Potential storm in the Gulf of Mexico

There is a system spinning up in the Gulf of Mexico today, and the US NHC should start tracking it formally later today.  Here’s what the forecast track models are showing:al91_mon

Most of the dynamic models are only showing it as a weak tropical storm at best, so while it might bring some winds and rain it shouldn’t cause too much damage.  Should cause little to no disruption to oil and gas interests unless something breaks that wasn’t supposed to.

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.

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.

Maysak continues towards Philippines; Damage near $1 Billion still predicted

Maysak is not as intense as yesterday, but is still an impressive and powerful storm at 130kts/150mph/240kph:
maysak_wed_am

Forecast track has been pretty steady to hit the northern Philippines island of Luzon in a bit over three days:
maysak_wed

On this track, and using the JTWC forecast intensity at landfall of 85 knots, the storm could cause upwards of $1 Billion dollars in damage.  For perspective, that is about 0.3% of GDP, or the equivalent of a $40 Billion dollar storm hitting the US.  That is about the same damage as Hurricane Ike, which hit Texas in 2008, and is the third most expensive storm in US history.  The Philippines has been hit be several intense storms the last few years, such as Haiyan in 2013 and Bopha in 2012 – in fact they have had 6 disasters that, in GDP equivalents, would have been worse than Hurricane Andrew, just since 2010.  Bad Luck, or changing climate ?

Typhoon Maysak

Typhoon Maysak  (WP042015) is a very powerful, 140kt/160mph/260kph storm, currently south of Guam.  The Joint Typhoon Warning Center (JTWC) forecast track has it headed towards the northern Philippines:
maysak

On this track it would make landfall with winds at around 95kts/180kph, and cause between $500 Million and a Billion dollars in damage.  Last year JTWC’s intensity forecasts were not so great.  The objective models, and the Japan Meteorological Agency Ensemble (pink line) forecasts also show the storm striking the northern Philippines:
maysak_tks

The JMA Ensemble forecast has a  weaker storm, only 80 knots at landfall.  80 vs 95 may not seem as much, but an 80knot wind only has 70% of the energy of a 95 knot wind; big difference in damage.

Typhoon Higos (WP022015) in the North Pacific

Typhoon Higos is moving through the North West Pacific, in the big blank area between Guam and Wake Island:
higos

Nothing in the way, no damage forecast.  It’s a bit unusual for this time of year, but our good records of the Pacific only go back to the 1940’s, so it’s a bit hard to draw any conclusions from this.  This is the second North West Pacific storm (the WP022015 designation is the Joint Typhoon Warning Center tracking number – WP is West Pacific, 02 is the second storm, 2015 the year).

Snow means it’s warmer???

Not a lot of major disasters lately (although the small ones obviously hurt the folks in the way), and I’ve been busy doing a climate analysis project for the UK DFID. The real time site always has the latest earthquakes, volcanoes, and hurricanes/tropical cyclones situation.

The recent snowstorms across the US have triggered the usual snarky comments from those who don’t accept the *fact* of anthropogenic climate change.  But anyone who has lived in the far north or arctic knows that it has to be “warm” to get snow.
Huh?
You read that right, but “warm” is a relative term.  Take a look at this graph, from Danial Cobb, science officer of the NWS/WFO in Caribou, Maine (click to embiggen):
snowratio

Not the biggest/fluffiest/deepest snow rates will be between -14 and -18 C.  OK, -16C (3.2F for you folks stuck in the 17th Century) isn’t warm if you are from the south, but it’s actually pretty “warm” for places that routinely see temperatures below zero F.  The other big issue is that the colder it gets, the less moisture the air can hold.  So colder air is naturally drier, and can’t hold as much snow.  So the “optimum” for both quantity and depth is somewhere between freezing and zero F.  Ironically, in the arctic, to get a blizzard, it has to warm up!  The other big issue is transporting moist air into the colder areas.  The models have predicted (and we seem to be seeing) more “latitudinal” (eg north-south) flow, which would cause more stormy and snowy weather – even though the overall temperatures are actually “higher” in relative terms.

Climate change is a very complex phenomena, intermixing human and natural changes and activities.  Far too many people on both sides of the debate do the discussion a disservice by simplistic, apocalyptic explanations.