Tropical Storm Douglas

Tropical Storm Douglas Track 1700 Hours July 27 2020
Tropical Storm Douglas Track 1700 Hours July 27 2020

Tropical Storm Douglas Wind SpeedsHurricane Douglas  – NWS Central Pacific Hurricane Center Honolulu HI 500 PM HST Mon Jul 27, 2020 (see Monday video below)

The satellite presentation for Douglas shows an exposed low-level circulation center (LLCC), with deep convection limited to the north quadrant. Subjective Dvorak satellite intensity estimates range from 3.5/55 kt, from SAB and HFO, to 4.0/65 kt from JTWC. UW-CIMSS ADT is 58 kt. Given these estimates and the continued degradation noted in satellite imagery, Douglas is assigned an initial intensity of 60 kt, making this system a tropical storm once again. The degraded satellite imagery is driven by continued 20 to 25 kt southwesterly wind shear which will remain a factor in this system’s future for the next 36 to 48 hours. The initial motion is 270/15, representing a persistent 12-hour westerly motion noted since the LLCC became exposed this morning. However, since fix time, a slight northward component has been detected.

Douglas continues to be steered by a deep ridge to its north and the expectation is for this system to continue on a west to west-northwest track through the remainder of its life. Wind shear is forecast to decrease somewhat after 48 hours, but global models, in particular, give Douglas no chance for redevelopment. The forecast track for Douglas is quite close to the previous one, falling within the southern third of the guidance envelope through 48 hours between HWRF and HMNI. This envelope is rather tight through 72 hours, after which Douglas is forecast to dissipate.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 22.9N 163.3W   60 KT  70 MPH - Tropical Storm (WNE Princeville, Hawaii)
 12H  28/1200Z 23.2N 165.8W   50 KT  60 MPH - Tropical Storm (WNW Puʻuwa, Hawaii)
 24H  29/0000Z 23.5N 169.3W   45 KT  50 MPH - Tropical Storm (WNW Puʻuwa, Hawaii)
 36H  29/1200Z 23.9N 173.3W   45 KT  50 MPH - Tropical Storm (WNW Johnson Atoll)
 48H  30/0000Z 24.2N 177.5W   40 KT  45 MPH - Tropical Storm (ESE Midway Atoll)
 60H  30/1200Z 24.8N 178.3E   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)
 72H  31/0000Z 25.6N 174.2E   30 KT  35 MPH - Low (WSW Midway Atoll)
 96H  01/0000Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Mon Jul 27, 2020 

Hurricane Hunters from the Air Force’s 53rd Weather Reconnaissance Squadron completed their final mission into Douglas a couple of hours ago, and the team at the Central Pacific Hurricane Center is extremely grateful for their unwavering support. Although the later passes didn’t find winds as strong as the initial passes of the mission, the central pressure remained steady. Additionally, Douglas’ satellite appearance has changed little since the last center penetration, and the initial intensity for this advisory has been maintained at 80 kt.

The initial motion estimate is 290/15 kt, with Douglas primarily being steered by a low- to mid-level ridge centered to the north of the cyclone. In the upper levels, Douglas lies between a ridge to the east and a trough to the west, and has been hanging tough in an environment characterized by significant southerly vertical wind shear. The expectation is that this debilitating wind shear will persist over the cyclone for the next couple of days, with significant weakening occurring as the cyclone gets sheared apart. The increasingly shallow system is then expected to be steered toward the west until dissipation occurs in a couple of days. The updated track forecast is close to the previous, as well as most of the reliable dynamical model guidance. The intensity forecast also leans more heavily on the dynamical models, and anticipates that a fairly rapid rate of weakening will soon commence.

FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 22.9N 160.4W   80 KT  90 MPH - Category 1 (WNE Princeville, Hawaii)
 12H  28/0000Z 23.3N 163.0W   70 KT  80 MPH - Category 1 (WNW Puʻuwa, Hawaii)
 24H  28/1200Z 23.7N 166.5W   60 KT  70 MPH - Tropical Storm (WNW Puʻuwa, Hawaii)
 36H  29/0000Z 24.1N 170.3W   50 KT  60 MPH - Tropical Storm (WNW Johnson Atoll)
 48H  29/1200Z 24.5N 174.1W   40 KT  45 MPH - Tropical Storm (ESE Midway Atoll)
 60H  30/0000Z 25.0N 178.2W   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)
 72H  30/1200Z 25.6N 178.1E   30 KT  35 MPH - Low (WSW Midway Atoll)
 96H  31/1200Z...DISSIPATED

NWS Central Pacific Hurricane Center Honolulu HI 500 PM HST Sun Jul 26, 2020 

In spite of increasing southerly vertical wind shear of more than 20 kt, a large burst of convection redeveloped around a ragged eye late this afternoon. Hurricane Hunters from the Air Force 53rd Weather Reconnaissance Squadron have departed Douglas after spending much of the day sampling the system, and another mission is scheduled for this evening. While the last passes through continued to show a slow increase in central pressure, aircraft data indicated that the winds had not changed much, and recent land-based radar showed winds in excess of 90 kt at around 6,000 ft. As a result, the initial intensity will be held at 75 kt for this advisory, which is in line with the PHFO Dvorak CI of 4.5.

Of greater importance, the aircraft data and land-based radars indicated that Douglas has taken a jog to the north today. While the low-level ridge to the north is providing significant steering, a weakness in the ridge aloft and increasing vertical wind shear, mainly at higher levels, have likely caused the hurricane to make a northward shift, resulting in an initial motion of 295/14 kt. Douglas will continue on this general motion tonight as it passes near Oahu and Kauai, eventually making a turn and an acceleration toward the west late Monday through Thursday. Due to the northward jog, the track forecast was nudged slightly to the north through Monday and is close to the middle of a tightly clustered guidance envelope through Thursday.

Slow weakening will continue, though Douglas will remain a hurricane as it passes near Oahu and Kauai tonight. SSTs will slowly increase along the forecast track, but southerly vertical wind shear will tilt the system and disrupt the circulation aloft, leading to gradual weakening through at least the next four days. The intensity forecast was changed little from the prior advisory and is near IVCN in the middle of the guidance envelope, though lower than the statistical guidance.

The motion of Douglas has allowed the Hurricane Warning for Maui County to be canceled. Given the close approach to both Oahu and Kauai along with the ongoing development of deep convection, the Hurricane Warning remains in place for Oahu and Kauai.

Key Messages

  • 1. Douglas will pass dangerously close to Oahu and Kauai tonight, producing a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores.
  • 2. It remains important that you do not focus on the exact forecast track of Douglas. Due to Douglas’ angle of approach to the islands, any wobble in the track could lead to drastic differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could extend well from the center and be realized over Oahu and Kauai.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near Oahu and Kauai.
FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 22.0N 157.3W   75 KT  85 MPH - Category 1 (ENE Kailua, Hawaii)
 12H  27/1200Z 22.5N 159.6W   70 KT  80 MPH - Category 1 (WNW Princeville, Hawaii)
 24H  28/0000Z 23.1N 162.7W   60 KT  70 MPH - Category 1 (WNW Princeville, Hawaii)
 36H  28/1200Z 23.5N 166.3W   55 KT  65 MPH - Tropical Storm (WNW Puʻuwa, Hawaii)
 48H  29/0000Z 23.9N 170.0W   50 KT  60 MPH - Tropical Storm (WNW Johnson Atoll)
 60H  29/1200Z 24.1N 173.8W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)
 72H  30/0000Z 24.2N 177.7W   40 KT  45 MPH - Tropical Storm (WSW Midway Atoll)
 96H  31/0000Z 25.0N 174.6E   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)
120H  01/0000Z 27.2N 167.7E   35 KT  40 MPH - Tropical Storm (ESE Tokyo, Japan)

NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Sun Jul 26, 2020 

Hurricane Hunters from the Air Force 53rd Weather Reconnaissance Squadron are back out sampling Douglas. The hurricane has been resilient, with deep convection persisting to the west and north of the center under increasing vertical wind shear. The Hurricane Hunters have found that the center pressure has risen slightly, and a blend of SFMR and adjusted flight level winds supports lowering the initial intensity to 75 kt. Island-based radars are detecting the mid-level circulation of Douglas, which could be tilted slightly to the north due to the wind shear.

Slow weakening is expected as Douglas passes near, or over, portions of the main Hawaiian Islands. SSTs will slowly increase along the forecast track, but southerly vertical wind shear will tilt the system and disrupt the circulation aloft, leading to gradual weakening through at least the next four days. However, Douglas is expected to remain a hurricane as it passes very near, or over, portions of the main Hawaiian Islands today and tonight. The intensity forecast was changed little from the prior advisory and is in line within a tightly clustered guidance envelope through 36 hours and near consensus thereafter.

Hurricane Hunter data was essential in determining the initial motion of 290/14 kt. Douglas will continue to be steered by a low- to mid-level ridge toward the west-northwest during the next couple of days, taking the center dangerously close to the islands from Maui to Kauai through tonight, where a Hurricane Warning remains in effect. The updated forecast track was changed little from the previous forecast and remains near the southern edge of a tightly clustered guidance envelope during the next couple of days. By day three, an acceleration toward the west is expected as the increasingly shallow system is steered along the low-level trade winds.

Key Messages

  • 1. Douglas will pass dangerously close to, or over, the islands today and tonight, bringing a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores.
  • 2. It is remains important that you do not focus on the exact forecast track of Douglas. Due to Douglas’ angle of approach to the islands, any wobble in the track could lead to significant differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near the islands. Hurricane force wind gusts are possible even within the tropical storm warning area. Winds will also be stronger at the upper floors of high rise buildings.
FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 21.2N 155.7W   75 KT  85 MPH - Category 1 (ENE Hana, Hawaii)
 12H  27/0600Z 21.8N 158.0W   70 KT  80 MPH - Category 1 (ENE Kawela Bay, Hawaii)
 24H  27/1800Z 22.6N 161.0W   65 KT  75 MPH - Category 1 (WNW Puʻuwa, Hawaii)
 36H  28/0600Z 23.1N 164.3W   55 KT  65 MPH - Tropical Storm (WSW Puʻuwa, Hawaii)
 48H  28/1800Z 23.4N 167.7W   50 KT  60 MPH - Tropical Storm (ESE Midway Atoll)
 60H  29/0600Z 23.8N 171.2W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)
 72H  29/1800Z 24.1N 175.2W   40 KT  45 MPH - Tropical Storm (ESE Midway Atoll)
 96H  30/1800Z 24.4N 177.0E   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)
120H  31/1800Z 25.6N 170.0E   30 KT  35 MPH - Depression (ENE Wake Island)

\NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Sun Jul 26, 2020 

Hurricane Hunters from the Air Force 53rd Weather Reconnaissance Squadron spent most of the night with Douglas, making 5 passes through the center. The final pass contained some of the strongest winds of the entire mission, with flight-level winds near 100 kt, SFMR winds up to 79 kt, and a relatively steady pressure reading near 983 mb. The initial intensity was maintained at 80 kt based on these valuable data points. Also of extreme value is the fact that the low-level center is south of the apparent center seen in conventional satellite imagery, and closer to the islands than might be otherwise expected. Although island-based radars are also detecting Douglas’ circulation, they are sampling the upper portions of the cyclone that are sheared northward due to southerly vertical wind shear.

Despite the vertical wind shear, Douglas has been slow to weaken, and this trend will continue today as Douglas passes near, or potentially over, the islands. Steadily increasing SSTs along the forecast track are expected to limit the rate of weakening, while the noted vertical wind shear may be confined to the upper-levels. While Douglas is on the western edge of a ridge aloft, leading to high-level southerly shear, a mid-level ridge is expected to build westward to the north of Douglas through Monday, likely allowing the low- to mid-level core of the cyclone to remain intact. The updated intensity forecast once again closely follows the consensus IVCN, and maintains Douglas as a hurricane until it passes west of the islands. Steady weakening will occur thereafter due to persistent southwesterly shear.

The mid-level ridge will continue to drive Douglas toward the west- northwest, with the current motion vector estimated to be 285/14 kt. The forecast track takes the center of Douglas dangerously close to the islands from Maui to Kauai through tonight, where a Hurricane Warning is in effect. The updated forecast track is very close to the previous forecast and the high-performing ECMWF guidance, and anticipates some acceleration toward the west in the later periods as the increasingly shallow system gets steered by the low-level trade wind flow.

Key Messages

  • 1. Douglas will pass dangerously close to, or over, the islands today, bringing a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east and north facing shores.
  • 2. It is remains important that you do not focus on the exact forecast track of Douglas. Due to Douglas’ angle of approach to the islands, any wobble in the track could lead to significant differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near the islands. Hurricane force wind gusts are possible even within the tropical storm warning area. Winds will also be stronger at the upper floors of high rise buildings.
FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 20.7N 154.3W   80 KT  90 MPH - Catagory 1 (ENE Hilo, Hawaii)
 12H  27/0000Z 21.4N 156.6W   75 KT  85 MPH - Catagory 1 (ENE Kapalua, Hawaii)
 24H  27/1200Z 22.3N 159.5W   70 KT  80 MPH - Catagory 1 (WNW Princeville, Hawaii)
 36H  28/0000Z 22.8N 162.7W   60 KT  70 MPH - Tropical Storm (WSW Puʻuwa, Hawaii)
 48H  28/1200Z 23.3N 166.1W   55 KT  65 MPH - Tropical Storm (ESE Johnson Atoll)
 60H  29/0000Z 23.7N 169.5W   50 KT  60 MPH - Tropical Storm (ESE Midway Atoll)
 72H  29/1200Z 24.0N 173.0W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)
 96H  30/1200Z 24.5N 179.5E   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)
120H  31/1200Z 25.5N 172.0E   30 KT  35 MPH - Depression (WSW Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Sat Jul 25, 2020 

The satellite presentation of Douglas is degrading somewhat, likely due to restricted outflow to the south and 26C SSTs. The U.S. Air Force 53rd Weather Reconnaissance Squadron sampled the hurricane this morning, and a blend of SFMR, flight level winds, and dropsonde data from two passes supports decreasing the intensity to 80 kt with a central pressure of 984 mb. Douglas continues to move toward the west-northwest (290 deg) at 16 kt. Douglas is being steered by a low- to mid-level ridge to the northeast and is nearing a weakness in the mid-level ridge. A continued motion toward the west-northwest and a slight decrease in forward motion will bring Douglas over or very near portions of the main Hawaiian Islands on Sunday. On Monday, a mid-level ridge is forecast to build to the north of Douglas, potentially inducing a turn toward the west, with some increase in forward speed.

The updated forecast track is very close to the previous forecast and lies close to the ECMWF toward the southern end of a rather tightly clustered guidance envelope. Weakening is expected through the forecast. Douglas will remain over an area of 26C SST today, which is expected to continue the gradual weakening trend. SSTs along the forecast track increase tonight, at the same time that Douglas will move into an area of increased vertical wind shear. This is expected to maintain a weakening trend, although at a fairly slow rate. The official intensity forecast has changed very little from the previous advisory, and generally follows a blend of the corrected consensus and statistical model guidance. Based on the latest forecast, a Hurricane Warning has been issued for Oahu. Tropical Storm Warnings remain in effect for Hawaii County and Maui County. A Hurricane Watch remains in effect for Hawaii County and Maui County, and a Tropical Storm Watch is in effect for Kauai County.

Key Messages:

  • 1. Douglas continues to approach the main Hawaiian Islands, potentially passing dangerously close to, or over, the islands late tonight through Sunday night. The close passage of Douglas brings a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores.
  • 2. It is vital that you do not focus on the exact forecast track or intensity of Douglas. Due to Douglas’ angle of approach to the islands, any small changes in the track could lead to significant differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near the islands. Hurricane force wind gusts are possible even within the tropical storm warning area. Winds will also be stronger at the upper floors of high rise buildings.
FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 19.5N 150.1W   80 KT  90 MPH - Category 1 (WSW Hilo, Hawaii)
 12H  26/0600Z 20.1N 152.1W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 24H  26/1800Z 21.0N 154.9W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 36H  27/0600Z 21.8N 157.7W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
 48H  27/1800Z 22.5N 160.4W   60 KT  70 MPH - Tropical Storm (ESE Kapaʻa, Hawaii)
 60H  28/0600Z 23.1N 163.5W   55 KT  65 MPH - Tropical Storm (WNW Paia, Hawaii)
 72H  28/1800Z 23.7N 167.0W   50 KT  60 MPH - Tropical Storm (ENE Johnson Atoll)
 96H  29/1800Z 24.5N 173.7W   45 KT  50 MPH - Tropical Storm (ENE Midway Atoll)
120H  30/1800Z 25.8N 180.0E   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Sat Jul 25, 2020 

The satellite presentation of Douglas has changed very little since the previous advisory, with the eye remaining cloud filled and difficult to locate with a high degree of certainty. The latest current intensity estimates from the satellite agencies came in at 5.0 (90 knots) from PHFO, 4.5 (77 knots) from JTWC and SAB, while the ADT from UW-CIMSS was 4.6 (80 knots). Based on the U.S. Air Force 53rd Weather Reconnaissance Squadron mission last evening finding maximum flight level winds of 108 knots (97 knots with appropriate wind reduction factor to the surface from the 700 mb flight level) and SFMR winds of 93 knots, we will conservatively lower the initial intensity to 90 knots with this advisory, but that may be generous. Douglas appears to have made a subtle shift toward the west overnight, and the initial motion for this advisory has been set at 290/16 knots.

The tropical cyclone will be going over the coolest sea surface temperatures (SSTs) along its forecast track during the next 12 to 18 hours before SSTs climb back to 26C or above. This should result in continued weakening despite relatively low vertical wind shear. Thereafter, the vertical wind shear slowly becomes less conducive for intensification, while SSTs become less hostile as they rise back to 26/27C or above. We expect that the increasing wind shear will win the battle through the remainder of the forecast track, and show slow and gradual weakening through 120 hours. The official intensity forecast has changed very little from the previous advisory, and generally follows a blend of the corrected consensus and statistical model guidance.

Douglas is forecast to continue to move off to the west-northwest today toward a weakness in the sub-tropical ridge north of the Hawaiian Islands, with a slight reduction in forward speed. The subtropical ridge is forecast to strengthen north of the state tonight through the remainder of the weekend and this should steer the tropical cyclone slightly more westward, and over or very near the Hawaiian Islands late tonight through Sunday night. Douglas is then expected to exit to the west of the island chain early next week. The official track forecast is virtually identical to the previous advisory, and continues to hug the southern end of the guidance envelope. This track is roughly in the middle of the deterministic GFS/ECMWF solutions and the GFS/ECMWF ensemble means, which is very close to the corrected consensus guidance HCCA.

Based on the latest intensity and track forecast, a Tropical Storm Watch has been issued for Kauai County. Tropical Storm Warnings remain in effect for Hawaii County and Maui County. A Hurricane Watch remains in effect for Hawaii County, Maui County and Oahu. Finally, a Tropical Storm Warning will likely be required for Oahu later today.

Key Messages

  • 1. Douglas continues to approach the main Hawaiian Islands, potentially passing dangerously close to, or over, the islands late tonight through Sunday night. The close passage of Douglas brings a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores.
  • 2. It is vital that you do not focus on the exact forecast track or intensity of Douglas, and remain prepared for changes to the forecast. Due to Douglas’ angle of approach to the islands, any small changes in the track could lead to significant differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near the islands. Winds will also be stronger at the upper floors of high rise buildings.
FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 19.1N 148.4W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 12H  26/0000Z 19.7N 150.6W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 24H  26/1200Z 20.6N 153.5W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 36H  27/0000Z 21.4N 156.3W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
 48H  27/1200Z 22.1N 159.4W   60 KT  70 MPH - Tropical Storm (ESE Kapaʻa, Hawaii)
 60H  28/0000Z 22.7N 162.6W   55 KT  65 MPH - Tropical Storm (WNW Paia, Hawaii)
 72H  28/1200Z 23.2N 166.0W   50 KT  60 MPH - Tropical Storm (ENE Johnson Atoll)
 96H  29/1200Z 24.1N 172.8W   45 KT  50 MPH - Tropical Storm (ENE Midway Atoll)
120H  30/1200Z 25.3N 179.2W   35 KT  40 MPH - Tropical Storm (WSW Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 500 PM HST Fri Jul 24, 2020 

The eye of Douglas has remained visible in conventional satellite imagery through the day today, and even cleared out for a little while this afternoon, indicating that Douglas remains a powerful hurricane. Subjective satellite current intensity estimates ranged from 4.5/90 kt to 5.5/105 kt, while ADT was near 5.5. Although the eye is clouding up again this afternoon, and surrounding convection is cooling, the initial intensity has been held at 100 kt for this advisory. The forward motion vector has changed little over the past 24 hours, and is measured to be 295/17kt, as Douglas continues to be steered by a mid-level ridge centered to the distant northeast.

As Douglas draws closer to the main Hawaiian Islands the next 2 days, it will round the western periphery of the ridge, allowing the cyclone to gain some latitude, with some reduction in forward speed. Thereafter, a mid-level ridge is forecast to build to the north of Douglas, potentially inducing a turn toward the west, with some increase in forward speed. The updated track forecast is nearly identical to the previous, lies along the southern side of a fairly tightly-clustered guidance envelope, and is very close to ECMWF ensemble guidance. On the forecast track, Douglas will move dangerously close to the Hawaiian Islands, and a Hurricane Watch is posted for all islands except Kauai County, which may need to be added on Saturday.

Douglas will be traversing an area of sub-26C SST for the next 36 hours or so, which is expected to lead a gradual weakening trend, despite vertical wind shear on the lighter side, especially by central Pacific standards. SSTs along the forecast track increase from 48 hours onward, at the same time that Douglas is expected to move into an area of increased vertical wind shear as it rounds the southwestern periphery of an upper-level ridge. This is expected to lead to a continued weakening trend, although at a fairly slow rate. The intensity forecast is very close to the SHIPS guidance, and close to the IVCN intensity consensus.

A Hurricane Hunter aircraft is en route to fly an initial mission into Douglas, and this valuable data is expected to be available for the next forecast update. Additional flights into Douglas are scheduled for tomorrow. In the meantime, a morning ASCAT pass was used to fine tune the wind radii analysis.

Key Messages

  • 1. Douglas continues to approach the main Hawaiian Islands, potentially passing dangerously close to, or over, the islands Saturday night through Sunday night. The close passage of Douglas brings a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores.
  • 2. It is vital that you do not focus on the exact forecast track or intensity of Douglas, and remain prepared for changes to the forecast. Due to Douglas’ angle of approach to the islands, any small changes in the track could lead to significant differences in where the worst weather occurs. Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.
  • 3. Terrain effects can cause strong localized acceleration of the wind through gaps and where winds blow downslope. These acceleration areas will shift with time as Douglas passes near the islands. Winds will also be stronger at the upper floors of high rise buildings.
FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 17.9N 145.1W  100 KT 115 MPH - Category 3 (WSW Hilo, Hawaii)
 12H  25/1200Z 18.8N 147.5W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 24H  26/0000Z 20.0N 150.7W   80 KT  90 MPH - Category 1 (WSW Hilo, Hawaii)
 36H  26/1200Z 20.8N 153.5W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 48H  27/0000Z 21.4N 156.4W   65 KT  75 MPH - Category 1 (ENE Paia, Hawaii)
 60H  27/1200Z 22.0N 159.4W   60 KT  70 MPH - Category 1 (WNW Puhi, Hawaii)
 72H  28/0000Z 22.6N 162.5W   55 KT  65 MPH - Tropical Storm (WNW WSW Puʻuwai,Hawaii)
 96H  29/0000Z 24.0N 169.5W   50 KT  60 MPH - Tropical Storm (ENE Johnson Atoll)
120H  30/0000Z 25.0N 175.5W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 1100 AM HST Fri Jul 24, 2020 

After a period of rapid intensification yesterday, Douglas’ satellite appearance has degraded somewhat over the past 12 hours or so. However, a fairly large but ragged and cloud-filled eye is still noted in conventional satellite images. Subjective Dvorak current intensity estimates were 5.5/105 kt from SAB and HFO, 5.1/93 kt from ADT, while SATCON estimated was near 100 kt. A blend of these led to an initial intensity estimate of 100 kt for this advisory.

The initial motion for this advisory is a steady 295/16 kt, as Douglas continues to be steered by a robust mid-level ridge centered to the northeast. As Douglas draws closer to the main Hawaiian Islands, it will be reaching the western periphery of the ridge, and model guidance indicates that this will allow the cyclone to gain some latitude over the next 2 days, with some reduction in forward speed. Thereafter, the mid-level ridge is forecast to subtly build to the north of Douglas, potentially inducing a turn toward the west, with some increase in forward speed. The updated track forecast is nearly identical to the previous, lies along the southern side of the guidance, and is very close to ECMWF guidance that has been performing well thus far with Douglas. On the forecast track, Douglas will move dangerously close to the Hawaiian Islands. A Hurricane Watch has been issued for Maui County and the Big Island, and may need to be expanded to additional areas later today or tonight.

The intensity forecast continues to anticipate a slow but steady weakening of the cyclone as it traverses cooler waters, and later encounters increased vertical wind shear as waters warm somewhat near the Hawaiian Islands. Little overall change to the ongoing forecast was made, and the updated forecast closely follows the GFS- and ECMWF-based SHIPS guidance, and is close to the intensity consensus IVCN.

Key Messages

  • 1. Douglas will continue to quickly approach the main Hawaiian Islands, passing dangerously close to, or over, the islands on Sunday. Dangerous, life-threatening surf will arrive ahead of the hurricane on Saturday. Heavy rain and increasing winds are possible on the Big Island starting Saturday night, and could quickly spread up the chain Sunday.
  • 2. It is important not to focus on the exact forecast track. Due to Douglas’ angle of approach to Hawaii, any small changes in the track could lead to significant differences in where the worst weather will occur.
  • 3. Wind gusts near mountains and higher terrain can be significantly enhanced as they blow downslope.
FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 17.0N 143.5W  100 KT 115 MPH - Category 3 (WSW Hilo, Hawaii)
 12H  25/0600Z 17.9N 145.9W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 24H  25/1800Z 19.1N 149.0W   80 KT  90 MPH - Category 1 (WSW Hilo, Hawaii)
 36H  26/0600Z 20.0N 151.9W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 48H  26/1800Z 20.8N 154.7W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
 60H  27/0600Z 21.3N 157.5W   60 KT  70 MPH - Tropical Storm (WSW Waimānalo Beach, Hawaii)
 72H  27/1800Z 21.8N 160.4W   55 KT  65 MPH - Tropical Storm (WSW Puʻuwai,Hawaii)
 96H  28/1800Z 23.0N 166.7W   50 KT  60 MPH - Tropical Storm (ENE Johnson Atoll)
120H  29/1800Z 24.2N 172.8W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)

NWS Central Pacific Hurricane Center Honolulu HI 500 AM HST Fri Jul 24, 2020

Douglas remains a powerful hurricane early this morning, although the satellite presentation has degraded quite a bit since last evening, with eye of the tropical cyclone now nearly completely cloud filled. The latest current intensity estimates from the satellite agencies came in with 5.5 (102 knots) from PHFO and SAB, 5.0 (90 knots) from JTWC, while ADT came in at 5.9 (112 knots). Taking a blend of the estimates above and accounting for recent satellite trends, the intensity with this advisory will be lowered to 105 knots. Douglas continues to move rapidly to the west-northwest, with an initial motion set at 295/16 knots.

Hurricane Douglas recently moved over slightly cooler sea surface temperatures (SSTs) of around 78F, and this seems to have been enough to lead to the weakening seen in satellite imagery. Despite relatively low vertical wind shear values forecast to affect the tropical cyclone during the next couple days, SSTs will remain unfavorable for intensification. The official intensity forecast calls for steady weakening during the next couple days as Douglas nears Hawaii, with the cyclone expected to be a category 1 hurricane or strong tropical storm approaching the eastern end of the state late Saturday night or Sunday. Continued weakening is then forecast as Douglas tracks westward over or near the other main Hawaiian islands and west of the state early next week. Depending on the amount of interaction with the high terrain of the Big Island and Maui, the tropical cyclone could weaken faster than indicated in the official forecast, which follows a blend of the corrected consensus and statistical model guidance.

Douglas is forecast to move rapidly off to the west-northwest during the next couple days toward a weakness in the sub-tropical ridge north of the Hawaiian islands. The subtropical ridge is forecast to strengthen north of the state over the weekend, and this should steer the tropical cyclone westward over or very near the Hawaiian Islands Sunday through Monday, before exiting to the west of the state. The official forecast continues to hug the southern end of the guidance envelope out of respect for the ECMWF, but if model trends continue, this track may need to be adjusted further northward in future advisory packages.

Based on the latest intensity and track forecasts, Hurricane or Tropical Storm watches will likely be required for portions of the eastern end of the state (Big Island and the Maui County Islands) later today.

Key Messages:

  • 1. Douglas is expected to move near or over portions of the main Hawaiian Islands Sunday through Monday, and there is an increasing chance that strong winds, dangerous surf, and heavy rainfall could affect portions of the state beginning late Saturday night or Sunday. Interests on the Hawaiian Islands should continue to monitor the progress of Douglas and the official forecasts as they evolve during the next few days.
FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 16.4N 141.9W  105 KT 120 MPH - Category 3 (WSW Hilo, Hawaii)
 12H  25/0000Z 17.4N 144.3W   95 KT 110 MPH - Category 3 (WSW Hilo, Hawaii)
 24H  25/1200Z 18.6N 147.5W   85 KT 100 MPH - Category 2 (WSW Hilo, Hawaii)
 36H  26/0000Z 19.6N 150.4W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 48H  26/1200Z 20.5N 153.4W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 60H  27/0000Z 21.1N 156.1W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
 72H  27/1200Z 21.7N 158.8W   55 KT  65 MPH - Tropical Storm (WSW Kōloa, Hawaii)
 96H  28/1200Z 22.5N 165.0W   50 KT  60 MPH - Tropical Storm (WSW Kōloa, Hawaii)
120H  29/1200Z 23.5N 171.5W   45 KT  50 MPH - Tropical Storm (ESE Midway Atoll)

NWS National Hurricane Center Miami FL 1100 AM HST Thu Jul 23, 2020

Visible satellite images show that Douglas is quite a powerful hurricane. The eye has become more crisp during the day, and infrared data also show that the eyewall convection has deepened. The initial wind speed is raised to 110 kt, which matches a blend of the latest TAFB/SAB Dvorak estimates. Douglas is beginning to move across the typical cool SST gradient of the eastern Pacific, implying that the hurricane is probably near its peak intensity. The cyclone should only slowly weaken on Friday and Saturday due to cooler waters along the predicted track and the vertical shear remaining low. As the hurricane approaches the Hawaiian Islands on Sunday, the SSTs increase but so does the shear. Since the shear generally dominates over marginally warm waters, a continued weakening is forecast. However, almost all of the guidance shows Douglas near hurricane strength as it moves close to Hawaii. The model guidance remains consistent, and no significant changes were made to the NHC wind speed prediction.

Douglas continues moving fairly quickly toward the west-northwest. A large mid-level ridge over the eastern and central Pacific should continue to steer the hurricane on this general course and speed for the next couple of days, with some deceleration and a westward turn by late in the weekend. The guidance is a little more divergent than the previous cycle, with a subtle northward model trend at longer range due to a weaker ridge forecast north of Hawaii, though the ECMWF and its ensembles have shifted a little southward. Given these mixed signals in the guidance, very little change is made to the previous NHC track forecast, and the new official forecast lies on the southwest side of the model envelope.

Key Messages:

  • 1. Douglas is expected to move near or over portions of the Hawaiian Islands this weekend, and there is an increasing chance that strong winds, dangerous surf, and heavy rainfall could affect portions of the state beginning on Sunday. Interests on the Hawaiian Islands should continue to monitor the progress of Douglas and the official forecasts as they evolve over the next few days. Watches could be issued on Friday.
FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 14.1N 137.3W  110 KT 125 MPH - Category 3 (WSW Hilo, Hawaii)
 12H  24/0600Z 15.0N 139.7W  110 KT 125 MPH - Category 3 (WSW Hilo, Hawaii)
 24H  24/1800Z 16.2N 142.8W  100 KT 115 MPH - Category 3 (WSW Hilo, Hawaii)
 36H  25/0600Z 17.4N 145.9W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 48H  25/1800Z 18.5N 149.0W   80 KT  90 MPH - Category 1 (WSW Hilo, Hawaii)
 60H  26/0600Z 19.4N 152.0W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 72H  26/1800Z 20.1N 154.9W   65 KT  75 MPH - Category 1 (ESE Laupāhoehoe Hilo, Hawaii)
 96H  27/1800Z 21.0N 160.5W   55 KT  65 MPH - Tropical Storm (WSW Puʻuwai, Hawaii)
120H  28/1800Z 21.5N 167.0W   45 KT  50 MPH - Tropical Storm (ENE Johnson Atoll)

NWS National Hurricane Center Miami FL 500 AM HST Thu Jul 23, 2020 

The intensity of Douglas has leveled off in the overnight hours with the eyewall convection weakening, but the eye temperatures becoming a lot warmer, suggesting that the system has become a little more steady state. The wind speed is kept at 105 kt, which nearly matches the latest CIMSS satellite consensus (SATCON). The cyclone has less than a day over warm water left to intensify before it encounters SSTs less than 26C. Douglas should only slowly weaken thereafter during the next few days due to the cooler waters along the predicted track since the vertical shear should remain low through Saturday. As the cyclone approaches the Hawaiian Islands on Sunday, while the SSTs increase, so does the shear, and thus a continued weakening is forecast. Model guidance is consistent from the last forecast, and no significant changes were made to the NHC wind speed prediction.

Douglas has been moving a little faster to the west-northwest, or 290/17. A large mid-level ridge over the eastern and central Pacific should continue to steer the hurricane on this general course and speed for the next couple of days, with some deceleration and a westward turn by late in the weekend. While the guidance remains in very good agreement, the only significant change to note is that this forecast is a bit faster than the previous one, but not as fast as the ECMWF or its ensemble mean.

Key Messages:

  • 1. Douglas is expected to move near or over portions of the Hawaiian Islands this weekend, and there is an increasing chance that strong winds, dangerous surf, and heavy rainfall could affect portions of the state beginning on Sunday. Interests on the Hawaiian Islands should continue to monitor the progress of Douglas and the official forecasts as they evolve over the next few days.
FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 13.6N 135.9W  105 KT 120 MPH - Category 3 (WSW Hilo, Hawaii)
 12H  24/0000Z 14.5N 138.3W  110 KT 125 MPH - Category 3 (WSW Hilo, Hawaii)
 24H  24/1200Z 15.8N 141.5W  105 KT 120 MPH - Category 3 (WSW Hilo, Hawaii)
 36H  25/0000Z 17.0N 144.6W   95 KT 110 MPH - Category 2 (WSW Hilo, Hawaii)
 48H  25/1200Z 18.1N 147.7W   85 KT 100 MPH - Category 2 (WSW Hilo, Hawaii)
 60H  26/0000Z 19.1N 150.6W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 72H  26/1200Z 19.8N 153.5W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
 96H  27/1200Z 20.7N 159.1W   55 KT  65 MPH - Tropical Storm (WSW Honolulu, Hawaii)
120H  28/1200Z 21.5N 165.5W   45 KT  50 MPH - Tropical Storm (WNW Puʻuwai, Hawaii)

NWS National Hurricane Center Miami FL 1100 PM HST Tue Jul 21, 2020

The overall appearance of Douglas has changed little over the past several hours. Satellite images show a continuation of dry air trying to be worked out of the eastern portion of the cyclone’s circulation. The latest satellite intensity estimates from TAFB and SAB indicate that the initial advisory intensity remains 55 kt.

The majority of intensity guidance continues to suggest that Douglas will soon overcome the dry air that has been holding the cyclone back from strengthening. And, the system is forecast to remain in a favorable environment for intensification for the next day or so. Beyond 36 h, the combination of cooler SSTs and dry air should cause Douglas to slowly weaken. The latest NHC forecast is a blend of the corrected consensus HCCA and the ICON and IVCN consensus aids. Based on this forecast, Douglas should become a hurricane sometime on Wednesday.

Douglas is moving westward at around 13 kt. The ridge to the north of the cyclone is forecast to become oriented east-to-west while building westward over the next day or so. This should induce a gradual turn to the west-northwest along with a slight increase in forward speed. This general west-northwest motion is then forecast to continue through the remainder of the 5-day period. The model guidance has trended a bit faster throughout the forecast period, and the official forecast now lies in between the clustered consensus aids and the previous official forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 11.9N 128.0W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  22/1800Z 12.0N 129.9W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  23/0600Z 12.9N 132.4W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  23/1800Z 14.1N 135.1W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  24/0600Z 15.5N 137.9W   85 KT 100 MPH - Category 2 (WSW Hilo, Hawaii)
 60H  24/1800Z 16.7N 140.9W   80 KT  90 MPH - Category 1 (WSW Hilo, Hawaii)
 72H  25/0600Z 17.8N 143.9W   70 KT  80 MPH - Category 1 (WSW Hilo, Hawaii)
 96H  26/0600Z 19.1N 149.7W   60 KT  70 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  27/0600Z 19.8N 155.3W   50 KT  60 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 1100 AM HST Tue Jul 21, 2020 

Douglas appears to have been trying to scour out a little bit of dry air on its western side during the day, although recent visible images suggest that deep convection is attempting to wrap entirely around the center. Because the convective pattern didn’t change much from earlier, Dvorak classifications from TAFB and SAB remain T3.5/55 kt, so the initial intensity is held steady on this advisory.

Strong ridging to the north of Douglas continues to impart a west-southwestward motion of the cyclone, or 255/13 kt. As mentioned this morning, the ridge is likely to take on a more east-west orientation as a mid-/upper-level low northeast of the Hawaiian Islands retrogrades westward, and this pattern evolution will allow Douglas to turn westward by tonight and then west-northwestward by late Wednesday. That general motion is forecast to continue for the remainder of the 5-day forecast period. The track guidance still showcases a faster ECMWF and slower GFS and HWRF solutions, and the overall envelope and model consensus aids have again nudged northward. The updated track forecast is therefore a little north of the previous one, mainly after 48 hours through day 5.

Once deep convection can isolate Douglas’s center from the ambient environment, low shear and warm sea surface temperatures of 28-29 degrees Celsius should allow intensification to resume. Despite this morning’s hiatus in strengthening, the SHIPS Rapid Intensification (RI) guidance continues to key in on a significant chance of RI during the next day or two. Therefore, the intensity forecast from this morning has been left unchanged, and it still generally lies between the HCCA and Florida State Superensemble, closer to the higher end of the guidance envelope. Douglas should reach its peak intensity in about 48 hours, after which time oceanic heat content values drop to zero, which should cause some gradual weakening.

Based on a partial ASCAT-A pass, Douglas’s tropical-storm-force wind radii were increased on the northern side.

FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 12.1N 125.4W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  22/0600Z 11.9N 127.1W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  22/1800Z 12.1N 129.5W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  23/0600Z 13.0N 131.9W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  23/1800Z 14.4N 134.5W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 60H  24/0600Z 15.7N 137.3W   85 KT 100 MPH - Category 2 (WSW Hilo, Hawaii)
 72H  24/1800Z 16.9N 140.2W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 96H  25/1800Z 18.5N 146.0W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)
120H  26/1800Z 19.0N 151.5W   55 KT  65 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 AM HST Tue Jul 21, 2020 

A recent SSMIS microwave pass indicated that Douglas’s low-level center is located very near the head of a broken band of convection which curls around the southern, western, and northern side of the circulation. This center is also now embedded beneath a Central Dense overcast in infrared imagery, near an area of cold overshooting cloud tops. TAFB and SAB Dvorak classifications have both risen to T3.5, and Douglas’s initial intensity is therefore raised to 55 kt.

Douglas continues to dip west-southwestward, or 255/13 kt, due to strong mid-level ridging to its north. A mid- to upper-level low located northeast of the Hawaiian Islands is forecast to retrograde westward over the next few days, which will allow the ridge to take on a more east-west orientation. As a result, Douglas is expected to turn westward later today and then move west-northwestward beginning overnight Wednesday into the weekend. The track guidance all agrees on this scenario, but there are some speed differences, bookended by slower GFS and HWRF solutions and a faster ECMWF solution. Overall, however, the new NHC forecast remains very close to the multi-model consensus aids, and no significant changes were made compared to the previous forecast, except maybe a slight northward adjustment on days 4 and 5.

The low-shear, warm sea surface temperature environment within which Douglas is moving is a recipe for continued strengthening, potentially at a rapid rate, for the next 48 hours. The intensity guidance has been trending higher, and the latest SHIPS Rapid Intensification (RI) indices are highlighting the increased chance of RI. For example, there is currently a 50/50 shot that Douglas’s winds will increase by 25 kt within the next 24 hours, and a 40-50 percent chance of a 30-kt increase during that period. Based on this guidance, the new HCCA and Florida State Superensemble solutions, and the intensity consensus, the NHC intensity forecast has been increased from the previous cycle and now shows Douglas becoming a hurricane later today with a higher peak occurring in about 2 days. Since oceanic heat content falls to zero along Douglas’s path by day 3, some gradual weakening is shown in the latter stages of the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 12.4N 124.2W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  22/0000Z 12.1N 126.0W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  22/1200Z 12.1N 128.5W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 36H  23/0000Z 12.6N 131.0W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 48H  23/1200Z 13.6N 133.7W   90 KT 105 MPH - Category 2 (WSW Hilo, Hawaii)
 60H  24/0000Z 14.9N 136.5W   85 KT 100 MPH - Category 2 (WSW Hilo, Hawaii)
 72H  24/1200Z 16.1N 139.4W   75 KT  85 MPH - Category 1 (WSW Hilo, Hawaii)
 96H  25/1200Z 18.0N 145.5W   65 KT  75 MPH - Category 1 (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 PM HST Mon Jul 20, 2020

Satellite data indicate that the cyclone is strengthening. The system now has a small but well organized central dense overcast with curved bands on the west side of the circulation. All of the satellite intensity estimates are of tropical storm strength, and based on that data the initial intensity is raised to 35 kt, making the system Tropical Storm Douglas.

The tropical storm is moving west-southwestward at 9 kt. A mid-level ridge situated to the north of Douglas off the northern Baja California coast should cause the storm to gradually turn westward during the next couple of days and then west-northwestward beyond that time. The models are in good agreement on this scenario, and only small changes were made to the previous prediction.

Douglas is expected to be in quite favorable conditions of low vertical wind shear, high amounts of moisture, and warm SSTs during the next few days. Given these conducive environmental conditions and the storm’s improved and compact structure, steady or possibly even rapid strengthening is possible during that time period. After a few days, however, a combination of higher shear, slightly cooler waters, and drier air should end the strengthening trend and induce weakening. The NHC intensity forecast lies near the higher end of the guidance. This forecast shows a faster rate of strengthening in the short term and more weakening at the end of the period compared to the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 13.1N 121.6W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  21/1200Z 12.5N 123.2W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  22/0000Z 12.0N 125.6W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  22/1200Z 11.9N 128.2W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 48H  23/0000Z 12.3N 130.8W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 60H  23/1200Z 13.2N 133.3W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  24/0000Z 14.2N 136.1W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  25/0000Z 15.9N 141.5W   60 KT  70 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  26/0000Z 16.6N 147.0W   45 KT  50 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 1100 AM HST Mon Jul 20, 2020 

Satellite imagery indciates that Tropical Depression Eight-E is getting better organized, with the formation of a small central dense overcast and banding features outside of the central convection. Satellite intensity estimates are 35 kt from TAFB and 30 kt from SAB, and recent scatterometer data indciate winds near 30 kt in the northwester quadrant. Based on these data, the initial intensity remains a possibly conservative 30 kt.

The initial motion is 235/6, with the depression still being steered by a portion of the subtropical ridge building between it and Tropical Depression Seven-E. This motion should persist with some increase in forward speed for 24-36 h, followed by a turn toward the west as the steering flow becomes more easterly. This should be followed by a turn toward the west-northwest between 48-60 h. The track guidance remains in good agreement on this scenario, and the NHC forecast is again in the middle of the guidance and close to the various consensus models.

The cyclone is over warm sea surface temperatures and in a light shear environment, and these conditions should persist for the next several days. The intensity guidance calls for steady strengthening through about 72 h, and the NHC forecast follows this trend near the upper edge of the intensity guidance envelope. The Rapid Intensification Indices of the SHIPS model suggest about a 20-25 percent chance of RI during the first 72 h of the forecast, and given the seemingly-favorable environment it would not be a surprise if the cyclone strengthened more than currently forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 13.5N 120.4W   30 KT  35 MPH - Depression (WSW Acapulco, Mexico)
 12H  21/0600Z 12.8N 121.7W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  21/1800Z 12.1N 123.9W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  22/0600Z 11.9N 126.6W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, Mexico)
 48H  22/1800Z 11.9N 129.4W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 60H  23/0600Z 12.4N 132.1W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  23/1800Z 13.4N 134.9W   75 KT  85 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  24/1800Z 15.0N 140.0W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
120H  25/1800Z 16.5N 145.5W   60 KT  70 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 AM HST Mon Jul 20, 2020 

Satellite imagery and overnight scatterometer data indicate that the low-pressure area to the southeast of Tropical Depression Seven-E has a well-defined circulation and sufficient organized convection to be considered a tropical depression. Thus, advisories are being initiated on Tropical Depression Eight-E. The initial intensity is 30 kt based on the scatterometer data and a subjective Dvorak intensity estimate from TAFB.

The initial motion is 240/6, with the depression being steered by a portion of the subtropical ridge building between it and Tropical Depression Seven-E. This motion should persist with some increase in forward speed for 24-36 h, followed by a turn toward the west as the steering flow becomes more easterly. This should be followed by a turn toward the west-northwest after 60h. The track guidance is in good agreement on this scenario, and the NHC forecast is in the middle of the guidance and close to the various consensus models.

The cyclone is over warm sea surface temperatures and in a light shear environment, and these conditions should persist for the next several days. The intensity guidance calls for steady strengthening through about 72 h, and the NHC forecast follows this trend near the upper edge of the intensity guidance envelope. The Rapid Intensification Indices of the SHIPS model suggest about a 20-25 percent chance of RI during the first 72 h of the forecast, so it is possible that the cyclone will strengthen more than currently forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 13.7N 119.8W   30 KT  35 MPH - Depression (WSW Acapulco, Mexico)
 12H  21/0000Z 13.1N 121.0W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  21/1200Z 12.4N 123.1W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  22/0000Z 11.8N 125.7W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, Mexico)
 48H  22/1200Z 11.7N 128.4W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 60H  23/0000Z 11.9N 131.1W   65 KT  75 MPH - Category 1 (ESE Hilo, Hawaii)
 72H  23/1200Z 12.7N 134.0W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
 96H  24/1200Z 14.5N 139.5W   70 KT  80 MPH - Category 1 (ESE Hilo, Hawaii)
120H  25/1200Z 16.5N 145.5W   60 KT  70 MPH - Tropical Storm (ESE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 PM PDT Sun Jul 19, 2020 

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

  • 1. A low-pressure system is located a little more than 1200 miles west-southwest of the southern tip of the Baja California peninsula. Although the low is beginning to move over cooler waters, the associated thunderstorm activity has increased over the past few hours, and this system could become a short-lived tropical depression later tonight or on Monday while it moves west-northwestward at 10-15 mph. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…medium…50 percent.
  • 2. An area of showers and thunderstorms located about 800 miles southwest of the southern tip of the Baja California peninsula is showing some signs of organization. Environmental conditions are expected to be conducive for development of this system, and a tropical depression could form around the middle of the week while it moves west-southwestward and then westward at about 10 mph. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sat Jul 18, 2020 

For the eastern North Pacific…east of 140 degrees west longitude: 1. A tropical wave continues to produce an area of showers and thunderstorms located about 1100 miles southwest of the southern tip of the Baja California peninsula. This system is expected to move west-northwestward, and some development is possible late this weekend and early next week before it moves into less favorable environmental conditions. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Jul 18, 2020

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

1. Shower activity has increased this morning in association with a tropical wave located about 1100 miles southwest of the southern tip of the Baja California peninsula. This system is expected to move west-northwestward, and some development is possible late this weekend and early next week before it moves into less favorable environmental conditions. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium...50 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Jul 18, 2020

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

1. Disorganized showers and thunderstorms located about 1000 miles southwest of the southern tip of the Baja California peninsula are associated with a tropical wave. This system is expected to move west-northwestward, and some development is possible late this weekend and early next week before it moves into less favorable environmental conditions. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Fri Jul 17, 2020

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

1. Disorganized showers and thunderstorms located about 1000 miles southwest of the southern tip of the Baja California peninsula are associated with a tropical wave. This system is expected to move west-northwestward, and some development is possible late this weekend and early next week before it moves into less favorable environmental conditions. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Jul 17 2020

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

1. Disorganized showers and thunderstorms located about 1000 miles southwest of the southern tip of the Baja California peninsula are associated with a tropical wave. This system is expected to move west-northwestward, and some slow development is possible late this weekend and early next week before it moves into unfavorable environmental conditions. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...30 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Jul 17, 2020

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

1. Disorganized showers and thunderstorms located about 1000 miles southwest of the southern tip of the Baja California peninsula are associated with a tropical wave. This system is expected to move west-northwestward, and some slow development is possible late this weekend and early next week before it moves into unfavorable environmental conditions. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Jul 17 2020

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

1. Disorganized showers and thunderstorms located about 1000 miles south-southwest of the southern tip of the Baja California peninsula are associated with a tropical wave. This system is expected to move west-northwestward, and some slow development is possible late this weekend and early next week before it moves into unfavorable environmental conditions. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Thu Jul 16, 2020

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

1. Disorganized showers and thunderstorms continue in association with a tropical wave located several hundred miles southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a couple of days while moving toward the west-northwest at 15 to 20 mph, and some development is possible over the weekend or early next week before the low reaches cooler waters. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Thu Jul 16, 2020

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

1. Disorganized showers and thunderstorms continue in association with a tropical wave located several hundred miles southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days while moving toward the west-northwest at 15 to 20 mph, and some development is possible over the weekend or early next week before the low reaches cooler waters. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Jul 16, 2020

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

1. Disorganized showers and thunderstorms continue in association with a tropical wave located several hundred miles southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days while moving toward the west-northwest at 15 to 20 mph, and some development is possible over the weekend or early next week before the low reaches cooler waters. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Jul 16, 2020

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

1. A tropical wave is producing an area of disorganized showers and thunderstorms several hundred miles southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days, and some development is possible over the weekend or early next week while it moves toward the west-northwest or northwest at 15 to 20 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Wed Jul 15 2020

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

1. A tropical wave is producing an area of disorganized showers and thunderstorms several hundred miles south-southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days, and some development is possible over the weekend or early next week while it moves toward the west-northwest or northwest. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Wed Jul 15, 2020

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

1. A tropical wave is producing an area of disorganized showers and thunderstorms several hundred miles south-southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days, and some development is possible over the weekend or early next week while it moves toward the west-northwest or northwest. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...20 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Wed Jul 15, 2020

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

1. A tropical wave is producing an area of disorganized showers and thunderstorms several hundred miles south-southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days, and some development is possible over the weekend or early next week while it moves toward the west-northwest or northwest. * 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 Wed Jul 15, 2020

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

1. A tropical wave is producing an area of disorganized showers and thunderstorms several hundred miles south-southwest of the coast of southwestern Mexico. An area of low pressure is forecast to form from this system in a few days, and some slight development will be possible over the weekend or early next week while it moves generally toward the west-northwest or northwest. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Tue Jul 14, 2020

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

1. An area of low pressure is forecast to form well west-southwest of the coast of Mexico in a few days. Some slight development of the system will be possible over the weekend while it moves generally west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

If this storm is named, it will become Tropical Storm Douglas.

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Video: Final Hurricane Douglas Update | KAUAI, HAWAII
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