http://www.nrlmry.navy.mil/nexsat-bin/nexsat.cgi?BASIN=CONUS&SUB_BASIN=focus_regions&AGE=Latest&CCA=NorthAmerica-CONUS-East&SSC=GulfOfMexico-x-x&PRODUCT=vis_ir_background&SUB_PRODUCT=goes&PAGETYPE=static&SIZE=Full&PATH=NorthAmerica-CONUS-East/GulfOfMexico-x-x/vis_ir_background/goes&&buttonPressed=Animate&ANIM_TYPE=Instant

I'll kick off this year's discussions with this link to a high-res satellite sequence showing an organising tropical disturbance headed for parts of Texas and Oklahoma that really don't want to be seeing it, having had their wettest Mays on record this year.

Recent model runs indicate that this one system could, in the space of a day or two, dump between 2 and 5 inches (approx. 50-125 mm) across a wide swathe of each state, and as much as 10 inches (250 mm) where convection trains over particularly unlucky locations.

The exact track remains uncertain, with the balance potentially shifting more toward Texas or Oklahoma - as yet we can't be sure who's going to fare worst.

It's possible that the system is also on the brink of transitioning into a fully tropical cyclone, having been of hybrid nature so far. This means a risk of strong winds to accompany the rain.... already the max. sustained speeds are as high as 50 mph.

Then there's the issue with having this system expected to track across a vast area of highly saturated soils and air with record-high moisture content for the time of year. In these conditions, the land can act like a shallow area of very warm ocean. In 2007, Tropical Storm Erin managed to intensify from a system with less than 25mph winds to near 60mph, all while over saturated soils and within a very moist atmosphere. Could history repeat itself in some guise 8 years on? Very concerning stuff.

As usual, much of this information is being relayed from an excellent blog post by Dr. Jeff Masters: 

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=3018

As a sidenote... check out this composite satellite sequence that lets you look back over a whole week of weather:

http://www.nrlmry.navy.mil/nexsat-bin/nexsat.cgi?BASIN=CONUS&SUB_BASIN=focus_regions&CCA=Europe-x-x&SSC=x-x-x&AGE=Latest&PRODUCT=vis_ir_background&SUB_PRODUCT=goes&SIZE=Thumb&PATH=Europe-x-x/x-x-x/day_natural_color/seviri&&buttonPressed=Animate&ANIM_TYPE=Instant

Bill has made landfall as a 60mph tropical storm, with locations such as Houston and Dallas in the line of fire for the excessive rain:

Some places could see as much from this one event as they did during the whole of the record-breaking May.

Remember the above is in inches so the totals are projected to be as high as 240 mm in the above image.

So far since landfall, Bill has shown little sign of weakening, in fact there are faint suggestions of improved organisation to the storm. Is the Brown Ocean Effect taking place? Too early to be sure.

In stark contrast to all this, a strong ridge of high pressure looks determined to keep Florida dry and hot for the foreseeable future, unusually so for some parts.

How about this: http://journals.ametsoc.org/doi/abs/10.1175/2011MWR3593.1

 - though the term 'Brown Ocean Effect' was dubbed by Anderson and Shepherd (2013), see

http://www.nasa.gov/content/goddard/brown-ocean-can-fuel-inland-tropical-cyclones/#.VX5Hf6Z4Es1)

for some great explanation and graphics regarding the behaviour of 2007's Erin 

I always enjoying looking through this thread in summer (to remind myself that summer exists in some places ), thanks SC 

The monsoon has arrived in Mumbai - nearly 8 inches of rain recorded over parts of the city yesterday/overnight and flooding continuing today, so I assume another high total once the data comes in:

http://www.ndtv.com/mumbai-news/mumbai-rain-high-court-schools-shut-down-political-events-cancelled-773208?utm_source=taboola

http://www.bbc.co.uk/news/world-asia-india-33197680

The monsoon is predicted to be weaker this year overall I think, possibly due to the El Nino link, so it'll be interesting to see how it pans out. 

http://timesofindia.indiatimes.com/india/IMD-Monsoon-to-be-good-through-June/articleshow/47727309.cms

http://synoptic.envsci.rutgers.edu/site/radimg/anim_serc.gif

http://i.imgbox.com/0vQazjZE.gif

Amazingly, Bill is still very much an organised system even though it's been inland for four days now.

The recent blow-up of convection right over the center (as of 4pm BST Saturday) is more like you'd expect to see if it was over open waters. There has reportedly been a drop in the minimum pressure associated with the system.

Model projections have the system merging with another low in a few days time and progressing east into the Atlantic, where another merger takes place, this time with a mature low to the southwest of Iceland. This has the effect of amplifying the pattern slightly, this allowing a ridge to develop from the Azores to the UK. 

In other words, ex-Bill is the reason for the changes seen over the past few days with respect to how things unfold later next week.

I'm off to Mexico on Wednesday and I'm hoping for some nice electrical storms to experience in the evenings but nothing too disruptive and plenty of sunshine during the day.  Hurricane force storms on the Caribbean coast are pretty rare at this time of year, so fingers crossed we're not the exception to the rule.

With some huge positive SST anomalies on the Pacific side of S. America, a token of the moderate to strong El Nino taking place, the risk of a tropical cyclone spinning up is higher than average, but hopefully climatology will guide those storms away from you Caz!

I'll be heading south soon too, but way over in the Med. so probably safe from hurricanes 

Quite a few storms in the western Pacific at the moment:

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/ab/abpwsair.jpg

Chan Hom

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp0915.gif

This one potentially looks nasty, currently forecast to make landfall about 150 miles south of Shanghai on the 10th as a Cat 4 equivalent. GFS has it further south again, striking northern Taiwan and possibly Taipei, so it's certainly one to watch wherever it ends up tracking.

Nangka

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp1115.gif

Nangka could head for Japan and is forecast to reach cat three (strengthening) by the end of the current forecast graphic, though there is a chance its track may swing it north-eastward just to the south east of Honshu.

Lingfa

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp1015.gif

Lingfa is crossing the Philippines currently and is heading to Taiwan but is much weaker and less organised.

Here's the latest global SST anomalies and corresponding absolute values, courtesy of NOAA:

We see what is close to a classic moderate to strong El Nino signature across the Pacific, the only real deviation being the small extent of the negative anomalies in the W. Pacific. It's this which is playing a large role in generating so many typhoons out there, from one side of the basin to the other.

Waters of 26*C or more can support tropical cyclones, and water of 28*C or more is usually good for super-typhoons. Once you get to 30*C or so then you're talking about the potential for some monstrous systems at the high end of the possible range i.e. 160-200 mph sustained winds. In the absolute values map we can see that across a vast area, wherever wind shear falls low and there is some deep convection around (which is true of large parts of the equatorial Pacific right now), there's the risk of strong typhoons developing.

Speaking of deep convection brings me nicely to what was the real trigger for the chain of cyclones currently in action across the Pacific - a record breaking MJO event. 

This event is very nearly off the scale, indicating exceptionally strong wind anomalies, associated with deep convection on an unusually widespread and intense scale across the W. Pacific.

The resulting cyclones are now driving one of the strongest westerly wind bursts (WWBs) ever seen across the Pacific at this time of year. This push against the usual easterly trade winds is what piles up warm water in the E. Pacific and can bring about - or in this case enhance - an El Nino event.

Having a WWB so powerful when there's already a moderate El Nino in place suggests that a strong event is easily achievable, on a par with that of 1997-'98. With this in mind, the E. Pacific could be a dangerous place over the coming 4-5 months, as hurricanes find themselves able to take advantage of the unusually high SSTs. There have already been a number of impressive storms in that region so far this year, including among the earliest on record relative to the traditional start of the season.

By contrast, El Nino's tend to generate hostile conditions for hurricanes in the Tropical Atlantic, with lots of high wind shear. On top of that we can see that much of the main development region (MDR) - stretching east from the Caribbean - is a degree or two cooler than average. Yet we do see positive SST anomalies across the northern half of the Gulf of Mexico and also the Subtropics, so these regions may be worth keeping an eye on, particularly the GOM as it only takes one severe landfalling system to make a season infamous.

Thanks SC - a very interesting set of events these storms then. If you get time, a bit of blurb on the MJO charts on your chart thread would be great 

Chan Hom has made landfall, apparently only as a Cat 2, though close to Shanghai and likely to bring flooding problems. I'd imagine given the local geography of Shanghai, that a really strong typhoon pushing up from the SSW (a little like Chan Hom) could produce serious storm surges there.

North Korea looks like getting a bout of torrential rain as the remnants pass directly overhead, which could be very welcome or disastrous.

http://www.weather.com/storms/typhoon/news/typhoon-chanhom-china-shanghai-okinawa-jul2015

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp0915.gif

Nangka is still trundling away in the Pacific, and looks to be doing some fairly acrobatic track changes in the next few days but is likely to eventually head for central/southern Japan as a Cat 1 or 2:

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp1115.gif

Japan has already suffered minor flooding from heavy rainfall in recent days, so I doubt they're too pleased at the prospect of a typhoon running up the length of the country.

There are 5 other tropical formations in the central/east Pacific currently which seems like a lot though I'm not sure whether it is or not. WTPN21 looks like it could develop into something more substantial off the Mexican coast in coming days:

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/ep9815.gif

In terms of the monsoon, after a strong start it has become much weaker into early July, which was forecast and seems to be being blamed on the strong El Nino:

http://www.deccanherald.com/content/488252/southwest-monsoon-comes-screeching-halt.html

A trough coming off The Carolinas has managed to morph into an Atlantic tropical storm named Claudette.

Meanwhile, in the Pacific...

Yeah. That basin takes the gold, the silver and the bronze.

Nangka and Dolores are the ones with the most potential in terms of future intensity, with some model runs turning them into real monsters. I have seen versions of Nangka with central pressures in the range of 890-910mb which is pretty extreme. Not only that but it looks like tracking toward Japan from the southeast, much like how Hurricane Sandy of 2012 approached the U.S.

Such an angle of attack makes a storm far more dangerous, especially if it holds up at near peak intensity until just before landfall, which is what recent model runs are suggesting. I fear that a substantial part of Japan is at risk of catastrophic damage.

Nangka made landfall a few hours ago as a relatively weak storm in the end, however rainfall will likely cause big problems. Weather.com saying as much as 3ft (36inches) could fall in some mountainous areas - that's the equivalent to an entire year's worth of rain if not more for many parts of the UK in just a few days:

http://www.weather.com/storms/typhoon/news/typhoon-nangka-west-pacific-japan-july2015

The radar loop still shows the structure of the storm shortly after landfall, and there's a pretty intense outer band heading towards Tokyo as well currently:

http://www.weatheronline.co.uk/cgi-app/radar?LANG=en&STRUCTUR=_&CONT=jaja&CREG=japan

The next storm, Halola, could also hit Japan. Possibly a bit further north this time, around Tokyo?

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/cp0115.gif

...and although Dolores is set to weaken and fizzle in the eastern Pacific, it's track is a little odd, taking it in a northward direction not far off the California coast. Not sure how often, if ever, ex-tropical storms swing back into Cali but I did see a few GFS runs a while back modelling just that with this storm. For now though I think it is more likely to stay off the coast. 

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/ep0515.gif

Well Dolores did swing back round as it slowly petered out, or at least it tracked near enough to coastal Cali to trigger thunderstorms. Turns out it isn't that common either, with both San Diego and LA breaking their July single day rainfall records on Saturday. Makes you wonder what's in store for the rest of the year in that part of the world as a result of El Nino...

http://www.latimes.com/local/lanow/la-me-ln-more-rain-and-thunderstorms-los-angeles-20150719-story.html

Accuweather are saying there could be some tropical storm development from a stalled front off the eastern seaboard in the next week or 10 days as well, though the models aren't picking up much currently:

http://www.accuweather.com/en/weather-news/tropical-system-atlantic-late-july-southeast-gulf-coast-watching-for-danny-erika/50550073

Elsewhere there seems to be a bit of a lull at the moment, with only Halola slowly making its way towards Japan. It now looks as though Halola won't be so bad, weakening to trop storm strength at landfall, but with it arriving in roughly the same area as Nangka, flooding could be a worry again:

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/cp0115.gif

and there's a trop cyclone formation warning off the west coast of Mexico, although it looks fairly weak at the moment and probably won't follow a track that brings it into contact with land: 

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/ep9915.gif

http://www.weather.com/news/news/most-floridians-unconcerned-hurricane-threat-poll

No hurricane has made landfall in Florida for 10 years, near enough. So 60% of 18-34 year olds think that there is no chance of it happening again - heads in sand time? But seeing how the present season is going, they could well be right for another year yet!

Behold!

http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/wv_lalo-animated.gif

There's a classic Cape Verde type tropical cyclone in the Atlantic. It's been a long time since I last had a chance to say that.

The recently named Tropical Storm Danny is a compact system, which opens the door to rapid changes in intensity, while also making it tough for the prediction models to get a good grip on it, except perhaps the highest resolution specialised models such as HWRF.

The track is predicted be generally WNW for the next few days to as long as a week. This would mean Danny bothering the Leeward Islands and other parts of the Caribbean. The exact path may make or break the storm - as mountains could easily finish off such a small system. Assuming it doesn't build a lot in size during that time... one can never be entirely sure with these things.

Trouble is, if Danny intensifies faster than anticipated - entirely possible given the small size - then a more NW track could occur, avoiding the Caribbean island chains, but probably taking the system into unfavourable conditions with high wind shear, leading to its demise.

Before if and when that happens, conditions look remarkably favourable, with wind shear as low as 5 knots and a large moisture shield around the storm which may protect it from extensive dry air to the north. It represents a major break in the usual regime of high wind shear brought by El Nino events.

In light of this, the official NHC outlook brings Danny up to Category 2 strength (at least 100mph max. sustained winds) by Sunday:

Despite all this, the Pacific remains a more dramatic place, with two super typhoons spinning away and projected to keep doing so for quite some time, not affecting any land areas until about a week from now:

(Enhanced image from the MTSAT satellite, collected from the Northwest Pacific at 1532 GMT Tuesday, showing twin typhoons Goni (left) and Atsani (right). Image credit: NOAA/NESDIS.)

http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2015/08/150819_himawari8_ir_STY_Atsani_anim.gif

Some stunning high-res IR imagery of category 5 Super Typhoon Atsani.

What's really striking is the sheer size of the eye feature, and how well you can see it's rapidly spinning nature.

Meanwhile, TS Danny is having trouble with dry air. Hardly news is it? 

Danny starting to make the news and NCEP expecting to switch to CWD status this weekend.

http://edition.cnn.com/2015/08/20/world/hurricane-danny/

The first Atlantic hurricane of the season, and what a compact one it is!

There's been some increase in size overnight though, and in fact Danny is looking rather impressive at the moment, with very deep convection despite a fairly dry environment around the system.

Here's an IR loop:

http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/rbtop_lalo-animated.gif

Danny could have sustained winds as high as 100mph now... awaiting the NHC update for the official assessment.

I wonder if this will change the pattern that had been plaguing us for 2 months non-stop and bring a better change to more HP dominated pattern?

Good question Jiries . It will depend on whether Danny recurves and engages with the mid-latitude westerlies.

At the moment the consensus is for a track that eventually landfalls in the U.S. without recurvature.

However, there are signs that the tropical Atlantic will be quite favourable for tropical cyclones in the near future, with a number of tropical waves emerging off Africa which have the potential to become future tropical storms or hurricanes.

It appears that a particular sequence of events involving SSTs etc. (about which I'm far from certain at this stage) has produced a rather unexpected break in the El Nino-driven state of affairs (high wind shear tearing tropical waves apart before they have a chance to develop).

Danny's doing well at the moment, having attained category 2 hurricane status earlier today. In fact, the system is currently moving through a region that was supposed to bring high wind shear and cause it a lot of trouble, but there's little evidence of such impacts on satellite and radar imagery (e.g. http://www.ssd.noaa.gov/PS/TROP/floaters/04L/imagery/wv-animated.gif).

It appears that the lower and upper levels of the cyclone have been so well structured (and connected) over the past 24 hours that the system has developed the ability to modify the wider atmosphere around it. Typically, this manifests as an anticyclone forming above the cyclone - counter intuitive I know, but the anticyclone is at the upper levels, meaning the associated winds spiraling outward are creating divergence above the hurricane, into which air can advance via vigorous updrafts from the surface level.

In a sense, the hurricane has forced the divergence to occur aloft, so creating the upper level anticyclone (ULAC). This feature is capable of suppressing the vertical wind shear that can take down tropical cyclones. So it is conceivable that Danny could defy recent NHC projections and plow through the region of less favourable conditions while shielded within a bubble of favourable conditions, so to speak.

Some recent model runs have begun to reflect this possibility, with a stronger system making it through to the more widely favourable conditions on the other side. If that happens, then the U.S. will start getting really concerned about the system's exact path - it may interact with mountainous terrain bordering the Caribbean, causing weakening, but then again, it could avoid that and approach the U.S. as a major threat.

Interesting times ahead in the tropics, then... and there I was starting to think I'd never be able to say that this season!

Slow burner 97L might be more of an impact on our weather, especially if it allows interaction with Danny. GFS had an Atlantic hurricane, which traced to pouch 24 but see that is no longer being made much of.

http://www.tropicaltidbits.com/storminfo/#97L

http://www.met.nps.edu/~mtmontgo/storms2015-atlantic.html

Very uncertain MJO but if it does reinvigorate in 8/1 could give the season a boost.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ALL_emean_phase_full.gif

http://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic=-51.63,16.12,2612

There's been a lot of discussion about whether what was once hurricane Danny has totally fallen apart in the far-eastern Caribbean. Yet nobody has thought to look at satellite-derived wind map linked above, which shows a distinct circulation still in place.

The question is, how reliable are those measurements?

You can also see how 98L, to the east of the Caribbean, has a distorted circulation which it needs to sort out if it's to become the next named tropical cyclone (Erika). As the system slows down over the coming day or so in an environment of moderate wind shear (10-20 knots) and over waters of 27-28*C (plenty high enough for tropical development), I can see it having a good shot at becoming a strong tropical storm or low end hurricane.

If it can then survive some higher wind shear near or within the Caribbean, it may become a serious threat to major land areas in about a week's time, as the broad-scale setup looks to be in favour of either too little recurvature or none at all (either way, not making it 'out to sea'). So it's one to keep an eye on!