TS Bonnie

It's too bad we had to waste the name Bonnie on this system, but the NHC nevertheless upgraded TD#3 to Tropical Storm (TS) Bonnie. I suppose if we are going to meet the forecast for numbers of named storms we have to get the numbers up.

Anyway, we have TS Bonnid which, as I write this, is moving through S. Florida with the heavies rains right over Miami - home for me. From the satellite picture it doesn't look like much, and as you can see from the current NHC track, it's a fast moving storm which should pass into the Gulf this afternoon and make landfall in Louisiana/Mississippi early Sunday morning. That's a good thing as it will give everyone here in Florida part of the weekend to relax. To see a larger version of these images, just click on them. Remember to hit your back button to return to the blog.

As to our flight schedule for Bonnie, we did have a G-IV flight planned for this afternoon at 1:30 pm and several P-3 flights over the next couple of days. The Hurricane Center, which tasks the Gulfstream G-IV missions, has decided not to waste another flight on Bonnie and has cancelled today's mission. I'm still waiting to here from the other folks about the P-3 flights. The first one is scheduled to depart this afternoon at 4:00 pm and the second at 4:00 am tomorrow morning (same aircraft - different crew). The plan is to repeat these on Saturday/Sunday, but with the storm being ashore early Sunday morning, I think we are limited to only three total missions. Frankly, I see no need for any of these flights considering the condition of the storm and its rapid movement, but that's not my call. I will certainly question the need, but I will provide the support if needed.

More later.

AL97 Just Won't Go Away

At 9:03 this morning, the NHC raised the probability of AL97 developing into a depression within 48 hours from orange (40%) to red, near 100%. At 11:00 am today AL97 will be classified as TD (tropical depression) #3. They will begin issuing advisories and putting up tropical storm watches along the South Florida coastline and Fla. Keys at that time. The Air Force reconnaissance aircraft will begin flying canned patterns into the system, determining among other things the exact center position every three hours. Our NOAA G-IV will also fly again this afternoon and evening, as they did yesterday, and I expect they will be tasked again for tomorrow. Today's pattern for the G-IV is shown to the right.
Please not that the forecast tracks have been moved further south and now have the storm moving through the Florida Straits and into the Gulf of Mexico. While this typically is cause for alarm along the Gulf coast, the intensity forecasts do not bring this storm to hurricane strength - yet.

We are awaiting word on tasking for the NOAA P-3 for tomorrow. The G-IV has been tasked once again for Friday. Since there will be frequent changes in events related to this storm, I shall continue to update the blog at appropriate times.

AL97 Begins to Fall Apart

As expected, it was an interesting day for AL97 and plans for us to fly this system. While the G-IV did fly its mission this evening, leaving MacDill AFB at 1:30 pm and still out there even though it's after 9:00 pm. The flights on the P-3 scheduled to begin at 4:00 am in the morning and continue every 12 hours for at least two days were, however, cancelled because the system weakened during the day for several reasons (shear, dry air entrainment, Saharan dust, etc.). The G-IV is still on the schedule for a second flight tomorrow, but I suspect it too will be cancelled in the morning.

So what did the flight today accomplish? As explained in my last posting it flew a mission to the east and southeast of Florida. The track is shown in that posting. I spoke of the plane and the dropsonde, but a visual is more explanatory, so I'm showing both here. The plane is shown to the right in the margin. The dropsonde is shown in a cut-away view and in a drawing suspended

from its parachute. As I have indicated before, the sonde is launched from the aircraft, falls towards the surface on its drogue chute at a speed of about 3,000 ft. per minute, all the while transmitting data back to the aircraft. The sample rate is two times a second (2 Hz) for temperature, humidity and pressure, and 4 times a second (4 Hz) for wind speed and direction. From 45,000 ft. it takes about 15 minutes for the sonde to reach the surface.

These data are processed onboard the aircraft and transmitted via high-speed satellite communications back to the NOAA computing center in Camp Springs, MD where they are assimilated (big word) into the model runs done every six hour. The data from this flight will go into the 00Z (8:00 pm) forecast run this evening.

As you can see from the forecast tracks issued at 18Z (2:00 pm) this afternoon where there were no dropsonde data, quite a spread has developed in the various track forecasts. The forecast with the dropsonde data in it will be published

later this evening, and we'll see what impact this flight had. Hopefully it will bring many of those lines into more agreement with each other. I'll let you know in the morning. Please bear in mind, though. Forecasting is not an exact science, and when the flapping of a butterfly's wings in China can ultimately affect the weather in Miami, FL, one has to find that elusive butterfly in order to do a better job. We'll be sure to be out with our nets for the next couple of days.

Well, here's a piece of luck. The forecast runs done at 8:00 pm have already been published and are shown at the right. These have the dropsonde data from the G-IV in them. Please note that the tracks are in much better agreement with each other than those shown in the 2:00 pm runs which did not contain any sonde data - again proving the value of this aircraft and its role in hurricane forecasting. Guess we caught a couple of butterflies.

The bad news is that the tracks are carrying whatever happens to AL97 into the Gulf and across the Deepwater Horizon oil spill area. Most of the models continue to weaken the system, but we'll have to wait a few days to see what it does when it gets to the Gulf. Keep your fingers crossed.

The Tropics Heat Up - Along Comes AL97

The tropics are starting to heat up. AL97, a disturbed area of weather north NW of Puerto Rico, is providing some excitement here and at the NHC, and while this morning it doesn't look too interesting, folks in Miami are warily watching it. The latest forecast tracks, seen to the left, leave no doubt about where it is headed - the only question is whether it will be a named strom by the time it gets there on Friday. Hopefully nothing serious develops since Friday is the day I return from Tampa to Miami and we prepare for our trip to Wisconsin next Monday.

At present AOC has been tasked by the Hurricane Center to begin flying its G-IV jet this afternoon at 1:30 pm on a track that is shown here. This will be about an 8 1/2 hour flight at altitudes from 41,000 ft. to 45,000 ft. AOC personnel will be dispensing GPS droopwindsondes at each of the points shown. These devices fall on a small parachute to the surface and radio atmospheric data back to the aircraft for processing and immediate transmission from the aircraft. The profile data (temperature, humidity, pressure and winds) are then utilized in a number of the forecast models used to predict the track of the storm. Since I covered this ground in my 2008 Blog, you may want to link back to it for a wealth of information on our facility, its aircraft and personnel. Just click on the month and posting in the right panel ts, hat may be of interest. The blob starts with the latest posting in that year and works back to the first one in May. For blow-ups of most of the picture and diagrams, just click on them. Remember to hit your back button to return to the blog.

I had promised to talk to you about AL96, but it didn't amount to anything even though we did fly research missions into and around it with one of our P-3s and the G-IV. Hopefully AL97 will have the same fate. More on that later.

The Anatomy of a Turboprop Engine and AL95

Hello all -

It's been a busy couple of weeks around AOC and the tropics. When last I wrote we had experienced an engine problem on a flight into Tropical Storm Alex and had to suspend the remaining several planned flights into that system. Well, as expected there was a serious failure in the gearbox - that very complex part of the engine that connects the turbine or jet section of the engine to the propeller. Hence, we had to swap out the engine for a spare unit that we keep on hand. As it was, our crack maintenance team was able to accomplish the change and the test flight in a 12-hour shift. That was good because another Gulf disturbance, AL96, was close on its heels. But, I'll save that for later. Thought I'd use this opportunity to talk about the anatomy of a turboprop engine such as we have on our P-3s.

Simply put, a turboprop engine is a jet engine connected to a propeller by a very complex gearbox. Also attached to several of the engines are generators, which supply the necessary power for operating the aircraft and scientific equipment aboard, as well as engine driven compressors (EDC) which provide for the pressurization onboard as well as helping to cool the fuselage. Some of these are shown in the following pics.

The left shot shows the entire engine and prop assembly on the aircraft. The right photo shows some of the components in the engine after removal. The view is the reverse side of the engine.

Here are a couple of additional photos - the first showing a mechanic preparing the spline of the shaft that comes from the gearbox to the propellor; the second showing the after section or exhaust from the turbine; the third of the location where the engine will be inserted onto the wing mount; and finally the entire motor being lifted on the hoist in preparation for insertion into the mount.

And there you have the cliff notes on a turboprop engine like the ones we use on our P-3s. Simply put, air comes in the intake on top of the engine behind the spinning prop, enters the compressor to build the pressure as it enters the turbine. There fuel is injected and ignited driving the connection to the very complex gearbox which in turn spins the propellor. 90% of the thrust to drive the aircraft through the air comes from the props and only 10% from the jet exhaust. Unlike regular jet engines, these run at a constant speed, and thrust is obtained by changing the pitch of the prop, thereby grabbing more air and thrusting it under the wing giving you speed and lift. Elementary, I'd say.

Enough for this episode. I'll talk about AL96, which was last week, tomorrow.

Best to all.