Tropical Storm Don unimpressive so far
Tropical Storm Don formed yesterday from an African tropical wave that crossed into the Gulf of Mexico, and the thus-far unimpressive storm appears poised to bring tropical storm conditions to the lower Texas coast by Friday night. An Air Force Hurricane Hunter plane arrived in the center of Don around 8am EDT this morning, and has found Don to be a small tropical storm with top winds near 40 mph. The 7:57am EDT center fix found a central pressure of 1002 mb, which is 2 mb higher than NHC was estimating in its 8am EDT advisory. However, a pass through the center at 9:49am EDT found the pressure had dropped 2mb, to 1000 mb. Top reliable surface winds seen by the Air Force plane with its SFMR instrument as of 9:45am EDT were 41 mph, at 8:10 am EDT. 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 10 - 15 knots of wind shear. The shear is from strong upper level winds out of the north. Since the atmosphere to the north of Don is relatively moist, the moderate shear will not be as damaging to the storm as if these winds had been blowing from the northwest, where the driest air lies. Thus the shear direction is often just as important as the strength of the shear, and in Don's case, the shear direction should not force significant amounts of storm-disrupting dry air into the core. Water temperatures in the Gulf of Mexico are near 29°C, which is 2.5°C above the 26.5°C threshold typically needed to maintain a tropical storm.
Figure 1. Morning satellite image of Don.
Satellite imagery shows that Don is a very small storm. Thus, the storm is vulnerable to pockets of dry air and modest-sized jets of wind shear that we can't see from the relatively coarse-resolution data collected by surface stations, hurricane hunter flights, and satellites. The moderate wind shear over Don is keeping Don's circulation tilted so that the surface center is displaced from the center at higher levels. This tilt is keeping the storm from intensifying. Latest visible satellite loops show a modest increase in the intensity of the thunderstorm's near Don's center began at 9am EDT, but this could be a transient burst and not a sign the storm is undergoing intensification.
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 be a boon or bane for Texas? The state is currently suffering through its worst drought in recorded history, and 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. However, we have a Goldilocks problem. We can't have Don intensifying into a hurricane, or its winds and flooding might bring hundreds of millions in damage. Neither do we 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. This forecast is low-confidence, though, since Don's small size makes it prone to sudden changes in strength, either upward or downward. NHC is giving Don just a 14% chance of intensifying into a hurricane in its 5am advisory, but this could easily change upward if Don manages to overcome its vertical tilt and start consolidating an eyewall. I put the odds of Don reaching hurricane strength at 30%. None of the computer models is predicting Don will become a hurricane.
A small system like Don is relatively difficult to resolve in some of the computer models we use to forecast tropical storm track, and the forecast tracks of Don from these models have a higher spread than usual. For those of you wondering about your odds of experiencing tropical storm force winds, I recommend NHC's wind probability forecast, which is showing that Corpus Christi and Port O'Connor, Texas have the highest chance of 39+ mph winds: 40%.
I'll have a new post this afternoon.
Jeff Masters
Reader Comments
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I'm thinking...(atagorda-May ay-Bay)
That was the evening, your right, it was a little heavy but short, wish my video camera could have worked because it was a great light show
Here's a gif I made to make it easier to compare this year to last year
That is different than normal... how?
http://srf.to/gomsat1
Well, the anomalies were cooler for most of the "preseason" and throughout June. However, we have seen a change in July where the SSTs have had a significant spike overall. These SSTs that we are seeing now were not predicted and if they continue, it will mean serious business in the meat of the season.
You can attribute the warming of the temps to light trade winds and a neutral to negative NAO. We have also had very little in the way of large dust outbreaks this year.
She was a nasty storm, the only time my area of the neighborhood had water ever reach past the sidewalk that is the only time me and my dad ever worried about flooding but so far it never has happened again. Or will Don do it? Dun Dun DUNNNNN!
As some of us have been saying. ;)
I miss DestinJeff.
That plus the bermuda high being stronger thn normal doesnt stack up well for anybody in the Atantic.
Excerpt:
SAL AND FRESH TRADES DOMINATING THE TROPICAL N ATLC ATTM AHEAD OF NEXT LARGE TROPICAL WAVE. GLOBAL MODELS HAVE BACKED OFF OF DEVELOPMENT...IN GENERAL OF THIS TROPICAL WAVE CURRENTLY ACROSS THE CENTRAL ATLC. HOWEVER...STRONG NELY WINDS AND BUILDING SEAS 9 TO 10 FT AND POSSIBLY HIGHER WILL SPREAD INTO THE AREA SUNDAY WITH THIS WAVE. GFS IS FASTER BY 5 DEGREES OR SO WITH THIS WAVE...WITH UKMET JUST BEHIND...AND ECMWF SLOWEST.
Don't shoot the messenger
Seems like the Western Pacific wants to make up for lost time. They are having one tropical cyclone after another.
haha, yes i know 290 is usually a mess and it moves at a snails pace but that day it was completely stalled from 610 (furthest i saw it stalled to the east) all the way out to brenham where it picked up a little
Most Emergency Management Agencies in coastal areas plan for one cat. up from what is forcast. For example: Don is forcast to be a TS when it makes L/F, so EMA's are setting plans in motion for a cat. 1 storm. This gives room for growth of the system and allows EMS's to have enough resources in place to respond after the storm w/o having to evac too many people or worry too much about any pre-storm prep that should have been done. This also cuts down on any search and rescue that may be needed.
When it comes to hurricane/TS response, It's better to have too many resources available and have to send some home.
Only specific storm/advisory. Will not auto update.
A. Yes
B. Maybe
C. Probably
D. Unlikely
E. No
Mexico
Zoom,Boxes and TFP's availible
1) Developing TUTT over the Central Atlantic into the Eastern Caribbean: This will pretty much create a "wall" of hostile upper level winds and will inhibit tropical waves coming across the Atlantic from developing.
2) Deep subsidence across the Main Development Region: The combination of Saharan air coming across the entire Atlantic as well as downward motion and reduced instability in the region will limit convection.
3) Only isolated pockets of favorable conditions across the entire Atlantic Basin: The only area that is somewhat favorable for development at this time are the SW Atlantic as the rest of the basin deals with either deep layered dry air and high pressures or hostile upper levels or both.
Before the last night tear down, i had it at min Cat 1..
not me....with his off-topic posts and 4th grade humor....he makes a mockery of weather-guessing!
Is that the pacific as a whole, or just the eastern pacific?
Just the EPAC.
Eh, we might tie it. If you'll remember back to last year, the conditions during August/September/October were nearly perfect for development, especially in the Eastern and Central Atlantic. A lot will depend on how many strong tropical waves we see emerging from Africa this year. Last year, we had a ton. This year has been lacking in the number/frequency of strong waves. The reason that we might tie last year's numbers is because of the 4 early storms we have had already. The MSLP forecast from the ECMWF for ASO looked remarkably similar to last season in the deep tropics, except a little more focused to the west with the negative anomalies. We'll see, but it's hard for the Atlantic to have back to back seasons of 19+ named systems.
haha dont forget that was a la nina year and conditions were nearly perfect just the tracks were bad because everything recurved lol well i see us getting anywehre from 15 to 18 storms so ill go with maybe
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