Tropical Storm Ana; Typhoon Noul

Tropical Storm Ana looks to strike the SC/NC border as a strong tropical storm.  Impact estimates are in the $3 Million range:
ana_track_sat

Of more concern is Typhoon Noul, which looks to brush the Philippines before impacting the southern Japanese islands.  And just behind it is Depression number seven, which looks to strengthen into a Typhoon over the next few days:
wpac_sat
Noul is projected to have impacts over $800 Million if it follows the current track.  A wobble to the left could easily double that value, while a wobble to the right could cut it by a factor of 5 or more.

AL012015 (Ana) Off the GA/SC Coast

The US National Hurricane Center has started tracking the system off the SEUS as “Subtropical Storm Ana”.  Here is the current forecast wind swath using my Taru(tm) model and the NHC forecast track:
ana_fri_am_track

Winds could reach tropical storm strength right along the coast where this think moves onshore, with widespread areas (seen in blue) of gust winds.  Impacts are forecasts to be light; it’s likely any efforts to prepare extensively (especially evacuations, shutdowns, etc.) would cost more than the storm itself, but it’s a good idea to review your hurricane plans, get dead limbs out of the way and clean up possible debris, prepare for some scattered power outages, those kinds of things.  Consider it a test run for the real thing.

So just what is a “subtropical storm”?  First some quick abbreviated definitions.  A tropical cyclone (the family that is commonly called hurricanes or tropical storms) is defined as warm core low pressure system with winds above a given threshold (34 knots).  Tropical low pressure systems have a relative, the extratropical cyclone or mid-latitude cyclone.  Extratropical cyclones are fairly common, but can form nor’easters, which are intense, cold-core low pressure systems, sort of the cold cousin of the hurricane.  Subtropical cyclones are hybrids.  The have a cold or cool core but are taking on some tropical characteristics such as the development of thunderstorms near the center of circulation. There is a spectrum of low pressure systems with various characteristics like wind fields, temperatures, and driving mechanisms. Like many things in nature, weather systems sometimes don’t fit into nice neat categories.

Potential storm off SEUS Coast

It looks like the first Atlantic storm of the season is spinning up just off the Georgia coast.  Here’s the latest (4pm) Visible band satellite image (click to embiggen any of the images):
al90thupm

The current track map shows lots of meandering over the Gulf Stream before it finally moves on, possibly hitting North or South Carolina:
al90_thupm

The HWRF model (the light blue line) brings the storm into the central SC coast as a big, diffuse low – maybe briefly reaching tropical storm strength.  Nothing serious to worry about, but worth checking over your emergency supplies for the essentials like SPAM.  Events like this usually rack up a few million dollars in impacts.  That may sound like a lot but in today’s environment it isn’t.

Nepal Aftershocks

There have been 26 major aftershocks as of 2pm EST (18Z), all along the mountain ranges to the west of the earthquake epicenter.  Some have been quite strong – two near the original quake were over m6.0.  These are causing additional damage, probably additional casualties, as well as panic and disrupting rescue efforts.  The initial impact estimate was close to $2 Billion; with each aftershock that number goes up, and is now pushing $2.5 Billion, with most of that in Nepal, but likely several hundred million in damage in neighboring India.

nepal_after18z
Click to embiggen

Massive shallow earthquake in Nepal, nearly $2 Billion in impacts expected

There has been a massive 7.9, shallow earthquake in central Nepal, impacting areas of China and especially India as well:
nepalquake

Overall economic impact to Nepal will easily exceed $1 Billion dollars, and impacts in India may exceed $500 Million.  Here’s what the model spread looks like.  Best estimate is $1.8 Billion, with  much of the uncertainty is due to construction quality.  Some scary but plausible scenarios are in the $6 Billion range, but the majority of models place impacts around $2 Billion:

nepal_impacts

Update: To put this in to context, the GDP of Nepal is about 66 Billion, so this event will be about 2% of GDP.  Recent “bad” natural disasters impacting the US like Hurricanes Sandy and Katrina were in the $50 to $80 Billion range, but that is only 0.4 or 0.5 % of the US GDP.  This earthquake would be a $320 Billion disaster in the US – something we’ve never experienced.

Early death reports are in the 500 range, but I would expect the final numbers to be well into the thousands.

This is a very vulnerable area, where the Indian subcontinent is ramming into Asia and uplifting the Himalaya Mountains, and previous severe earthquakes near Kathmandu have been devastating.

Maysak and the Philippines

Maysak should make landfall Sunday morning Philippines time (this evening US time) as a moderate tropical storm with peak winds around 55kts (63 mph, 100kph).  Impacts look to be in the $30 to $40 million range – much, much less than the forecast indicated a few days ago.  Here is the wind swath forecast using the latest JTWC track/intensity and my Taru model.

maysak_sat

Maysak: much weaker landfall, impact on Philippines forecast less than $150 Million

maysak_thu

Very different impact forecast than yesterday, and yet another good example of the complexity of forecasting the impacts of natural hazards.  The landfall intensity has decreased from 85 knots to 65 knots – a 25% decrease in wind speed.  But the impact forecast dropped by nearly 90% to from over a Billion dollars to about $130 Million!  Why?  Because the amount of force the wind creates (the “dynamic pressure”) is related to the square of the wind speed, not the wind speed itself.  So the pressure from a 65 knot wind is only 58% of the pressure of an 85 knot wind.  But it’s a bit more complex than that, and damage relates to a number of complex factors that ends up being a higher power factor of the wind difference above a threshold.  So for a typical house, an 85kt wind might cause 16% damage, whereas a 65 knot wind would only cause 4% damage.  Another factor in this case is that the swath of damaging winds is smaller, and misses the densely populated areas near the Capital, Manila.  Put all that together, and while the track doesn’t look that different, and the winds are a bit less, the damage forecast is dramatically different.  Which is a good thing – the Philippines really doesn’t need another disaster given the last few years of Typhoons and earthquakes.