Tropical Weather Discussion


abio10 pgtw 232300
msgid/genadmin/joint typhoon wrncen Pearl Harbor hi//
subj/significant tropical weather advisory for the Indian Ocean
ref/a/msg/joint typhoon wrncen Pearl Harbor hi/231951zjan2019//
ref/b/msg/joint typhoon wrncen Pearl Harbor hi/232221zjan2019//
narr/ref a is a tropical cyclone warning. Ref b is a tropical
/cyclone formation alert.//
1. North Indian Ocean area (Malay Peninsula west to coast of Africa):
   a. Tropical cyclone summary: none.
   B. Tropical disturbance summary: none.
2. South Indian Ocean area (135e west to coast of Africa):
   a. Tropical cyclone summary:
      (1) at 231800z, tropical cyclone 11s (eleven) was located near
16.5s 122.1e, approximately 84 nm north of Broome, Australia, and
had tracked southwestward at 12 knots (kts) over the past six hours.
Maximum sustained surface winds were estimated at 35 knots gusting
to 45 knots. See ref a (wtxs31 pgtw 232100) for further details.
      (2) no other tropical cyclones.
   B. Tropical disturbance summary:
      (1) the area of convection (invest 93s) previously located
near 20.9s 40.2e, is now located near 21.9s 40.8e, approximately 186
nm west-northwest of tollara, Madagascar. Animated enhanced infrared
satellite imagery shows significantly diminished deep convection
near the low level circulation center (LLCC) and a large area of
deep convection in a convergent zone well to the northeast of the
LLCC. A 231916z AMSU 89 ghz microwave image shows a few small rain
bands around the LLCC and very little deep convection associated
with the circulation. A 231918z metop-a ascat pass shows a highly
asymmetric wind field with a large swath of 25 to 30 knot winds to
the northeast. 93s is in a marginal environment with excellent
poleward outflow, fair equatorward outflow, moderate (15 to 20 knot)
vertical wind shear (vws), and marginal (26 to 28 celsius) sea
surface temperatures (sst). The global models predict that the
system will track southward to southeastward, possibly intensifying
slightly, while transitioning from a hybrid tropical/subtropical
circulation into an extratropical system as it enters the mid-
latitude westerlies. Maximum sustained surface winds are estimated
at 25 to 30 knots. Minimum sea level pressure is estimated to be
near 1001 mb. The potential for the development of a significant
tropical cyclone within the next 24 hours is downgraded to medium.
See ref a (wtxs21 pgtw 232230) for further details.
      (2) no other suspect areas.
3. Justification for reissue: downgraded area in 2.B.(1) to medium.//

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