What has changed to allow for better prediction?

The development of regional dynamical models with improved cloud physics (e.g. HWRF/HMON) that can simulate rapid intensification.

Global models nowadays have better resolution and physics that can predict steering currents (and thus the tracks) more accurately.

Back in the early 2000s more reliance had to be placed on statistical-dynamical models.

Invest 95W (becoming better defined and organized, could become a TC as it drifts northwestward)

Recent satellite imagery and ASCAT both indicate the area of low pressure east of the Philippines is becoming better defined with organizing convection. Wind in the vicinity of the low level center is estimated at 15-20 knots The system is tracking westward along the southern periphery of a low to mid level subtropical ridge across the West Pacific.

Invest 95W is located in a favorable environment with low (<10 kt) VWS and modest upper divergence in all quadrants. Global models indicate upper level winds could remain fairly light over the next couple of days as the system tracks west-northwestward.

Thereafter some mid-level shear could be present, partly associated with a nearby Invest 94W. During this time, the system could be tracking northwestward closer to central to northern Philippines and the South Chin Sea, under the weak steering of the subtropical ridge.

Invest 95W rapidly intensifies to Tropical Storm Conson (18W)

Expected to track across Philippines and South China Sea at or near typhoon strength

Invest 95W has rapidly organized into a strong tropical storm. Deep convection with very cold cloud tops of -80C persists over the center. Microwave imagery reveals a well defined low to mid level center with a partial eyewall. The 12z initial intensity is assessed at 60 knots above Dvorak estimate of T3.5, in line with surface observation of 10-minute average wind of 62 knots at an elevation of 60 meters. Thus, the system has strengthened by 40 knots over the past 24 hours.

Upper level winds continue to be conducive with low (5-10 knots) upper VWS and weak dual outflow channel to the north and south. The system is tracking west-northwestward under the steering of a subtropical ridge to the north and east.

During the next couple of days, the dominant steering ridge to the north that is currently extending into Mainland China is forecast to retreat eastward in response to a eastward-propagating major trough. This will result in a steady northwest track across the Philippines into the South China Sea. Beyond 72h, the western extension of the steering ridge is expected to rebuild slightly after the trough departs, resulting in a more westward track across the Central to Northern part of the South China Sea, toward the vicinity of Hainan Island.

Alternatively, an inspection of the average models wind field and steering analysis from CIMSS favor a western solution at least in the near term as TS Conson is expected to be relatively strong.

Throughout the forecast, little binary interaction with the developing TD 19W is expected at this time as the current forecast keeps a decent separation between the two systems.

Confidence in the 5-day track forecast is medium.

Global and regional models maintain a trailing upper level anticyclone NE of the system center which will at least provide modest dual outflow channel throughout its track across the South China Sea. In addition, they also forecast a low mid-to-upper level shear environment that should limit the ingestion of any drier air downstream of its track. Therefore, at least steady strengthening is anticipated in the long term. It should be noted that the 06z HWRF run intensifies the system to near 120 knots just before landfall over Leizhou Peninsula, so there is a chance of attaining higher intensity than forecast

Overall, the 5-day intensity forecast is also of medium confidence.

Intensity forecast:

06/12z: 60 kt (TS)

07/12z: 60 kt

08/12z: 55 kt

09/12z: 60 kt

10/12z: 70 kt (Cat 1 Typhoon)

11/12z: 80 kt

Typhoon Chanthu (19W)

Typhoon Chanthu has tracked westward along the southern periphery of the deep-layered steering ridge. Current environment is favorable for further strengthening with low VWS (<10 kt diagnosed by CIMSS) and radial outflow partly enhanced by a TUTT cell to the northeast of the cyclone. SST is also favorable at 30C).

Typhoon Chanthu has maintained an expansive area of deep convection (cloud tops -80 to -90C). At the time of writing, IR imagery clearly depicts a rapidly developing upper level eye, indicative of continued rapid intensification.

A westward track is anticipated during the next couple of days. After 48 h, the system will be approaching the southwestern side of the main steering ridge. At the same time, global models all show a building near equatorial ridge southeast of the system. This pattern will drive a general northwest trajectory throughout the remainder of the forecast.

Toward the end of the forecast, the ECMWF shows the system approaching the southeast side of a secondary ridge anchored over Mainland China, leading to a decrease in forward speed. The current track forecast favors this scenario.

There are notable track differences between models, with the latest GFS showing a more poleward track across Taiwan. This might be partly due to a weaker ridge to the north and more robust mid-level southerly flow. In view of this, there is low confidence in track forecast beyond 48 h.

Ocean analysis from CIMSS shows an area of extremely high OHC west of 125E. When is cyclone tracks across the area, poleward outflow associated with an upper level anticyclone could cause a secondary phase of intensification, barring the occurrence of hard-to-predict eyewall cycles. This is reflected in the present intensity forecast.

By the end of the forecast period, decreasing OHC and slower translation speed (with the possibility of land interaction) will cause a steady decline in intensity.

Intensity forecast:

07/12z: 70 kt (Cat 1 Typhoon)

08/12z: 110 kt (Cat 3 Typhoon)

09/12z: 115 kt (Cat 4 Typhoon)

10/12z: 125 kt

11/12z: 105 kt (Cat 3 Typhoon)

12/12z: 85 kt (Cat 2 Typhoon)

Super Typhoon Chanthu

Super Typhoon Chanthu has tracked northwestward along the southeast side of the deep-layered subtropical ridge. Initial intensity at 12z is estimated at 145 kt to reflect a sustained impressive cloud pattern and in line with subjective Dvorak numbers of T7.0/7.5 and in close agreement of SATCON (146 kt at 13z). The eye temperature analyzed by ADT was 17C with surrounding cloud tops temperature of -78C.

Super Typhoon Chanthu continues to track over warm waters of 30C with high OHC. Deep-layered VWS is low at <10 kt. These conditions will persist over the next day or so as the system nears Taiwan, which will help maintain Super Typhoon intensities.

While upper level poleward outflow could be sustained, VWS is forecast to increase slightly during the next 2-3 days. In addition, land interaction with Taiwan (downslope flow in the western semi-circle) and decreasing OHC/SST will lead to gradual weakening.

The system is forecast to be relatively slow-moving beyond day 3 and cold upwelling from ocean with low OHC will serve to weaken the system further. The decrease in forward speed shown in the models is explained by surrounding high pressures generating weak steering currents.

A slow turn toward the east is forecast by day 5 due to the shift of the steering ridge toward the south of the system and surrounding height falls. Confidence in track forecast is medium.

Intensity forecast:

10/12z: 145 kt (Cat 5 Typhoon)

11/12z: 130 kt (Cat 4 Typhoon)

12/12z: 105 kt (Cat 3 Typhoon)

13/12z: 90 kt (Cat 2 Typhoon)

14/12z: 65 kt (Cat 1 Typhoon)

15/12z: 55 kt (TS)

Invest 94L

Microwave imagery a few hours ago shows increased banding north of the center. Aircraft reconnaissance has measured near TS-winds in the NE quadrant of the system. IR loop shows sustained central convection over the past few hours slightly offset to the NE due to ongoing moderate VWS.

During the next day or so, the disturbance is expected to track north-northwestward along the western extension of the subtropical ridge in the West Atlantic. Beyond 48 h, models show the secondary mid-level ridge currently residing over SE US sliding eastward, giving some room for the system to turn to the NE.

After landfall, the system should weaken and be steered by low level flow. Near the end of the forecast period, models indicate the building of a low level ridge ahead of the system. This feature should cause the system to move slowly until dissipation over land.

The system is forecast to track across very warm waters of 30-31C and experiece moderate poleward outflow across the west side of an upper level anticyclone tapping into the mid-latitude westerlies, which will fuel continuous bursts of central convection. However, upper level southwesterlies flow will also induce moderate to strong westerly VWS and will serve to mitigate the chance of rapid intensification. Thus gradual intensification is forecast until its landfall near 48 h. The current intensity forecast lies above intensity consensus at 12z but is not as bullish as the HWRF 06z deterministic run which shows a hurricane landfall.

Intensity forecast:

12/12z: 30 kt (disturbance)

13/12z: 40 kt (TS)

14/12z: 55 kt ... (near TX coast)

15/12z: 25 kt (TD)

16/12z: 15 kt (post-tropical)

Update: NHC upgraded Invest 94L to Tropical Storm Nicholas at 15z, with maximum winds of 35 knots.

The increased initial intensity could result in higher landfall intensity than 55 knots and Nicholas could become a Category 1 hurricane in 2 days.

Nicholas becomes a Category 1 hurricane off Texas coast, with maximum sustained winds of 65 knots/75 mph.

The hurricane will maintain a NE track and make landfall in the next few hours. Little change in strength is expected during this time due to strong westerly (~30 kt) westerly shear.

After landfall, weakening should commence.

Tropical Storm Chanthu (19W)

TS Chanthu has tracked slowly northeastward along the northwest periphery of the Pacific subtropical ridge. Current conditions are marginal with warm SST (28C) offset by dry air entrainment from the southeast and moderate (20 kt) westerly shear. The cloud pattern of the system has degraded and is now consisting of a small cold overcast partially obscuring the LLC.

Chanthu is expected to accelerate toward the east as height gradient tightens near the base of a propagating mid-latitude trough. The system will interact with the trough, causing extra-tropical transition by 48 h.

Gradual weakening is expected during the next couple of days under the influence of stronger westerly shear and land interaction.

Intensity forecast:

16/12z: 50 kt (TS)

17/12z: 40 kt

18/12z: 35 kt (Extratropical)

Tropical Depression 21W

Convection in association with a low pressure area in the South China Sea has increased in organization (subjective Dvorak classification at 12z is T1.5/25kt). Thus the low pressure area is upgraded to a tropical depression.

The depression is in a favorable environment with low (10-15 kt) easterly VWS with a dual channel outflow. SST is at 29C. The system is tracking west-northwestward along the southern periphery of a low to mid-level steering ridge

A general northwestward track toward Vietnam is anticipated, with gradual intensification under favorable environment (good westward outflow and low to moderate (10-20 kt) easterly VWS). The system is expected to make landfall as a tropical storm. Dissipation over land is expected at around 48 h.

Intensity forecast:

22/12z: 25 kt (TD)

23/12z: 40 kt (TS)

24/12z: 20 kt (remnant low)

Invest 92W

Convection has increased in the proximity of a low pressure area, located just east of Mindanao, Philippines (near 9N 127E). Animated SWIR imagery and a much earlier ASCAT pass suggests a fairly defined low level circulation. The ASCAT pass also indicated surface winds of 20 knots in the western quadrant, although recent deep convection remains somewhat disorganized.

Upper level environment is favorable for intensification with low (10 knots) VWS and strong divergence in all directions. SST is 30C. The system is tracking westward along the southern periphery of a deep-layered ridge to the north.

Global models are in agreement of a westward track across the Philippines in the couple of days with gradual intensification and the system is likely to become a tropical depression.

Beyond Day 2, the system should begin to turn northward as the primary steering ridge to the north weakens and low to mid level southerlies associated with an equatorial ridge strengthen. Near the end of the forecast period, the system could turn more northwestward as it nears the subtropical ridge axis stretching across southern China.

Environmental conditions are expected to be conducive for strengthening over the next 3-4 days, with radial outflow, low VWS, high mid-level RH and warm SST (29-30C) and all these factors suggest significant intensification. Models also develop an upper level ridge to the northeast of the system which could induce slight easterly shear.

Intensity forecast:

03/12z: 20 kt (LPA)

04/12z: 25 kt (TD)

05/12z: 35 kt (TS)

06/12z: 55 kt

07/12z: 70 kt (Cat 1/Typhoon)

08/12z: 85 kt (Cat 2/Typhoon)

Invest 92W develops into TS Lionrock in the South China Sea and makes landfall over Hainan Island.

At 12z, TS Lionrock was located near 19N 110E. Maximum sustained wind was estimated at 40 knots based on a ship report, which was slightly higher than T2.5/35kt. The system has tracked NNW slowly along the western periphery of a low to mid level steering ridge.

Upper level environment continues to be favorable but the strengthening trend has likely leveled off due to proximity to land. Land interaction will weaken the system down to 35 knots. After emerging into the Gulf of Tonkin, southerly VWS is expected to increase along with a surge of the northeast monsoon and no significant strengthening is anticipated.

Some models indicate that Lionrock will lose some latitude due to the low level influence of the northeast monsoon by 48 h and the current forecast follows this scenario as Lionrock is expected to be relatively shallow. The track forecast before between 24 h to 48 h is slightly slower than GFS/ECMWF deterministic run to account for weak mid-level steering.

The system will make a second landfall in Vietnam by 72 h.

Intensity forecast:

08/12z: 40 kt (TS)

09/12z: 35 kt

10/12z: 35 kt

11/12z: 20 kt (LPA)

TS Kompasu (24W)

At 12z, TS Kompasu was located near 18.5N 127E. Maximum sustained winds were estimated at 45 knots. The system has been tracking steadily westward during the past few hours. The circulation, though, broad, has become better defined over the past day and thus it was upgraded to TS Kompasu. The system is benefiting from favorable outflow in the northern quadrant associated with an upper anti-cyclone, though outflow is relatively weak in the southern quadrant. VWS is moderate at 15 knots.

A general westward track across the western extension of a low to mid level ridge to the north, toward the central part of the South China Sea. Global models maintain modest outflow toward the west and south during the next couple of days, while easterly VWS is expected to remain at near 15 to 20 knots. Therefore, the system is expected to intensify gradually until eventual landfall in Hainan.

Track guidance is in good agreement and confidence in track forecast is high.

Intensity forecast:

10/12z: 45 kt (TS)

11/12z: 55 kt

12/12z: 70 kt (Cat 1 Typhoon)

13/12z: 60 kt

14/12z: 25 kt (TD)

TD 16E

Intensity forecast:

10/12z: 30 kt (TD)

11/12z: 45 kt (TS)

12/12z: 70 kt (Cat 1)

13/12z: 85 kt (Cat 2)

14/12z: 35 kt (TS)

Revised intensity forecast:

TS Kompasu:

10/12z: 45 kt (TS)

11/12z: 55 kt

12/12z: 65 kt (Cat 1 Typhoon)

13/12z: 55 kt

14/12z: 25 kt (TD)

TD 16E:

10/12z: 30 kt (TD)

11/12z: 45 kt (TS)

12/12z: 70 kt (Cat 1)

13/12z: 95 kt (Cat 2)

(Note that TD 16E could make landfall in Mexico as a major hurricane since further strengthening is anticipated after 13/12z)

14/12z: 40 kt (TS)

Invest 92E (a tropical cyclone appears to be forming south of Mexico)

Earlier ASCAT at 04z shows a slightly elongated circulation associated with an area of low pressure with maximum winds of 20-25 knots. Since that time, satellite imagery suggests the low level circulation is becoming better defined with organized central convection, indicating a tropical depression or storm is forming. Current environment is favorable with high (30C) SST and good upper level flow (light VWS and strong dual channel outflow).

The system is tracking westward under the steering influence of a mid-level ridge to the north. The current steering ridge is forecast by global models to weaken, thus allowing 92E to turn more poleward after 24 h.

Conditions will continue to be favorable, and intensity guidance has been consistently showing significant strengthening during the next couple of days. In particular, the SHIPS rapid intensification index shows a 42% chance of a 65-kt increase in intensity in the next 72 h. However, beyond 48 h, the SHIPS guidance and global models output suggest possible increase in southerly mid-shear with dry air entrainment into the circulation from the west.

As the system is expected to make landfall as a significant tropical cyclone not far in the future, tropical storm/hurricane warnings are likely to be issued.

Intensity forecast:

22/12z: 30 kt (disturbance)

23/12z: 50 kt (TS)

24/12z: 75 kt (Cat 1)

25/12z: 80 kt ... near the coast

26/12z: 20 kt (remnant low)

Hurricane Rick (has rapidly intensified over the past 24 hours from TD to a Category 1 hurricane)

Invest 92E quickly consolidated into a tropical cyclone shortly after the last post. It is now assessed as a Category 1 hurricane based on Dvorak estimates of T4.0/65 kt, an increase of 35-kt in maximum winds over the past 24 hours, meeting the criteria of rapid intensification. Recent microwave imagery suggests the development of a mid-level pinhole eye.

Current upper level environment remains ideal for additional rapid intensification with light (<10 kt) VWS and strong divergence in all quadrants in the next 24 hours. Beyond 24 h, an increase in southerly shear along with drier air entrainment could cause its intensity to level off, just prior to landfall over southern Mexico.

The present forecast track has been shifted to the east by 1 degree longitude, partly due to earlier erosion of the steering ridge to the north. The intensity forecast has also been raised significantly due to ongoing rapid intensification.

Tropical Storm/Hurricane Watch is in effect along portions of the coast and TS/Hurricane Warnings could be posted later today.

Intensity forecast:

23/12z: 65 kt (Cat 1)

24/12z: 105 kt (Cat 3)

25/12z: 100 kt ... near the coast

26/12z: 30 kt (TD)

27/12z: Dissipated

Indian Ocean - Low pressure area expected to form in the southern Bay of Bengal

General situation: The MJO is currently weak with the MJO index lying just within the unit circle, closer to phase 4-5 (Maritime Continent). An intraseasonal signal manifesting as anomalous upper divergence has persisted between 60-120E, favoring deep convection.

Meanwhile, a monsoon trough (associated with anomalously strong equatorial westerlies) in the Bay of Bengal continues to produce large areas of disorganized convection. Although there is no discernible LLC yet, global models generally develop a low pressure system in that area during the next couple of days, with some indicating further development, as the low pressure system tracks northwestward.

Environmental conditions are expected to be neutrally favorable with weak upper westward outflow and moderate easterly VWS. The potential for significant tropical cyclone development is medium as this time.

Invest 91B

A broad area of low pressure has formed in the western Bay of Bengal. Deep convection has persisted over the well-defined center, with signs of further organization. Current intensity of the low pressure area is estimated at 25 knots, based on a swath of 20-25 knot winds depicted by earlier ASCAT, as well as a subjective Dvorak estimate of T1.5/25 kt.

Upper level environment is favorable for additional development, with relatively strong outflow to the west and north, associated with an upper level ridge, that is partially offset by moderate (15-20 kt) southeasterly VWS. SST is also favorable at 29C. Mid-level humidity analysed by the GFS is above 70%. The low pressure area continues to track northwestward along a subtropical ridge centered to the northeast.

The ECMWF, GFS and HWRF all support further consolidation over the next 24 hours, until landfall over the southeast coast of India.

In the long term, the remnants of the low pressure area could re-emerge over the Arabic Sea. Drier mid-level environment and stronger southerly shear is expected to lower the chance of re-development. As such, the present forecast terminates at 48 h.

Although it is not explicitly indicated in the intensity forecast, the system could peak at 35 knots (Cyclonic Storm) prior to landfall, in view of the expected favorable environment and the uncertainty in initial intensity estimate.

Intensity forecast:

10/12z: 25 kt (Depression)

11/12z: 30 kt (Deep Depression/Inland)

12/12z: 20 kt (Depression/Inland)

Low pressure area expected to form in the eastern Bay of Bengal

Dynamical models are in general agreement that an area of upper divergence and increased convection will remain across the eastern Indian Ocean and the Maritime Continent next week, which is partly associated with the MJO. Some models suggest eastward propagation of the area of enhanced convection to the West Pacific in the long term.

The ECMWF and GFS develop an area of low pressure in the eastern Bay of Bengal during the next few days. SST in that area is currently at 29C, which is slightly above normal. An anomalous upper anti-cyclone centered across the Tibetan Plateau should induce persistent moderate to strong easterly VWS and environmental conditions are expected to be marginally favorable for TC development during the next week or two.

The potential system is forecast to track westward across the Bay of Bengal under the influence of a mid-level ridge to the north.

Given the model support and the expected upper level environment, there is a moderate confidence of tropical cyclone development during the next week in the aforementioned general area.

Invest 94W (likely develop as a tropical cyclone in the Andaman Sea/Bay of Bengal)

A large area of deep convection has persisted near a poorly-defined low pressure area (located at 8N 101E), in the Gulf of Thailand, with weak mid-level turning offset to the west of the low level circulation. Shortwave IR imagery and upper level analysis from CIMSS indicates the system is in an area of moderate to strong easterly VWS (20 knots). Upper westward outflow is strong and is fueling expansive deep convection in the western quadrant of the system.

Figure 1.29/06z GFS surface pressure forecast at t=54h.

Global models agree that the low pressure system will track west-northwestward into Andaman Sea with gradual intensification. SST is the area is 29-30C.

Figure 2. 29/06z HWRF 200mb forecast run at t=54h.

Poleward outflow in the vicinity of the system is expected to improve in the next couple of days. In addition, the system should begin to round the southwest periphery of the primary mid-level steering ridge by Day 3, when mid and upper level flow should become better aligned.

These factors favor additional tropical development and a tropical cyclone is likely to form in the next couple of days, while the system crosses the east-central Bay of Bengal.

In the extended range, a landfall along the east coast of India cannot be ruled out. Possible inhibiting factors include an increase in southerly VWS and dry air entrainment.

Invest 94W in the Bay of Bengal, expected to become a Cyclonic Storm in the next couple of days.

Deep convection has become better organized in the northwestern quadrant of the partially exposed low level circulation (LLC). Since a couple of days ago, the LLC has also become better defined. The position of the center is now estimated at 12N 88E with medium confidence. Maximum sustained winds are estimated at 25 knots. Subjective Dvorak estimates from JTWC is T1.5/25kt.

The relatively shallow system is tracking northwestward along the southwestward periphery of a low to mid-level ridge. The anticyclone will be the primary steering mechanism and will be responsible for the anticipated turn to the north during the next couple of days.

Upper level shear is favorable at 10-20 knots from a southeasterly direction. Strong outflow toward the west and north has contributed to the maintenance of deep convection in the NW quadrant. Models show gradual alignment of the mid and low level vortices and slow development over the next day or so, when environmental conditions are expected to be favorable for development.

Beyond 36 hours, interaction with dry air and increased southerly VWS should end the development trend or cause weakening.

The present intensity forecast lies on the conservative side, noting that the recent HWRF runs were backing off from substantial strengthening. As the system is expected to remain shallow during its approach to the Indian coast, the track forecast is laid to the west of GFS deterministic run to account for low level steering.

Intensity forecast:

02/12z: 25 kt (Depression)

03/12z: 35 kt (Cyclonic Storm)

04/12z: 40 kt

05/12z: 25 kt (Inland)

06/12z: 20 kt (Inland/Dissipated)

Invest 95W is expected to develop into a tropical cyclone east of the Philippines by next week

An area of disorganized convection across the West Pacific is associated with a weak low pressure area (Invest 95W) centered near 4N 144E. The system is currently located in a weak steering environment and has remained quasi-stationary. Model analysis shows the circulation of 95W extends upward to 500hPa.

Upper level analysis reveals a marginal environment with weak upper level outflow and low to moderate (10-20 kt) south to southwesterly VWS. However, upper level anticyclonic flow is expected to become much better established northeast of the system. At the same time, the mid-level ridge currently centered near the Philippines is forecast to extend eastward in the next few days, steering 95W westward. The direction alignment of mid and upper level flow is expected to contribute to low to moderate shear environment, while upper level westward and poleward outflow improves. In addition, the MJO is at phase 7 (West Pacific) and will enhance deep convection in the area.

Global models are in strong agreement of a developing tropical cyclone east of the Philippines during the next few days and TC genesis confidence is high.

The system is expected to move westward, and gain some latitude when it reaches to southern periphery of the mid-level steering ridge, in a general direction toward the central part of the Philippines, while gradually intensifying.

09/06z GFS 500hPa forecast, valid at t=102 hours.

Although models do indicate some mid-level dry air to the north of 95W, increased outflow and high SST (30C) will support a strong mid-level vortex to resist dry air entrainment, which is also shown by the models.

Overall, it appears that there is a high likelihood of a developing tropical cyclone moving toward the Philippines next week.

SST analysis at 09/06z, showing a large area of 30C waters that could support significant development.

I thought it said 'Hurricane Tycoon' for a second

That would be a horrible cash-in that I would definitely buy into

Tropical Depression expected to make landfall in the Visayas, Philippines as a significant typhoon

The tropical disturbance that I have been tracked over the past few days becomes better defined on satellite.

It is moving toward the west-northwest steadily. Upper level environment is almost ideal for strengthening with dual outflow channel (toward the northwest and southwest) contributing to excellent outflow and low VWS (5-10 knots) from a southeasterly direction. A 12-hour ago ASCAT pass reveals surface winds of 25 knots about a hundred miles northwest of the center.

Since 09z, a central cold overcast has been developing. Subjective Dvorak estimates have risen to T1.5/25 kt at 12z, suggesting the cloud pattern is sufficiently organized for tropical cyclone classification. The initial intensity is assessed at 25 knots.

The system should remain on the southwestern flank of an upper level anticyclone and outflow and VWS will remain favorable. In addition, along track SST is between 29 and 30C which is another favorable factor. Some mid-level dry air is present along-track, but warm SST and a sufficiently strong mid-level vortex will help mitigate this factor. Therefore, significant intensification is forecast for the next 4 days, gradually taking the system to major typhoon strength. After landfall, land interaction will weaken the system slightly.

Although the forecast does not indicate this, but rapid intensification (a 30-kt increase in strength within 24 hours) is possible based on the forecast environment.

Numerical guidance from GFS and HWRF has trended a bit lower with intensity in the 06z cycle. But I prefer to give more weight to earlier runs given the structure of the storm (the mid-level vortex seems fairly aligned with the LLC on satellite) and thus is higher than the 06z runs.

The system will be steered west-northwestward in the next 5 days due to the extending subtropical ridge to the northeast. At present, models do not indicate significant trough/weakness in the ridge that could cause a deviation to the north.

Global models are in fairly good agreement with its track and confidence in track forecast is high.

Intensity forecast:

12/12z: 25 kt (Tropical Depression)

13/12z: 40 kt (Tropical Storm)

14/12z: 60 kt

15/12z: 80 kt (Cat 1 Typhoon)

16/12z: 100 kt (Cat 3 Typhoon)

17/12z: 95 kt (Cat 2 Typhoon)

Typhoon Rai (28W)

Now a strengthening typhoon that takes aim at the Philippines

Earlier today, a 89 GHz microwave imagery at 04z reveals a small but complete eyewall with much warmer brightness temperature in the eastern quadrant of the cyclone. This may have been due to the ingestion of dry mid-level air into the circulation that has suppressed convection. However, at 12z, the cloud pattern has become better organized with symmetrical deep central convection obscuring the center. The latest Dvorak estimates were between T4.5/77kt and T5.0/90kt. ADT around 12z was near 85 kt. On this data, the 12z intensity is raised to a possibly conservative of 80 knots.

The typhoon is located in a favorable area with high (29-30C) SST, low (15 knots) VWS and moderate easterly outflow. Thus steady strengthening is expected during the next 18 hours prior to landfall in the Visayas around 16/06z. After landfall, land interaction should weaken the system slightly until it crosses into the Sulu Sea. Thereafter, increased poleward outflow will fuel a second intensification phase.

Beyond 72 h, much lower SST coupled with increased mid-to-upper level shear will weaken the system significantly, as the cyclone begins to turn northward. The forward speed of the weakening storm should begin to decrease by day 5 as low level north-easterlies compete with mid-level steering.

For the Central Philippines, widespread rain with 3-day rain accumulations exceeding 300 mm is possible along its path.

There is high confidence in track forecast, and intensity forecast confidence is medium.

As the northeast monsoon and cold SST (<26C) is expected to weaken the system, only gale force winds are expected in the vicinity of Hainan Island in the long term. However, upper level winds will transport tropical moisture toward China coast next week and may result in heavier rainfall especially to the northeast of the system.

Intensity forecast:

15/12z: 80 kt (Cat 1 Typhoon)

16/12z: 95 kt (Cat 2 Typhoon)

17/12z: 85 kt

18/12z: 95 kt

19/12z: 70 kt (Cat 1 Typhoon)

20/12z: 45 kt (Tropical Storm)

Typhoon Rai makes landfall over Surigao and tracks across the Visayas.

The typhoon underwent a period of rapid intensification shortly after the previous post and reached an estimated peak of 130 knots (Category 4) before making landfall at around 06z. Since then the infrared eye is no longer evident and the cyclone has weakened some due to land interaction and shear.

The typhoon signal number 4 is still in effect for part of the Visayas.

At 12z the estimated intensity was 110 knots. The storm is expected to further weaken to 90 knots prior moving over the Sulu Sea, after which some strengthening in the South China Sea is expected.

Typhoon Rai: At least 375 dead after powerful storm hit Philippines as governor pleads for more aid

There has been a significant economic losses but the death toll is much lower than the previous deadliest typhoons. This might be due to early warnings and evacuations.

The 2021 Typhoon Season is coming to an end. The chance of having another tropical cyclone in the north hemisphere is becoming lower. This season features less tropical activity than normal (relative to 1991-2020) in terms of Accumulated Cyclone Energy (ACE), while having slightly higher number of named storms than average.

The North Atlantic basin continues to generate more named storms than average (21), while also having more ACE than average (145).

The strongest tropical cyclone in 2021 was Surigae (Northwest Pacific basin) with an estimated 1-minute wind of 165 knots according to JTWC.

A new thread will be created for the 2022 season.