Moderators StretchCT Posted July 11, 2022 Moderators Share Posted July 11, 2022 (edited) Tropical Storm Darby Discussion Number 5 NWS National Hurricane Center Miami FL EP052022 1100 AM HST Sun Jul 10 2022 Darby is a small but fairly well-organized tropical cyclone. 1-minute GOES-17 imagery has been quite helpful to diagnose the system's structure, which consists of a handful of curved bands around the periphery of the circulation, with pulsing convection near the center that has, at times, wrapped nearly all the way around. Earlier microwave imagery showed hints that Darby was starting to mix-out some of the dry-air entrainment that was noticed this morning, with even a hint of a mid-level eye becoming evident on an SSMIS 91-GHz microwave channel at 1421 UTC. The latest subjective Dvorak intensity estimates were a consensus CI 3.5/55-kt, which is the basis for Darby's current intensity this advisory. Over the next 36-48 hours, the biggest question related to Darby's future intensity is just how effective the tropical cyclone will be at preventing additional dry-air intrusions into its inner core. Because the system has a very small core, it could be prone to rapid intensity changes, both up and down, even due to seemingly small fluctuations to its larger-scale environment. While SHIPS guidance indicates that the deep-layer 200-850 mb shear should remain under 10 kt for the next 48 hours, the direction of the shear vector is from the north, where there is drier mid-level air. In addition, there is some sneaky higher northerly mid-level shear that may have played a role in dry air disrupting the convective structure of Darby last night and this morning. In any event, assuming the TC is able to close off its tiny inner core, at least steady intensification is still anticipated in the short-term. The latest NHC intensity forecast still peaks Darby as an upper-end Category 1 hurricane by 48 hours, which is on the high end of the guidance, but closest to the latest SHIPS forecast. Afterwards, northwesterly shear increases, helping to import even drier mid-level air, and sea-surface temperatures decrease below 26 C, which will likely lead to rapid weakening of the small system towards the end of the forecast period. The latest forecast now indicates Darby becoming a post-tropical remnant low in 120 hours, not long after it crosses the 140-degree longitude. Darby remains on a due westward heading at 270/14 kt. The cyclone continues to be steered westward by a prominent mid-level ridge to its north. By 36 hours though, Darby will begin to approach a weakness in this mid-level ridge, which should allow the system to begin gaining latitude. While the track guidance continues to exhibit relatively low across-track spread, there is substantially more along-track spread between the various deterministic members. Notably, the UKMET continues to be on the fast-leftward end of the guidance envelope, which does not seem realistic since Darby is more vertically deep than that model currently depicts. The latest track forecast continues to place more emphasis on the slower and stronger guidance, notably the GFS and ECMWF forecasts, which results in the track forecast being a little slower and a bit further north than the reliable guidance aids HCCA and TVCE. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 14.4N 119.1W 55 KT 65 MPH 12H 11/0600Z 14.5N 121.1W 65 KT 75 MPH 24H 11/1800Z 14.6N 123.7W 75 KT 85 MPH 36H 12/0600Z 14.8N 126.2W 80 KT 90 MPH 48H 12/1800Z 15.0N 128.7W 80 KT 90 MPH 60H 13/0600Z 15.5N 131.4W 70 KT 80 MPH 72H 13/1800Z 16.2N 133.8W 60 KT 70 MPH 96H 14/1800Z 17.8N 138.7W 40 KT 45 MPH 120H 15/1800Z 18.5N 144.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Papin Edited July 15, 2022 by StretchCT 1 Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Sat 1 Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 (edited) Since the 11am advisory yesterday, Darby has rapidly intensified from 65mph to 105mph. In other words, skipped double dog dare and went straight to triple dare. Here's a timeline. Edited July 11, 2022 by StretchCT Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 The eye is pretty amazing. Looks higher than 105mph too. Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 CIMSS has a new product out too. has it closer to 120 mph. Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Darcy now a Major - 105mph to 120mph in three hours. 03:15 AM HST Mon Jul 11 Location: 14.6°N 123.0°W Moving: W at 16 mph Min pressure: 968 mb Max sustained: 120 mph Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Still strengthening - now forecast to peak at 140mph. Because of constraints on ADT, the current strength may be conservative. 5:00 AM HST Mon Jul 11 Location: 14.6°N 123.4°W Moving: W at 15 mph Min pressure: 965 mb Max sustained: 125 mph Spoiler Hurricane Darby Discussion Number 9 NWS National Hurricane Center Miami FL EP052022 500 AM HST Mon Jul 11 2022 What a difference 24 hours makes! Darby has been rapidly intensifying for the last 12-18 hours, with the eye continuing to clear out on GOES-17 infrared satellite imagery surrounded by a thick ring of cold -65 to -75C cloud top temperatures. It is clear that the tropical cyclone was able to mix out the remaining dry air near its center last night and the last several microwave passes from GMI at 0732 UTC and AMSR2 at 0959 UTC have an impressive presentation with a thick ring of eyewall convection on the 89-GHz channel. Subjective Dvorak satellite estimates from TAFB and SAB are constrained due to Dvorak rules, but their data-T numbers were both T5.5/102 kt. The most recent CI number from the UW-CIMSS objective Advanced Dvorak Technique (ADT) was at T6.0/115 kt. Favoring the higher ADT estimate more, the current intensity is set to 110 kt, though this could be conservative. There are no obvious signs currently that would prevent Darby from intensifying further. There are few indications that an eyewall replacement cycle is imminent from the earlier microwave imagery and SHIPS guidance indicates the storm remains in a very low shear (near 5 kt) environment and over sufficently warm sea-surface temperatures (27-28 C). Thus, rapid intensification is forecast to continue over the next 12 h, and the NHC foreast intensity peaks Darby at 120 kt, which matches the latest ECMWF- and GFS-based SHIPS which have correctly been on the high side of the guidance envelope. After 36 hours, Darby is expected to move into sub 26C SSTs, and westerly shear is forecast to increase between 48-72 hours. Thus, the small vortex of Darby could weaken rapidly after 36 hours, with the latest intensity forecast still making the system a post-tropical cyclone at the end of the forecast period. Darby is continuing westward along at the same general speed and heading at 270/13 kt, steered primarily by a mid-level ridge centered to its north. The hurricane is expected to approach a slight weakness in the ridge after 24 hours, allowing the cyclone to gradually shift to a more west-northwestward track between 36-72 hours. However, by the end of the forecast period, as Darby becomes shallow vortex, its track will likely bend back westward as the low-level trade wind flow becomes dominant. The latest track forecast is not all that different from the previous one, choosing to remain close to a consensus of the GFS and ECMWF forecasts (GEFX) which remains just a bit north of the consensus aids HCCA and TVCE, which are influenced by the further south tracks of the weaker HWRF/HMON/UKMET guidance. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 14.6N 123.4W 110 KT 125 MPH 12H 12/0000Z 14.7N 125.6W 120 KT 140 MPH 24H 12/1200Z 14.8N 128.1W 120 KT 140 MPH 36H 13/0000Z 15.0N 130.5W 105 KT 120 MPH 48H 13/1200Z 15.4N 133.2W 85 KT 100 MPH 60H 14/0000Z 15.9N 135.8W 70 KT 80 MPH 72H 14/1200Z 16.7N 138.5W 55 KT 65 MPH 96H 15/1200Z 17.5N 143.3W 35 KT 40 MPH 120H 16/1200Z 17.3N 149.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Papin Will note the general failure of the intensification models with this one. Not even 24 hours ago it was at 80kt peak. Now peaking at 130kts Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Vis meso sat view Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Still looks strong, though the ADT seems to have leveled off. Weakening flag is on for a few samples (next to Limit). Have to wonder if there is/will be an ERC. Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 NWS National Hurricane Center Miami FL EP052022 1100 AM HST Mon Jul 11 2022 ...DARBY STILL SMALL BUT NOW A MIGHTY CATEGORY 4 HURRICANE... SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION ----------------------------------------------- LOCATION...14.7N 125.0W ABOUT 1135 MI...1830 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H PRESENT MOVEMENT...W OR 275 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...954 MB...28.17 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM HST (2100 UTC), the center of Hurricane Darby was located near latitude 14.7 North, longitude 125.0 West. Darby is moving toward the west near 15 mph (24 km/h) and this motion is expected to continue today with a gradual turn to the west-northwest beginning by Tuesday. Maximum sustained winds have increased to near 140 mph (220 km/h) with higher gusts, making Darby is a powerful category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Darby is expected to peak in intensity in the next day or so and then begin a weakening trend by midweek. Darby remains a small system, with hurricane-force winds only extending outward 10 miles (20 km) from the center and tropical-storm-force winds extending outward up to 60 miles (95 km). The estimated minimum central pressure is 954 mb (28.17 inches). Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 11, 2022 Author Moderators Share Posted July 11, 2022 Discussion has that it might max out at 145mph. Also of note: Sat is impressive and improved, tops not any cooler but eye is warmer. "the presentation on visible images is similarly spectacular with a few mesovortices seen rotating around the eye exhibiting a classic stadium effect. " Also notes ADT underestimates smaller cyclones and that eyewall cloudtops are going through diurnal process. It has increased winds 65kts in 24 hrs. Spoiler Hurricane Darby Discussion Number 10 NWS National Hurricane Center Miami FL EP052022 1100 AM HST Mon Jul 11 2022 Darby's satellite presentation continues to be very impressive, and has improved further since this morning. While convective cloud tops associated with the eyewall convection have not cooled much more, hovering between -65 to -75 C, the eye temperature has warmed further, with the warmest pixel fluctuating between +18-20C. The presentation on visible images is similarly spectacular, with a few mesovorticies seen rotating around in the eye exhibiting a classic stadium effect, and the GOES-GLM occasionally showing some inner core flashes. The latest UW-CIMSS objective Dvorak estimate has stabilized somewhat at T6.1/117 kt despite the warming eye temperature. However, very small tropical cyclones like Darby are often underestimated using objective Dvorak guidance, as was seen during similarly small systems, like Dorian in 2019 when it near the Bahamas. I also suspect the eyewall cloud tops have warmed a tad due to diurnal fluctuations and could cool once again during the typical nighttime max. The current intensity this advisory will be set at 120 kt, indicating a remarkable intensification rate of 65 kt in the past 24 hours. A little bit of additional intensification is possible in the short term and the latest intensity forecast now peaks Darby as a 125-kt hurricane in 12 hours, very close to the GFS-SHIPS guidance. It is notable that this was also the peak intensity that a similarly-small Hurricane Felicia also reached in this same general vicinity last July. While shear is expected to remain very low through 48 hours, sea-surface temperatures do start to decrease and drop below 26C in 36 hours, which should begin a weakening trend by Wednesday. Vertical wind shear then begins to increase more after 48 hours, which will likely induce more rapid weakening of the small cyclone. Both the GFS- and ECMWF model simulated IR-brightness temperature shows deep convection collapsing on Friday, and the latest forecast now makes Darby post-tropical by 96 hours. Darby is still moving westward at 275/13 kt. The track philosophy has not changed this cycle, as a mid-level ridge is steering the hurricane generally westward. A slight weakness in the ridge after 24 hours should allow Darby to take a more west-northwestward track in the 36-72 hour forecast period. As Darby becomes more shallow at the end of the forecast period, its track is forecast to bend back westward as the low-level trade wind flow becomes dominant. The latest track forecast is similar to the previous advisory, still favoring a blend of the GFS and ECMWF forecasts, but ends up near the TVCE consensus aid towards the end of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 14.7N 125.0W 120 KT 140 MPH 12H 12/0600Z 14.8N 127.0W 125 KT 145 MPH 24H 12/1800Z 14.9N 129.7W 120 KT 140 MPH 36H 13/0600Z 15.1N 132.2W 100 KT 115 MPH 48H 13/1800Z 15.6N 134.7W 80 KT 90 MPH 60H 14/0600Z 16.3N 137.3W 65 KT 75 MPH 72H 14/1800Z 17.0N 140.0W 50 KT 60 MPH 96H 15/1800Z 17.4N 145.3W 35 KT 40 MPH...POST-TROPICAL 120H 16/1800Z 17.3N 151.4W 30 KT 35 MPH...POST-TROP/REMNT LOW This is as close as I can get it. Maybe @MaineJaycan through a closer one up. Link to comment Share on other sites More sharing options...
Admin MaineJay Posted July 11, 2022 Admin Share Posted July 11, 2022 31 minutes ago, StretchCT said: Discussion has that it might max out at 145mph. Also of note: Sat is impressive and improved, tops not any cooler but eye is warmer. "the presentation on visible images is similarly spectacular with a few mesovortices seen rotating around the eye exhibiting a classic stadium effect. " Also notes ADT underestimates smaller cyclones and that eyewall cloudtops are going through diurnal process. It has increased winds 65kts in 24 hrs. Reveal hidden contents Hurricane Darby Discussion Number 10 NWS National Hurricane Center Miami FL EP052022 1100 AM HST Mon Jul 11 2022 Darby's satellite presentation continues to be very impressive, and has improved further since this morning. While convective cloud tops associated with the eyewall convection have not cooled much more, hovering between -65 to -75 C, the eye temperature has warmed further, with the warmest pixel fluctuating between +18-20C. The presentation on visible images is similarly spectacular, with a few mesovorticies seen rotating around in the eye exhibiting a classic stadium effect, and the GOES-GLM occasionally showing some inner core flashes. The latest UW-CIMSS objective Dvorak estimate has stabilized somewhat at T6.1/117 kt despite the warming eye temperature. However, very small tropical cyclones like Darby are often underestimated using objective Dvorak guidance, as was seen during similarly small systems, like Dorian in 2019 when it near the Bahamas. I also suspect the eyewall cloud tops have warmed a tad due to diurnal fluctuations and could cool once again during the typical nighttime max. The current intensity this advisory will be set at 120 kt, indicating a remarkable intensification rate of 65 kt in the past 24 hours. A little bit of additional intensification is possible in the short term and the latest intensity forecast now peaks Darby as a 125-kt hurricane in 12 hours, very close to the GFS-SHIPS guidance. It is notable that this was also the peak intensity that a similarly-small Hurricane Felicia also reached in this same general vicinity last July. While shear is expected to remain very low through 48 hours, sea-surface temperatures do start to decrease and drop below 26C in 36 hours, which should begin a weakening trend by Wednesday. Vertical wind shear then begins to increase more after 48 hours, which will likely induce more rapid weakening of the small cyclone. Both the GFS- and ECMWF model simulated IR-brightness temperature shows deep convection collapsing on Friday, and the latest forecast now makes Darby post-tropical by 96 hours. Darby is still moving westward at 275/13 kt. The track philosophy has not changed this cycle, as a mid-level ridge is steering the hurricane generally westward. A slight weakness in the ridge after 24 hours should allow Darby to take a more west-northwestward track in the 36-72 hour forecast period. As Darby becomes more shallow at the end of the forecast period, its track is forecast to bend back westward as the low-level trade wind flow becomes dominant. The latest track forecast is similar to the previous advisory, still favoring a blend of the GFS and ECMWF forecasts, but ends up near the TVCE consensus aid towards the end of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 14.7N 125.0W 120 KT 140 MPH 12H 12/0600Z 14.8N 127.0W 125 KT 145 MPH 24H 12/1800Z 14.9N 129.7W 120 KT 140 MPH 36H 13/0600Z 15.1N 132.2W 100 KT 115 MPH 48H 13/1800Z 15.6N 134.7W 80 KT 90 MPH 60H 14/0600Z 16.3N 137.3W 65 KT 75 MPH 72H 14/1800Z 17.0N 140.0W 50 KT 60 MPH 96H 15/1800Z 17.4N 145.3W 35 KT 40 MPH...POST-TROPICAL 120H 16/1800Z 17.3N 151.4W 30 KT 35 MPH...POST-TROP/REMNT LOW This is as close as I can get it. Maybe @MaineJaycan through a closer one up. How close up you want? Here is the link to the CIRA RAMMB site, zoomed in at max. https://rammb-slider.cira.colostate.edu/?sat=goes-17&sec=mesoscale_02&x=1205.961669921875&y=923.7295532226562&z=4&angle=0&im=60&ts=1&st=0&et=0&speed=130&motion=loop&maps[borders]=white&mops[borders]=1&mhidden[borders]=1&lat=0&p[0]=band_02&opacity[0]=1&pause=0&slider=-1&hide_controls=1&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&draw_color=FFD700&draw_width=6 1 Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 12, 2022 Author Moderators Share Posted July 12, 2022 No change in strength per the updates, but ADT is definitely taking a hit. Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 12, 2022 Author Moderators Share Posted July 12, 2022 MIMIC showing some erosion from dry air in the NW quad, also showing some rebuild of an eyewall Link to comment Share on other sites More sharing options...
Meteorologist so_whats_happening Posted July 13, 2022 Meteorologist Share Posted July 13, 2022 On 7/11/2022 at 4:38 PM, StretchCT said: Still looks strong, though the ADT seems to have leveled off. Weakening flag is on for a few samples (next to Limit). Have to wonder if there is/will be an ERC. Wow very impressive storm and with a -PDO/ La Nina it is even more impressive to me. Maybe Hawaii may get some healthy rains from this. 1 Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 13, 2022 Author Moderators Share Posted July 13, 2022 Down to 115mph - sunset loop 11:00 AM HST Tue Jul 12 Location: 14.6°N 131.2°W Moving: W at 17 mph Min pressure: 966 mb Max sustained: 115 mph Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 13, 2022 Author Moderators Share Posted July 13, 2022 13 Jul 2022 - 15:00 UTC ...EYE OF DARBY MAKES A SURPRISE REAPPEARANCE... ...HURRICANE STILL FORECAST TO WEAKEN DURING THE NEXT FEW DAYS... As of 5:00 AM HST Wed Jul 13 the center of Darby was located near 15.0, -135.4 with movement W at 16 mph. The minimum central pressure was 977 mb with maximum sustained winds of about 105 mph. Link to comment Share on other sites More sharing options...
Moderators StretchCT Posted July 15, 2022 Author Moderators Share Posted July 15, 2022 Darby still a hurricane! ...HURRICANE DARBY SLOWLY WEAKENING FAR EAST-SOUTHEAST OF THE HAWAIIAN ISLANDS WITH MORE RAPID WEAKENING EXPECTED SOON... SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION ----------------------------------------------- LOCATION...17.0N 142.1W ABOUT 870 MI...1405 KM E OF HILO HAWAII ABOUT 1070 MI...1725 KM ESE OF HONOLULU HAWAII MAXIMUM SUSTAINED WINDS...100 MPH...155 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES Link to comment Share on other sites More sharing options...
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