Mission Plan :

Figure 1. Plot of the intensity forecasts of the operational intensity models (GFDL,HWRF, and SHIPS) as well as the NHC official forecast (OFCL) for 0600 UTC 7 November. Also shown are the RI index probabilites of RI (dashed orange lines) every 6 h and the climatological probability of RI (solid orange lines.) The NHC operational intensity estimates are shown in black. The yellow diamonds indicate the time that each 24-h period of RI commenced. The center times of the P-3 and G-IV missions are designated by the pink letters.

The goal of this experiment was to fly coordinated P-3 and G-IV aircraft missions to capture the rapid intensification (RI) phase of a mature tropical cyclone. Figure 1 shows a summary of the relevant information regarding the Paloma experiment. The NHC best track intensity trace (black) shows that Paloma intensified most rapidly commencing at around 0600 UTC on 7 November when the first G-IV and P-3 missions were being flown. It can be seen that none of the operational intensity models forecasted rapid intensification for the 0600 UTC 7 November forecast cycle. Also, while the RI index probability of RI (dashed orange line) was about 3 to 4 times the climatological average of 7% (solid orange line), it was lower than it had been earlier in the time period, suggesting that the overall conditions had become somewhat less conductive than they were earlier. Interestingly, the official NHC forecast (red line) did call for a 30 knot increase in 24 h, which does qualify as RI using the Kaplan and DeMaria (2003) definition. However, even this forecast was too low.

This G-IV research mission flight plan was designed to obtain symmetric data coverage in Paloma's near storm environment by dropping sondes at 23 locations (see below) between 2-4 ° radius of Paloma's center while the P-3 was flying in a coordinated pattern within about 1.25 ° of Paloma's center collecting radar data, dropping dropsondes and AXBTs.

Mission Summary :

The jet left MacDill AFB, FL at 02:00 UTC. The flight plan was executed as designed, although the storm was east of the forecast position and thus the radial coverage on the east side was perhaps a little less than originally planned.

Figure 2. Naval Research Laboratory GOES IR deptiction of Paloma at 0615 UTC 7 November.

Paloma was a minimal hurricane with a central pressure of 985 mb and maximum sustained winds of 65 kt at the nominal time (0600 7 November) of the G-IV mission. The 200 mb G-IV data indicate that a fairly good anticyclone had been established over Paloma and, indeed, the SHIPS data show that the 200-850 mb shear was 9 kt and 200 mb divergence was 73 x 10⁷ s^-1 both of which are considered farily conductive for rapid intesification. Never-the-less, GOES IR imagery from 0615 UTC (Fig. 2) on the 7th indicates that Paloma was still somewhat asymmetric at this time.

Figure 3. NOAA P-3 tail radar cross-section plots of Paloma at 0554 UTC (top) and 0839 UTC (bottom) on 7 November. The cross-section at 0554 UTC is from north to south while the 0839 UTC cross-section is northwest to southeast. (Figure courtesy of Michael Black)

Interestingly, Paloma remained at the same intensity from 00 to 06 UTC on the 7th, which represents the only 6 h time period up to the time of landfall when Paloma wasn't intensifying. The G_IV data suggest that the temporary halt in Paloma's intensification may have been the result of the injection of some mid-level dry air as indicated by the 500 mb and 700 mb plots shown below. The potential impact of the dry air on Paloma is consistent with the P-3 radar imagery (Fig. 3) for this time period which indicate that the radial and vertical extenet of the convection on the west side of the storm is less than it is on the east side of the storm. Never-the-less, a comparison of the 0554 and 0839 UTC P-3 lower fuselage radar plots (Fig. 4) suggest that Paloma's convective sturcture was becoming better organized toward the later portion of the flight, which is consistenet with Paloma's increase in intensity to 75 kt by 1200 UTC on the 7th.

Figure 4. NOAA P-3 lower fuscelage radar depiction of Paloma at 0554 UTC (top) and 0839 UTC (bottom) on 7 November. (Figure courtesy of \ Michael Black)

The G-IV recovered at MacDill AFB, FL by 11:00 UTC.

Problems :

The sondes worked failrly well and all 23 sondes were transmitted with no back-up sonde launches required. There was one sonde that stopped transmitting prior to reaching the surface and another that had no data below 500 mb. Also, another sonde had no wind data from 300-600 mb which AOC crew attributed to interference caused by lightning.