IFEX daily log
Thursday, July 14, 2005
All three planes are available for flights starting today. Convection flared up over
the target region during the overnight hours. Northeasterly shear is still evident over the
region, preventing any development in the immediate future. The forecast situation
shows that Emily has undergone a rapid intensification episode and is now a hurricane. It
has entered the southeastern Caribbean sea, and the forecast has now shifted somewhat to
the north, bringing the storm just south of Jamaica and predicting landfall further north
along the Yucatan peninsula. The possibility of tasking for at least one of the P-3Õs is
now higher, though it seems still unlikely that they will be tasked in the next several days.
In the East Pacific, the southwesterly flow persists, and QuikScat imagery
suggests a cyclonic rotation south of the Gulf of Tuheanapec (see Fig. 1). Convection
developed overnight in various regions; one associated with the suspected wave and other
convection near the Gulf of Tuehanapec. Shear remains moderate over the region, but
with the persistence of the southwesterly flow in the area, a cyclonic shear axis that arises
as a result of flow, and the possible approach of another wave in the next 24 h, it still
appears possible that genesis could occur after 2-3 days. The flight plan for N42RF calls
for a survey pattern (see Fig. 2) where the plane will fly west along 10 N, from 89 to 97
W. Then it will turn NE to 12 N 93 W, then turn NW to 14 N 97 W. It will then turn east
along 14 N to 92 W, then turn southeast to 12 N 90 W. Then S to 11 N 90 W, and finally
east to 11 N 89 W. A total of 23 sondes are planned and 8 BTÕs. If there is any
significant convective development along the way, the aircraft will deviate to map out the
flow field associated with it, provided the deviation will not seriously alter the flow
fields. The plane will fly at 14,000 ft.
N43RF will fly a pattern that depends on what is found by N42RF. The takeoff
for N43RF is scheduled for 05 UTC, and the ER-2 is scheduled to take off at 06 UTC for
a coordinated mission with N43RF.
Along the flight of N42RF, there is not a clear sign of a shift in wind direction at flight
level that may indicate a tropical wave at this altitude for the beginning of the flight
(15,000 ft or 600 mb; see mission summary 050714H). Winds started out from 195 just
offshore of Costa Rica, then switched to 225 about 200 nm offshore. Moving further
west the flight-level winds turned to westerly, then generally stayed there for much of
this part of the pattern. A visible satellite image (Fig. 3) shows generally isolated
convection along the flight track, except for are an larger area of convection about 150-
200 nm south-southeast of the Gulf of Tuahenapec. N42RF may deviate from track
somewhat to target this convection, if it remains and appears widespread by the time the
aircraft reaches it. Upon passing 12 N, 93 W, there is a NW-SE oriented line of
stratiform rain, with some convective elements embedded within it, about 10-20 nm to
the southwest of the aircraft track. At 12.5 N 93.75 W, there was a pronounced wind
shift from southwest to west-northwest at flight level. This may be indicative of the
horizontal shear axis discussed previously, or it may be related to the rainfall seen off to
the left of the aircraft. As flight has continued, it is evident that the flight-level wind field
is rather chaotic along about 13-14 N. Multiple wind shifts have been detected, but in
general there is northerly and northeasterly flow at flight-level west of 95 W and
southwesterly flow east of there, especially closer to 90 W. A flare-up of moderate
convective and stratiform rain did occur centered at 12 N 96 W while N42RF was in the
pattern (Fig. 4). The aircraft flew within about 20 nm of the convection, so the tail radar
should have sampled some of that. The vertical shear still appears to be moderate to
somewhat high, so there are doubts as to whether this system will have a reasonable
chance of developing. Future decisions on whether to deploy to Acapulco after
tomorrowÕs flights will hinge on the likelihood of this developing. We may not want to
go there if this is likely to just be a null case.
N43RF flew their mission with an 11 PM takeoff. They repeated the survey
pattern flown by N42RF during the daytime mission.
Rob Rogers
HRD Field Program director
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