Don battling dry air and wind shear
Tropical Storm Don continues to be an unimpressive low-end tropical storm as it continues northwest towards the Texas coast. Don formed yesterday afternoon from an African tropical wave that moved into the Gulf of Mexico under a region of low wind shear. Don's formation date of July 27 is nearly a month ahead of the usual August 23 date for the arrival of the season's fourth named storm of the year. There is currently no hurricane hunter airplane in Don, and a new airplane is not due in the storm until tonight. The last center fix at 1pm EDT found surface winds of 45 mph and a central pressure of 1005 mb, a 4 mb rise from earlier this morning. Water vapor satellite images show a region of dry air to the northwest of Don, over the western Gulf of Mexico. Wind shear as diagnosed by the University of Wisconsin CIMSS group and the SHIPS model show a moderate 5 - 15 knots of shear from strong upper level winds out of the north. This shear is creating problems for Don by injecting dry air into the system. Visible satellite imagery from early this afternoon showed the presence of surface arc-shaped clouds expanding outwards to the north from the center of Don. These type of clouds are a sign that the storm is struggling with dry air. When dry air at middle levels of the atmosphere gets injected into thunderstorms due to wind shear, the dry air tends to create strong downdrafts that rob the storm of moisture. These downdrafts spread out at the ocean surface and create arc-shaped surface cumulus clouds.
Figure 1. Visible satellite image of Don from pm EDT July 28, 2011, showing arc-shaped surface clouds--the tell-tale sign of dry air interfering with the storm's organization.
Figure 2. The latest drought map for Texas shows that over 75% of the state is in exceptional drought--the highest category of drought. Image credit: U.S. Drought Monitor.
Forecast for Don
The big question for Don is, will it bring significant rains to Texas? According to the National Climatic Data Center, the six-month period ending in June 2011 was the driest on record. Average rain between January and June was more than eight inches (203 millimeters) below average in Texas, and the state experienced record heat between April and June. The heat and lack of rain have brought exceptional drought--the highest category of drought--to over 75% of the state. Don has the potential to bring some decent drought-busting rains to the state. If Don can expand in size and intensify to a 50 - 55 mph tropical storm, it has the capability to bring hundreds of millions of dollars worth of beneficial rains to the state. We don't want Don to stay in its current state, which is too small and weak to bring significant rains to Texas. If Don follows the current NHC forecast, which brings the storm up to a moderate-strength tropical storm, that would be just right. Don's small size makes it prone to dry air and wind shear, though, and it is uncertain whether the storm can overcome these problems enough to become a significant rain maker. NHC gave Don a 12% chance of intensifying into a hurricane in the 11am advisory, which is a reasonable forecast, since Don is running out of time to get its act together in time to become a hurricane. None of the computer models is predicting Don will become a hurricane.
For those of you wondering about your odds of experiencing tropical storm force winds, I recommend NHC's wind probability forecast. The 11 am version of this forecast shows that Port O'Connor, Texas has the highest chance of tropical storm-force winds (39+ mph): 45%.
New hurricane archive search feature
The autocomplete entities in the wunderground search box has been extended to include hurricanes, so you can now search for a storm by name, year, or basin. Here are some examples in case you feel like exploring your new options:
By name:
Hurricane David - Atlantic, 1979
David, Major Hurricane - Atlantic, 1979
Major Hurricane David - Atlantic, 1979
By year:
2005 Hurricanes Atlantic
2007 Hurricanes Eastern Pacific
By basin:
Hurricanes Western Pacific 2011
Hurricanes Atlantic 2008
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Tropical Storms Atlantic 2005
Tropical Depressions Indian Ocean 2011
Subtropical Storms Eastern Pacific 2010
Extratropical Storms Western Pacific 1988
I'll have a new post Friday morning.
Jeff Masters
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Winds near 40mph.
000130 2448N 09134W 8429 01553 0063 +188 +178 131029 030 034 002 00
and its trying too make a run for hurricane
Not entirely convinced that Don is up near hurricane strength at the minute, will have better idea when the next recon gets to the centre in a few minutes. However, even if Don is at 50/55mph I'd say a hurricane watch is needed. I agree with landfall somewhere between Brownsville and Corpus Christi.
LOL that info you this posted is way old DON is way better now
No, weak tropical storm's do not have an eye. What Don is doing now is building an eye-wall, right where that deepest convection can be seen on satellite. Once he is finished, which should be sometime tomorrow, he will likely begin to show an eye. They usually appear when the storm reaches 60 mph (from experience).
P451 look at the actual HH data - the center is at roughly 24.5 and 92 - superimpose that on the latest IR and a much different picture shows.
Silly Don.....
WC-130J
On 12 October 1999, the U.S. Air Force took delivery of its first WC-130J aircraft. Nine others are scheduled for delivery by late-2000.
In September 1998, the C-130J Development System Office (DSO) at Wright-Patterson AFB, OH, signed a contract with Lockheed Martin Aeronautical Systems, Marietta, GA, to modify six C-130Js to the "W", or weather, configuration. This involved installing and integrating special avionics and weather sensors, as well as making structural modifications. The DSO later exercised contract options to modify an additional four C-130J aircraft.
The WC-130Js will replace the existing fleet of ten WC-130H-model aircraft. The "J-models" are based on the familiar C-130 platform that the Air Force has flown for more than 40 years, but with many improvements, including new engines and avionics, as well as the addition of two mission computers and two head-up displays.
Sensors mounted on the outside of WC-130Js provide real-time temperature, humidity, barometric pressure, radar-measured altitude, wind speed and direction. These are used to calculate a complete weather observation every 30 seconds. These aircraft also deploy dropsondes, instruments ejected out the aircraft and deployed by parachute through the storm to the sea. During descent, they gather real-time weather data and relay it back to the aircraft.
This information is transmitted by satellite directly to the National Hurricane Center for input into the national weather data networks. Forecasters use the data to better predict the path of a storm or hurricane.
He might well achieve that before landfall, but he's not nearly as well organized as some people are saying.
ON APPROACH
IR NIGHT VIEW
True, but convection appears to be building over the center in the last couple of images (as per SSD). I don't really see any reason why that should change.
+1
um he is right, the center is on the north side of the convection
Hurricane Hunters found that the center had relocated to about the center of the main convection. if what you are saying is true, it shouldnt be this organized and shouldnt be building an eyewall like it is.
DON would not be makeing a run for hurricane if it was
thank you
true, does seem to be getting its act together
hurricane status is not out of the question
Careful, you'll get harassed for mentioning something that isn't Don! Haha
That wave not looking bad though, certainly looks like it could steadily organise and we may see Emily some stage next week.
Please do not engage in personal attacks or bickering.
yup oh DON now have a T # of 3.0
their not at the center yet are they?
Thats as of 15 minutes ago Taz... know it all...
A. Nonexistent
B. Low
C. Medium
D. High
Link
000930 2427N 09149W 8437 01489 9954 279 142 107010 013 024 002 03
wow...
995.4 mb.
oh my RI RI
Holly jesus!
Viewing: 801 - 851
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