Western Pacific Tropical Analysis: July 26, 2017

Since my last post a week ago, an amazing five tropical storms have developed across the Tropical Western Pacific. Typhoon Noru and Tropical Storm Kulap developed over the basin’s subtropics, very small Tropical Storms Roke and Sonca developed on either side of Luzon, and the recently named Tropical Storm Nesat has emerged from the monsoon trough in the western Philippine Sea. Noru, Sonca, and Nesat are still active currently, although Tropical Depression Sonca hardly counts since it is now well inland over Southeast Asia. It is possible that additional storms may develop in the coming days, but thanks in part to weak steering currents, the establishment of a reverse-oriented monsoon trough, and possible storm interactions, the predictability in the current forecast period is remarkably low.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

Having existed for over five days now, Typhoon Noru is the longest-standing storm in the basin and, if some of the guidance solutions are to be believed, could possibly still be hanging around ten days from now. As of 1500Z July 26, a satellite bulletin from JTWC placed Noru at 30.18ºN, 154.59ºE. JMA’s and JTWC’s latest intensity estimates for Noru are 70 kt and 80 kt, respectively, making it the first typhoon of the 2017 Pacific Typhoon Season. Noru has spent its life thus far looping around the subtropical waters of the Western Pacific.

Noru’s steering has been dominated by two factors the past several days, a blocking mid-latitude ridge and Tropical Storm Kulap. The former has prevented Noru from escaping north into the mid-latitudes, while the latter resulted in Fujiwhara interaction between the two systems. The interaction helped to keep Noru further east in some more favorable conditions while Kulap was flung westward to Noru’s north, where it met its demise in more hostile conditions. With Kulap now gone, Noru is again able to move west and then west-southwest as the primary steering mechanism transitions from a mid-latitude blocking ridge to a subtropical ridge anchored over the northern East China Sea between China, South Korea, and Japan. Members of guidance are actually in good agreement in the near term with this scenario. Conditions along the way will likely be similar to what the system is experiencing now: enough dry air to keep a lid on intensification, but favorable enough otherwise. I would not be surprised to see Noru remain within 10 kt of its current intensity as it carries out its west-southwestward dip over the next four days.

From then on, the forecast gets more dicey. After completing the west-southwestward dip, Noru will be over warmer waters than those found near 30ºN where the system currently is, but also in close proximity to Nesat and a strengthen monsoon trough extending eastwards. In other words, steering becomes very complex, and forecasting beyond four days out becomes a nightmare. The current trend in guidance has Noru heading back east beginning around day five around 25ºN while possibly interacting with new monsoon trough development, but previous solutions have shown everything from escaping north to interacting with Nesat until one or the other’s demise. Some guidance (particularly American guidance) continues to blow Noru up into an exceptionally powerful storm, but I remain skeptical of such solutions. This skepticism has paid off thus far, as Noru has yet to become a major typhoon. Forecasting intensity with so much uncertainty with everything else remains a fool’s errand anyhow, but if forced to put out an intensity forecast for the taus beyond hour 96, it would probably remain very near the current analyzed intensity.

The following tweet from Philippe Papin explains not only the uncertainty with Noru, but in the entire basin far better than I can.

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I want to briefly touch on Tropical Depression Sonca. Sonca made landfall along the Vietnam coast over 24 hours ago from the time of this entry, but the system has held together amazingly well as it treks inland across Southeast Asia. As mentioned, JMA is still classifying Sonca as a tropical depression despite having crossed about half way to the Bay of Bengal. As expected from a system well inland, Sonca’s biggest threat will come in the form of heavy rain.

Tropical Storm Nesat is the newest of the currently classified systems in the Tropical Western Pacific. As of 1800Z July 26, a JTWC satellite bulliten placed Nesat at 17.40ºN, 127.64ºE. Nesat is the system I first mentioned in my July 16th entry that would consolidate along the monsoon trough in late July. Nesat’s development has been just about the only thing that has been predictable in the Tropical Western Pacific recently, and keeping with the recent theme, that predictability only goes down from here.

As seen in the loop above, Tropical Storm Nesat is characterized by strong, cold central core convection. However, it appears that the system may be taking on the Central Cold Cover pattern, or CCC pattern. Such patterns are usually a result of some mid-level shear undercutting the anvil, and bands 9 and 10 from Himawari-8 do indicate that light northerly shear of this variety is occurring. A recent GPM pass also indicates that most of Nesat’s convective structure is confined to the south of the center. Considering Nesat’s present state, development in the immediate short term if any should be slow to occur.

Nesat is currently moving with a slow north-northwestern motion. This general motion to the northwest or north-northwest should continue for the next couple of days. At the time, it appears that will remain far enough away from Noru to avoid any direct interaction with the typhoon, but such a scenario cannot be completely ruled out at this time, especially if Nesat tracks a little slower than currently expected. As it stands right now, Nesat is expected to be near Taiwan by tau 72. Northerly and then easterly shear may be something that Nesat has to contend with its entire life, but it is possible that the system could intensify into a typhoon before landfall.

92W is one of the two invests currenly declared across the Tropical Western Pacific. Located in the South China Sea, 92W is developing along the same monsoon trough that Tropical Storm Nesat emerged from. It is possible that development could occur with this invest, but easterly shear, partially from the larger and stronger Nesat, would likely keep any development weak before moving inland into southern China.

Invest 93W is the other active invest. The system is located well east in the basin’s subtropics, near where Kulap originated from. At the moment, I do not expect development due to the magnitude of vertical wind shear, but this is an area worth keeping an eye on, especially once Noru moves WSW and helps draw out monsoon southwesterlies across the basin.

As mentioned early on in this post, more development is possible over the next several days as the monsoon trough begins to extend well east across the entirety of the basin. The monsoon trough is expected to take on a reverse-orientation (more north the further east along the monsoon trough, opposite of a typical setup), extending the eastern end well above 20*N. Such a scenario offer up not only an opportunity for multiple new storms, but also interactions between these yet to develop system. Guidance almost always struggles with such a scenario, but most members agree on the general idea. The specifics remain to be seen though, and I’m not even going to pretend to know how it will all play out. Partially for entertainment purposes, the 12Z July 26 GFS run is provided below.

Thank you all for being patient with me getting this new post up as I have been dealing with moving into a new place. The next update should be up this weekend. Until the next entry is posted, analyses and updates in forecast philosophy will arrive in the comments section.

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Western Pacific Tropical Analysis: July 19, 2017 – Subtropic Shenanigans

After an exceptionally quiet start to the 2017 Pacific Typhoon Season, the Tropical Western Pacific is about to enter a more active period, and some of this activity appears like it will becoming from some unlikely sources. Three invests are currently declared across the basin, and all have at least some shot at earning a name. From west to east, invests 95W and 97W are currently located over the eastern waters of the Subtropical Western Pacific, and hail from non-tropical origins. Invest 95W, which is also a JMA tropical depression, probably has the most immediate chance at development in the basin, but the future of 97W looks particularly interesting. Invest 96W resides in the South China Sea and has a chance to follow in Talas’s footsteps. The remnants of a convective complex off the southeastern Kyushu coast may also become tagged as an invest at some point. The monsoon trough also returns to the Philippine Sea this week, and the potential for development here beyond the five day period appears higher than average.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

Of all the development prospects, Tropical Depression/Invest 95W is presently the furthest along. Per JMA as of 18Z July 19, the system was positioned at 26.5ºN, 161.2ºE and moving with only a slow westward drift. JMA has begun to issue advisories on Tropical Depression 95W, meaning that they are expecting to upgrade it to a tropical storm within 24 hours. Should their current forecast verify, it would be named “Noru.”

95W is one of two invests currently designated that have non-tropical origins (the other is 97W a little to the east). Unlike with 97W though, the low level vorticity isn’t now just working its way down to the surface and has been around for a few days. The most recent ASCAT pass of 95W revealed a fairly organized but not quite closed circulation with winds of 25-30 kt just east of the center. Considering the improved convective evolution and development of upper level outflow since the time of that pass, it’s not hard to imagine that 95W could end up being named as the JMA is currently forecasting. In fact, I would be surprised if 95W is not named at this point. Regardless, 95W will be in no hurry moving to the WNW and then NW as it rounds the southwestern edge of a blocking mid-latitude ridge.

Intensity guidance is not particularly aggressive with 95W, and the only member that brings it above the 64 kt typhoon threshold is the HWRF. Considering the abnormally warm waters that currently reside in the Subtropical Western Pacific, moist surrounding airmass, and sheltered location from stronger upper level winds below the blocking ridge, such a forecast doesn’t seem outlandish. However, I’d be more inclined to think a 50-60 kt peak intensity is more likely. Favorable conditions will only last about 96 hours at most before 95W arrives in the hostile exit region of a splitting jet rounding the top of the subtropical ridge centered over China.

Back in the South China Sea, a disturbance located near the eastern end of a weak monsoon trough has been designated as Invest 96W. As of 18Z July 19, the ATCF position for 96W was at 13.7ºN, 116.4ºE, or just west of the Philippines. 96W has been characterized by intermittent and disorganized bursting convection and does not appear to be particularly well marked at the time. 96W is currently experiencing a decently favorable setup reminiscent of the recent Tropical Storm Talas. In fact, 96W is expected to follow a very similar path to Talas. However, 96W’s initial organization is not on par with Talas initially. This difference in organization may prevent 96W from becoming a classifiable tropical storm. With about 72 hours before the system is expected to move inland near the China/Vietnam border, it wouldn’t catch me off-guard to see 96W develop. However, the poorer initial organization coupled with a slightly weaker belt of monsoon southwesterlies make me believe that no development is the most likely outcome.

The last and probably most interesting of the three currently designated invests is 97W. Like 95W, 97W currently resides in the waters of the Subtropical Western Pacific. As of 18Z July 19, the ATCF position for 97W was at 24.1ºN, 178.6ºE. This places 97W to the east of 95W and very near the boundary of the basin with the Central Pacific. 97W is an upper level low that has begun to work its way down to the surface.

Invest 97W has become somewhat of the guidance’s darling as it meanders northwest and then west-northwest across the Subtropical Western Pacific. After fully working its way down to the surface and becoming warm core, the majority of the last few guidance suites have blown up 97W into an intense system over the Subtropical Western Pacific. This is a fairly unusual solution; intense systems are fairly rare in the Pacific subtropics. Most of the intensification appears to occur after the system has moved to the northwest some, into approximately the area vacated by 95W. As previously mentioned, it is an area of sufficiently warm sea surface temperatures, abundant moisture, and low shear, so strengthening shouldn’t be totally unexpected. However, climatology does not favor some of the sub-950 mb solutions seen in recent guidance.

While modeled conditions currently look favorable for 97W over the next week, it won’t take much to introduce some hostilities. 97W is currently dancing around near the subtropical jet stream. The subtropical jet stream is currently expected to weaken and move east-southeastwards away from 97W. However, should it exert its influence on 97W longer than expected, the more intense solutions would fail to come to fruition. Alternatively, the splitting jet expected to impact 95W could extend eastwards and bring upper shear to 97W or the blocking mid-latitude ridge could introduce dry air subsidence trough subsidence that 97W could then entrain. The point is it takes absolutely perfect conditions to be maintained for an appreciable time period to get a strong system in the subtropics, and I’m not entirely sold that is currently the case. At the moment, I am expecting 97W to achieve a maximum intensity of 75-85 kt in about 5 days. However, at this point, this is an extremely low confidence forecast. The one thing that is almost for certain is that 97W should make for an entertaining system to track after an exceptionally quiet start to the 2017 Pacific Typhoon Season.

One more system that is not currently designated but deserves a mention currently lies off the southeast coast of the Japanese island of Kyushu. The system originates from a Mesoscale Convective Complex that moved off the coast about 24 hours ago and appears to be gaining some organization. However, the window for this system to develop is rather small. Strong upper level northeasterly winds are expected to begin raking over the system in about 36 hours, undoing any organization that occurs up to that point. Brief development isn’t an impossibility, but it is also not expected at this time. It wouldn’t surprise me to see this system tagged as Invest 98W though.

In addition to all the current systems in various states of development, the monsoon trough is expected to extend back to the east and into the Philippine Sea within the next five days. It is around that time that guidance is beginning to pick up on an emerging system in the Philippine Sea. It’s still too early to forecast an intensity for a system that has yet to even form an initial disturbance, but I do believe that this potential system’s ceiling is the highest yet observed the season. Whether that potential is realized is yet to be seen, but confidence in development is considerably higher than average. This possible system is most likely to track northwest or north-northwest into a break in subtropical ridging, in the general direction of Taiwan and the southern Ryukyus.

My next entry will likely arrive this weekend, but with packing and moving in my near future, it is not a 100% certainty. Until the next entry arrives, analyses and updates in forecast philosophy will arrive in the comments section.

Western Pacific Tropical Analysis: July 16, 2017

After a surge in the Southwest Monsoon, Severe Tropical Storm Talas has managed to develop in the South China Sea and headlines the Tropical Western Pacific. After skirting Hainan, the system is headed for a north-central Vietnam landfall, and Talas brings the threat for heavy rainfall along its track as it moves inland. Talas is the only system to monitor in the near term, but there are some signs in the medium range that the Southwest Monsoon may extend back across The Philippines, reestablishing the monsoon trough in the Philippine Sea in late July.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

As mentioned, Severe Tropical Storm Talas is currently the center of attention in the basin. As of 12Z, Talas was positioned at 18.5*N, 107.2*E. This is along the southern edge of the Gulf of Tonkin, and closing in on the north-central Vietnam shoreline. 50 kt is the consensus intensity estimate from both JMA and JTWC at the time.

Talas has strengthened more than I had expected thus far. I was skeptical it would gain enough organization to become classified in the days leading up to its development, but persistent convective activity near the vorticity maximum allowed the system to properly consolidate and become a named system while in the open water of the South China Sea. Since that time, Talas has managed to steadily strengthen up to the time of this post. As of 06Z July 16, Talas even managed to meet JMA’s 50 kt severe tropical storm threshold, the intensity it still carries as of the most recent 12Z analysis. However, time has just about run out for Talas, and the system will be making landfall on the Vietnam coastline in a matter of hours. Heavy rainfall is the greatest threat Talas carries with it as it moves inland across Southeast Asia.

Elsewhere across the Tropical Western Pacific, conditions remain generally hostile for tropical cyclone development. The tropical upper tropospheric trough (TUTT) remains oriented east/west along 20*N across much of the basin, and a breakoff TUTT low is currently traversing westwards across the Philippine Sea. Mid-level heights also remain higher than usual, indicating subsidence from the upper levels remains an issue. However, arguably the biggest issue that currently is plaguing the basin is the lack of low level equatorial westerlies extending east across the basin. These westerlies, associated with the Southwest Monsoon, are essential for establishing the monsoon trough, from which the vast majority of basin activity originates. Without these monsoon westerlies/southwesterlies, and by extension the monsoon trough, it becomes much more difficult to get tropical cyclogenesis, even with otherwise favorable conditions.

In the near term, not much is expected to change across the Tropical Western Pacific. However, guidance appears to be trying to bring the monsoon trough back in the medium range. Beginning in about seven days, ensemble means extend the monsoon southweserlies back across the Philippines and into the Philippine Sea. It’s too early to be confident in any type of tropical cyclogenesis around that period, but coupled with falling mid-level heights, conditions appear to be trending towards more favorable conditions towards the end of July.

My next entry will likely arrive by Wednesday. Until the next entry is posted, analyses and updates in forecast philosophy will arrive in the comments section.

Western Pacific Tropical Analysis: July 13, 2017

The Tropical Western Pacific remains rather quiet at the moment, but at least two area will have a non-zero chance for tropical development in the next few days. The first area is currently located in the subtropical waters south of Japan has been tagged as Invest 93W. The window for 93W is brief though, and I do not expect it to develop. The second area is only just becoming discernible in the South China Sea as a modest surge in the Southwest Monsoon begins to transpire. While I do believe that development chances are higher with this emerging disturbance than they are with 93W, development prospects are still not especially good. Should it develop, the system’s ceiling will remain very low. No other areas are expected to emerge with development prospects over the next seven days.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

As mentioned my previous entry, a piece of energy became orphaned from its parent system from the mid-latitudes. This system has lingered in the subtropical waters south of Japan near Chichijima for the past couple of days. In that time it has gained enough organization to become tagged as Invest 93W. As of 18Z July 12, 93W was positioned at 25.1*N, 140.8*E. An RGB composite visible loop of 93W is provided below

As it stands right now, 93W is probably near the zenith of its organization. From this point onwards, it will likely begin a losing battle with westerly shear and dry air (both seen in the July 13 00Z Chichijima sounding). An upper level low is located to the system’s north is the primary reason for these increasingly hostile shear, and the dry air is in constant supply due to upper level convergence/subsidence on the system’s northwest flank. These two factors will bring 93W to its demise over the next 2 or so days as it continues to meander the subtropical waters in the vicinity of Chichijima.

Further to the southwest in the Tropical Western Pacific, a modest surge in the Southwest Monsoon is beginning to ramp up across the South China Sea. This surge is amplifying convergence near the tip of the low level jet, leading to increased convective activity. Over the next few days, surface pressure falls from this thunderstorm activity should help to spawn a broad and weak circulation. The 12Z EMCWF’s depiction of this evolution is provided below.

The main question with this potential system is will it have enough time to tighten its broad monsoon circulation enough to be classified before moving inland over southeastern Asia in about four days. At the moment, I am leaning a little more towards it staying too broad, giving it about a 40% chance at classification. Even if it does earn classification, any system that develops will remain weak due to the time constrains mentioned above.

Aside from these two prospects, the Tropical Western Pacific will remain uncharacteristically hostile for at least the next week. At the low levels, there is very little hint of any monsoon southwesterlies anywhere east of the Philippines. Without these southwesterlies needed to maintain the monsoon trough, any disturbances along the Intertropical Convergence Zone have been weak and unable to develop. Aloft, 500 mb heights remain higher than normal, indicating continued upper level subsidence. An anticyclonic wave break in the mid-latitude Western Pacific has also helped to reinforce the Tropical Upper Tropospheric Trough, which is currently covering an abnormally large area across the heart of the basin. Both the 500 mb normalized height anomalies and 355 K Potential Vorticity from the July 12 18Z GFS is displayed below.

If no tropical development occurs by this weekend, 2017 year to date Accumulated Cyclone Energy (ACE) will fall below that of 2010, making 2017 one of the three least active seasons up to that point since 1970.

My next entry will be posted this weekend (Probably Sunday). Until the next entry is posted, analyses and updates in forecast philosophy will arrive in the comments section.

Western Pacific Tropical Analysis: July 9th, 2017

Keeping the status quo so far this year, The Tropical Western Pacific will likely remain relatively quiet for at least the next week. Upper level subsidence will continue to rule, and any disturbance that does manage to gain at least minimal organization will likely struggle with a PV Streamer-enhanced Tropical Upper Tropospheric Trough. A disturbance originating from the tail end of a lifting trough south of Japan and a potential disturbance on a monsoon trough near the Philippines have some chances at development, but an absence of tropical cyclogenesis is the most likely outcome over the next seven days.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

The biggest reason I am currently so bearish with development prospects has to do with upper level subsidence. Guidance is persistently painting the Tropical Western Pacific south of 25*N or so with heights of 1-2 standard deviations above normal (seen below in the EPS 500 mb heights and normalized anomalies from 12Z, July 9). Now, this is in the tropics, so given the relatively small variability in heights aloft, a 1 or 2 SD increase in heights isn’t resulting in a death ridge. However, these heights are a symptom of something else occurring: upper level subsidence. This sinking aloft helps to squelch typical tropical convection. It isn’t an end all of potential tropical cyclones, but it takes a disturbance featuring more robust low level convergence to overcome this impediment. Additionally, an anticyclonic wave break in the Mid-Latitude North Pacific should reenforce the Tropical Upper Tropospheric Trough, stretching it east/west across much of the basin between 15-20*N (illustrated in 18Z GFS’s depiction of 355K cyclonic PV from July 9). The long and short of it all is that the Tropical Western Pacific is not particularly favorable for tropical development at the moment.

The first area of interest that has at least some small potential for development currently exists south of Japan (pictured and annotated below). An area of convection has developed with a bit of mid level vorticity left behind by a parent mid-latitude trough.

Steering currents should remain weak for the next couple of days in the subtropical waters south of Japan, so the orphaned disturbance will not be moving much. Modest northerly shear of around 15 kt and a punch of dry air from the mid-latitudes (both pictured from July 9 18Z GFS output below) should keep the disturbance from developing before rejoining the mid-latitude flow in 3-4 days, but since it will be sitting over water as warm as 30*C, it doesn’t hurt to keep an eye on it. Still, I put development chances well below 10%.

Part way through the week, a surge in the southwest monsoon from the Bay of Bengal should help sharpen the monsoon trough in the vicinity of The Philippines (pictured below via 12Z ECMWF MSLP and 850 mb winds initialized July 9). This should lead to increased convection over the South China Sea and western Philippine Sea. A surge in the southwest monsoon, even a more modest one like currently modeled, is often a winning formula for tropical cyclogenesis this time of year, but considering the upper level subsidence that exists across most of the basin, it’s not surprising that guidance is only lukewarm with development prospects this go around. Canadian guidance is the most bullish with development (as is typical), while American guidance is very bearish (no GEFS members develop a system). European guidance lies somewhere in the middle. Short term trends with European guidance have trended towards some sort of development just east of The Philippines, but it not at a confidence inspiring level as of yet. The operational ECMWF picked up development for the first time on the July 9 12Z cycle with at least modest ensemble support (12Z July 9 EPS MSLP normalized spread pictured below). Considering any development would still be 5-6 days from now, more consistency will be needed in successive guidance suites to accurately ascertain proper development prospects, but I’d probably put a 30% chance or so of development from the monsoon trough on either side of the Philippines by the end of the week.

My schedule does not look particularly heavy this week, so I may be able to fit in a mid week update this week. If not, the next entry will arrive around this time next week. Until the next entry is posted, analyses and updates in forecast philosophy will arrive in the comments section.

Blog Preview & State of the Western Pacific

Howdy to all! This is my first blog in several months and the first one in its new location. I had previously been posting my blogs on Weather Underground, but after having been a member for over ten years, the site has changed format and no longer allows me to publish them there. I had been mulling about a few options, but with the Northern Hemisphere likely about to pick up with tropical activity, I decided to pull the trigger with WordPress. Since I’m new to WordPress, there may be some hiccups and design changes, at least initially. Blog formatting will likely remain about the same though, with a new entry roughly once per week, usually centered on the Tropical Western Pacific. This first entry will be a little different though. To get things started off, I will be discussing what has happened so far in the 2017 Pacific Typhoon Season.

***NOTE: While I would consider myself well-learned in meteorology, I am still a student with more to learn before becoming a degreed meteorologist. This forecast is not from an official source and should not be treated as such. For official information, please refer to your local weather agency.***

As of 18Z, July 7th, the 2017 Pacific Typhoon Season has seen five JTWC systems classified as at least tropical depressions, and of these five, three became JMA named tropical storms. Tropical Depression 01W originally developed in the Philippine Sea and regenerated in the South China Sea in January. February and March were devoid of classified systems, and things were quiet until the second half of April, when Tropical Depression 02W developed just east of the Philippines, not far from where 01W developed about three months prior. About a week later, the first named storm developed in the central Philippine Sea. Named “Mufia” by the JMA, the system only amounted up to a weak, short-lived tropical storm with no land impacts.

May was once again was devoid of tropical cyclone activity, and June only saw one system, Tropical Storm Merbok. Merbok was a system that developed in the South China Sea and quickly moved north into Southern China, never having much time to strengthen. Mufia and Merbok were the only two names storms in the first half of the calendar year.

Just in the past week, the year’s third tropical storm, named Nanmadol by the JMA, impacted Japan. Nanmadol developed on July 1st and headed on a brisk northwestward trajectory towards the southern Japanese Ryukyus. The system and passed just barely west of Ishigakijima rated as a Severe Tropical Storm by JMA and a strong Tropical Storm by JTWC (since JTWC doesn’t have a Severe Tropical Storm Classification). However, satellite and radar trends coupled with obs from Ishigaki indicated that Nanmadol may have just exceeded the threshold for typhoon intensity. Regardless, Nanmadol is the strongest storm recorded thus far this season in the Tropical Western Pacific. Nanmadol then recurved within the East China Sea and made landfall on the western coast of Kyushu, near the Japanese city of Nagasaki. After passing along the southern Shikoku and Honshu, Nanmadol lost tropical characteristics by 12Z, July 4th.

So far this Pacific Typhoon Season, storms have been fairly weak as well as few and far in between. This has led to a low total in Accumulated Cyclone Energy (ACE). I like to use ACE (along with a few other metrics) to keep track of seasonal tropical cyclone activity since it factors in both storm strength and longevity. As of 18Z July 7th, only 4.1775 units of ACE (10**4 kt**2) have been accumulated thus far this year in the Tropical Western Pacific. This is well below the 1970-2016 average of 45.6272 units by the end of July 7th. In fact, since 1979, only 1983, 1998, and 2010 have had lower ACE totals by July 7th. A graph showing the progress of 2017 ACE compared to the last several years dating back to 2010 as well as the 1970-2016 average has been provided near the top of this post. Tropical cyclone activity does climatologically begin to ramp up this time of the year, but it is going to take a rather active period to make up the deficit that has already developed.

A return to more normal posts featuring analysis and forecasting will begin next week. Should some interesting feature catch my eye, I will post about it in the comments section.