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2020 Typhoon/Hurricane Season

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Response to 2020 Typhoon/Hurricane Season 2020-07-25 11:01:19


Hurricane Hanna (08L)

Aircraft data and satellite estimates indicate that tropical storm Hanna has just strengthened into a minimal hurricane. It is now about to make landfall along Texas coast. Warm SST and large envelop of tropical moisture surrounding the system has enabled it to develop a dual outflow channel and strengthen more than earlier intensity guidance, despite light to moderate northerly VWS. Symmetrical deep convection continues to develop and it has a microwave eyewall. Aircraft reported a maximum flight level wind of about 75 knots at 700mb and SFMR readings up to 65 knots. Subjective Dvorak classification is at T4.0/65 knots. Minimum sea level pressure in the center of the embedded eye is near 980mb, Based on the relatively low pressure readings and impressive appearance on microwave and infra-red imagery, it is assessed as a 70-knot hurricane, or equivalent to a Category 1 hurricane.

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It will make landfall in the next 12 hours. Surface observations indicate that tropical storm force winds extend outward up to 90 miles from center. Hurricane force winds are within 30 miles from center. It is moving westward. The rainband associated with the eyewall is affecting the immediate coastal areas. Some strengthening to 75 or 80 knots is possible prior to landfall.


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Response to 2020 Typhoon/Hurricane Season 2020-07-30 01:20:38


Tropical Storm Isaias (09L)

The broad area of disturbance over a hundred miles south of Puerto Rico has acquired a slightly better defined center per 01z ASCAT, which showed an area of 35-40 knot winds well to the north of the center. The system has also maintained an expansive area of convection near center. Consequently, it is now designated a tropical storm with an initial intensity of 40 knots. It is moving WNW at 20 knots along the deep layered subtropical ridge.


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The trough northwest of the system has created a slight weakness in the steering ridge and thus the cyclone should remain on a general northwestward course across the Caribbean closer toward the southeastern US. Although on the synoptic scale the steering currents will remain relatively steady, global models have hinted at the possibility of center reformation north of Hispaniola. This may be due to enhanced friction convergence into mountainous terrain as well as the loose structure of the system (ASCAT reveals weaker convergence on the southern quadrant of the cyclone). There is considerable uncertainty to its track.


Assuming center reformation occurs, the system could pass just to the east of Florida several days later.

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The upper anticyclone that is currently providing excellent poleward outflow will continue to be anchored northeast of the tropical storm. The CIMSS products have analysed a 15-20 knot magnitude of VWS, but the swift motion in phase with upper level flow could mitigate some of the negative effects. No significant change in upper level flow is expected.


There is also an area of drier mid-level air in the path of the tropical storm. The large circulation argues for some dry entrainment into the system, limiting intensification potential.

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That said, the tropical storm could approach the US at near hurricane intensity.


Monsoon depression in the South China Sea.

Besides, an area of low pressure has formed and moved into the South China Sea. It is being monitored for tropical cyclone transition. Regardless, the system could bring strong winds and rain to the south China coast in the next few days.


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Hurricane Isaias

The large tropical storm has strengthened to a Category 1 hurricane. Mountains blockage of low level inflow and periods of mid level dry air entrainment from the moderate westerly shear have caused its intensity to fluctuate a bit over the past 24 hours. Still, very warm SST (29-30C) and robust anticyclonic outflow in the vicinity of the tropical cyclone continued to support vigorous central convection. Aircraft reconnaissance data currently support an intensity of 70 knots. A partially closed eyewall is also seen on radar, helping to fight off some of the mid-level dry shear.


Slight intensification in the near term appears likely and the system could reach a peak strength of 75-80 knots on its approach to southeast Florida. At the same time, upper level winds off the SE US will veer to the southwest in response to an approaching trough and VWS should increase in this area.


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Therefore, gradual weakening is expected during its closest approach to Florida. However, the forecast intensity and proximity to land suggest hurricane conditions are possible across central to southeastern Florida and hurricane warnings are now in effect across some parts of the state.


By 72 hours, the cyclone will have turned northeast in response to the trough and track parallel to the East Coast, while gradually losing tropical characteristics in a baroclinic environment. Tropical storm or gale force winds are also possible in the northeastern coast.


Its parallel track across the coast could diminish the risks of deadly storm surge.


This is the latest rainfall projections from the Weather Prediction Center.

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For the northwest Pacific

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A tropical disturbance organized into a tropical depression today. Subjective Dvorak estimates are T2.0/30kt and a recent ASCAT shows an area of 25-30 knots. Hence the initial intensity estimate is set at 30 knots. There is a window of opportunity for the tropical depression to strengthen to a weak tropical storm during the next day or so, while the system moves northwestward.


The depression is now in an area of light VWS (10-15 knots), with good upper level outlow toward the south and northeast. Beyond 24 hours, an upper trough that is providing ventilation will begin to slide eastward while the anticyclone across mainland China will build eastward, restricting poleward outflow and inducing some amount of northeasterly VWS.

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The depression is quite compact and it could intensify at a faster rate than a large system and reach a peak of 40 knots when it is close to Taipei and China's east coast. Current expectation favors a stronger ridge as advertised by the European model. Tropical storm conditions could occur within 60 miles from center and the system will pass around 100 miles from Taipei.


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Response to 2020 Typhoon/Hurricane Season 2020-08-08 00:30:23


2020 could favor a "hyperactive" Atlantic hurricane season.

Besides the total number of storms formed, the ACE index is another measure of tropical cyclones activity.

The index is calculated based on the square of maximum wind speed (in knots) of a tropical or subtropical system over its lifetime as a storm or hurricane.


So far the Atlantic hurricane season has been more active than normal and statistics can be found here.


Historically, August to October is the busiest period of the year.


Northwest Pacific.

Invest 94W is currently centered a few hundred miles east of Luzon Island, Philippines, near 17N 127E. Visible imagery shows a slowly consolidating curved band over the elongated center. 00z ASCAT reveals an area of 25 knot wind over a hundred miles southeast of the broad center, associated with the monsoon flow, but is not wrapping into the center.


VWS is light and will remain so during the next couple of days. A mid to upper level trough across China will erode the subtropical ridge ahead of the system and cause a northward track across the East China Sea into Korean peninsula.


The approaching trough will cause improve poleward outflow, especially in the west side of the storm. An anticyclonic outflow could develop as a result, fueling additional strengthening.


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Along track SST is also favorable at well above 26C until in the vicinity of Korean Peninsula.


Forecast track is now a little to the east of the ECMWF solution and brings the peak intensity to 50 knots prior to landfall.


A second area of rotation is a little west of of Luzon. Upper level conditions are a little less conducive with moderate easterly VWS impinging on the circulation and the system appears to have slightly less room for development. Still, tropical cyclone formation is not ruled out at this point, when it begins to track northeast to northward along monsoonal flow.


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Tropical Depression (07W)


The disturbance located west of Luzon has developed organized convection with a closed circulation. Initial intensity at 12z is estimated at 30 knots based on ASCAT and Dvorak classification of T2.0/30kt.

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Current VWS is easterly at 15-20 knots.


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The depression is forecast to strengthen during the next couple of days to a tropical storm, while it gains latitude and heads toward an area of lower VWS and stronger outflow from a closed upper cold low. Some slightly drier mid-level air is present northwest of the system.


Environmental conditions will support strengthening to a 45 knot storm prior to landfall over southeastern China.


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Response to 2020 Typhoon/Hurricane Season 2020-08-18 08:25:14


Severe Tropical Storm Higos (Western Pacific)

An area of low pressure in the vicinity of Luzon gradually developed into a severe tropical storm and was named Higos. Note-worthily, its incipient disturbance has already acquired a well-defined mid-level circulation, despite initial weak surface winds and it is likely that its vertical structure has contributed to significant development in the South China Sea.


Vigorous convection has persisted over its center and the system soon developed a well-defined CDO. Towards sunset, its rainbands began to be captured on HKO radar and as at 12z, the system has maintained a partial eyewall on radar that has wrapped 50% around the LLCC.


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Upper level conditions are favorable with an upper anti-cyclone present above the system, providing low VWS and good radial outflow. Steering flow analysis reveals TC Higos is located on the southwest portion of the subtropical ridge, with weak easterly flow aloft. Therefore it should continue WNW to NW closer to the coast of China. I am favoring the slightly more eastern solution provided by the GFS.


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Higos is forecast to continue strengthening and make landfall over Guangdong as a minimal typhoon. Locally, the Strong Wind Signal No.3 is already in force in Hong Kong and will soon be changed to the Gale Signal. Strong winds generally persist over southern part of Hong Kong. A partial ASCAT shows gale force winds extend outward up to 90 miles to the north.


Invest 97L and 98L (North Atlantic)

Two disturbances are monitored by the NHC for tropical cyclone development. There is a little bit of westerly shear above 97L but environmental conditions are expected to improve as the trough across US and Caribbean become replaced with upper level ridging stretching toward the west. Upper level flow is favorable for 98L during the next week.


Both systems have high likelihood of becoming tropical cyclones tracking into US offshore. Stay tuned.


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Response to 2020 Typhoon/Hurricane Season 2020-08-20 11:00:17


North Atlantic

Invest 97L and TD 13

Satellite imagery shows both Invest 97L and 98L have developed a good low level circulation with well-organized convection. Officially, 98L was upgraded to a 30-knot depression (TD 13), consistent with ASCAT and Dvorak estimates of T2.0/30kt from TAFB. I would argue that 97L has acquired tropical depression status at 12z with well-defined cloud lines and formative banding loosely wrapping into the center.


Present conditions favor strengthening for both low pressure systems. TD 13 is located in an area of light VWS and is approaching warmer SST, slightly offset by mid-level dry air entrainment (humidity between 50%-60%) and these argue for slow organization during the next day or so followed by faster intensification rate as the system develops a stronger core. As for 97L, it is benefiting from very warm SST (30C) and good outflow from an upper level anticyclone. However, VWS is on the moderately high side (15-20 knots southerly VWS). In addition, the system will pass over land, limiting short-term intensification potential.


97L will then emerge into the Gulf of Mexico in a few days, where conditions are expected to be conducive for additional strengthening, mainly due to reasonably high humidity and strong outflow tapping into mid-latitude trough and warm seas. Shear vector is also favorable. On day 5, the system could be a strong tropical storm, heading northwestward along the western periphery of the subtropical ridge and poses a threat to southwestern Gulf coast.


TD 13 should continue on a WNW course toward southeastern US, with the possibly of passing over Florida as a hurricane and then moving into eastern Gulf of Mexico, although the official intensity forecast does not explicity show a hurricane landfall.


Its future track could be north of the ECMWF deterministic runs as a stronger system will be steered by mid-level flow instead.

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Below graphs are selected models ensemble forecast by the GFS and ECMWF, for each of the system.

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West Pacific (tropical cyclone formation likely)

Convection associated with 90W has persisted. The low level center is estimated to be east of Luzon. An upper level low to the north and equatorial northeasterlies give rise to low shear environment with dual channel outflow. A near equatorial ridge will steer the system slowly northward to northeastward as it intensifies, passing east of Taiwan and close to Ryukyu Islands. The subtropical ridge could temporarily build back in response to a short wave ridge, pushing it farther northward toward southwestern Japan and Korea. Additional intensification is expected and it is likely to be a typhoon at this stage.

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TS Laura and Marco (resp. 13 & 14L)

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Laura's satellite signature is surprisingly impressive for a tropical cyclone traversing over mountains. Infra-red satellite images show a well-defined mid-level circulation over south-central DR embedded under very intense convection. The upper level outflow is also well-established. This is probably a result of very favorable upper level environment, with low VWS (less than 10 knots). The airplane currently investigating the tropical cyclone has found flight level winds (700mb) of 55-60 knots and maximum reliable SFMR wind of 45-50 knots, suggesting the cyclone has strengthened some despite being over land. These winds are recorded in the northern quadrant of the system. Dropsode data does not indicate significant dry air entrainment and I suppose that the large convective mass has mixed out most of the dry air. The current intensity is thus estimated at 50 knots.


Even though the deepest convection is located closer to southern coast, cyclonic vorticity from low level wind field north of the island may still lead to reformation of center north of the MLC. Thus, I will not forecast a track as far west as the global models, for now. As a result, I will follow the HWRI more closely and anticipate a landfall in the vicinity of southwestern LA.

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Intensity forecast is also challenging. My best bet is that the system will hold its strength (45 knots) during its track across DR and Hispaniola. After that, there is a 36 hour window of opportunity for it to take advantage of the very favorable environment and a period of rapid intensification seems probable. I will now forecast a 90 knot landfall (Category 2) but it should be noted that high intensities cannot be ruled out at this point.


After a period of faster intensification, the trend has slowed for Marco. It has moved into the Gulf of Mexico and the center is located east of previous forecast. One significant change since the previous discussion is that Marco is now forecast to adopt a more easterly track during the next day, probably as a response to upper level flow and it is now expected to make landfall over the northern Gulf coast, before turning more westward due to a building ridge. 12z data still support an intensity of 60 knots, a little below Category 1 hurricane threshold. VWS has increased to near 20 knots, in a SW'ly direction and shear is expected to continue to affect Marco. The combination of modest dry air and shear, offset by high SST, should lead to slow strengthening to a borderline hurricane over the Gulf and its eventual landfall as a strong TS/minimal hurricane.


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Typhoon Bavi (West Pacific)

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Bavi is now a 65-knot typhoon. This estimated is based on the higher of Dvorak classification of T4.0/kt and SATCON estimate of slightly over 50 knots. It is forecast to intensify to a peak of 90 to 100 knots over the East China Sea, as a result of very high (30-31C) SST, light VWS (the current subtropical jet will give way to southerly flow from a developing anticyclone). The only inhibiting factor is the presence of dry air associated with upper trough subsidence. Apart from a west shift in future track, the reasoning is largely the same as the previous discussion and the system is still anticipated to track mainly northward, closer toward Korean peninsula and Northeastern China.


It is not very common for northern China to experience a typhoon landfall. Typhoon typically recurves northeast well before this point, but in this case, intense Rossby wave breaking will give rise to a high latitude ridge in the Sea of Japan that will steer the cyclone northward.


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Response to 2020 Typhoon/Hurricane Season 2020-08-26 08:14:30


Major Hurricane Laura

Aircraft reconnaissance reveals and area strong upper level winds (near 100 knot at 650mb) and maximum surface wind of near 95 knots. In addition, subjective Dvorak estimates at 12z come in at T5.5/102kt. Thus Laura is now a major hurricane with maximum winds of 100 knots. The data also reveals that hurricane winds are quite expansive in the NE quadrant with a radius of 60-75 miles. Minimum extrapolated surface pressure is down to 963mb.


Rapid intensification could continue for another 12 hours or so until shortly before landfall and Laura is forecast to become a Category 4 hurricane, with winds of 120 knots, at the time of landfall. During its final approach, VWS could increase but it would not be enough to weaken the very inertially stable circulation.


There has been no significant change in track forecast.


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Check here for official information and potential hazards.


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Response to 2020 Typhoon/Hurricane Season 2020-08-28 23:22:33


Severe tropical Storm Maysak (10W)

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Severe tropical storm Maysak, located well east of the Philippines, remained slow moving between two ridges far to the north and south. The weakness in mid-level subtropical ridge to the east, associated with an upper level low, is expected to fill in and cause a poleward movement across the West Pacific in the next couple of days.


Current intensity is estimated at 55 knots, held higher than a subjective Dvorak estimate of T3.0/45kt, based on microwave estimates and ADT lying between 55-60 knots. Environment is favorable for intensification, with SSTs between 30-31C, low VWS (10 knots) and excellent upper level outflow to the north and south.


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There is a small spread between global models output with JMA lying on the western envelope and ECMWF/GFS on the eastern envelope in long range solutions. I prefer the eastern solutions offered by ECMWF/GFS considering the orientation of the shortwave trough that is expected to erode the higher latitude ridge across the Yellow Sea and the expected strengthening of the near equatorial ridge to the south. Furthermore, the temporarily building weak ridge to the NW will help keep a distance between the cyclone and the aforementioned shortwave trough to keep the trough neutrally tilted.


In-storm environment will continue to support steady to rapid strengthening for at least the next 72 hours and the cyclone could reach a peak intensity of 125 knots, when it is north of the Ryukyu Islands, before weakening due upwelling caused by lower OHC and slightly higher westerly VWS. This is in close agreement with the latest HWRF run.


The system could potentially affect western Japan and Korea as a strong tropical cyclone.


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Typhoon Maysak


The typhoon reached an estimated peak intensity of 120 knots earlier. The winds have decreased since and it is currently a 90iu_163214_779242.jpg-kt typhoon, which is about to make landfall near the SE coast of Korean Peninsula.


The estimated minimum central pressure at this time is around 950hPa. A station has recorded a MSLP of 956hPa.


It is also a rather large typhoon with tropical-storm winds extending outward up to 200 miles from center, and typhoon-force winds up to 75 miles from center.


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Response to 2020 Typhoon/Hurricane Season 2020-09-02 21:11:30


At 9/2/20 12:16 PM, Sobolev wrote: Typhoon Maysak

The typhoon reached an estimated peak intensity of 120 knots earlier. The winds have decreased since and it is currently a 90-kt typhoon, which is about to make landfall near the SE coast of Korean Peninsula.

The estimated minimum central pressure at this time is around 950hPa. A station has recorded a MSLP of 956hPa.

It is also a rather large typhoon with tropical-storm winds extending outward up to 200 miles from center, and typhoon-force winds up to 75 miles from center.


That's two typhoons to hit the Korean Peninsula in less than a week. That may be three, judging by the formation of Haishen.


Isn't Maysak a major typhoon after hitting Category 4 though?


At 9/2/20 09:11 PM, RydiaLockheart wrote:
At 9/2/20 12:16 PM, Sobolev wrote: Typhoon Maysak

The typhoon reached an estimated peak intensity of 120 knots earlier. The winds have decreased since and it is currently a 90-kt typhoon, which is about to make landfall near the SE coast of Korean Peninsula.

The estimated minimum central pressure at this time is around 950hPa. A station has recorded a MSLP of 956hPa.

It is also a rather large typhoon with tropical-storm winds extending outward up to 200 miles from center, and typhoon-force winds up to 75 miles from center.
That's two typhoons to hit the Korean Peninsula in less than a week. That may be three, judging by the formation of Haishen.

Isn't Maysak a major typhoon after hitting Category 4 though?


She is equivalent to a Category 2 hurricane at landfall. It peaked at Category 4 a day prior.

Maysak and Haishen are the two typhoons that affect Korea and Japan.


Maysak is one of the strongest typhoon to hit Korea, pressure-wise.


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Response to 2020 Typhoon/Hurricane Season 2020-09-03 10:26:24


Typhoon Haishen

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Typhoon Haishen, centered in the West Pacific, has tracked west-northwestward steadily along the southern periphery of a subtropical ridge. Low VWS, anticyclonic outflow in all directions enhanced by a cut-off low to the NE, and high SST (30-31C) all enabled the system to steadily strengthen to a typhoon. Current intensity is estimated to be 100 knots, based on SATCON values of 98kt and Dvorak classification of T5.5/102kt.


Apart from a slight decrease in OHC, the along-track environment will remain highly favorable for development. This is mitigated by a steady pace toward the NW.


Synoptic analysis shows that the major trough in Eastern China will remain in place throughout and this should drive the system steadily to the NW and then N as the cyclone begins to round the subtropical ridge axis. Despite the apperance of a formative pin-hole eye on IR imagery, microwave imagery still shows a well-developed outer eyewall. This "concentric" structure is limiting the rate of intensification in the near term. That said, the HWRF forecasts the outer eye to shrink and this will enable the storm to deepen again.


Thus, given the favorable environment, the cyclone could rapidly strengthen to a Super Typhoon with winds near 130kt (equivalent to a Category 4 hurricane) during the next couple of days when the typhoon is still well south of Japanese mainland. By 48 hours, the system will be moving over seas with relatively low OHC, and some cold upwelling could be expected to cause the system to maintain its intensity.


By 60 hours, Haishen will be turning to the NNW, a few hundred miles south of western Japan, into increasingly less supportive OHC. Moreover, modest barolinic forcing in the mid-latitudes will cause the wind field to expand also. The net result is a weakening trend in terms of maximum wind speed. However, favorable outflow will aid to reduce the rate of weakening. By the time she reaches the 30N latitude, the wind speed could be a little above 100 knots.


The 00z guidance has trended east compared with previous runs, but in light of the position of the blocking ridge to the north, I would only deviate slightly from past model runs until a trend is clear.


In long range, the cyclone could threaten to make landfall over South Korea again as a strong system again.


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Response to 2020 Typhoon/Hurricane Season 2020-09-04 22:59:31


Typhoon Haishen (was 'unofficially' a Super Typhoon with Category 5 winds)

This is a special update. Haishen managed to rapidly strengthen by 40 knots within a day and had momentarily attained Category 5 status at 04/00z. Just before that time, Haishen has maintained a thick ring of deep convection with cloud tops temperature around -75C and an eye temperature between 10 to 20C. Subjective Dvorak classification with a T7.0/140kt.


Various satellite estimates near 00z were clustered between 135 to 140kt, with SATCON intensity as high as 138kt. On this basis, the typhoon was upgraded to 140kt, making it the first Category 5 system of the North Hemisphere typhoon season.


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Since then, Haishen began to pass over waters with lower OHC and maximum winds have decreased to 125 kt as at 05/00z. Gradual weakening is expected and the typhoon could skirt the southwest coast of Japan as a 105kt system and make landfall on or pass very close to the SE coast of Korean Peninsula, as a typhoon with 80kt winds.


There is no change in forecast track.


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Response to 2020 Typhoon/Hurricane Season 2020-09-08 08:19:49


North Atlantic (Invest 94L)

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An area of low pressure in the western Atlantic has maintained an area of cloudiness east of the weak center.

Moderate westerly shear continues to affect the system but shear is forecast to decrease as an upper anticyclone strengthens downstream of the trough across continental US. The low level circulation appears to be closed.


Environment conditions are otherwise favorable and a brief tropical storm could form while the system moves westward to west-northwestward toward southeastern US. Global models generally maintain a weak surface circulation during the next few days, while SHIPS anticipates it to become a tropical storm.


This disturbance will be monitored for tropical cyclone development.


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Response to 2020 Typhoon/Hurricane Season 2020-09-11 08:36:54


Tropical Wave off Florida coast (Tropical Cyclone formation likely)

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A tropical wave a couple of hundred miles southeast of Florida is producing vigorous convection. Recent infra-red imagery suggests a defined mid-level circulation is present over the surface wave axis.


Environmental conditions are expected to be conducive for development over the next several days and a tropical cyclone is likely to form as the system moves westward into the eastern Gulf of Mexico.


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Specifically, an upper trough in the subtropical jet to the west will create a downstream ridge in the vicinity of the system and fend off westerly flow aloft, while enhancing poleward outflow and creating a light VWS environment at the same time.

A TUTT that is easily discernible on vapor loop will also enhance upper northwesterly flow at the back of the tropical wave, and will possibly create an anticyclonic/dual outflow channel that will help to sustain organized convection.


Precipitable water products indicate an area of high moisture content (probably related to high SSTs and weak synoptic-scale ascent) in the Gulf of Mexico ahead of the system's path.


The disturbance is forecast to gradually round the low to mid-level steering ridge axis while a mid-level trough propagates to from the NW (turning northwestward toward the central Gulf coast). Global models indicate gradual organization into a sharp trough and finally to a closed low over the eastern Gulf.


In light of the favorable environment and good initial structure, the disbursement has a high chance of becoming a tropical depression/storm during the next couple of days and additional updates will be given as necessary.


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Response to 2020 Typhoon/Hurricane Season 2020-09-12 05:07:30


Tropical Storm 19L (could hit central Gulf coast as a Category 1 hurricane)

The tropical wave described in previous update continues to produce organized convection. The surface circulation is also closed. Recent Doppler radar loop shows sustained winds as strong as 40-50 mph. Subjective Dvorak classification at 06z was T2.5/35kt, shortly before landfall in south Florida. Based on these, the low pressure area is upgraded to a tropical storm of 35 knots.


The latest statistics and dynamical model guidance shows the possibility of attaining hurricane strength when the tropical cyclone is close to landfall near 72 hours. Global models have also trended significantly stronger compared with previous runs.


Environmental conditions in the eastern Gulf of Mexico are still expected to be quite conducive.

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The caveat is that there will not be aircraft data until tomorrow and model forecast could still change after the data are fed into models. Owing to the early stage of development, there is still a far amount of uncertainty in the subsequent evolution.


Current model shows that the system still have 2-3 days of warm waters and low VWS before approaching the coast and it is reasonable to assume a standard development rate of 15 knots per day, bringing the tropical storm to hurricane status at landfall (near 70 knots).


Regarding to its track, there are a large spread between model guidance. The 00z GFS and ECMWF have trended toward a stronger ridge and a more westerly track. This is reasonable since the trough that is expected to erode the current steering ridge will be a short-lived feature. Thus, current expectation is that the system will begin to track more NW in the short-term in response to the weakening of the steering ridge, and beyond 2 days, the steering ridge will begin to build back, resulting in a general WNW track toward the central Gulf coast.


The recuvature scenario depicted in the above model suite is considered less likely, but this could be indicative of an increase in mid-level shear.


Toward landfall, the tropical cyclone could decrease in forecast speed as the ridges to the north and south compete.


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I don't remember the Atlantic Ocean to be so busy:

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They weren't joking that the conditions for storms formation will be extremely favorable this season.


Equal medal chances for everyone!

Response to 2020 Typhoon/Hurricane Season 2020-09-14 11:08:25


At 9/14/20 10:53 AM, HerbieG wrote: I don't remember the Atlantic Ocean to be so busy:

They weren't joking that the conditions for storms formation will be extremely favorable this season.


Are Teddy or Vicky expected to make it across the Atlantic or are they going to steer north and be fish storms?

Response to 2020 Typhoon/Hurricane Season 2020-09-15 09:38:49


Invest 90W in the West Pacific (future TS Noul)

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A broad area of low pressure is presently located near Central Philippines. Deep convection has persisted for at least 24 hours and is now offset to the west of the center, due to moderate easterly shear. There is a robust outflow channel to the west. A TUTT cell is also ventilating the system from the east but this feature is predicted to weaken.


GFS model analysis field shows good along track mid-level moisture. Global models depict steady strengthening and the system is likely to become a tropical depression during the next day or so, while moving westward across the South China Sea.


Persistent northeasterly shear from a semi-permanent upper level high building eastward from China will limit intensification. Warm SST and moisture will promote gradual strengthening to 60 knots prior to landfall in Vietnam.


I expect a track just south of the ECMWF run because of the anticipated interaction between convection and NE shear. Intensity forecast is between GFS southern ensembles and HWRF.


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Response to 2020 Typhoon/Hurricane Season 2020-09-15 10:50:49


This is way ahead of it's time

Response to 2020 Typhoon/Hurricane Season 2020-09-16 04:00:48


Not only the Atlantic Ocean is now active, we got a nicely looking medicane in the Mediterranean Sea:

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Equal medal chances for everyone!

Response to 2020 Typhoon/Hurricane Season 2020-09-16 10:37:05


At 9/16/20 04:00 AM, HerbieG wrote: Not only the Atlantic Ocean is now active, we got a nicely looking medicane in the Mediterranean Sea:


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The best source of direct information is satellite pictures. I only have infrared data and it is producing cloud tops of -60C (equivalent to LG on BD Dvorak) with good banding. Probably closer to T3.5/55kts at this time but I will set the intensity to 50 knots based on relatively warm cloud tops.


Moderate (around 20kts) of southerly shear is present at this time, explaining the cloud tops displaced north of the center.

GFS model analysis shows marginal thermodynamic environment for a strong tropical storm, with colder-than-tropics temperature of less than -10C at 500mb and topopause height around 200mb. There is also some evidence of dry air wrapping from the south and east. Despite these, cloud signature has improved slightly over the past 12 hours.


Could it make a run for a minimal hurricane? Global models do suggest such a possibility. They deepen it to sub-990mb. However, just as systems of subtropical origin, ASCAT reveals a large wind field so lower pressures may not equate to higher winds associated with smaller systems. In fact, I am giving it a 30% chance of achieving hurricane status, although I admit that I have very little guidance.


Latest updates on tropical cyclones

I mainly focus on WPac and NATL basin.

Response to 2020 Typhoon/Hurricane Season 2020-09-18 09:32:09


Tropical Depression 22L in the Gulf of Mexico (could affect Texas coast as a strong TS)

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A tropical depression has formed near the Bay of Campeche. Satellite estimates and flight recon data support an intensity of 30kt. It is tracking NNE slowly along the western edge of a ridge stretching from the West Atlantic into eastern Gulf of Mexico. Infrared imagery suggests that the low level center is displaced to the south of poorly organized deep convection and this is likely due to ongoing southwesterly VWS (analysed at 15-20kt by CIMSS).


Upper convergence is producing subsidence across Yucatan Peninsula and the associated dry air could be entraining into the circulation from the south and east. This is reflected in model analysis and precipitable water products. Overall environment is marginal and significant strengthening appears unlikely in the short term.


A continued track to the NNE is expected during the next couple of days. Afterwards, a stronger continental ridge will build and translate eastward, resulting in weak steering current and subsequent turn to the west or northwest. In the near term, southerly shear will dominate and this could result in a more northern and faster track than ECMWF. This could be followed by slower motion than is depicted by the GFS since I expect a stronger ridge, taking it close to south Texas coast in a few days.


The GFS has a much stronger circulation in the near term and this is probably the cause of more significant dry Continental air entrainment from the north, associated with a frontal boundary. I expect less entrainment since short term development is anticipated to be slow.


As it tracks farther west, a temporary upper level anticyclone is forecast to build. resulting in lower VWS. This is reflected in ECMWF and GFS-based SHIPS output and together with high SST, a faster intensification rate could be expected. At the same time, the cold front will start to lift northward and moisture levels could improve.


By day 4 or 5, VWS is forecast to increase again, halting the intensification process. A stronger system is more likely to track with upper level winds and thus I predict a sharper re-curvature to the N or NE on Day 5.

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The maximum intensity that could be achieved is roughly estimated to be 60kts. A slight weakening trend may occur on Day 5, but still the system is expected to remain a significant tropical storm by the end of forecast period.


Latest updates on tropical cyclones

I mainly focus on WPac and NATL basin.

Response to 2020 Typhoon/Hurricane Season 2020-09-18 23:34:34


Update on TD 22L (now TS Beta)

TD 22L has strengthened into a tropical storm. It is stronger than previously thought and based on aircraft data, the intensity is set at 50 knots. Further strengthening is anticipated and it could reach a peak of 75 knots and be near Texas coast as a hurricane of 70 knots. There is no significant change in track.


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Hurricane Teddy

Besides, hurricane teddy will track northwestward along the southwestern periphery of subtropical ridge axis. A northward track toward Atlantic Canada is expected under the steering of a cut-off low and a high latitude blocking ridge. Large swells will spread to Western Atlantic and major impacts are expected Canada. Guidance are now in reasonably good argeement.

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Latest updates on tropical cyclones

I mainly focus on WPac and NATL basin.