Windspeed Posted September 27, 2021 Share Posted September 27, 2021 This is a low res scan from the onboard radar from most recent recon pass west to east through Sam. The author seems uncertain about the maturity of the outer band, but this looks very much like degradation due to strong subsidence off the SW quad outer eyeband/wall. Also explains the semi-trichoidal motion. We're probably halfway through the current EWRC (at this given scan). Link to comment Share on other sites More sharing options...
NorthHillsWx Posted September 27, 2021 Share Posted September 27, 2021 From a “look perspective” it’s hard to imagine how a storm could be any stronger presentation wise about 5-8 hours ago. It definitely degraded since recons departed and even more so once recon arrived. A small tight core like Sam has it wouldn’t take much degradation for wind speed to come down quickly, unlike larger storms. There is literally zero hard evidence to support a cat 5 from earlier. However, sat estimates almost always fail to get the exact intensity and have a low bias for tiny storms, like Sam. It would honestly shock me if this didn’t peak at least 140 kts just from the ferocity of that satellite shot and the speed those eyewall towers were moving. Also, the pressure is consistent with a cat 5 storm of this size. That being said, there is zero hard evidence this made it to cat 5 and then does it really matter if it only maintained that intensity for a couple of hours? To us, yes, but NHC issues advisories based on intensity at time of advisory or based on hard evidence between them. Lacking the latter, this is going to stay a 4 in post analysis. Ida has a chance for an upgrade bc there was hard evidence, from wind measurements on land, recon, and pressure that it did reach the threshold. This to me was likely a stronger storm at peak but will be very unlikely to be upgraded without the hard evidence of nonstop recon and ground truth. 3 Link to comment Share on other sites More sharing options...
Wannabehippie Posted September 27, 2021 Share Posted September 27, 2021 First pass was 932MB second pass is 943. ERC causing the pressure to go up or did they miss the area of lowest pressure? Link to comment Share on other sites More sharing options...
OSUmetstud Posted September 27, 2021 Share Posted September 27, 2021 2 minutes ago, Wannabehippie said: First pass was 932MB second pass is 943. ERC causing the pressure to go up or did they miss the area of lowest pressure? Looks real. 941mb estimated on the latest dropsonde. Pressure rise of 12mb. Link to comment Share on other sites More sharing options...
NorthHillsWx Posted September 27, 2021 Share Posted September 27, 2021 I bet they mention in the 11:00 advisory that it’s possible Sam attained cat 5 for a period this afternoon Link to comment Share on other sites More sharing options...
OSUmetstud Posted September 27, 2021 Share Posted September 27, 2021 2 Link to comment Share on other sites More sharing options...
NorthHillsWx Posted September 27, 2021 Share Posted September 27, 2021 4 minutes ago, OSUmetstud said: That’s an awesome animation. 1 Link to comment Share on other sites More sharing options...
Castaway Posted September 27, 2021 Share Posted September 27, 2021 Sam seemed to struggle yesterday on the sw quadrant as well for awhile. Just remembering observing it yesterday for hours. Beauty representation earlier. Looks good now, despite the skidding on the sw. Based on pure hunch and eyeballing, it should kick out again and produce some acts of major+ characteristics next hours into tomorrow. Link to comment Share on other sites More sharing options...
Amped Posted September 27, 2021 Share Posted September 27, 2021 Does look like there's some wind shear eating apart the western side of the storm. Link to comment Share on other sites More sharing options...
Amped Posted September 27, 2021 Share Posted September 27, 2021 It's weakening faster than IDA after landfall. 1 Link to comment Share on other sites More sharing options...
Vice-Regent Posted September 27, 2021 Share Posted September 27, 2021 12 minutes ago, Amped said: It's weakening faster than IDA after landfall. Good let's see what happens. Save the heat for the big momma. 1 Link to comment Share on other sites More sharing options...
Wannabehippie Posted September 27, 2021 Share Posted September 27, 2021 11:00 PM AST Sun Sep 26 Location: 14.7°N 50.8°W Moving: NW at 7 mph Min pressure: 943 mb Max sustained: 145 mph Link to comment Share on other sites More sharing options...
Wannabehippie Posted September 27, 2021 Share Posted September 27, 2021 Link to comment Share on other sites More sharing options...
Wannabehippie Posted September 27, 2021 Share Posted September 27, 2021 Did a bit of dry air entrain in, which weakened Sam? Link to comment Share on other sites More sharing options...
WxWatcher007 Posted September 27, 2021 Share Posted September 27, 2021 Link to comment Share on other sites More sharing options...
NorthHillsWx Posted September 27, 2021 Share Posted September 27, 2021 6 minutes ago, WxWatcher007 said: Rapid, rapid decay right there. Wow 1 Link to comment Share on other sites More sharing options...
NorthHillsWx Posted September 27, 2021 Share Posted September 27, 2021 1 hour ago, Amped said: It's weakening faster than IDA after landfall. You’re not lying! This looks like a major that just made landfall. Just even more impressive how resilient Ida was after landfall to maintain that intensity over land/marsh while watching this storm collapse over open ocean Link to comment Share on other sites More sharing options...
WxWatcher007 Posted September 27, 2021 Share Posted September 27, 2021 It has recovered a bit in the last few frames (not shown above), but it’s really fascinating to contrast how the inner core rapidly organized yesterday to what we’ve seen this evening. 2 Link to comment Share on other sites More sharing options...
Scorpion Posted September 27, 2021 Share Posted September 27, 2021 Damn that’s brutal reminds me of what happened to Frances and Isabel lol. Such a low latitude that’s really strange. I wonder if it can recover. Link to comment Share on other sites More sharing options...
yoda Posted September 27, 2021 Share Posted September 27, 2021 Hurricane Sam Advisory Number 19 NWS National Hurricane Center Miami FL AL182021 500 AM AST Mon Sep 27 2021 ...SAM EXPECTED TO REMAIN A MAJOR HURRICANE FOR SEVERAL DAYS... ...HURRICANE HUNTER AIRCRAFT TO INVESTIGATE SAM LATER TODAY... SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...15.2N 51.4W ABOUT 800 MI...1290 KM ESE OF THE NORTHERN LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H PRESENT MOVEMENT...NW OR 315 DEGREES AT 8 MPH...13 KM/H MINIMUM CENTRAL PRESSURE...952 MB...28.12 INCHES WATCHES AND WARNINGS -------------------- There are no coastal watches or warnings in effect. DISCUSSION AND OUTLOOK ---------------------- At 500 AM AST (0900 UTC), the center of Hurricane Sam was located near latitude 15.2 North, longitude 51.4 West. Sam is moving toward the northwest near 8 mph (13 km/h). This general motion is expected to continue for the next several days, with an increase in forward speed beginning on Thursday. Maximum sustained winds are near 130 mph (215 km/h) with higher gusts. Sam is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Little change in strength is expected during the next day or so. Thereafter, some slow weakening is forecast through midweek, although Sam should remain a major hurricane. Sam is a small hurricane. Hurricane-force winds extend outward up to 30 miles (45 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km). The estimated minimum central pressure is 952 mb (28.12 inches). HAZARDS AFFECTING LAND ---------------------- SURF: Swells generated by Sam will reach the Lesser Antilles today and impact these islands for the next several days. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 1100 AM AST. $$ Link to comment Share on other sites More sharing options...
yoda Posted September 27, 2021 Share Posted September 27, 2021 Hurricane Sam Discussion Number 19 NWS National Hurricane Center Miami FL AL182021 500 AM AST Mon Sep 27 2021 The satellite presentation of Sam deteriorated overnight, as GOES-16 infrared imagery showed periodic disruptions to Sam's inner core convection. The eye has not been readily apparent in conventional satellite imagery for much of the night, although very recent imagery suggests an eye could be re-emerging. Data from the reconnaissance aircraft last night indicated that an eyewall replacement cycle (ERC) was underway, and some dry mid-level air impinging on the western side of the circulation could also be negatively impacting Sam. No recent high-resolution microwave data is available, but an earlier scatterometer pass revealed that the tropical-storm-force wind radii had expanded just a bit in the eastern semicircle of the hurricane. The initial intensity is lowered to 115 kt for this advisory based on a blend of the objective and subjective Dvorak current intensity estimates. A NOAA hurricane hunter aircraft is scheduled to investigate Sam later this morning, which will provide crucial data to assess changes in Sam's structure and intensity. The initial motion is estimated to be northwestward, or 315/7 kt. A subtropical ridge to the north and northeast of Sam will remain the primary steering mechanism over the next several days, and Sam is expected to maintain a northwestward heading through midweek. Then, a mid- to upper-level trough is forecast to dig southward over the western Atlantic late this week. The deep-layer southerly flow ahead of this feature should cause Sam to move faster toward the north-northwest by 96 h, followed by a northward acceleration thereafter. The NHC forecast track is shifted slightly to the right of the previous one through the first 48-60 h of the forecast period, which accounts for the more northwestward initial motion observed during the past 12 h. Otherwise, the NHC track is virtually unchanged as the guidance has remained fairly consistent. Sam's intensity has likely peaked now that an ERC has commenced, but environmental conditions should allow Sam to persist as a major hurricane for the next several days. Sea-surface temperatures are expected to be 28 deg C or greater along Sam's track through 120 h, and the vertical wind shear is forecast to remain weak (< 10 kt) through at least midweek. Thus, the official NHC intensity forecast only shows very gradual weakening during the next several days, generally following the HCCA and IVCN consensus aids. Given the lower initial intensity of Sam, the latest NHC forecast is once again lower than the previous one. By 120 h, southerly shear associated with the deep-layer trough is forecast to increase over Sam, which should induce more weakening by this weekend. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 15.2N 51.4W 115 KT 130 MPH 12H 27/1800Z 15.9N 52.2W 115 KT 130 MPH 24H 28/0600Z 16.8N 53.3W 115 KT 130 MPH 36H 28/1800Z 17.7N 54.4W 115 KT 130 MPH 48H 29/0600Z 18.6N 55.6W 110 KT 125 MPH 60H 29/1800Z 19.6N 57.1W 110 KT 125 MPH 72H 30/0600Z 21.0N 58.8W 110 KT 125 MPH 96H 01/0600Z 24.9N 61.6W 110 KT 125 MPH 120H 02/0600Z 30.5N 62.0W 105 KT 120 MPH $$ Forecaster Reinhart Link to comment Share on other sites More sharing options...
StantonParkHoya Posted September 27, 2021 Share Posted September 27, 2021 Hope it misses Bermuda 2 Link to comment Share on other sites More sharing options...
WxWatcher007 Posted September 27, 2021 Share Posted September 27, 2021 As impressive as the rapid intensification was, the period of weakening has been fascinating as well. It looks like the ERC, which reorganizes a hurricane's inner core, provided the opening for relatively light shear to impart dry air into the more vulnerable core, causing significant disruption. Link to comment Share on other sites More sharing options...
Amped Posted September 27, 2021 Share Posted September 27, 2021 It has weakened enough that it could RI again. Link to comment Share on other sites More sharing options...
yoda Posted September 27, 2021 Share Posted September 27, 2021 I know it was only one pass... but 943mb to 966mb in 12 hours... wow Dry air really did a number on Sam until recently Link to comment Share on other sites More sharing options...
SnowenOutThere Posted September 27, 2021 Share Posted September 27, 2021 Trying to wrap the convection around an eye again on visible so it might get its act together. Link to comment Share on other sites More sharing options...
nycwinter Posted September 27, 2021 Share Posted September 27, 2021 1 hour ago, yoda said: I know it was only one pass... but 943mb to 966mb in 12 hours... wow Dry air really did a number on Sam until recently maybe it was upwelling since the storm is crawling along Link to comment Share on other sites More sharing options...
Wannabehippie Posted September 27, 2021 Share Posted September 27, 2021 Looks like Sam is trying to regenerate a bit. Eye is popping back out. Link to comment Share on other sites More sharing options...
yoda Posted September 27, 2021 Share Posted September 27, 2021 Link to comment Share on other sites More sharing options...
Amped Posted September 27, 2021 Share Posted September 27, 2021 Eye is out again. Sam's fighting it's way back quickly over the last few hours. Link to comment Share on other sites More sharing options...
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