUA FROM 10N-14N. A LARGE CLUSTER OF STRONG CONVECTION IS
NEAR JAMAICA FROM 16N-19N BETWEEN 75W-78W. A SIMILAR CLUSTER OF
STRONG CONVECTION IS FURTHER S FROM 12N-16N BETWEEN 76W-78W.
THIS CONVECTION APPEARS TO BE MORE ASSOCIATED WITH UPPER
DIFFLUENCE AHEAD OF AN UPPER LOW SW OF CUBA.
Link
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT SUN JUN 10 2007
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
SHOWER AND THUNDERSTORM ACTIVITY HAS DIMINISHED IN ASSOCIATION WITH
A TROPICAL WAVE LOCATED ABOUT 425 MILES SOUTHWEST OF THE CAPE VERDE
ISLANDS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER BLAKE
But...after TS Barry, I thought tropical systems didn't have to have thunderstorms anymore. hehehe
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