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
By category:
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
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 — Blog Index
I give it a pretty good chance i just don't see things continuing to be hostile for don and im sure when he gets that first break he'll take to it and start, but everythings changes so you gotta keep a good eye on things, but for your question i give a high chance of developement.
THE LARGE-SCALE MODELS AGAIN FORECAST MODERATE SHEAR TO CONTINUE
UNTIL DON MAKES LANDFALL. THIS AND CONTINUED INTERACTION WITH DRY
AIR OVER THE WESTERN GULF OF MEXICO IS LIKELY TO IMPEDE
INTENSIFICATION...AND THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT
THAT DON WILL MAKE LANDFALL AS A TROPICAL STORM AND NOT AS A
HURRICANE. THE NEW INTENSITY FORECAST CALLS FOR A LITTLE LESS
STRENGTHENING DURING THE FIRST 12-24 HR DUE TO THE PRESENCE OF
SHEAR AND ARC CLOUDS...THEN CALLS FOR DON TO REACH A PEAK INTENSITY
OF 50 KT NEAR LANDFALL. AFTER LANDFALL...THE CYCLONE SHOULD WEAKEN
TO A TROPICAL DEPRESSION BY THE 48 HR POINT AND TO A REMNANT LOW BY
THE 72 HR POINT.
To be honest, I have yet to see the COC myself. Pray tell, where is it? :/
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011
400 PM CDT THU JUL 28 2011
DON HAS A CLASSIC SHEAR PATTERN IN SATELLITE IMAGERY THIS AFTERNOON
WITH STRONG BURSTS OF CONVECTION OCCURRING NEAR AND SOUTH OF THE
CENTER. ANALYSES FROM THE SHIPS MODEL AND FROM CIMSS AT THE
UNIVERSITY OF WISCONSIN INDICATE 10-15 KT OF NORTHERLY VERTICAL
WIND SHEAR CONTINUING OVER THE STORM. IN ADDITION...A STREAM OF
ARC CLOUDS/GUSTS FRONTS ON THE EASTERN SIDE OF THE CIRCULATION
SUGGESTS THAT DRY AIR IS BEING ENTRAINED INTO THE CONVECTION. DATA
FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SHOWED THE
CENTRAL PRESSURE RISING TO 1005 MB...WHILE THE AIRCRAFT WINDS
SUPPORTED AN INITIAL INTENSITY OF 40 KT.
THE INITIAL MOTION IS NOW 305/14. DON REMAINS TO THE SOUTH AND
SOUTHWEST OF A DEEP-LAYER RIDGE OVER THE SOUTHEASTERN UNITED
STATES...AND THE LARGE-SCALE MODELS FORECAST THIS FEATURE TO
PERSIST FOR THE NEXT 36-48 HR. THIS SHOULD STEER DON GENERALLY
NORTHWESTWARD TO WEST-NORTHWESTWARD UNTIL LANDFALL ON THE TEXAS
COAST IN ABOUT 36 HR. THE TRACK GUIDANCE...WHICH SHIFTED NORTHWARD
BETWEEN 06Z AND 12Z...HAS SHIFTED SOUTHWARD FOR THIS ADVISORY. THE
NEW FORECAST TRACK HAS BEEN ONLY SLIGHTLY ADJUSTED TO THE SOUTH AND
LIES ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE. SOME ADJUSTMENT
TO THE FORECAST TRACK MAY BE NECESSARY IF THE TRACK GUIDANCE
STABILIZES AROUND A TRACK SOUTH OF THE CURRENT FORECAST.
THE LARGE-SCALE MODELS AGAIN FORECAST MODERATE SHEAR TO CONTINUE
UNTIL DON MAKES LANDFALL. THIS AND CONTINUED INTERACTION WITH DRY
AIR OVER THE WESTERN GULF OF MEXICO IS LIKELY TO IMPEDE
INTENSIFICATION...AND THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT
THAT DON WILL MAKE LANDFALL AS A TROPICAL STORM AND NOT AS A
HURRICANE. THE NEW INTENSITY FORECAST CALLS FOR A LITTLE LESS
STRENGTHENING DURING THE FIRST 12-24 HR DUE TO THE PRESENCE OF
SHEAR AND ARC CLOUDS...THEN CALLS FOR DON TO REACH A PEAK INTENSITY
OF 50 KT NEAR LANDFALL. AFTER LANDFALL...THE CYCLONE SHOULD WEAKEN
TO A TROPICAL DEPRESSION BY THE 48 HR POINT AND TO A REMNANT LOW BY
THE 72 HR POINT.
FORECAST POSITIONS AND MAX WINDS
INIT 28/2100Z 24.9N 91.3W 40 KT 45 MPH
12H 29/0600Z 25.8N 93.1W 40 KT 45 MPH
24H 29/1800Z 26.8N 95.2W 45 KT 50 MPH
36H 30/0600Z 27.8N 97.5W 50 KT 60 MPH...INLAND
48H 30/1800Z 28.8N 100.0W 30 KT 35 MPH...INLAND
72H 31/1800Z 30.5N 103.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 01/1800Z...DISSIPATED
$$
FORECASTER BEVEN
Don will probably stay in his current state until about 12-18 hours before landfall. He desperately needs to get away from the northerly shearing winds. I think once he gets closer to the Texas coastline, the shear looks to relax some and he will try to strengthen some as most tropical cyclones do when making landfall in Texas. The shape of the Texas coastline tends to do that, just like the shape of the Bay of Campeche. The limiting factor for intensification before landfall might be the arid-like airmass that is entrenched over Texas.
Edit: After looking at water vapor, the airmass doesn't appear to be terribly dry. However, I'd bet if we looked at soundings from different layers, they would be drier towards the mid and lower levels.
Notice all the stratocumulus clouds surrounding the entire wave to the north. Very indicative of a stable, dry environment.
I see Levi's here and some of the other usual suspects, so I know the fort is in good hands. Busy with school, Michael, and life...But I'll be around more when the season heats up.
Floater - Rainbow Color Infrared Loop
woo hoo...JUNKIE!!! long time no see
And Keith, that'd be a K for Krystal...And no thank-you! I have swore those things off for the rest of my life thanks to this crew...lol
91.3W, 24.9N, On the edge of the convection on the northern side.
Krystal? Blech. Five Guys. Or Smashburger. Or Moo Yah.
Final stregnth at landfall is:
a: 40-45mph
b:50-55mph
c:60-65mph
d:70mph- or a cat 1 hurricane
im going with C
That remains the only inhibiting factor of development imo, which is why I do not believe it will develop until just before it reaches the islands.
Yeah, agree completely...But the deal was people would give money to disaster relief if I ate something like 15 of them in two hours...Without throwing up.
Hey Storm! What happened to the website?!
If that happens, at least he shouldn't be strong enough to mess up the hotel we stay at in Fulton. It is right across from Fulton Harbor.
If you ever find yourself in the Rockport-Fulton area (assuming you haven't ever done this), visit Fulton Mansion. About 2 blocks back from the mansion (on what used to be the same property) there is a big oak tree in the front yard of what may be an abandoned house. In that tree is a very unusual object: The "wheel" of a windmill, blades and all. It was deposited there by the 1919 Corpus Christi hurricane.
Ahhh.
I couldn't even down one Krystal "burger."
Link
My family and i have 2nd house down there and go quite often but havent been there to the mansion but we like rockport alot and the lighthouse inn.
My ex wife and kids live in Rockport. I hope the kids are safe.
True that.
It is under the convection, "completely", depends on how you use the word. It is towards the northern end of the convection, so it's not a good setup for steady strengthening. (still struggling some with wind shear) It really needs to be in the center of the convection.
He is looking better though. If he can continue the trend he should begin at least some slow intensification.
OUCH...
Take a tour and ask the guide how high the water got in the mansion in 1919. Then realize how far above the Bay the mansion was built.
I agree, but it does look like all the models are in agreement. We should have a system near the northen islands in a wetter environ.
Don will more than likely be something weak so they will be safe, we got a 2nd house down there and we're not to worried
Glad I wasnt seeing things. Thanks for conferming, Its still a lopsided system but it looks much better than it has in the past and is on its way to minimal strengthening of about 60 at landfall IMO.
Groovin baby'
Viz
RGB
Rainbow
Serious watch Mid Atl
Godaddy messed up when I renewed the server, but I'm about to shut it down anyway. I may put it back up on a cheaper server one day, but $500 a yr is way more server than I need for what I have on there. Plus I am going to be slammed for the next yr with school. In the fall, I'm taking 21 credit hrs.
I miss the site too though.
I know they are safe where they are. I was throwing it out as a bit of comic relief (didn't mention anything about the ex wife's safety)
Floater - Rainbow Color Infrared Loop
Zoom,Boxes and Tropical Points active
Viewing: 151 - 201
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 — Blog Index