Tropical Depression 17, Galloping Gertie and a Not Too Exciting Thursday Night


SPC Severe Outlook 1106 12Z to 1107 12Z

SPC Severe Outlook 1106 12Z to 1107 12Z

for a more recent update on hurricane paloma, CLICK HERE

If you look at the SPC outlook above, you notice that the slight risk area is really small down to the south. While there were some big storms on Wednesday in the plains, the dynamics to support more in the way of potential strong storms kinda go by the wayside on Thursday. Couple that with the fact that the front comes through here on Thursday night, and you lose any potential for fireworks. One more warm day today then a chance for rain and perhaps a rumble of thunder on Thursday night. Cooler air on Friday with perhaps some sunshine. As I mentioned several days ago, I had thought this scenario would unfold. We’ll be warmer than I was anticipating for Friday but the real push of cold air comes in on Saturday and with the clouds, we may be hard pressed to come out of the 40’s. Sunday, the sun breaks through but we still only get to the low 50’s. Really not a great weekend shaping up.

Tropical Depression 17 IR Satellite 1106 0515Z

Tropical Depression 17 IR Satellite 1106 0515Z

Tropical Depression 17: As expected, the little area developing off the Nicaraguan

Tropical Depression 17 Forecast Track 1105 10 PM EST

Tropical Depression 17 Forecast Track 1105 10 PM EST

coast has developed quite nicely. The satellite image seems to show some decent outflow and the upper winds in the region are rather weak so it has a good chance of becoming Tropical Storm Paloma. In fact, the majority of the models take it hurricane status with one even wanting to make it a cat 3 with over 100 kt winds. That seems unlikely though. Its drifing northwest and may even get over land for a time but should start to move north and then north northeast as it moves about a ridge to the east. As the front that is moving through our area on Thursday comes along, it should dig deep enough into the Gulf to pick this guy up and, as it does so, it moves into some pretty strong westerly winds. That would take the storm across the northern Caribean toward Cuba and across Cuba into the Bahamas. Odds are, if it doesn’t do that, then it would be farther east and maybe even affect Haiti which doesn’t need any more storms. But, its possible. Those upper winds I suspect will mess it up and that is why I wouldn’t think that a major hurricane is in the cards, nor one that would affect the US. The discussion and spaghetti models are below.

A Big Mistake

Tacoma Narrows Bridge: A Big Mistake

On This Date In History: On this date in 1940 one of the greatest engineering boondoggles was uncovered in Washington. The Tacoma Narrows Bridge opened in July 1940 to great fanfare. With a span of 2800 feet, it was the third longest bridge in the world. The builder decided to save money by making the bridge only 39 feet wide to support just two lanes of traffic. It was designed to withstand winds of 120 mph. People flocked to the bridge after it’s opening, not just because it was faster than the ferry, but also because moderate winds that are common in the area would make the bridge sway and even undulate up and down. Drivers reported losing sight of the autos in front of them when the bridge waved. The bridge gained the moniker “Galloping Gertie.”

All the fun and games came to a crashing end on this date in 1940 (November 7) when steady winds of just 42 mph made the bridge sway…and then leap. It continued throughout the day until the entire structure failed. The bridge had been closed but the last man let across lost control of his car and, in fear of being tossed 190 feet into the Tacoma Narrows below, he fled on foot. He tried to retrieve the family cocker spaniel from the back seat but the pup would have none of it. As he reached the end of the bridge, the bridge collapsed spectacularly with the dog as the only casualty.

The result of the collapse was analysed and is a common subject in college physics classes. Basically, the wind was in tune with the natural harmonics of the bridge. The more the wind blew, the greater it increased the amplitude of the harmonics creating a wave. Its a similar phenomena as when a singer breaks a glass. To avoid a similar fate, bridges today, including the one that replaced “Galloping Gertie” have damping and aerodynamic features built in and wind tunnels are used to test the ability of the structure to resist wind and prevent compromise of the integrity of the structure.

Here is the 1940 Newsreel Footage of the Collapse of the Tacoma Narrows Bridge

Here is a different, color film on video of the collapse

Whatever man builds, can come down. Gravity and other forces are constantly at play. There are some things in life in which compromise can be a good thing. But engineers cannot afford to not get it right the first time. It kinda reminds me of what US Grant often said, “man proposes; God disposes.” These days we often teach our kids that close is good enough. If that is your methodology, mommas don’t let your babies be engineers.

TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172008
1000 PM EST WED NOV 05 2008

Tropical Depression 17 Spaghetti Model 1106 00Z

Tropical Depression 17 Spaghetti Model 1106 00Z

PAST FEW HOURS…AND DVORAK T-NUMBERS FROM SAB AND TAFB AT 0000 UTC
SUPPORTED AN INTENSITY OF 30 AND 35 KT…RESPECTIVELY. ANALYSIS OF
AMBIGUITIES FROM A QUIKSCAT PASS AT 2334 UTC SUGGESTS THAT THE
HIGHEST WINDS OUTSIDE OF RAIN NEAR THE CENTER WERE AROUND 25
KT…REASONABLY SUGGESTING THAT WINDS ARE NEAR 30 KT IN THE
CONVECTION. ALSO…NOAA BUOY 42057 WELL NORTH OF THE CENTER
REPORTED A PEAK WIND OF 29 KT AT 2200 AND 2300 UTC…AND A GUST OF
33 KT. BASED ON ALL OF THIS EVIDENCE…THE INITIAL INTENSITY IS
SET AT 30 KT. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL
INVESTIGATE THE CYCLONE LATER TONIGHT AND MAY FIND THAT THE SYSTEM
HAS REACHED TROPICAL STORM STATUS.

THE DEPRESSION HAS BEEN MOVING SLOWLY NORTHWEST OVER THE PAST FEW
HOURS. A SLOW MOVEMENT TOWARD THE NORTHWEST IS EXPECTED TO CONTINUE
FOR THE NEXT 24 HOURS…WITH A GRADUAL TURN TOWARD THE NORTH
EXPECTED BY 48 HOURS AS THE CYCLONE ROUNDS THE WESTERN EDGE OF THE
UPPER-LEVEL ANTICYCLONE CENTERED TO ITS EAST. LATER IN THE
PERIOD…AN UPPER-LEVEL TROUGH IS FORECAST TO DIG INTO THE GULF OF
MEXICO…AND WILL CAUSE THE CYCLONE TO TURN TOWARD THE NORTHEAST
WITH AN INCREASE IN FORWARD SPEED. THE CURRENT TRACK FORECAST IS
SLIGHTLY FASTER THAN THE PREVIOUS ADVISORY THROUGH ABOUT 36
HOURS…BUT IS STILL SLOWER THAN MOST OF THE MODEL GUIDANCE. AFTER
36 HOURS…THE FORECAST TRACK IS ADJUSTED TO THE LEFT OF THE
PREVIOUS FORECAST TOWARD THE DYNAMICAL MODEL CONSENSUS…TVCN.

Tropical Depression 17 Spaghetti Model Intensity Graph 1106 00Z

Tropical Depression 17 Spaghetti Model Intensity Graph 1106 00Z

VERY FAVORABLE FOR INTENSIFICATION THROUGH ABOUT 72 HOURS. THE
GFDL AND HWRF BOTH MAKE THE CYCLONE A HURRICANE WITHIN 36 TO 48
HOURS…AND FORECAST AN INTENSITY NEAR MAJOR HURRICANE STATUS BY 72
HOURS. THE SHIPS MODEL FORECASTS THE SYSTEM TO BE NEAR HURRICANE
INTENSITY AT 48 HOURS BUT DOES NOT SHOW AS MUCH STRENGTHENING
BEYOND THAT TIME. THE INTENSITY FORECAST WAS ADJUSTED UPWARD…AND
IS IN EXCELLENT AGREEMENT WITH THE ICON INTENSITY MODEL CONSENSUS.
HOWEVER…IF THE CYCLONE IS ABLE TO ESTABLISH AN INNER CORE…MORE
RAPID INTENSIFICATION MAY OCCUR THAN IS FORECAST HERE. BEYOND 72
HOURS…THE VERTICAL WIND SHEAR INCREASES RAPIDLY AS THE CYCLONE
INTERACTS WITH THE WESTERLIES…AND WEAKENING IS FORECAST AT THOSE
TIME PERIODS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 06/0300Z 14.3N 82.1W 30 KT
12HR VT 06/1200Z 14.8N 82.5W 40 KT
24HR VT 07/0000Z 15.6N 82.9W 50 KT
36HR VT 07/1200Z 16.4N 83.1W 60 KT
48HR VT 08/0000Z 17.3N 83.2W 70 KT
72HR VT 09/0000Z 19.0N 82.0W 90 KT
96HR VT 10/0000Z 20.5N 79.5W 70 KT
120HR VT 11/0000Z 23.5N 74.5W 50 KT

$$
FORECASTER BRENNAN/STEWART

One Response

  1. […] I had thought that November 6 was November 7 all day and then got all messed up. But, it’s still some cool video….both the newsreel and the color video. Hurricane Paloma NHC Forecast Track 1107 10pm […]

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