{"id": "1225710356480393219", "title": "Tropical Cyclone Discussion", "adv_date": "2026-11-08T09:00:00Z", "msg": "741\nWTPA44 PHFO 080845\nTCDCP4\n \nTropical Storm Pena Discussion Number   7\nNWS Central Pacific Hurricane Center Honolulu HI   CP042026\nIssued by NWS National Hurricane Center Miami FL\n1100 PM HST Sat Nov 07 2026\n \nThis evening, Pena's vertical coherence appears to be unraveling. On \nGOES-18 satellite, its structure is looking increasingly fragile, \nwith the earlier deep convection weakening near the center, with a \nmore recent burst primarily east of the center. A 04 UTC WSFM \nmicrowave pass suggested that Pena has become more vertically \ntilted, with the low-level cloud features on the 37-GHz channel \nindicating the surface circulation running out ahead of the \nmid-level vortex seen on the 89-GHz channel. This was recently \nconfirmed by a 0644 UTC ASCAT-B pass, which showed an elongated \nlow-level circulation centered east of the deepest convection. The \npeak wind retrieval from the instrument was only 31 kt, though an \nASCAT-C pass just received had some higher winds. The 06 UTC \nsubjective Dvorak estimates from PHFO and PGTW still supported  \n45-55 kt, but objective estimates from UW-CIMSS have decreased to \n36-43 kt. Given the rather anemic scatterometer data, the initial \nintensity is lowered to 40 kt this advisory.\n\nThe tropical storm's westward motion has slowed a bit over the past \n6 h, with an estimated motion of 270 degrees at 6 kt. A zonally \noriented low- to mid-level ridge stretches across the Central \nPacific to the north of Pena. This feature should result in the \ntropical storm maintaining a general westward motion for the next \n2-4 days. However, there is also a prominent low-level westerly-wind \nburst occurring south of Pena resulting in an enhanced monsoonal \ncirculation. This feature, combined with a strengthening low-level \nridge could allow Pena to lose some latitude in 24-60 h. Towards \nthe end of the forecast period, the ridge begins to shift eastward, \nwhich could provide an opportunity for Pena to gain more latitude by \nthe end of the forecast, assuming the tropical cyclone is still \naround. The track guidance this cycle is quite similar to the prior \none for the first 24-36 h, though the better performing track aids \n(HCCA, GDMI, WN3I) now show a more southward track in 36-72 h. Thus, \nthe updated NHC track forecast was nudged further south during this \nperiod once again, blending these more reliable track aids with the \nprevious forecast. \n \nPena's structural degradation this evening makes its intensity \nforecast rather tricky. Environmental conditions appear favorable at \nfirst glance, with warm 29 C sea-surface temperatures expected along \nthe storm's track, and deep-layer shear remaining under 10 kt for \nthe bulk of the SHIPS guidance forecast. However, the increasing \nvertical tilt of Pena's vortex appears to be preventing it from \ntaking advantage of these favorable environmental conditions, and \nthis evening's scatterometer data indicates Pena has weakened from \nearlier today. Another factor worth considering is the monsoonal \ncirculation south of Pena, which is producing a lot of convective \noutflow in the path of the tropical storm. Pena is also a rather \nsmall tropical cyclone, and is likely more sensitive than usual to \nless than pristine environmental conditions. The intensity guidance \nthis evening is lower than earlier, with all of the hurricane \nregional models now showing Pena remaining either a weak tropical \nstorm or degenerating into a trough of low pressure. The updated NHC \nintensity forecast now shows a little short-term weakening, followed \nby gradual intensification beginning in 36 h. This assumes Pena \nsurvives, and is able to eventually respond to the more favorable \nenvironmental conditions. This forecast now leans more on a blend of \nthe hurricane-regional model guidance and AI-based guidance, with \nless weight on the statistical-dynamical aids. It is also possible \nPena dissipates as a tropical cyclone sometime during this forecast \nperiod, as suggested by the 00 UTC HAFS runs. Needless to say, this \nis a low confidence intensity forecast. \n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  08/0900Z 11.5N 155.0W   40 KT  45 MPH\n 12H  08/1800Z 11.5N 156.3W   35 KT  40 MPH\n 24H  09/0600Z 11.5N 158.1W   35 KT  40 MPH\n 36H  09/1800Z 11.4N 160.3W   40 KT  45 MPH\n 48H  10/0600Z 11.3N 162.5W   45 KT  50 MPH\n 60H  10/1800Z 11.1N 164.4W   45 KT  50 MPH\n 72H  11/0600Z 10.9N 166.4W   50 KT  60 MPH\n 96H  12/0600Z 11.0N 172.0W   50 KT  60 MPH\n120H  13/0600Z 12.5N 177.4W   50 KT  60 MPH\n \n"}