ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM Tropical Storm Pilar Discussion Number 6 NWS National Hurricane Center Miami FL EP192023 1000 PM CDT Sun Oct 29 2023 A small but concentrated convective burst has been persisting near the estimated center of the tropical cyclone tonight. After the prior advisory, we received a fortuitous GPM microwave pass valid at 2252 UTC that suggested the low-level circulation may have tightened up some but was located just south of the deepest convection. Subjective Dvorak intensity estimates were up to T2.5/35 kt form TAFB and T2.0/30 kt from SAB. The objective estimates from ADT, SATCON, and D-PRINT/MINT are all between 34-36 kt, and thus the latest advisory is set at 35 kt this advisory, upgrading TD19-E to Tropical Storm Pilar. A more pronounced east-northeastward motion appears to be starting, estimated at 060/4 kt. A continued motion to the east-northwest is anticipated over the next 24-48 hours as Pilar's primary steering influences are an equatorial ridge south of the storm providing deep-layer westerlies in addition to a mid- to upper-level cutoff low over the northwestern Caribbean that is interrupting the more typical ridging that would be present to the north over Mexico. The guidance is in general agreement on this scenario, but how far east the tropical storm gets in the next 48 h remains uncertain, with the latest HWRF and HAFS-B runs far enough east to affect the Gulf of Fonseca with tropical storm conditions. For this reason, the tropical storm watch has been extended eastward to portions of the Pacific coast of Honduras and Nicaragua this advisory. On Tuesday, Pilar is expected to stall and move very slowly as low to mid-level ridging attempts to build back in to the north of the tropical cyclone and a strong cold front induces a significant gap wind flow event in the Gulf of Tehuantepec. By the middle of this week, the enhanced low-level flow associated with the ridge and gap winds are forecast to push Pilar away from Central America to the west-southwest as a weakening tropical storm. As discussed previously, the confidence of when or how sharp this turn away from Central America will be is low given the inconsistent model guidance over the past day. The NHC track this cycle is just a bit closer to the coast and a touch east of the prior track, but is roughly in between the TVCE and HCCA consensus aids. A small core may be starting to take shape given the earlier microwave imagery, and the persistent area of convection that Pilar has been maintaining over the last 3-6 hours near the estimated center. Most of the guidance maintains this small core structure with intensification while the storm remains embedded in moderate (15-20 kt) easterly vertical wind shear but is over warm 28-29 C sea-surface temperatures in a moist mid-level air environment. The latest NHC intensity forecast still takes Pilar to near hurricane intensity in 36 h, on the higher end of the intensity guidance but not far off the hurricane-regional guidance solutions. Afterwards, it seems likely a combination of the dry mid-latitude gap-wind flow in addition to possible cool upwelling of the shallow warm waters due to slow motion near the coast of Central America could begin a weakening trend. If the latest HWRF and HAFS-B runs end up being correct, land interaction could also result in weakening. The intensity forecast beyond 48 h is a little lower than the prior advisory, as it is looking more likely that a combination of moderate shear and additional dry stable air could prevent the storm from re-intensifying even after it begins to move back over warmer ocean waters away from its own cold wake. Key Messages: 1. Heavy rains from the tropical depression will produce flash and urban flooding, along with mudslides in areas of higher terrain along the Pacific coast of Central America, including El Salvador, through Wednesday. 2. Tropical storm conditions are possible by early Tuesday into Wednesday along portions of the Pacific coast of El Salvador, Honduras, and Nicaragua where a Tropical Storm Watch is now in effect. Interests elsewhere along the Pacific coast of Guatemala, and Nicaragua should monitor the progress of this system as additional watches or warnings could be needed tomorrow. 3. Swells generated by the depression will begin to affect portions of the Pacific coast of Central America, including El Salvador, beginning on Monday. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 11.0N 92.0W 35 KT 40 MPH 12H 30/1200Z 11.2N 91.3W 45 KT 50 MPH 24H 31/0000Z 11.6N 90.2W 55 KT 65 MPH 36H 31/1200Z 12.0N 89.4W 60 KT 70 MPH 48H 01/0000Z 12.3N 88.9W 55 KT 65 MPH 60H 01/1200Z 12.0N 88.9W 45 KT 50 MPH 72H 02/0000Z 11.2N 89.7W 35 KT 40 MPH 96H 03/0000Z 9.9N 93.0W 35 KT 40 MPH 120H 04/0000Z 9.0N 97.5W 35 KT 40 MPH $$ Forecaster Papin NNNN