Sandy is now a category 1 hurricane with estimated maximum sustained winds of 85 mph and central pressure of 970 hPa (see picture).  My community is all aflutter about this storm, particularly since our forecast models are not in agreement–some suggest the storm will intensify and head straight in to the Middle Atlantic coastline, some take it out to sea, and others move it out to sea before swinging it westward to hit New England or the Canadian maritimes.

Hurricane Sandy is not well formed at this time

Such uncertainty is not unusual under the present circumstances:  we have a storm that will undergo what we call extratropical transition as it moves northward (changing energy sources in the process) and interacts with the stronger flow and temperature gradients of the midlatitudes.  Very complex interactions that greatly reduce predictability.

Let me illustrate.

First, lets start with the gold standard.  The best hurricane prediction system is embarrassingly not American, but the European Center (ECMWF) high-resolution global model (note to U.S. Congressmen and Senators–you folks need to attend to this issue!).   A model that has the equivalent of 15-km grid spacing over the entire planet.

You will not believe the forecast.  Here is the sea level pressure analysis (solid lines, the shading is relative humidity) as the storm makes landfall along the Delaware coast.  A 940 hPa low! That is very low.

And here is the associated wind field–sustained 50 kts plus over the ocean.

If this were true there would be major coastal damage.  Most models tend to overdo such systems, but still, a huge threat.

But this is 2012 and we can do a lot better than a single “deterministic” forecast….there is plenty of uncertainty in the forecasts and one way we deal with that is with ensemble forecasts..running the model many times, starting a bit differently or with varying physics (e.g., different ways of describing clouds, precipitation, and the like).  Ensembles are run with less resolution than the single high-resolution forecast shown above.

Here is the sea level pressure output from the ECMWF ensemble mean (the average of all the simulations) on the left side (solid lines) and the single high-res forecast on the right, both for 5 AM PDT on Monday, 29 October.  The ensemble mean is a bit washed out (we are averaging the pressures of many runs and those diffusing things a bit), and the lowest mean pressure somewhat offshore of the high-res run.  The color shading indicates that thelevel of uncertainty, based on the differences between the ensemble runs,  is considerable.

Here is the same figure for 24 h later (Tuesday morning).  The ensemble mean (left side) low center is making landfall on New England, but there is a lot of uncertainty.  Clearly most of the ensembles are making landfall, but some forecast lows stay out to sea.   The bottom line:  a real threat, but it is not nearly 100%.

What about the American model, the GFS?  Statistics show it is now tied for number two with the UKMET office model.  Our high-res version (resolution about 25 km) does something very different (see graphics showing sea level pressure–black lines, and precipitation–shading).  The storm stays offshore for a long time, bypassing the central Atlantic states and then swings towards the Canadian Maritime Provinces.

Saturday, 11 AM PDT

Monday 11 PM PDT

Wednesday 2 PM PDT

The East Coast is safe?   Don’t be so sure.  Let’s check the U.S. global ensemble (much coarser than the European Center, unfortunately) at 5 AM on Tuesday..   The solid line is the mean (or average) pressure and the colors indicate uncertainty–orange is the most uncertain–where the simulations disagree the most. Wow…HUGE uncertainty.  Some solutions are taking the storm into the mid-Atlantic states like the European Center model, while others are heading the storm offshore.

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Here is the ensemble mean and uncertainty the next day. The ensemble mean makes landfall on the U.S.:  many solutions are hitting the NE states, but some move offshore (like our single high-res solution).

So what do you come away with from all this?  First, you know what it is like to be a meteorologist in a real-world, very serious situation.  There is the potential for substantial loss of life, damage, and disruption.  Large costs to protect assets.  What would you recommend?  This is why meteorologists make the big bucks (right!).

Our models..both high res and ensembles..indicate there is a real threat to the U.S., from roughly Virginia to New England.  Folks in that region should pay close attention to the forecasts–which will get more certain as we get closer to landfall.  Not too soon to think about preparation.  There is still considerable uncertainty–and next week we could see anything from a catastrophic storm to nothing.  There is considerable chance of a serious landfall since our best model is going that way and BOTH U.S. and ECMWF ensemble systems showing a considerable number of forecasts with that solution.

There are many things I have not discussed here…how the tropical storm interacts with the midlatitude winds and why that produces uncertain forecasts…that will have to be for another time.   And yes, it is going to rain in Seattle this weekend.

A storm far more intense than the Perfect Storm, of book and movie fame.

One of the most intense landfalling cyclones in several years and perhaps the equal of the great Columbus Day Storm of 1962 that brought 100 mph plus winds to large swaths of the Pacific Northwest.

The storm that will strike the East Coast early next week is eerily like the Columbus Day Storm and the famous Perfect Storm in several ways.  Each of these started as a typhoon or hurricane and  transitioned into a powerful midlatitude cyclone, undergoing what we call extratropical transition.

As I will describe below, although there is still some uncertainty, the major modeling systems, American and European, have now locked on to a very similar solution.

Hurricane Sandy is now a Category 1 storm with sustained winds about 75 mph and a central pressure of 971 hPa.  Now located just north of the Bahamas and still over warm water.

At the same time, an upper level trough is approaching from the west and the interactions between the two will cause Sandy to morph into a hybrid storm, expand,  and intensify rapidly.  The National Weather Service is doing something very rare:  adding more radionsonde (weather balloon) launches (four times a day instead of twice day)…a very wise investment.

This figure shows the situation on Saturday, showing the upper trough over land (red line) and an upper low over Sandy (purple circle) (the figure is for 500 hPa–about 18,000 ft above sea level).  These will join up during the next few days.

Sandy will not only grow larger, but the pressure will fall, and the winds will increase.  Perhaps the most dramatic description of this process (but not technically quite accurate) was given by a supposed meteorologists in the Perfect Storm movie, click on the picture to view it:

Click to see video

Until recently, two of our most important models (the European Center model and the U.S. GFS) were substantially at odds, with the European model taking the storm into Maryland/Delaware and the U.S. model taking the storm out to sea.   In more recent runs, the U.S. high resolution model began recurving the storm back to the East Coast, first over New England and now across Long Island, with the European Center model not changing very much.

But now European Center model has moved northward, the GFS model swings inland earlier, so the differences have diminished.

Lets talk a look.  First the U.S. GFS.  Here is a series of surface pressure analyses from this morning’s run (solid line are sea level pressure and shading is relative humidity.  A very deep low moves in off the ocean at 8 PM PDT Monday with a pressure of around 950 hPa (the Columbus Day Storm was about 960 hPA), then swings in over Long Island on Tuesday morning, then moves in a circle just inland, and eventually moves northward on Wednesday.  This is extraordinary behavior–to have a deep low just circle about for a day, before heading out of the region.  And deadly.

The winds would be very strong and damaging…sustained winds of 50-70 knots over the water with higher gusts.  Here is the wind forecast at 2 PM on Tuesday morning.  Winds are in knots (see legend).  Lots of sustained winds above 50 knots over the Atlantic and some coastal locations.

What about the European Center forecasts?  A sub-940 hPa low makes landfall on central New Jersey, circles around, and then moves northward.  The European Center and GFS models tend to overdo the deepening in this situations, so I don’t believe we will see anything below 950-960 hPa.

We are talking about huge events, if either of these forecasts are correct–or if the truth is somewhere in between.  Heavy rain, powerful winds over a long period, storm surges north of the low center.   This will make the Perfect Storm look like a zephyr.

Is there still uncertainty now that the major models are converging?  You bet.  There is some probability that the real storm will moves out to sea.  To get a handle on this, lets take a look at the last European ensemble prediction (left panel below) and the their high-resolution forecast (right panel) for 5 AM PDT on Tuesday.   The shading is a measure of uncertainty…how much the ensemble members disagree.

The high resolution forecast shows a huge, powerful storm making landfall.  Importantly, the ensemble (the mean of many different forecasts) show a low center at a similar position, perhaps a bit farther north.  This provides some confidence in the high-res forecast.  But the shading shows there is considerable uncertainty still, with the shading offshore suggesting a few of the forecasts were for a low farther offshore.  So, this is not 100% now…but a very good bet at this point.

I think you can appreciate the technology…high resolution forecasts show us some possibilities, with ensemble prediction giving us a measure of the uncertainty in the forecasts.  No forecast is complete without a quantification of the uncertainty.  Nothing is 100%.   And certainly not a complex, sensitive situation like this one.

It is exceedingly rare to get rain when the temperature rises above 100°F, since those kind of temperatures usually require a high pressure system with sinking air that discourages rainfall. Monday’s rain in Needles was due to a flow of moisture coming from the south caused by the Southwest U.S. monsoon, a seasonal influx of moisture caused by the difference in temperature between the hot desert and the cooler ocean areas surrounding Mexico to the south. According to weather records researcher Maximiliano Herrera, the previous record for hottest rain, which I blogged about in June, was a rain shower at 109°F (43°C) observed in Mecca, Saudi Arabia on June 5, 2012 and in Marrakech, Morocco on July 10, 2010. The 11% humidity that accompanied Monday’s rain shower at 115° in Needles was the lowest humidity rain has ever occurred at anywhere on Earth in recorded history, according to Mr. Herrera.

Figure 1. True-color MODIS satellite image of California and Arizona taken at 1:25 pm PDT August 13, 2012. Developing thunderstorms surround Needles, CA, and the line of clouds to the southwest of the city would develop into a thunderstorm that brought rain to the city at 4 pm PDT, at a temperature of 115°F. Image credit: NASA.

A “very rare” heat wave for Phoenix
The heat wave that brought Needles’ record hot rain has broken an exceptional number of heat records in Phoenix, Arizona the past two weeks. According to the Phoenix NWS office, the “almost unbearable heat” of the first two weeks of August is a “very rare” event, and August 1 – 14, 2012 was the warmest such 2-week period in city history. The average temperature on August 6 – 13 was 100°F or higher each of the eight days, tying the record for most consecutive days with an average temperature of 100°. The temperature peaked at 116° on August 8, just 6° below Phoenix’s all-time record of 122° set on June 26, 1990. The forecast for Phoenix call for a bit of relief–highs are expected to be a relatively modest 105° today, and down near 100° by Friday.

Figure 2. Morning satellite image of 93L over the Central Atlantic.

93L close to tropical depression status
A large tropical wave (Invest 93L) is located in the Central Atlantic about 700 miles east of Bermuda. Satellite loops this morning show a surface circulation has formed, and heavy thunderstorm activity has increased to the point where 93L should be considered a tropical depression, if the heavy thunderstorms can persist through this afternoon. Wind shear is light, and ocean temperatures are warm, near 28°C. The latest Saharan Air Layer Analysis from the University of Wisconsin shows that 93L has moistened its environment considerably, and dry air should no longer be a significant impediment to development. The 8 am EDT run of the SHIPS model predicts that wind shear will remain in the low range through the weekend, and I expect this system will become Tropical Storm Gordon by Friday. The storm will not affect Bermuda, but residents of the Azores Islands should keep an eye on 93L, which could pass through the islands as early as Sunday night. In their 8 am Tropical Weather Outlook, NHC gave 93L an 80% chance of becoming a tropical depression by Friday morning.

Elsewhere in the tropics
In the Gulf of Mexico, a fall-like cold front is expected to stall out early next week, and the GFS model is predicting something could start to spin up near the Texas/Mexico border on Monday. Wind shear is predicted to be low to moderate, and cold fronts stalled out over the Gulf of Mexico often serve as the seed for tropical storms.

Most of the models predict development of a new tropical wave off the coast of Africa 6 – 7 days from now.

Figure 1. Departure of temperature from average as analyzed by the GFS model, for February 2, 2012. Remarkably cold air was present over Europe and western Alaska, while very warm air was over central North America and Siberia. This image is being generated experimentally by wunderground, and will be regularly available on our web site in the future.

Meanwhile, a snow drought for the U.S.
In the U.S., it’s been the opposite story, with temperatures 10 – 15°F above average continuing this week over much of the nation. January 2012 is in the weather record books as the 3rd least-snowy January for the contiguous U.S. since snow records began in 1966, and December 2011 ranked as the 11th least snowy December on record. With no major snow storms in the offing over at least the next ten days, it’s looking probable that the non-winter of 2011 – 2012 will set numerous record-low seasonal snowfall totals. The National Weather Service sends out a daily “Weather and Almanac” product for several hundred major U.S. cities that we make available on wunderground. I went through yesterday’s statistics for those cities that reported measurable snow this winter. Only nine cities out of 166 major U.S. cities in the lower 48 states reported above-average snowfall as of February 1; 157 cities received below-average snowfall. The big winner in the snow sweepstakes has been Alaska, which is boasting 8 of the top 10 locations for heaviest snowfall this winter. While the 27.75 feet of snow that has fallen on Valdez has gotten a lot of attention, more remarkable is the 18.8 feet of snow Yakutat has received. That’s more than 12.5 feet above what they usually have by this time of year.

The big losers in the snow stats for this winter are the cities along the lake effect snow belts on the Great Lakes. Most notably, Syracuse, New York is nearly four feet of snow below average for this time of year. Perhaps more exceptional is Williston, North Dakota, which has received just 1.8″ of snow this winter–more than two feet below their average for February 1.

America’s deadliest tornado season since 1953 continued its relentless onslaught of violent tornadoes yesterday. Numerous destructive and deadly tornadoes raked Oklahoma, Texas, Kansas, and Arkansas, killing at least nine people. Yesterday’s deadliest tornado hit El Reno and Piedmont, Oklahoma, about 30 miles to the west and northwest of Oklahoma City. Four people died, and one child is missing. Video of the damage from this tornado near the town of Piedmont shot by a news9.com helicopter shows damage characteristic of an EF-4 tornado, with many homes completely demolished and swept off their foundations. This tornado produced a wind gust of 151 mph at an Oklahoma Mesonet station in El Reno, Oklahoma.

Figure 2. Doppler velocity image of the supercell thunderstorm that spawned the Piedmont, Oklahoma tornado.

Figure 3. Top wind gusts recorded by the Oklahoma Mesonet yesterday showed that over 2/3 of the state received gusts of 40 mph or greater, and ten stations got gusts in excess of 58 mph (the definition of a severe thunderstorm.) A remarkable gust of 151 mph was recorded in El Reno, about 30 miles west of Oklahoma City.

Joplin, Missouri got a scare last night when Doppler radar showed a rotating thunderstorm approaching the city from the southwest. A tornado warning was issued and the sirens sounded, but the storm passed just to the northwest of the city, bringing Joplin only heavy rains, wind gusts to 41 mph, and intense lightning. A tornado warning forced the evacuation of NOAA’s Storm Prediction Center (SPC) in Norman Oklahoma late yesterday afternoon, and the center was out of commission for a 50-minute period. However, yesterday’s dangerous tornadoes missed the most heavily populated areas of Oklahoma, and SPC was able to resume normal activity after the storms cleared Oklahoma City. The center logged 47 reports of tornadoes yesterday, bringing the preliminary 4-day total of the current outbreak to 153 twisters. With more tornadoes expected today over a wide swath of the country from Arkansas to Ohio, this week’s tornado outbreak is likely to rank as one of the top ten tornado outbreaks in history. This year already has the two largest tornado outbreaks in history, the April 25 – 28 outbreak (327 tornadoes) and the April 14 – 16 outbreak (162 tornadoes.)

This year’s tornado death toll is in the 495 – 499 range, making it the deadliest year for tornadoes in the U.S. since 1953, when 519 people died. That year, three heavily populated cities received direct hits by violent tornadoes. Waco, Texas (114 killed), Flint, Michigan (115 killed), and Worcester, Massachusetts (90 killed) all were hit by violent F-4 or F-5 tornadoes. A similar bad tornado year occurred in 1936, when violent tornadoes hit Tupelo Mississippi (216 killed), and Gainesville, Georgia (203 killed.)

Figure 4. Satellite image taken at 22:32 UTC (6:32pm EDT) May 24, 2011, showing a line of tornadic thunderstorms over Oklahoma, Texas, and Kansas. Image credit: NASA/GSFC.

Figure 5. Radar image of an unusual “J”-shaped tendril emerging from a tornadic thunderstorm near Dallas, Texas. This storm had unusually high radar reflectivity (note the pink colors of 70 dbZ echoes), because of large hail in the storm. This thunderstorm produced softball-sized hail (4.5 inch diameter.)Video 2. Chase video of several Oklahoma tornadoes intercepted yesterday by Reed Timmer of tornadovideos.net.

The Joplin tornado an EF-5, and the costliest tornado in history
The Springfield, Missouri office of the National Weather Service announced yesterday that storm surveys of the 7-mile long, 3/4 mile-wide path of damage carved by the Joplin tornado revealed that winds in the violent tornado exceeded 200 mph, making it the 4th EF-5 tornado of the year. The twister roared through Joplin beginning at 5:41pm CDT on Sunday, May 22. In nine terrifying minutes, the tornado killed at least 125 people, injured 750 more, and destroyed 2,000 buildings. NOAA’s Storm Prediction Center (SPC) rates this year’s Joplin tornado as the 8th deadliest U.S. tornado of all-time, and the deadliest since at least 1947, when a violent F-5 tornado hit Woodward, Oklahoma, killing 181.

Catastrophe risk modeling firm EQECAT said yesterday that insured damages from the Joplin tornado could be between $1 billion and $3 billion dollars. According to NOAA’s National Severe Storm Laboratory, the costliest tornado between 1890 – 1999 was the May 3, 1999 Oklahoma City tornado, which did $1 billion in damage (1999 dollars.) There were no tornadoes during the period 2000 – 2010 capable of causing $1 billion in damage; the only two EF-5 tornadoes during that period, the 2007 Greensburg, Kansas tornado and the 2008 Parkersburg, Iowa tornado each did less than $300 million in damage. Thus, with the possible exception of this year’s Tuscaloosa-Birmingham tornado of April 27, the Joplin tornado is probably the most damaging tornado of all-time.

Another “High Risk” day for severe weather and violent tornadoes today
The Storm Prediction Center has placed portions of seven states, from Arkansas to Indiana, in their “High Risk” region for severe weather potential, and warn of the potential for long-lived strong or violent tornadoes. This is their second consecutive “High Risk” forecast day, and fourth of the year. A high risk forecast was also issued on April 27, which was the busiest tornado day in world history, with 198 tornadoes occurring in a 24-hour period. Over 300 people died. The other “High Risk” forecast by SPC came during the final day of the April 14 – 16 outbreak over the Southeast U.S. Fifty-two tornadoes hit that day, and 26 people died in North Carolina and Virginia. The severe weather threat will diminish considerably on Thursday, when only a slight risk of severe weather is expected from Alabama to New York.

Figure 5. Severe weather threat for Wednesday, May 25, 2011.

Joplin tornado the 7th U.S. billion-dollar weather disaster of 2011
The Joplin tornado is the 7th U.S. weather disaster of 2011 costing more than a billion dollars. With hurricane season still to come, 2011 has an excellent chance of beating 2008′s record of nine billion-dollar weather disasters. The billion dollar weather disasters of 2011 so far:

1) 2011 Groundhog Day’s blizzard (($1- $4 billion)
2) April 3 -5 Southeast U.S. severe weather outbreak ($2 billion)
3) April 8 – 11 severe weather outbreak ($2.25 billion)
4) April 25 – 28 super tornado outbreak ($3.5 – $6 billion)
5) Mississippi River flood of 2011 ($9 billion)
6) Texas drought ($1.2 billion)
7) Joplin tornado ($1 – $3 billion)

Links
The New York Times has an interactive tornado fatality map showing how this year’s killer tornadoes have mostly clustered over the Southeast U.S., with the glaring exception of the Joplin, Missouri tornado.

NOAA’s Visualization Laboratory has an impressive animation of the satellite imagery during the month of April, showing the locations of all the tornadoes as they happened.

Helping out tornado victims
For those who want to lend a helping hand to those impacted by the widespread destruction this month’s severe weather has brought, stop by the Red Cross website, or portlight.org blog. Portlight has been very active bringing aid to the victims of this year’s tornadoes.