Tropical Storm Norman

Tropical Storm Norman Track 1100 Hours September 8 2018

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Sat Sep 08 2018

Deep convection near the exposed low-level circulation center (LLCC) of Norman(see Friday video below)  dissipated around 07Z last evening, and has not returned as of advisory time, with only a small area of convection present about 90 nm north of the center. The LLCC has remained clearly visible in infrared and fog product satellite imagery during the night. The subjective Dvorak current intensity estimate came in at 3.0/45 kt from PHFO, while JTWC estimated 3.0 or 45-50 kt using the subtropical method. The latest objective estimates remain lower, with CIMSS SATCON showing 43 kt, and CIMSS ADT 2.3/32 kt. The overnight ASCAT pass missed Norman, but a 0648Z ScatSat pass found winds of 40 kt in the northeast quadrant. The initial intensity is lowered to 50 kt for this advisory, reflecting an assumed gradual spindown from the stronger winds measured by the 53rd Weather Reconnaissance Squadron aircraft on Friday, and this may be generous.

Norman appears to have turned more to the northwest during the night, likely in response to the loss of deep convection, and the initial motion estimate for this advisory is 320/8 kt. All of the reliable guidance insists that the current northwest motion is temporary, and that Norman will quickly resume a north-northwest motion today, becoming almost due north thereafter, as it moves between a deep-layer ridge centered to the east and a cutoff low to the west. The guidance envelope did not shift much from the previous advisory. The new track forecast is on the left side of the reliable guidance for the first 24 hours due to the current motion, then near the previous forecast and the consensus HCCA and TVCE aids thereafter.

The CIMSS vertical wind shear estimate for this advisory is 235/52 kt, and very strong southwest vertical wind shear of 45 to 55 kt is expected to persist over Norman for the next 36 hours or so, with some decrease possible thereafter. However, the system is forecast to be moving over cool SSTs below 25C by that time. Also, the SHIPS and experimental ECMWF-based SHIPS guidance now both categorize Norman as extratropical in 24 hours. This seems plausible given the asymmetric wind field observed by the ScatSat pass, the fact that the system already is acquiring a rather subtropical appearance, and Norman’s increasingly shallow warm core as depicted by the FSU phase-space diagrams. The new intensity forecast continues to weaken Norman, and makes it a post-tropical gale center in 36 hours. If Norman does not regain deep convection near the LLCC soon, it will likely be declared post-tropical considerably sooner than shown in this forecast.Tropical Storm Norman Distances 0500 Hours September 8 2018

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 26.0N 154.4W   50 KT  60 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 12H  09/0000Z 27.4N 154.8W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 24H  09/1200Z 29.1N 154.9W   40 KT  45 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 36H  10/0000Z 31.2N 154.7W   40 KT  45 MPH - POST-TROPICAL (ENE Honolulu, Hawaii)
 48H  10/1200Z 32.9N 154.5W   35 KT  40 MPH - POST-TROPICAL (ENE Honolulu, Hawaii)
 72H  11/1200Z 34.5N 155.0W   30 KT  35 MPH - POST-TROP/REMNT LOW (ENE Honolulu, Hawaii)
 96H  12/1200Z 35.5N 156.5W   25 KT  30 MPH - POST-TROP/REMNT LOW (ENE Honolulu, Hawaii)
120H  13/1200Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 1100 PM HST Fri Sep 07 2018

The exposed low-level circulation center (LLCC) of Norman  remains clearly evident in infrared and fog product satellite imagery this evening, with diminishing deep convection confined only to the northeast quadrant in a strongly sheared pattern. The subjective Dvorak current intensity estimate came in at 3.5/55 kt from PHFO, while JTWC estimated 3.0 or 45-50 kt using the subtropical method. Objective intensity estimates are lower, with CIMSS SATCON showing 44 kt, and CIMSS ADT 2.8/41 kt. Recent satellite images since the 06Z synoptic time also show the remaining deep convection becoming increasingly separated from the LLCC. Out of respect for the stronger winds found around midday today by the 53rd Weather Reconnaissance Squadron aircraft penetration as well as the 2001Z ASCAT pass, will lower the initial intensity for this advisory only slightly to 55 kt.

The initial motion estimate for this advisory is 335/8 kt. Norman continues to move to the north-northwest between a deep-layer ridge centered to the east, and a longwave trough to the northwest. The latest track guidance has shifted a bit more to the right, in better agreement with the motion of Norman during the past 18 hours or so, and shows the cyclone continuing on a north-northwest to northward course during the next 2 to 3 days. The new track forecast lies close to the consensus HCCA and TVCE objective aids, and was shifted only slightly to the right from the previous forecast.

The CIMSS vertical wind shear estimate for this advisory is 230/56 kt, and is supported by recent GOES satellite-derived upper-level wind retrievals. Very strong wind shear of 45-55 kt will persist over Norman for the next 36 hours, with some decrease possible thereafter. However, the system is forecast to be moving over cool SSTs below 25C by that time. The combined effects of the shear and increasingly cool water should cause Norman to steadily weaken to a remnant low by 72 hours, then dissipate by day 5. It is worth noting that the GFS and ECMWF models maintain Norman as a stronger system, possibly transitioning toward extratropical after 72 hours, while the hurricane dynamical and statistical models show more rapid weakening. The official intensity forecast compromises between these extremes, and delays dissipation as compared to the statistical guidance, but does not keep Norman as strong as the GFS/EC and does not show extratropical transition. If the recent loss of deep convection near the LLCC persists, Norman could become post-tropical considerable sooner than indicated in this forecast.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 25.6N 153.6W   55 KT  65 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 12H  08/1800Z 26.8N 154.0W   50 KT  60 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 24H  09/0600Z 28.6N 154.3W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 36H  09/1800Z 30.3N 154.3W   40 KT  45 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 48H  10/0600Z 32.3N 154.0W   35 KT  40 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 72H  11/0600Z 34.5N 154.5W   30 KT  35 MPH...POST-TROP/REMNT LOW - (ENE Honolulu, Hawaii)
 96H  12/0600Z 35.5N 156.0W   25 KT  30 MPH...POST-TROP/REMNT LOW - (ENE Tabuaeran atoll, Kiribati)
120H  13/0600Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Fri Sep 07 2018

Strong southwesterly shear ripped thunderstorms from the center of Norman overnight, and the partially exposed low-level circulation center (LLCC) is now evident in visible satellite imagery. With thunderstorms limited to the northern semicircle, subjective Dvorak intensity estimates ranged from 3.0/55 kt from PGTW/SAB to 4.0/65 kt from PHFO. A blend of these data supports lowering the initial intensity to 60 kt for this advisory.

Norman is moving toward the north-northwest between a deep-layer ridge centered to the east, and a longwave trough to the northwest, and the initial motion estimate for this advisory is 340/8 kt. A general motion toward the north-northwest and then north is expected to continue as the steering flow changes little through day 3. The updated forecast track again is shifted to the right of the previous due to significant shifts in the guidance envelope, and the updated forecast lies close to the HCCA and TVCE. Toward the end of the forecast period, a severely weakened and shallow Norman is expected to briefly move toward the northwest before dissipating on day 5.

Norman will continue to weaken as it will remain embedded in an environment characterized by 40-50 kt of vertical wind shear. The updated intensity forecast closely mimics the previous forecast and ICON. Continued rapid weakening in the short term should taper off somewhat on days 2 and 3 as the low-level remnant slowly spins down over gradually decreasing SSTs. A more rapid decrease in SSTs on days 4 and 5 should ensure decay, then dissipation. The official forecast delays dissipation as compared to the statistical guidance, with preference given to dynamical model guidance that indicates that Norman will weaken more slowly.Hurricane Norman Distances 1100 Hours September 7 2018

FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 24.0N 152.8W   60 KT  70 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 12H  08/0600Z 25.0N 153.6W   50 KT  60 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 24H  08/1800Z 26.4N 154.6W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 36H  09/0600Z 27.8N 155.0W   40 KT  45 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 48H  09/1800Z 29.4N 154.7W   35 KT  40 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 72H  10/1800Z 32.0N 154.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  11/1800Z 34.5N 156.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  12/1800Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Fri Sep 07 2018

Norman continues to be torn apart by 40 to 45 kt vertical wind shear this morning, with 1200 UTC infrared imagery showing the low level circulation center (LLCC) becoming exposed. All remaining deep convection has been sheared to the northwest through northeast of the LLCC. Outflow is best to the north through northeast and almost non-existent elsewhere. Subjective Dvorak current intensity estimates were 4.0/65 kt from all three analysis centers, with the latest ADT from UW-CIMSS at 61 kt. Given this agreement and the continuous deterioration of this system, initial intensity is set at 65 kt for this advisory.

Initial motion is 315/08 kt. The emergence of the LLCC from beneath layered clouds removed all doubt concerning Norman’s position and makes motion estimates easier. This tropical cyclone continues to move northwest along the western flank of a ridge and toward an upper trough to its north. The entire track guidance envelope shifted to the right, with GFS now along the right side after running within the left third of the envelope 12 hours ago. After a small shift to the left through 24 hours, along GMNI, to account for initial motion, the forecast track was shifted significantly to the right to stay within the guidance envelope. The current track now lies between HWRF and TVCE ensemble guidance from 36 through 120 hours.

Norman will continue to experience 40 to 50 kt of vertical wind shear through 48 hours. This will continue to weaken the tropical cyclone rather rapidly, particularly in light of the cooler sea surface temperatures ahead. Norman is forecast to become a remnant low by day 3, following the IVCN weakening curve. However, SHIPS intensity guidance depicts a remnant low by day 2, so this status may come sooner.Hurricane Norman Distances 0500 Hours September 7 2018

FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 23.0N 152.6W   65 KT  75 MPH - Category 1 (ENE Honolulu, Hawaii)
 12H  08/0000Z 23.8N 153.6W   55 KT  65 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 24H  08/1200Z 25.1N 154.7W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 36H  09/0000Z 26.5N 155.4W   40 KT  45 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 48H  09/1200Z 28.3N 156.0W   35 KT  40 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 72H  10/1200Z 31.5N 156.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  11/1200Z 34.5N 157.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  12/1200Z 37.8N 158.7W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Thu Sep 06 2018

Norman  is weakening, but only slowly thus far. The center feature is gradually becoming less distinct in visible and infrared satellite imagery, but a 1717 UTC SSMIS pass shows a well-defined eye feature with eyewall convection persisting around most of the low level center. Despite a very gradual degradation in the satellite presentation, the intensity estimates remain 5.0 from PHFO, JTWC, and SAB, while the UW-CIMSS ADT had 102 knots. Have lowered the initial intensity to 95 kt for this advisory, as a blend between the subjective and objective estimates.

The initial motion estimate is 315/8. Norman is headed toward a gradually digging upper level trough to the north of the main Hawaiian Islands. The track guidance is in fairly good agreement with a continued northwest motion over the next 36 to 48 hours. After 48 hours, forecasting whatever remains of Norman becomes increasingly more challenging. Some of the guidance, like the ECMWF, HMON, and HWRF, show Norman beginning to get picked up by the broad circulation of a large low over the north Pacific near the date line. Other models, such as the GFS and NAVGEM, have a shallower, decoupled circulation that slows and then begins to track westward. There is a very large guidance spread in the 96 to 120 hour time frame, but by then Norman is expected to be a remnant low. Our official forecast shows a bit slower motion in the later periods, and remains close to the consensus guidance which is splitting the difference in these two scenarios.Hurricane Norman Distances 1100 Hours September 6 2018

Norman will continue to experience rapidly increasing shear, expected to be near or greater than 40 kt within 24 hours. This should initiate a more rapid weakening trend. Although sea surface temperatures are marginal now, the circulation will be moving over cool sub-26C SSTs beyond 48 hours. The rate of weakening in this forecast is similar to the previous advisory. Norman is expected to become a remnant low in 4 to 5 days, but this could happen even sooner.

FORECAST POSITIONS AND MAX WINDS
 
INIT  06/2100Z 21.4N 150.9W   95 KT 110 MPH - Category 2 (E Hilo, Hawaii)
 12H  07/0600Z 22.1N 151.7W   85 KT 100 MPH - Category 2 (E Hilo, Hawaii)
 24H  07/1800Z 23.1N 152.8W   70 KT  80 MPH - Category 1 (E Hilo, Hawaii)
 36H  08/0600Z 24.1N 153.9W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  08/1800Z 25.2N 155.0W   40 KT  45 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  09/1800Z 27.1N 156.7W   30 KT  35 MPH - Tropical Storm (E Hilo, Hawaii)
 96H  10/1800Z 28.6N 158.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  11/1800Z 30.4N 159.8W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Thu Sep 06 2018

Increasing southwesterly vertical wind shear of around 25 kt has begun to take its toll Norman  . Although deep convection remains vigorous in the inner core, the eye is no longer apparent on infrared imagery. Subjective Dvorak current intensity estimates came in at 5.0/90 kt from all fix agencies. CIMSS ADT continues to suggest a stronger system at 105 kt, and given the resilience of the convection near the center, the initial intensity will be conservatively dropped to 100 kt.

The initial motion is set at west-northwest (300 degrees) at 7 kt. Norman will gradually turn toward the northwest today as the hurricane heads into a weakness in the deep ridge centered far to the northeast. The northwestward motion will persist through the weekend as Norman interacts with a mid- to upper-level trough sitting to the northwest. The track forecast was changed little from the prior advisory through 72 hours and was shifted slightly to the right the prior advisory thereafter. The track forecast is nearest to TVCE and HCCA and is down the middle of a guidance envelope that has a significant increase in spread with time. Although the GFS and ECMWF are slightly left of the official track, none of the reliable guidance would lead to a direct impact from Norman on the main Hawaiian Islands. However, as the tropical cyclone will remain in our general vicinity for the next couple of days, people should continue to monitor the progress of this system.

Weakening will continue. As Norman enters a weakness in the deep ridge, it is encountering increasing southwesterly vertical wind shear that is being produced by the mid- to upper-level trough parked to the northwest. This wind shear will steadily increase through Saturday and remain in place through at least Sunday. In addition, SSTs will begin to cool later today. The combined effect will be steady weakening, which will likely render Norman a post-tropical remnant low on late Sunday or Monday. The intensity forecast is essentially an update of the prior advisory and runs down the middle of a fairly tightly clustered guidance envelope near ICON through the next 72 hours. Guidance spread increases at 96 hours, and with vertical wind shear expected to remain high, the forecast favors SHIPS, which continues to weaken Norman.Hurricane Norman Distances 0500 Hours September 6 2018

FORECAST POSITIONS AND MAX WINDS
 
INIT  06/1500Z 20.7N 150.5W  100 KT 115 MPH - Category 3 (E Hilo, Hawaii)
 12H  07/0000Z 21.4N 151.3W   90 KT 105 MPH - Category 2 (E Hilo, Hawaii)
 24H  07/1200Z 22.4N 152.4W   75 KT  85 MPH - Category 1 (ENE Honolulu, Hawaii)
 36H  08/0000Z 23.5N 153.5W   60 KT  70 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 48H  08/1200Z 24.6N 154.8W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 72H  09/1200Z 26.7N 156.8W   30 KT  35 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 96H  10/1200Z 28.7N 158.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  11/1200Z 30.9N 160.9W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Wed Sep 05 2018

Norman appears to have rapidly intensified overnight. Although the eye has become slightly less distinct during the past couple of hours, the satellite fix agencies (SAB, JTWC, and PHFO) were in unanimous agreement that the subjective Dvorak current intensity estimate was 5.5/102 kt. In addition, the most recent UW-CIMSS ADT estimate was 5.8/110 kt. Based on these estimates, we have increased the initial intensity to 100 kt for this advisory.

Norman has been moving just south of due west, or 265 deg, at 10 kt. It is being steered by a deep subtropical ridge located to the north and northeast. The western edge of this ridge is forecast to erode later today as an upper-level trough digs down toward the region north of the Hawaiian Islands during the next couple of days. As a result, the forecast guidance is showing an increasing spread in the track forecasts starting in 48 hours. This is likely due to the way the different models forecast the weakening of the western flank of the ridge due to the upper-level trough. This weakening of the ridge is expected to cause Norman to slow its forward motion and gradually turn toward the west-northwest starting later today. This will likely be followed by a turn toward the northwest starting later tonight or early Thursday, and continuing into this weekend. The latest forecast track has been shifted to the left of the previous forecast, and remains close to the middle of the guidance envelope through the next 2 days. Even though the guidance spread increases during days 3 through 5, all of the models support the general northwestward motion persisting. The latest official forecast is also very close to the FSSE, TVCE, HCCA and GFEX consensus model guidance.Hurricane Norman Distances 0500 Hours September 5 2018

Norman is expected to remain a hurricane for the next couple of days. The latest CIRA ocean heat content (OHC) analysis appears to support it remaining near major hurricane intensity today. Vertical wind shear has gradually increased to near 15 kt based on the latest UW-CIMSS estimate, which may be contributing to some of the degradation of the eye this morning. By tonight, most of the guidance is in good agreement that Norman will start to weaken under the effects of increasing southwesterly vertical wind shear, cooler SSTs, and drier environmental conditions. This weakening will likely persist through day 5, when Norman is forecast to become a remnant low. The intensity forecast follows similar trends of the prior advisory, and favors the latest ICON guidance.

The NOAA Gulfstream IV aircraft is scheduled to conduct another mission to sample the environment around Norman later today. The valuable data collected during this mission will be used to improve the initialization of the various hurricane forecast models that we use to predict the motion and intensity of Norman later today and tonight.

FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 19.5N 147.7W  100 KT 115 MPH - Category 3 (E Hilo, Hawaii)
 12H  06/0000Z 19.8N 148.9W  100 KT 115 MPH - Category 3 (E Hilo, Hawaii)
 24H  06/1200Z 20.4N 150.2W   90 KT 105 MPH - Category 2 (E Hilo, Hawaii)
 36H  07/0000Z 21.4N 151.3W   80 KT  90 MPH - Category 1 (E Hilo, Hawaii)
 48H  07/1200Z 22.6N 152.3W   70 KT  80 MPH - Category 1 (ENE Honolulu, Hawaii)
 72H  08/1200Z 24.9N 154.3W   45 KT  50 MPH - Tropical Storm (ENE Honolulu, Hawaii)
 96H  09/1200Z 27.0N 156.5W   30 KT  35 MPH - Tropical Storm (ENE Honolulu, Hawaii)
120H  10/1200Z 28.6N 158.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS Central Pacific Hurricane Center Honolulu HI 500 PM HST Tue Sep 04 2018

DISCUSSION AND OUTLOOK

At 500 PM HST (0300 UTC), the center of Hurricane Norman  was located near latitude 19.8 North, longitude 145.5 West. Norman is moving toward the west near 12 mph (19 km/h). A continued westward motion with a decrease in forward speed is expected tonight. Norman will turn toward the west-northwest on Wednesday, then turn toward the northwest on Wednesday night and Thursday.

Maximum sustained winds are near 80 mph (130 km/h) with higher gusts. Some increase in intensity is expected during the next 24 hours, with Norman expected to remain a hurricane into Thursday.

Hurricane Norman Distances 1700 Hours September 4 2018

Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km).

The estimated minimum central pressure is 984 mb (29.06 inches).

HAZARDS AFFECTING LAND

SURF: Large swells generated by Norman will reach the Hawaiian Islands this evening and will continue to build into Thursday. These swells will produce large surf along east facing shores of the islands through at least Thursday night.

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Tue Sep 04 2018

Norman has been holding its own during the night. The overall satellite presentation has remained generally steady during the last several hours, with some recent development of new deep convection very close to the estimated low-level circulation center. A recent 1122Z AMSR microwave pass showed a rather well-defined eye. Subjective Dvorak current intensity estimates came in at 4.5/77 kt from PHFO/SAB, and 4.0/65 kt from JTWC. We have held the initial intensity unchanged at 75 kt for this advisory.

The hurricane is now tracking due west, with an initial motion estimate of 270/15 kt. Westward motion is expected to continue today and tonight, with a considerable decrease in forward speed as Norman nears the southwestern periphery of a strong subtropical ridge centered to the northeast. Thereafter, the cyclone will gradually turn to the west-northwest then to the northwest as it moves around the end of the ridge and is increasingly steered by a large deep-layered trough over the North Pacific. The reliable guidance envelope shows very good agreement with this scenario, including the location and timing of the northwest turn. The new official forecast is shifted ever so slightly to the left through the first 48 hours mainly due to the more westward initial motion, and is simply an update of the previous forecast track thereafter. This is in best agreement with the FSSE guidance, and is also very close to the consensus HCCA and TVCE guidance.Hurricane Norman Distances 0500 Hours September 4 2018

The CIMSS initial vertical wind shear estimate was only 9 kt from the south-southwest, and SHIPS guidance shows light wind shear persisting for another 36 hours as Norman continues tracking around the subtropical ridge. Norman is also now moving into an area of slightly higher ocean heat content as per the current CIRA analysis. Intensity guidance generally shows little change through the next couple of days, with some of the guidance including CTCI and HWFI showing an intensity increase between the 12- and 36-hour forecast times. After 48 hours, a rapid increase in wind shear, a drier surrounding airmass, and progressively cooler sea surface temperatures should cause steady weakening. The new intensity forecast has been adjusted upward slightly from 12 to 48 hours to better match the guidance envelope, with a similar weakening trend to the previous advisory thereafter.

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 19.9N 143.4W   75 KT  85 MPH - Category 1 (E Hilo, Hawaii)
 12H  05/0000Z 19.9N 145.1W   75 KT  85 MPH - Category 1 (E Hilo, Hawaii)
 24H  05/1200Z 19.9N 147.0W   80 KT  90 MPH - Category 1 (ENE Hilo, Hawaii)
 36H  06/0000Z 20.4N 148.6W   80 KT  90 MPH - Category 1 (ENE Hilo, Hawaii)
 48H  06/1200Z 21.2N 149.9W   75 KT  85 MPH - Category 1 (E Lāhainā, Hawaii)
 72H  07/1200Z 23.6N 151.8W   55 KT  65 MPH - Tropical Storm (ENE Hilo, Hawaii)
 96H  08/1200Z 26.5N 154.0W   40 KT  45 MPH - Tropical Storm (ENE Hilo, Hawaii)
120H  09/1200Z 29.0N 155.5W   30 KT  35 MPH - Tropical Storm (ENE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 PM PDT Mon Sep 03 2018

Norman continues to slowly weaken. Satellite images indicate that the banding features are not as well organized as they were earlier today, and the cloud tops have warmed some during the past few hours. The Dvorak classifications have decreased, and a blend of the latest estimates supports lowering the initial intensity to 80 kt.

Norman continues to move quickly westward at 18 kt steered by a strong subtropical ridge to its north-northeast. This general heading, but with a significant decrease in forward speed, is expected during the next day or two while Norman nears the edge of the ridge. Thereafter, a turn to the northwest and then north-northwest is expected while Norman moves around the ridge and toward a large deep-layer trough over the northern Pacific. There remains a fair amount of spread on where and when Norman makes the turn, but the guidance did not change much overall this cycle. Therefore, only small changes were made to the previous advisory, and this forecast lies close to the middle of the guidance envelope.

Norman could weaken a little more overnight and on Tuesday, but the guidance shows the intensity flattening out in the 24- to 48-hour time period. After that time, however, a sharp increase in shear, cooler waters, and a drier air mass should cause more significant weakening. The NHC intensity forecast is largely an update of the previous one and in line with the IVCN and HCCA consensus models.

Now that Norman has crossed into the central Pacific basin, future advisories on this system will be issued by the Central Pacific Hurricane Center.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 19.8N 140.2W   80 KT  90 MPH - Category 1 (E Hilo, Hawaii)
 12H  04/1200Z 20.0N 142.5W   75 KT  85 MPH - Category 1 (E Hilo, Hawaii)
 24H  05/0000Z 20.1N 144.9W   70 KT  80 MPH - Category 1 (E Hilo, Hawaii)
 36H  05/1200Z 20.2N 147.0W   70 KT  80 MPH - Category 1 (ENE Hilo, Hawaii)
 48H  06/0000Z 20.6N 148.7W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  07/0000Z 22.5N 151.1W   65 KT  75 MPH - Category 1 (ENE Honolulu, Hawaii)
 96H  08/0000Z 25.3N 153.3W   50 KT  60 MPH - Tropical Storm (ENE Honolulu, Hawaii)
120H  09/0000Z 28.1N 155.2W   35 KT  40 MPH - Tropical Storm (ENE Honolulu, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Mon Sep 03 2018

Corrected to remove G-IV flight reference for this afternoon

Satellite images indicate that Norman  is weakening. The eye is no longer apparent on infrared imagery, and the cloud tops are warming throughout the central dense overcast. The initial wind speed is reduced to 95 kt, which is close to a blend of the Dvorak CI numbers from TAFB and SAB. Continued weakening is likely over the next several days due to a combination of marginal SSTs, light or moderate shear, and a dry mid-level environment. The new forecast is very similar to the previous one, except lower in the short term to account for the current intensity.

Norman has turned westward and is still moving at about 17 kt. A fast westward motion is anticipated over the next few days while a large subtropical ridge holds firm over the central Pacific Ocean. However, a weakness in the ridge from 150W-155W should cause Norman to turn more northwestward after day 3. Model guidance is showing considerable spread at long range, with the UKMET and its ensemble closer to Hawaii, while almost all of the other guidance is much farther northeast. There continues to be a westward shift in the guidance, so the official forecast has been shifted westward at long range. It should be noted, however, that there isn’t much support for the UKMET solution in the rest of the guidance, so it seems to be an outlier at this time.

Hurricane Norman Distances 0500 Hours September 3 2018
Hurricane Norman Distances 0500 Hours September 3 2018
FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 19.3N 136.6W   95 KT 110 MPH - Category 3 (SSW Hilo, Hawaii)
 12H  04/0000Z 19.7N 139.2W   85 KT 100 MPH - Category 1 (SSW Hilo, Hawaii)
 24H  04/1200Z 20.0N 142.3W   75 KT  85 MPH - Category 1 (SSW Hilo, Hawaii)
 36H  05/0000Z 20.2N 144.8W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 48H  05/1200Z 20.3N 146.9W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 72H  06/1200Z 21.3N 150.1W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  07/1200Z 24.0N 152.5W   60 KT  70 MPH - Tropical Storm (SSW Hilo, Hawaii)
120H  08/1200Z 27.5N 154.5W   45 KT  50 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 AM PDT Mon Sep 03 2018

Its possible that Norman  has peaked, perhaps permanently this time. Cloud tops have notably warmed around the eye, which itself has become less distinct in IR imagery overnight. The initial intensity has been lowered to 110 kt based on a blend of subjective Dvorak final-T and CI numbers from TAFB and SAB, and the UW-CIMSS ADT. Based on trends over the past hour or two, it’s possible Norman has weakened even more than indicated. All of the intensity guidance suggests that Norman should steadily weaken over the next several days due to a combination of marginal SSTs, moderate shear, and a drier surrounding environment, though this was the case last night as well shortly before Norman quickly re-intensified to major hurricane strength. Since another sudden period of intensification doesn’t appear imminent, the new NHC intensity forecast is very close to the consensus through day 5, and only minor changes were made from the previous advisory.

The estimated initial motion is now 285/17 kt. Norman should continue moving very quickly toward the central Pacific over the next 24 hours as it is steered by a strong subtropical ridge to the north. By later this week, all of the global models forecast that the hurricane will slow down, and then turn toward the northwest toward a weakness in the ridge. There is still a fair amount of spread in the track guidance, particularly regarding the speed of Norman after it begins to turn northwestward around day 4 or 5, so confidence is in this portion of the track forecast is low. The new NHC track forecast has been adjusted slightly south of the previous advisory for the first 72 h, following the HCCA and TVCX consensus aids, but is fairly similar after that. Based on the current forecast, Norman is expected to cross into the central Pacific later today.Hurricane Norman Distances 2300 Hours September 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 19.0N 134.6W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 12H  03/1800Z 19.5N 137.3W   95 KT 110 MPH - Category 2 (SSW Hilo, Hawaii)
 24H  04/0600Z 20.0N 140.4W   85 KT 100 MPH - Category 1 (SSW Hilo, Hawaii)
 36H  04/1800Z 20.2N 143.2W   80 KT  90 MPH - Category 1 (SSW Hilo, Hawaii)
 48H  05/0600Z 20.4N 145.4W   75 KT  85 MPH - Category 1 (SSW Hilo, Hawaii)
 72H  06/0600Z 21.2N 149.0W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  07/0600Z 23.5N 151.5W   60 KT  70 MPH - Tropical Storm (SSW Hilo, Hawaii)
120H  08/0600Z 27.0N 153.5W   50 KT  60 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Sun Sep 02 2018

Norman  has made a remarkable and surprising come back today. Satellite images reveal a distinct eye surrounded by a ring of very deep convection, and Dvorak T-numbers from both TAFB and SAB reached T6.0 around 1200 UTC. These numbers have leveled off since then. On this basis, the initial intensity has been increased to 115 kt, making Norman again a Category Four Hurricane on the Saffir-Simpson Scale. The hurricane, however, will begin to approach lower SSTs, and although some of the intensity models are more aggressive in forecasting strengthening, the NHC forecast prefers the consensus IVCN, and forecasts a gradual weakening beyond 12 to 24 hours.

Norman is moving toward the west-northwest at 16 kt. There is a strong subtropical ridge anchored to the north of Norman, and this flow pattern will continue to steer the hurricane between the west and west-northwest at the same speed for the next 2 to 3 days. By then, the ridge is forecast to be weaker and a turn toward the northwest is expected by the end of the forecast period. Track guidance is in very good agreement, and unanimously, all models forecast the gradual turn to the northwest beyond 4 days. The NHC track forecast is in the middle of the envelope and is not much different from the earlier one.Hurricane Noman Distances 0500 Hours September 2 2018

FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 17.6N 129.1W  115 KT 130 MPH - Category 4 (SSW Hilo, Hawaii)
 12H  03/0000Z 18.2N 131.5W  115 KT 130 MPH - Category 4 (SSW Hilo, Hawaii)
 24H  03/1200Z 19.1N 134.7W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
 36H  04/0000Z 20.0N 138.2W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)
 48H  04/1200Z 20.5N 141.5W   80 KT  90 MPH - Category 1 (SSW Hilo, Hawaii)
 72H  05/1200Z 21.0N 146.0W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  06/1200Z 22.0N 150.0W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
120H  07/1200Z 24.0N 153.0W   55 KT  65 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Sat Sep 01 2018

Hurricane Norman – Since the previous advisory, a well-defined closed eye  has remained apparent in microwave satellite data, and a cloud-filled eye has appeared in visible satellite imagery during the past couple of hours. Satellite intensity estimated haven’t changed since the previous advisory, so the initial intensity remains 90 kt, which is supported by a 1501Z SATCON estimate of 88 kt and a Dvorak CI value of T5.0/90 kt.

Norman’s initial motion estimate is now 275/12 kt based on microwave and visible satellite eye position estimates. There are no significant changes to the previous track forecast and reasoning. The hurricane is expected to be steered by a strong deep-layer subtropical ridge to the north, resulting in a westward motion for the next 12-24 hours, followed by a west-northwestward motion at a faster forward speed. The latest model guidance is tightly packed about the previous forecast track through 96 hours, with much less divergence after that compared to previous model runs. Therefore, the new forecast track is essentially just an extension of the previous advisory track, and lies close to a blend of the HCCA, FSSE, and TVCE consensus track models.Hurricane Norman Distances 1500 Hours September 1 2018

The GFS and ECMWF models are forecasting the 15-20 kt of vertical wind shear that has been affecting Norman to steadily decrease for the next 60-72 hours, possibly becoming near zero if the ECMWF upper-level wind forecasts verify. Since the hurricane is expected to remain over 27 deg C and warmer SSTs for the next 48 hours, only slow weakening is forecast and that is due mainly to occasional intrusions of drier and more stable air coming in from the northwest, where a large field of cold-air stratocumulus clouds is currently lurking close by. The HWRF and HMON models continue to forecast Norman to re-strengthen into a major hurricane during the next 24 hours, but this scenario is being discounted at this time due to Norman’s proximity to the aforementioned stratocumulus cloud field. By 72 hours, increasing southwesterly shear and cooler SSTs should combine to induce more significant weakening. The NHC intensity forecast is similar to the HCCA and IVCN consensus model forecasts.

FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 16.3N 125.1W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)
 12H  02/0600Z 16.6N 127.0W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)
 24H  02/1800Z 17.4N 130.1W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 36H  03/0600Z 18.2N 133.2W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 48H  03/1800Z 19.1N 136.5W   80 KT  90 MPH - Category 1 (SSW Hilo, Hawaii)
 72H  04/1800Z 20.4N 142.0W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  05/1800Z 21.4N 146.4W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
120H  06/1800Z 22.2N 149.6W   60 KT  70 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 AM PDT Sat Sep 01 2018

Norman continues to weaken due to the effects of moderate northeasterly shear of about 20 kt, as analyzed in SHIPS diagnostics. The hurricane has taken on a traditional IR shear pattern structure, with a tight gradient of brightness temperatures observed up-shear of the estimated center position. Satellite intensity estimates have continued to drop and no longer support keeping Norman at major hurricane strength. The initial intensity has been lowered to 95 kt, just above the latest SATCON estimate, but this still could be generous.

The shear affecting Norman is expected to continue for at least the next 24 h. Some of the dynamical models hint that the shear could relax between 24-48 h, which would likely bring an end to Norman’s weakening trend. While it is not explicitly reflected in the intensity forecast, a decrease in shear could even allow the hurricane to briefly restrengthen. Recent microwave imagery indicates that the mid- to lower-level inner-core and eye of Norman are still intact. If this structure can survive the next 24 h of shear, reintensification would be more likely. By 72 h, the hurricane will reach drier, more stable air and moderate SSTs, and these factors will likely cause it to steadily weaken through the remainder of the forecast period.Hurricane Norman Distances 0500 Hours September 1 2018

The cyclone appears to have finally turned westward, and the initial motion is 265/7 kt. No significant changes have been made to the track forecast. Norman is still expected to move westward to west-northwestward for the next several days, steered primarily by an extensive deep-layer ridge to the north. The models remain in good agreement on the track of Norman throughout the forecast period, and the official track forecast is near the middle of the guidance envelope and very close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 16.3N 123.0W   95 KT 110 MPH - Category 2 (SSW Hilo, Hawaii)
 12H  01/1800Z 16.3N 124.4W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 24H  02/0600Z 16.6N 126.8W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 36H  02/1800Z 17.3N 129.8W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 48H  03/0600Z 18.2N 132.9W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 72H  04/0600Z 19.9N 139.1W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  05/0600Z 21.0N 143.5W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
120H  06/0600Z 21.5N 147.0W   60 KT  70 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 AM PDT Fri Aug 31 2018 Norman

Norman appears to have weakened over the past several hours. Cloud tops around the eye have warmed, and the eye itself has become less distinct. Several recent microwave overpasses show little indication that an eyewall replacement cycle is underway, but it is possible that our ability to observe such a cycle is limited by the resolution of the available instruments. Satellite intensity estimates from all agencies have decreased and supported at most an intensity of 125 kt at 0600 UTC. Given the continued warming of cloud tops near the inner core since that time, the initial intensity has been lowered to 120 kt.

Due to the lower initial intensity, the intensity forecast has also been lowered slightly, particularly for the first 24 h. Gradual weakening is expected through the forecast period, though larger short-term fluctuations in intensity due to eyewall replacement cycles are possible, if not likely, while Norman remains a hurricane. By the end of the forecast period, a faster weakening rate is anticipated as Norman is forecast to move over cooler SSTs and reach a drier environment. The NHC forecast is near the center of the intensity guidance envelope and near the intensity consensus.Hurricane Norman Distances 2300 Hours August 30 2018

The hurricane has continued to move west-southwestward at 8 kt. Almost no change has been made to the track forecast, which remains close to the various consensus aids. The hurricane should turn westward, and then west-northwestward, as it is steered primarily by a deep-layer ridge to the north for the next 5 days. With the exception of the UKMET global model, which is an outlier to the south, the global and regional dynamical models are in good agreement on the future path of Norman, and confidence in the track forecast is fairly high.

FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 16.9N 120.2W  120 KT 140 MPH - Category 4 (SSW Hilo, Hawaii)
 12H  31/1800Z 16.6N 121.4W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 24H  01/0600Z 16.3N 123.1W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 36H  01/1800Z 16.3N 125.1W  105 KT 120 MPH - Category 3 (SSW Hilo, Hawaii)
 48H  02/0600Z 16.7N 127.4W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
 72H  03/0600Z 18.4N 133.0W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 96H  04/0600Z 19.5N 139.0W   70 KT  80 MPH - Category 1 (SSW Hilo, Hawaii)
120H  05/0600Z 20.5N 143.5W   55 KT  65 MPH - Tropical Storm (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 530 AM PDT Thu Aug 30 2018

Satellite data show that Norman continues to rapidly strengthen. Objective Dvorak data T-numbers from UW/CIMSS have increased to T6.5 or higher and the latest TAFB subjective data T-number is T6.5.

These estimates support an initial intensity of 125 kt, making Norman a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. As a result of the increased initial intensity, the NHC intensity forecast has been adjusted upward through 36 h, but it is otherwise unchanged. There has been no change to the NHC track forecast.

Hurricane Norman Distances 0230 Hours August 30 2018
Hurricane Norman Distances 0230 Hours August 30 2018
FORECAST POSITIONS AND MAX WINDS

INIT  30/1230Z 17.8N 117.7W  125 KT 145 MPH - Category 4 (SSW Hilo, Hawaii)
 12H  30/1800Z 17.9N 118.5W  135 KT 155 MPH - Category 4 (SSW Hilo, Hawaii)
 24H  31/0600Z 17.6N 120.1W  135 KT 155 MPH - Category 4 (SSW Hilo, Hawaii)
 36H  31/1800Z 17.0N 121.6W  125 KT 145 MPH - Category 4 (SSW Hilo, Hawaii)
 48H  01/0600Z 16.3N 123.3W  115 KT 130 MPH - Category 4 (SSW Hilo, Hawaii)
 72H  02/0600Z 16.2N 127.1W  105 KT 120 MPH - Category 3 (SSW Hilo, Hawaii)
 96H  03/0600Z 18.0N 132.0W   95 KT 110 MPH - Category 2 (SSW Hilo, Hawaii)
120H  04/0600Z 20.0N 137.5W   75 KT  85 MPH - Category 1 (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Wed Aug 29 2018

Norman’s   cloud pattern has continued to organize with numerous convective bands and excellent upper-level outflow. More importantly, satellite images show an eye feature which has been depicted intermittently. Dvorak numbers from TAFB and SAB have reached T4.0, and on this basis, Norman is being upgraded to hurricane status in this advisory. The environment of low shear and warm ocean continues to be ideal for intensification, and guidance continues to be pretty aggressive in bringing the winds up fast. The NHC forecast indicates rapid intensification, and predicts Norman to become a major hurricane in about 24 hours.

Norman appears to be moving toward the west or 270 degrees at 8 kt. The high pressure ridge which is controlling the motion of the hurricane is expanding westward, and the flow pattern around the ridge should steer Norman on a west or even west-southwest track for the next 3 to 4 days. Track guidance continues to be in remarkably good agreement, and models are tightly clustered at least for the next 3 to 4 days. The NHC forecast is very similar to the previous one, and continue to lie very close to the corrected consensus HCCA and the multi-model aids. The confidence in the track forecast is quite high at this time.Hurricane Norman Distances 1400 Hours August 29 2018

FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 17.6N 116.1W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
 12H  30/0600Z 17.8N 117.3W   80 KT  90 MPH - Category 1 (SSW Hilo, Hawaii)
 24H  30/1800Z 17.9N 118.8W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
 36H  31/0600Z 17.5N 120.5W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 48H  31/1800Z 17.0N 122.0W  115 KT 130 MPH - Category 4 (SSW Hilo, Hawaii)
 72H  01/1800Z 16.0N 125.5W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 96H  02/1800Z 16.0N 130.0W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
120H  03/1800Z 17.5N 135.0W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Wed Aug 29 2018

The cloud pattern has continued to improved in organization, and SSMIS data at 1400 UTC indicate that an inner core is beginning to form. The area of convection is large with a well defined cyclonically curved band wrapping around the system, while the upper-level outflow is expanding westward. Based on objective and subjective T-numbers, the initial intensity has been set at 55 kt. The environment of low shear and warm waters is ideal for Normanto intensify, and in fact, the Rapid Intensification (RI) indices are quite high. On this basis, the NHC forecast calls for Norman to become a hurricane by tonight and a major hurricane in a day or so.

The best estimate of the initial motion is toward the west-northwest or 285 degrees at 9 kt. The hurricane is ready to start moving more westward or even on a west-southwestward track as the nose of the ridge to the north begins to expand westward and amplify. Most of the models captured the building of the ridge, and unanimously forecast the cyclone to move west-southwestward for the next 2 to 4 days. The confidence is the forecast during the first 3 to 4 days is high since track models are really clustered. The new NHC forecast is not too different from the previous one, and it lies between the corrected consensus HCCA and the multimodel aids.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 17.8N 115.7W   55 KT  65 MPH - Tropical Storm (SSW Hilo, Hawaii)
 12H  30/0000Z 17.9N 116.6W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
 24H  30/1200Z 18.1N 118.2W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)
 36H  31/0000Z 17.9N 119.8W  105 KT 120 MPH - Category 3 (SSW Hilo, Hawaii)
 48H  31/1200Z 17.5N 121.4W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 72H  01/1200Z 16.2N 124.8W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 96H  02/1200Z 16.0N 129.0W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
120H  03/1200Z 17.5N 134.0W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 AM MDT Wed Aug 29 2018

Even though there has been a dearth of microwave imagery overnight, Norman’s infrared satellite signature has the look of a cyclone ready to strengthen significantly over the next couple of days. Banding continues to increase, with the convective canopy expanding in nearly all quadrants. Norman’s initial intensity is set at 50 kt based on a blend of Dvorak estimates from TAFB and SAB. Ocean waters of nearly 30 degrees Celsius and low shear for the next couple of days are offering an ideal environment for Norman to rapidly intensify. The various Rapid Intensification (RI) indices continue to show high probabilities, and overall the new intensity guidance is higher than the previous forecast during the first 36 hours. Based on these numbers, the updated NHC intensity forecast has been bumped upward, close to the Florida State Superensemble and intensity consensus aids, but still not nearly as high as the HWRF or HCCA models. It wouldn’t be surprising at all for the forecast intensities to be increased further in subsequent advisory packages, and Norman is likely to become a hurricane later today.

Norman is moving westward, or 275/9 kt, to the south of the subtropical ridge, which extends westward from northern Mexico. The ridge is forecast to build westward during the next few days, causing Norman to continue westward–or even west-southwestward–at a fairly steady pace for the next 4-5 days. Except for the GFS, which appears to be a bit of a northern outlier, the remainder of the track guidance is tightly clustered, at least for the first 3 days. After that time, the overall guidance envelope has shifted slightly northward, requiring a subtle northward adjustment of the NHC official forecast by day 5. This new forecast generally lies closest to the HCCA and Florida State Superensemble aids.Tropical Storm Norman Distances 0500 Hours August 29 2018

FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 17.5N 114.6W   50 KT  60 MPH - Tropical Storm (SW Socorro Island, Mexico)
 12H  29/1800Z 17.8N 115.8W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
 24H  30/0600Z 18.0N 117.3W   85 KT 100 MPH - Category 2 (SSW Hilo, Hawaii)
 36H  30/1800Z 18.1N 118.9W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
 48H  31/0600Z 17.8N 120.5W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 72H  01/0600Z 16.7N 124.1W  110 KT 125 MPH - Category 3 (SSW Hilo, Hawaii)
 96H  02/0600Z 16.0N 128.0W  100 KT 115 MPH - Category 3 (SSW Hilo, Hawaii)
120H  03/0600Z 17.0N 132.5W   90 KT 105 MPH - Category 2 (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 AM MDT Tue Aug 28 2018

Since the previous scatterometer pass around 0430 UTC, the satellite presentation has improved significantly. The cloud pattern now consists of a couple of cyclonically curved convective bands, with the center of the system located on the northeastern edge of a circular area of thunderstorms, as indicated by a GMI microwave pass at 1201 UTC. Satellite intensity estimates from TAFB and SAB are T2.5 and T2.0, respectively, on the Dvorak scale, and on this basis, advisories are initiated on Tropical Depression Sixteen-E with an initial intensity of 30 kt.

The depression has plenty of time to intensify given that the environmental conditions of warm ocean and light shear are expected to prevail during the next 5 days. The NHC forecast calls for the depression to become a hurricane in about 2 days with additional strengthening thereafter. The forecast is very close to the intensity consensus model, and follows the trend of most of the guidance.

Since genesis has just occurred, the initial motion is somewhat uncertain. The best estimate is toward the west-northwest or 295 degrees at 9 kt. The depression is currently located on the southwestern edge of a subtropical high, and this flow pattern will continue to steer the depression on the same general track during the next day or two. After that time, the nose of the ridge is expected to amplify, and will force the cyclone to turn toward the west or even west-southwest. This is very consistent with the track guidance, and the NHC forecast lies in between the HCCA corrected consensus model and the other consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 17.1N 111.8W   30 KT  35 MPH - Tropical Storm (SW Socorro Island, Mexico)
 12H  29/0000Z 17.7N 112.9W   35 KT  40 MPH - Tropical Storm (SW Socorro Island, Mexico)
 24H  29/1200Z 18.4N 114.6W   45 KT  50 MPH - Tropical Storm (NE Clarion Island, Mexico)
 36H  30/0000Z 18.8N 116.4W   55 KT  65 MPH - Tropical Storm (W Socorro Island, Mexico)
 48H  30/1200Z 18.9N 118.1W   65 KT  75 MPH - Category 1 (SSW Hilo, Hawaii)
 72H  31/1200Z 18.5N 121.8W   80 KT  90 MPH - Category 1 (SSW Hilo, Hawaii)
 96H  01/1200Z 17.5N 126.0W   85 KT 100 MPH - Category 1 (SSW Hilo, Hawaii)
120H  02/1200Z 17.0N 130.0W   85 KT 100 MPH - Category 1 (SSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 AM PDT Tue Aug 28 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located about 1500 miles east-southeast of the Hawaiian Islands.

Showers and thunderstorms associated with an area of low pressure located about 550 miles south-southwest of the southern tip of the Baja California peninsula have changed little in organization overnight. However, environmental conditions are still conducive for development, and a tropical depression is expected to form later today or on Wednesday while the system moves west-northwestward at about 10 mph. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Mon Aug 27 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located about halfway between the western coast of Mexico and Hawaii.

Showers and thunderstorms associated with an area of low pressure located about 500 miles south of the southern tip of the Baja California peninsula have changed little in organization over the past several hours. However, environmental conditions are still favorable for development and a tropical depression is expected to form tonight or Tuesday while the system moves west-northwest to northwest at 10 to 15 mph. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high...90 percent.

If this system is named, it will be Tropical Storm Norman.

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Aug 27 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located more than 1400 miles west-southwest of the southern tip of the Baja California peninsula.

1. Showers and thunderstorms associated with an area of low pressure located about 475 miles southwest of Manzanillo, Mexico, continue to show signs of organization. Satellite imagery indicates that the circulation is currently elongated and lacks a well-defined center. Environmental conditions are expected to be conducive for additional development of this disturbance, and a tropical depression is likely to form tonight or Tuesday while the system moves generally west-northwestward at around 10 mph. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

2. Another area of low pressure is forecast to form well south or southwest the coast of southwestern Mexico later this week. Conditions are expected to be conducive for gradual development of this system this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Aug 27 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located more than 1400 miles west-southwest of the southern tip of the Baja California peninsula.

1. Showers and thunderstorms associated with an area of low pressure located about 450 miles southwest of Manzanillo, Mexico, are showing some signs of organization. Environmental conditions are expected to become more conducive for the development of this disturbance, and a tropical depression is likely to form within the next day or two while the system moves generally west-northwestward at around 10 mph. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sun Aug 26 2018

For the eastern North Pacific…east of 140 degrees west longitude:

The National Hurricane Center is issuing advisories on Tropical Storm Miriam, located about 1300 miles west-southwest of the southern tip of the Baja California peninsula.

1. A broad area of low pressure located about 500 miles south-southwest of Manzanillo, Mexico continues to produce disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for the development of this disturbance over the next several days, and a tropical depression is likely to form later thisweek while the system moves westward to west-northwestward at 10mph.
* Formation chance through 48 hours…medium…60 percent.
* Formation chance through 5 days…high…90 percent

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Aug 26 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on recently upgraded Tropical Storm Miriam, located more than 1200 miles west-southwest of the southern tip of the Baja California peninsula.

1. A broad area of low pressure located about 500 miles south of Manzanillo, Mexico, continues to produce a large area of cloudiness and disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for the development of this disturbance over the next several days, and a tropical depression is likely to form by the middle of the week while the system moves westward to west-northwestward at 10 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Aug 26 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on newly formed Tropical Depression Fifteen-E, located more than 1000 miles west-southwest of the southern tip of the Baja California peninsula.

A broad area of low pressure located nearly 500 miles south of Manzanillo, Mexico, is producing a large area of cloudiness and disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for development of this disturbance over the next several days, and a tropical depression is likely to form by the middle of the week while the system moves westward to west-northwestward at 10 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Sat Aug 25 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A well-defined low pressure system located about 1100 miles southwest of the southern tip of the Baja California peninsula continues to show signs of organization. Environmental conditions are conducive for development, and a tropical depression is likely to form during the next day or so while the system moves westward at around 10 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

2. A broad low pressure system located about 500 miles south-southwest of Acapulco, Mexico, is producing a large area of cloudiness and disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for gradual development of this disturbance over the next several days, and a tropical depression is likely to form by the middle of next week while the system moves westward to west-northwestward at 10 mph. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…80 percent.

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