Friday, August 25, 2017

Extraordinary Radar Imagery for Hurricane Harvey

The importance of having weather radars along our coasts is highlighted by the amazing imagery from the NWS radars at Brownsville and Corpus Cristi.

Here is one at 6:44 AM PDT this morning. The circular eye of Hurricane Harvey is obvious.   Look closely and you will see evidence of a double eye.  This often occurs as a hurricane goes through a eyewall replacement cycle, in which an exterior eyewall develops and then shrinks in radius and intensifies.   Storm often strengthen as the outer eye wall  tightens inward around the low center.


With coastal radars, hurricanes (and other storms) can be examined comprehensively as they approach land.  They are in fact, the CAT scans or MRIs of the meteorological profession.    The importance of such coastal radars is why many of us pushed for a radar on the Washington coast at Langley Hill and why folks in Oregon are pushing for a radar on the Oregon coast---the last great gap in U.S. coastal radar coverage.  The central pressure of Hurricane Harvey is about 950 hPa.   The Columbus Day Storm of 1962 was similar:   955 hPa.

Our ability to follow hurricanes is not limited to weather radar.  Improving satellite imagery, such as from GOES-16, provides amazing views from space (see below).  You can even see a very small hurricane eye.

And during the last few days Air Force and NOAA aircraft have been traveling in the storm, taking flight level observations and dropping instrumented packages called dropsondes.   Here is a graphic that show the winds at flight level from an aircraft now in the storm.


We can no longer be surprised by approaching coastal storms or hurricanes with all these assets.  But our models are still inadequate for predicting variations in intensity and there is some research suggesting that intensity prediction more than a day out may not be possible....we will see.

Current model runs are unanimous that Harvey will strike the south/central Texas coast later today and that there will be a huge amount of rain.  They disagree about intensity and subsequent path (see below).  But nearly all suggest at least a CAT 2-3 storm, with max winds exceeding 110 mph.



12 comments:

Deek Deek said...

Thanks Cliff. They're doing it again-hype: "a storm the likes of which we have never seen". Ah, haven't we seen a few cat 5 storms in the past vs this one at cat 2-3?

M. Hilberts said...

While wind damage is more "spectacular" for people outside the affected area, the real Hurricane damage is usually due to precip or surge. With this storm being so slow moving/static there could potentially be a lot of damage. So while a faster cat 5 storm can do more short term devastation, the medium term effect with more cumulative precip of this storm could have a lot more impact.
I would not call the "hype" FAKE NEWS! just yet ;)

Mike c said...

Shouldn't there be more ways to categorize a hurricane, besides Category 1-5 (which only describes sustained wind speed)? Couldn't the overall size or amount of moisture it is likely to bring to an area also be scaled?

Unknown said...

Deek Deek, if the forecasted rain totals for SE Texas materialize over the next 5 or so days, this will indeed be a storm the likes of which we have never seen.

- Douglas

The Woog said...

What's so fascinating about this, and I think re-enforces the need for funds being put into weather, forecasting, climate, etc. is if you look at what was predicted just a few days ago.

http://www.nhc.noaa.gov/archive/2017/al09/al092017.discus.012.shtml - that's the forecast discussion 12.

The written guidance on WEDNESDAY said:
"Although not explicitly forecast below, we are anticipating Harvey being a hurricane at landfall after the 48 hour forecast point. This forecast agrees well with the guidance, almost all of which shows a quickly intensifying cyclone approaching the Texas coast."

And although the forecast mentions "quickly intensifying" what was posted for winds was:
INIT 23/1500Z 21.5N 92.5W 30 KT 35 MPH
12H 24/0000Z 22.3N 93.2W 35 KT 40 MPH
24H 24/1200Z 23.8N 93.9W 40 KT 45 MPH
36H 25/0000Z 25.2N 94.9W 50 KT 60 MPH
48H 25/1200Z 26.7N 96.3W 60 KT 70 MPH - that was the prediction 60 hours ago - 130MPH gusts were just recorded with sustained winds of 105MPH.

This reminds me of 2015's super hurricane over the Mexican pacific coast where on day 1 is was a slight storm and something like 36 hours later, a massive hurricane, that if it took a slightly different course, could have done a real number on Puerto Vallarta.

Here's my question: how common are rapidly intensifying tropical systems? I've been following storms since Andrew and other than Matthew which was named and then 2 days later became a Cat 5 and (yes!) Patricia - this rapid intensification *seems* to be rare. But we've now watched this happen 3 years in a row. Is this just climate and odds and weather or does this point to something a bit more serious? Or is this not rare at all and it's my memory that stinks?

What's seems to be clear is that we're not real good at predicting rapid intensification in a short amount of time, right?

Praying for those in Texas!

Kenna Wickman said...

Deek, check out the comments on the Cat6 blog at wondergound.com

Unlike the eclipse traffic around here, this storm is really powerful arriving onshore at Cat 4 and the amount of water it will dump on Texas over the next few days is equal or greater to Washington's annual rainfall.

If anything they may have under-hyped this storm. We'll know more tomorrow or whenever FEMA (assuming there is anyone running that agency - thanks Trump!) goes and makes an assessment. My guess is that this will rival Sandy or even Katrina.

Rrrnay said...

Category 4 at landfall with a huge storm surge and now it's stalled, dumping rain. The "hype" was right.

swflowcape said...

Cliff, start talking about the big story developing here.

NWS has this storm refusing to leave South Texas. Some discussion as to why there is no upper air support to transport this system north or northeast would be nice. Some upper level charts would be desired since the new format at NWS is making it difficult for me to obtain the upper level forecast models. Thanks.

TheWildLine said...

20 trillion (20,000,000,000,000) gallons of water will be dropped on Texas in the next few days, possibly even more.

Water coming out of the sky the likes of which we have never seen before with human eyes.


https://grist.org/article/a-texas-size-flood-threatens-the-gulf-coast-and-were-so-not-ready/

Placeholder said...

Remember when the Worldwide Church of AGW declared that Texas was in a permanent drought?

Luci said...

Cliff, why do we need coastal radars? Would not Satellite Derived Radar Reflectivity suffice. See http://www.worldwindsinc.com/spaceradar.htm

David Mason said...

While it's certainly not a "cut and dry" question, it's definitely not a cut and dry answer either. Seems instead like the scientific jury is still out.

From climatecentral.org:

Harvey

August 30, 2017

Catastrophic flooding continues to engulf much of southeastern Texas in the wake of Harvey, a Category 4 hurricane that made landfall Friday night near Rockport, Texas. The National Hurricane Center reports that parts of Houston received more than 50 inches of rain since the heavy rains began last weekend. The flooding has forced more than 30,000 people into 230 shelters across the state, according to the Federal Emergency Management Agency. At least 38 deaths have been linked to the storm.

Flood-weary Louisiana has not escaped Harvey’s destructive forces. Tropical Storm Harvey made landfall on the Louisiana coast near the Texas border Wednesday morning. Forecasts call for as much as two feet of rain in parts of the state. This comes one year after historic flooding in south Louisiana claimed 13 lives, affected hundreds of thousands of people, and caused an estimated $10.3 billion in damages. The area is still struggling to recover.

Scientists with World Weather Attribution (WWA) and the National Oceanic and Atmospheric Administration conducted an attribution analysis of last year’s heavy rains in Louisiana and found that human-caused climate change nearly doubled the odds of that storm. For more details about that study, check the Analyses section.

Scientists with World Weather Attribution (WWA) and the National Oceanic and Atmospheric Administration conducted an attribution analysis of last year’s heavy rains in Louisiana and found that human-caused climate change nearly doubled the odds of that storm. For more details about that study, check the Analyses section. WWA has received a large number of questions about the role of climate change in Hurricane Harvey and the accompanying torrential rains. Researchers with WWA are looking into whether an attribution analysis may be done, following the same methods as the Louisiana analysis. A necessary input for such a study is the amount of rain that fell, which will only be known when the rains end. In addition, the availability of other necessary inputs to such a study, and hence whether WWA can perform an attribution analysis, will also be known by then.
Please check back later for further updates.

To this lawyer (and non-scientist,) this is NOT the same as saying there is NO connection. It looks like it's saying it's possible but it's too early to tell. Indeed, we are dealing with human factors and human effects that have NEVER been produced in this manner at this speed before. All we can do, and should do, is pay careful, careful attention