Mission Plan :

NOAA 43RF will participate in an EMC Tail Doppler Radar mission (with an option to conduct HRD's TC-Ocean Interaction Experiment) into Hurricane Ike. The flight called for a rotated figure four pattern with an IP northwest of the center. The leg lengths were to be ~105 nm flown at 8,000 ft (pressure altitude) and GPS dropsondes would be launched in the center, in areas with insufficient scatterers to derive Doppler winds and in selected locations where AXBTs will be launched. AXBTs and AXBT/GPS dropsonde combos will be targeted in areas coincident with a pre-storm ocean survey mission flown on 08 September. Doppler wind and Super Ob analyses will be transmitted off the plane in real-time, if possible. The flight track, 16 GPS dropsonde points and 20 AXBT points are shown in Fig. 1. The flight track with overlaid pre-storm ocean survey/AXBT drop points are shown in Fig. 2.

Fig. 1: Flight track (red line) for EMC Tail Doppler Radar mission 20080910I1. GPS dropsondes, AXBTs and AXBT/GPS dropsonde combos that were launched are indicated by black circles, white circles and circled crosses respectively.

Fig. 2: Flight track (white line) for EMC Tail Doppler Radar mission 20080910I1. The 20080908I1 pre-storm ocean survey flight track (black line) and AXBT drop points (black circles) are also indicated. Hurricane Ike's forecast track is shown by the black line with forecast points (red circles). Altimeter-derived ocean heat content values are indicated by the colored shading.

Mission Summary :

1. Synoptic Situation

   On 10 August, Hurricane Ike was positioned between a large deep layer ridge to the east and a smaller deep layer ridge located over southeast Texas (Fig. 3, left). Vertical wind shear analyses from UW-CIMSS indicated ~10-15 of shear over Ike (Fig. 3, right). Figures 3 (right) and 4 also indicate that this northwesterly shear was being enhanced by 100-500 hPa inflow around the western semicircle of the storm. This upper-level flow was also restricting the outflow in this region of the storm.

   
   Fig. 3: (Left) plot of 250-850 hPa deep layer mean steering [magnitude (direction) of the steering flow is indicated by colored shading (white streamlines) and the storm location is indicated by the red hurricane symbol] for 10 Sept 1200 UTC. (Right) vertical wind shear [magnitude (direction) of the wind shear is indicated by yellow contours (orange streamlines)]) for 10 Sept 1200 UTC. Images courtesy of UW/CIMSS.
   
   Fig. 4: Plot of mid to upper-level GOES water vapor winds for 10 Sept 1200 UTC. Image courtesy of UW/CIMSS.

2. Mission Specifics

   Take-off was from MacDill at 0808 UTC. Hurricane Ike was located at ~23.5°N 84.8°W, its intensity was 70 kt (964 hPa) and its forward motion was 300 degrees at 7 kt. Figure 5 indicates that Ike's convection was quite asymmetric, with the deepest convection (-70° to -80°C cloud tops) located to the east and northeast of the center. A 1330 UTC H*Wind surface wind analysis confirmed that the asymmetry of the surface wind field was similar to the asymmetry seen in the infrared satellite imagery (Fig. 5). Surface winds in the western semicircle of the storm were significantly weaker than those around the eastern semicircle.

   
   Fig. 5: Plots of (left) GOES-12 IR imagery for 10 Sept 1255 UTC and (right) HRD H*Wind surface wind analysis for 10 Sept 1330 UTC. Images courtesy of NRL/Monterey and NOAA/AOML/HRD.

   Figure 6 shows images from the SSMIS (91 GHz) and TRMM (Precipitation Radar) satellites. Both products indicate that Ike had a broad outer eyewall located approximately 75 nm from the center. This was confirmed by 43's LF radar, which also showed the presence of a smaller inner pinhole eye. The western side of the outer eyewall was consistently open throughout the 7.25 hr mission and near the end of the flight the outer eyewall also appeared to be open to the north and northeast.

   
   Fig. 6: Plots of (left) SSMIS 91 GHz microwave imagery and (right) the TRMM Precipitation Radar for 10 August 1133 and 1048 UTC respectively. Images courtesy of NRL/Monterey.

   The flight pattern was executed as planned. Thirteen GPS dropsonde/AXBT combos, 3 GPS-only and 7 AXBT-only drops were made during the mission. The lowest GPS dropsonde pressure observed during the mission was 956.9 hPa at drop #9, during a pass through the center at 1149 UTC. One Doppler wind and one Super Ob analysis were transmitted off the P-3 in real-time during this mission.