Mission Summary
20100903N1 Aircraft 49RF
Extratropical Transition Mission Hurricane Earl

Aircraft Crew (49RF)
Aircraft Commander
Flight DirectorRich Henning
Flight DirectorJack Parrish
Electronics Technician
AVAPS Operator
Dropsonde Operator

Scientific Crew (49RF)

Proposed flight track

Mission Plan :

NOAA 49RF will fly an HRD-tasked Extratropical Transition mission around Hurricane Earl. The G-IV will leave MacDill AFB 1730 UTC and will recover back at MacDill AFB, FL by 0150 UTC next day.

Prepared by the
Hurricane Research Division
Aircraft: N49RF
Altitude: FL410-450
Proposed takeoff: 31/1730Z
deg min deg min hh:mm

Mission Summary :

We didn't plan on doing it...but when the actual location of Earl's center was not as far north as originally planned when we arrived nearby just prior to 19:00 Z, we shifted our first drop location further SW so that it would be in a similar storm relative spot to what had been planned. This resulted in a situation where the track to our second drop to begin the rest of the pattern would just happen to take us over the center of Earl. With only a small amount of convection to dodge in what was left of the western eyewall, we safely released a sonde into what Jack Parrish and I thought would be what remained of the eye about 42,000 feet below (no visible swirl or any other visible clues to use...just an amorphous CDO beneath the plane) in hopes it would spiral inward radially from just SE of the center to just east and then ENE and finally into the center at splash.

As it turned out....we just barely missed the surface center by only a few miles (maybe less). The last USAF recon fix at 17:17 Z had a center eye sonde pressure of 961mb. Our 18:59:27 Z attempt splashed with 962 mb and SE winds of 49 knots. This would suggest the MSLP dropped a little in those two hours (maybe back down to as much as 957 if you use the 10 kts = 1 mb miss of the center rule of thumb). However when NOAA 43 showed up in the center at 21:30 Z. ...we saw something strange....they released two sondes (from 12,000 feet or 645 mb) into what used to be the eye with one showing 45 knots of SE wind and 961 mb (very similar to ours) and a second drop at the exact FL center that showed only 9 kts of surface wind....but instead of 956 or 957mb, it measured just 960 mb. I'm not sure I understand how there can be 36 knots of additional wind generated across 1 mb of gradient in the center. Seems very odd.

That center drop showed a 10 °C warm anomaly at 300 and 400 mb in the core (as compared to surrounding dropsondes and to the nearby Upton NY and Chatham MA 12:00 Z soundings). The two drops that bracketed the center are also appended below and their skew Ts attached (18:48:08 Z to the west (with 75 kts at about 400 meters) and 19:07:50 Z east of the center (with 87 knots at just under 1000 meters)). The three drops across this center pass suggest that the vortex circulation extended up to around 300 mb with SW shear above that up through our 170 mb flight level.

Later on we had a sonde a little further SSE of the center with 83 knots of SSW wind down at 871 mb so Earl still had a strong connection feeding it high theta e air. I was also impressed by the fact that another sonde showed an surface air temp of 27.6°C (with 44 kts of sfc wind) at greater than 39°N. I'm not sure I can recall seeing air that warm in a TC boundary layer as far north as New Jersey.

Between the unusually warm BL temps, and what was still an almost perfectly aligned (vertically stacked) core with a strong warm anomaly still lingering directly over the surface center (in spite of the shear), what was designed as an extratropical transition research flight was a study in what was still a 100 percent tropical barotropic system (at least this afternoon) hanging in there in spite of an increasingly baroclinic environment at a very high latitude.

For the first time in a G-IV TC mission we used 100% AVAPS II sondes and had a perfect 18 for 18 with no failures and all 18 coded surface winds!!!

Problems :

Rich Henning
Sept. 4, 2010

Mission Data :

NetCDF file

Page last updated September 3, 2010
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