Record warmth in Atlantic Main Development Region for hurricanes

By: Dr. Jeff Masters , 4:52 PM GMT on March 08, 2010

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Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes were at their highest February level on record last month, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. The region between 10°N and 20°N, between the coast of Africa and Central America, is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)


Figure 1. The departure of sea surface temperature (SST) from average for March 7, 2010, as derived from the AMSR and AVHRR satellite data. Image credit: NOAA.

SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.02°C above average during February. This easily beats the previous record of 0.83°C set in 1998. SSTs in the Main Development Region are already warmer than they were during June of last year, which is pretty remarkable, considering February is usually the coldest month of the year for SSTs in the North Atlantic. The 1.02°C anomaly is the 6th highest monthly SST anomaly for the MDR on record. The only other months with higher anomalies all occurred during 2005 (April, May, June, July, and September 2005 had anomalies of 1.06°C - 1.23°C).

What is responsible for the high SSTs?
Don't blame El Niño for the high Atlantic SSTs. El Niño is a warming of the Pacific waters near the Equator, and has no direct impact on Atlantic SSTs. Instead, blame the Arctic Oscillation (AO) or its close cousin, the North Atlantic Oscillation (NAO). The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High. They are some of the oldest known climate oscillations; seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores-Bermuda High, the AO/NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. The winter of 2009 - 2010 has seen the most negative AO and NAO patterns since record keeping began in 1950, which caused a very cold winter in Florida and surrounding states. A negative AO/NAO implies a very weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region were 1 - 2 m/s (2.2 - 4.5 mph) below average (Figure 2). Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean has heated up significantly, relative to normal, over the winter. This heating is superimposed on the very warm global SSTs we've been seeing over the past decade, leading to the current record warmth. Global and Northern Hemisphere SSTs were the 2nd warmest on record in both December and January.


Figure 2. Sea level pressure averaged for the period December 2009 - February 2010 (left) and the sea level pressure averaged for the period December - February from the long-term mean (1968 - 1998). This winter, the Azores-Bermuda High was about 3 - 4 mb weaker than in a typical winter, due to strongly negative AO/NAO conditions. Image credit: NOAA/ESRL.


Figure 3. Departure of surface wind speed from average for December 2009 - February 2010. Winds were about 1 - 2 m/s (2.2 - 4.5 mph) lower than average over the Atlantic hurricane Main Development Region (MDR). Image credit: NOAA/ESRL.

What does this imply for the coming hurricane season?
According to Dr. Phil Klotzbach of the University of Colorado, February temperatures in the MDR are not strongly correlated with active hurricane seasons. The mathematical correlation between hurricane season Accumulated Cyclone Energy (ACE) and February SSTs is only 0.26, which is considered weak. Past hurricane seasons that had high February SST anomalies include 1998 (0.83°C anomaly), 2007 (0.71°C anomaly), and 1958 (0.68°C anomaly). These three years averaged 13 named storms, 8 hurricanes, and 3 intense hurricanes, which is considerably higher than the average of 10, 6, and 2. The big question is, how long will the strong negative AO/NAO conditions keep the Azores-Bermuda High weak? Well, the AO has risen to near-neutral values over the past week, and the latest 2-week forecast from the GFS model show that the AO and NAO will not be as strongly negative during March. This should allow the Azores-Bermuda High to strengthen some this month and increase the trade winds over the MDR. However, I still expect we'll set a record for warmest-ever March SSTs in the Main Development Region. Longer term, the crystal ball is very fuzzy, as our ability to predict the weather months in advance is poor. The long-range NOAA CFS model is predicting SSTs in the Atlantic MDR will be about 0.70°C above average during the peak months of hurricane season, making it one of the top five warmest years on record--but not as warm as the unbelievable Hurricane Season of 2005, which averaged 0.95°C above normal during August - October. The other big question is, when will El Niño fade? El Niño is currently holding steady at moderate intensity, and I expect that will continue through at least mid-April. It is possible El Niño will linger long enough into the year that it will create increased wind shear that will suppress this year's hurricane season.

Brazilian disturbance
An area of disturbed weather off the coast of Brazil, near 24S 36W, has changed little over the past two days. This disturbance still has a slight potential to develop into subtropical or tropical depression by Wednesday, according to the latest runs of the ECMWF, GFS, and NOGAPS models. Satellite imagery shows little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 27°C, about 1°C above average, which is warm enough to support a tropical storm. The system is small, limiting its potential to become a tropical cyclone. I don't think it will become a subtropical depression.

I'll have a new post on Wednesday.
Jeff Masters

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401. Levi32
6:15 PM GMT on March 09, 2010
BBL
Member Since: November 24, 2005 Posts: 635 Comments: 26547
400. Levi32
6:14 PM GMT on March 09, 2010
Quoting RTLSNK:
1. Big storm over Alaska.
2. Four earthquakes in Alaska.
3. Coincidence or corollary?

Update time = Tue Mar 9 18:03:29 UTC 2010


MAG UTC DATE-TIME
y/m/d h:m:s LAT
deg LON
deg DEPTH
km Region
MAP 2.7 2010/03/09 15:55:16 59.715 -151.443 75.9 KENAI PENINSULA, ALASKA
MAP 4.6 2010/03/09 14:52:29 51.306 -173.562 35.0 ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA
MAP 5.7 2010/03/09 14:06:52 51.579 -173.520 35.0 ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA
MAP 2.7 2010/03/09 13:18:46 60.370 -150.940 33.3 KENAI PENINSULA, ALASKA



I get 3 or more quakes of magnitude 3.0 or higher within 50 miles of my house every day. I'm skeptical of any supposed correlation between weather and earthquakes. It makes no sense to me.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
399. Levi32
6:12 PM GMT on March 09, 2010
Invest 90Q is forecast to move south or southwestward over the next couple days as the cut-off upper low under which it resides phases with the westerlies to the south. Today is the best day for the system to try to earn a name, because as the system moves south SSTs will get progressively cooler and conditions aloft will deteriorate as the upper low becomes an open shortwave trough.



Member Since: November 24, 2005 Posts: 635 Comments: 26547
398. RTLSNK
6:11 PM GMT on March 09, 2010
1. Big storm over Alaska.
2. Four earthquakes in Alaska.
3. Coincidence or corollary?

Update time = Tue Mar 9 18:03:29 UTC 2010


MAG UTC DATE-TIME
y/m/d h:m:s LAT
deg LON
deg DEPTH
km Region
MAP 2.7 2010/03/09 15:55:16 59.715 -151.443 75.9 KENAI PENINSULA, ALASKA
MAP 4.6 2010/03/09 14:52:29 51.306 -173.562 35.0 ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA
MAP 5.7 2010/03/09 14:06:52 51.579 -173.520 35.0 ANDREANOF ISLANDS, ALEUTIAN IS., ALASKA
MAP 2.7 2010/03/09 13:18:46 60.370 -150.940 33.3 KENAI PENINSULA, ALASKA

Member Since: September 3, 2008 Posts: 0 Comments: 20599
397. StormChaser81
6:09 PM GMT on March 09, 2010
Here you go Nice close up View.

Member Since: August 11, 2008 Posts: 0 Comments: 2315
396. HurricaneHunterGal
6:07 PM GMT on March 09, 2010
Member Since: August 17, 2009 Posts: 0 Comments: 249
395. Levi32
6:06 PM GMT on March 09, 2010


Floater Visible Image ^(Click image for loop)^
Member Since: November 24, 2005 Posts: 635 Comments: 26547
394. Levi32
6:05 PM GMT on March 09, 2010
From GOES-12, 15:00 UTC:

Member Since: November 24, 2005 Posts: 635 Comments: 26547
393. nrtiwlnvragn
6:04 PM GMT on March 09, 2010
Floater page for 90Q (90SL)
Member Since: September 23, 2005 Posts: 14 Comments: 10873
392. Levi32
6:03 PM GMT on March 09, 2010
From METEOSAT 12:00 UTC:

Member Since: November 24, 2005 Posts: 635 Comments: 26547
391. Levi32
6:00 PM GMT on March 09, 2010
Quoting StormChaser81:


Again wrong invest that's Madagascar lol. They have that map mixed up since it just got put on the site.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
390. StormChaser81
5:59 PM GMT on March 09, 2010
e
Member Since: August 11, 2008 Posts: 0 Comments: 2315
389. Levi32
5:58 PM GMT on March 09, 2010
Terra MODIS visible image from 6 hours ago:



Notice the small area of convection developing over the center. This convection is shallow due to the cold water but is a sign that the system is truly subtropical with a low-level warm core structure.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
388. Levi32
5:57 PM GMT on March 09, 2010
Quoting StormChaser81:






Wrong Invest, that's 90S not 90Q (It is officially Invest 90Q now, not 90L):



Member Since: November 24, 2005 Posts: 635 Comments: 26547
387. StormChaser81
5:55 PM GMT on March 09, 2010
Quoting JeffMasters:

Jeff Masters



Member Since: August 11, 2008 Posts: 0 Comments: 2315
386. Levi32
5:55 PM GMT on March 09, 2010
GFS Cyclone-Phase Diagram confirms shallow warm-core system, but cold-core aloft. This means the system is subtropical.

Member Since: November 24, 2005 Posts: 635 Comments: 26547
385. Levi32
5:53 PM GMT on March 09, 2010
90L is located beneath an upper-level low NE of Uruguay, which combined with the SSTs means this system is likely subtropical in nature.

GFS initial 500mb



GFS Initial 200mb

Member Since: November 24, 2005 Posts: 635 Comments: 26547
384. tornadodude
5:52 PM GMT on March 09, 2010
thanks for the maps guys
Member Since: June 28, 2006 Posts: 24 Comments: 8201
383. atmoaggie
5:52 PM GMT on March 09, 2010
Quoting tornadodude:


oh wow, this is definitely interesting, what are the sst's like in that area?

thanks

Monday 8th March 2010 12 Z

Member Since: August 16, 2007 Posts: 6 Comments: 12461
382. Levi32
5:51 PM GMT on March 09, 2010
Invest 90L is over SSTs of 24-25C:

Member Since: November 24, 2005 Posts: 635 Comments: 26547
381. Grothar
5:50 PM GMT on March 09, 2010
Quoting atmoaggie:

I dunno. It doesn't make much sense to me.

Meteo France buoy data available at NDBC real time with history and plots, yet our own AOML drifter data is hard to come by easily. Go figure. Heck, NDBC even has wave buoy data in the Red Sea from a platform owned by King Abdullah University of Science and Technology!

In 24 hours of monitoring, I ended up with 18,000 obs from 4000 platforms (only those not available at NDBC). NDBC has closer to 700 platforms...including the DARTs (water level only). It is all in the NOAA gateway, just waiting to be used.


Are you familiar with the DODS framework? I believe it was created to share info to the end user . It uses the OPeNDAP software. But I believe NDBC use the netCDF to serve the data. I do not understand all the strings between historical data finding "real-time info" The more I look into this the more confused I become (That is not common for Grothar, HAHA). I would have assumed that these systems were created to serve different purposes rather than be independently developed for the same purpose. Why no interface. Theis should definitely be a International effort, especially after such recent events. It is making less sense to me the more I read. What is your take?
Member Since: July 17, 2009 Posts: 69 Comments: 25321
380. ElConando
5:50 PM GMT on March 09, 2010
Quoting Levi32:
Blizzard Warning was canceled here earlier this morning which made me wonder what the heck? But it has been re-issued as of 20 minutes ago.


Current Conditions

Homer, Alaska (Airport)
Updated: 48 min 4 sec ago

10 °F
Heavy Snow
Windchill: -12 °F
Humidity: 80%
Dew Point: 5 °F
Wind: 30 mph from the WSW

Wind Gust: 39 mph
Pressure: 28.92 in (Rising)
Visibility: 0.0 miles
Elevation: 82 ft


WESTERN KENAI PENINSULA-
INCLUDING THE CITIES OF...KENAI...SOLDOTNA...HOMER...
COOPER LANDING
813 AM AKST TUE MAR 9 2010

...BLIZZARD WARNING IN EFFECT UNTIL 3 PM AKST THIS AFTERNOON FOR
THE KACHEMAK BAY...


THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A BLIZZARD
WARNING...WHICH IS IN EFFECT UNTIL 3 PM AKST THIS AFTERNOON FOR
KACHEMAK BAY.

STRONG SOUTHWEST WINDS 30 TO 50 MPH WILL CONTINUE THROUGH THIS
MORNING AND DIMINISH THIS AFTERNOON TO 20 MPH. THESE WINDS ARE A
RESULT OF A STRONG PRESSURE GRADIENT OVER COOK INLET ASSOCIATED
WITH THE LOW THAT MOVED ONSHORE OVER PRINCE WILLIAM SOUND LAST NIGHT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING. FALLING AND BLOWING SNOW WITH STRONG WINDS
AND POOR VISIBILITIES ARE LIKELY. THIS WILL LEAD TO WHITE-OUT
CONDITIONS...MAKING TRAVEL EXTREMELY DANGEROUS. ALL TRAVEL AND
OUTDOOR ACTIVITY IS STRONGLY DISCOURAGED.


Nice tanning weather...
Member Since: September 6, 2009 Posts: 2 Comments: 3710
379. tornadodude
5:49 PM GMT on March 09, 2010
Quoting JeffMasters:
Brazilian disturbance is up as 90L on the NRL web site:



Could be a subtropical depression or storm if it develops some more convection and hangs together another 6 - 12 hours.

Jeff Masters


oh wow, this is definitely interesting, what are the sst's like in that area?

thanks
Member Since: June 28, 2006 Posts: 24 Comments: 8201
378. Levi32
5:49 PM GMT on March 09, 2010
Quoting JeffMasters:
Brazilian disturbance is up as 90L on the NRL web site:



Could be a subtropical depression or storm if it develops some more convection and hangs together another 6 - 12 hours.

Jeff Masters


Wow thank you for waking us up Dr. Masters! I don't know how I missed that. Haven't even looked at it since yesterday.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
377. Dr. Jeff Masters , Director of Meteorology (Admin)
5:47 PM GMT on March 09, 2010
Brazilian disturbance is up as 90L on the NRL web site:



Could be a subtropical depression or storm if it develops some more convection and hangs together another 6 - 12 hours.

Jeff Masters
376. PcolaDan
5:47 PM GMT on March 09, 2010
WOW!!!! Talk about moving next door!

Chile quake moves city more than 10 feet

(CNN) -- The magnitude-8.8 earthquake that rocked the west coast of Chile last month was violent enough to move the city of Concepcion at least 10 feet to the west and the capital, Santiago, about 11 inches to the west-southwest, researchers said.

The quake also shifted other parts of South America, as far apart as the Falkland Islands and Fortaleza, Brazil.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
375. Chicklit
5:46 PM GMT on March 09, 2010
Yuppers, PColaDan. Second that!
Levi, how many feet of snow has fallen there in one week?!
Member Since: July 11, 2006 Posts: 14 Comments: 11172
374. Floodman
5:45 PM GMT on March 09, 2010
Amy, tdude...how os everyone?

Levi, I remember Katrina too; she was nothing, a blob we were watching and in the course of 24 hours she went bang! The worst of Katrina was waking up Sunday morning and realizing she had gone from a CAT3 to a CAT5 and that she wasn't shifting east...it seemed as though she was aiming for the tree in my front yard
Member Since: August 2, 2006 Posts: 10 Comments: 9922
373. Levi32
5:44 PM GMT on March 09, 2010
Blizzard Warning was canceled here earlier this morning which made me wonder what the heck? But it has been re-issued as of 20 minutes ago.


Current Conditions

Homer, Alaska (Airport)
Updated: 48 min 4 sec ago

10 °F
Heavy Snow
Windchill: -12 °F
Humidity: 80%
Dew Point: 5 °F
Wind: 30 mph from the WSW

Wind Gust: 39 mph
Pressure: 28.92 in (Rising)
Visibility: 0.0 miles
Elevation: 82 ft


WESTERN KENAI PENINSULA-
INCLUDING THE CITIES OF...KENAI...SOLDOTNA...HOMER...
COOPER LANDING
813 AM AKST TUE MAR 9 2010

...BLIZZARD WARNING IN EFFECT UNTIL 3 PM AKST THIS AFTERNOON FOR
THE KACHEMAK BAY...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A BLIZZARD
WARNING...WHICH IS IN EFFECT UNTIL 3 PM AKST THIS AFTERNOON FOR
KACHEMAK BAY.

STRONG SOUTHWEST WINDS 30 TO 50 MPH WILL CONTINUE THROUGH THIS
MORNING AND DIMINISH THIS AFTERNOON TO 20 MPH. THESE WINDS ARE A
RESULT OF A STRONG PRESSURE GRADIENT OVER COOK INLET ASSOCIATED
WITH THE LOW THAT MOVED ONSHORE OVER PRINCE WILLIAM SOUND LAST NIGHT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING. FALLING AND BLOWING SNOW WITH STRONG WINDS
AND POOR VISIBILITIES ARE LIKELY. THIS WILL LEAD TO WHITE-OUT
CONDITIONS...MAKING TRAVEL EXTREMELY DANGEROUS. ALL TRAVEL AND
OUTDOOR ACTIVITY IS STRONGLY DISCOURAGED.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
372. PcolaDan
5:44 PM GMT on March 09, 2010
Quoting Chicklit:
cool beans.


The word cool is no longer allowed in here. ;) Warm is nice.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
371. ElConando
5:44 PM GMT on March 09, 2010
Quoting SWFLgazer:
I remember Katrina from here in Naples. The storm came ashore near Miami and was expected to continue slightly North of West and exit the state near Ft Myers. If it had taken this route, it would have crossed some dry land, taken a longer route across the state, and probably weakened. Instead of moving North of Naples it moved to the SW, taking the shortest possible route across the state from Miami into Florida Bay and the route it took was totally across the Everglades with its shallow but hot water; water that generally is even hotter than the Gulf water itself. Katrina lost little if any strength crossing the state. Luckily, I slept through it all.


It was downgraded to a tropical storm when it left S Fla.
Member Since: September 6, 2009 Posts: 2 Comments: 3710
370. Chicklit
5:41 PM GMT on March 09, 2010
cool beans.
Member Since: July 11, 2006 Posts: 14 Comments: 11172
369. tornadodude
5:40 PM GMT on March 09, 2010
So, any thoughts on the possible severe weather tomorrow across the arklatex?

looks like there could be some tornadoes for sure
Member Since: June 28, 2006 Posts: 24 Comments: 8201
368. tornadodude
5:36 PM GMT on March 09, 2010
Member Since: June 28, 2006 Posts: 24 Comments: 8201
367. tornadodude
5:34 PM GMT on March 09, 2010
Quoting Chicklit:
there ya go...thanks!



no problem!

(:
Member Since: June 28, 2006 Posts: 24 Comments: 8201
366. Chicklit
5:33 PM GMT on March 09, 2010
Quoting tornadodude:


well I mean, its an area of low pressure that doesnt seem to be moving too fast, and is drwing some warm moist air up from the gulf
there ya go...thanks!
Member Since: July 11, 2006 Posts: 14 Comments: 11172
365. tornadodude
5:31 PM GMT on March 09, 2010
Quoting Chicklit:
spring? is there a more technical answer?


well I mean, its an area of low pressure that doesnt seem to be moving too fast, and is drwing some warm moist air up from the gulf
Member Since: June 28, 2006 Posts: 24 Comments: 8201
364. Chicklit
5:29 PM GMT on March 09, 2010
spring? is there a more technical answer?
Member Since: July 11, 2006 Posts: 14 Comments: 11172
363. atmoaggie
5:22 PM GMT on March 09, 2010
Quoting Grothar:


Hey Atmo, you are really getting good. I may have to change my opinion about you. LOL Enjoyed the info on the bouys. Interesting stuff. Got to wonder why info is not shared as much as it should??

I dunno. It doesn't make much sense to me.

Meteo France buoy data available at NDBC real time with history and plots, yet our own AOML drifter data is hard to come by easily. Go figure. Heck, NDBC even has wave buoy data in the Red Sea from a platform owned by King Abdullah University of Science and Technology!

In 24 hours of monitoring, I ended up with 18,000 obs from 4000 platforms (only those not available at NDBC). NDBC has closer to 700 platforms...including the DARTs (water level only). It is all in the NOAA gateway, just waiting to be used.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
362. tornadodude
5:22 PM GMT on March 09, 2010
Quoting Chicklit:

Good afternoon.
What's going on in the heartland?


looks like spring, give it a week or so and there will be storms lighting it up
Member Since: June 28, 2006 Posts: 24 Comments: 8201
361. Levi32
5:18 PM GMT on March 09, 2010
Quoting 47n91w:


We too have radar problems with lake-effect in the Great Lakes region. I live 59 miles from a radar site, but the 0.5 degree beam is 4800 feet above my head at my house. And lake-effect is usually beneath 2000 or 3000 feet, so there isn't much anyone can do. However, personal webcams online have helped my local NWS Office in making decisions.

And I can't stress enough how important trained Spotters are! Radar is only a tool, which has its advantages and disadvantages. Ground truth is invaluable. COOP observers are another source of data for the NWS, and now CoCoRaHS is filling in a more gaps. I below to all three groups, but in Homer's case, a Spotter that is able to call the NWS with updates is able to fill in that blind-spot.


Oh really, I guess I'm used to seeing lake-effect show up quite well on radar around the Great Lakes. It definitely helps to have spotters when the NWS can't see everything with its tools.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
360. Chicklit
5:15 PM GMT on March 09, 2010

Good afternoon.
What's going on in the heartland?
Member Since: July 11, 2006 Posts: 14 Comments: 11172
359. Levi32
5:12 PM GMT on March 09, 2010
Quoting jeffs713:

Is the low pressure center basically sitting NW of you over water?


Well the main storm-center that moved ashore is actually to our northeast, close to Seward. What usually sets this up is after a storm moves inland or off to our east, the cold advection on the back side, if it is strong enough, forms a mesoscale low over Cook Inlet, usually only discernible by MODIS high-resolution satellite or radar if there is enough precipitation. On the current loop I posted below, you can see how there might be a spin southwest of Kenai on the radar. This mesoscale low enhances upward motion over the water and sweeps snow showers right up Kachemak Bay (the bay south of Homer).

When the mesoscale low sets up that far away, we usually only get a few inches of snow, but sometimes the low sets up much closer, and can dump a lot in a hurry. Last January (2009) we had an incredibly strong mesoscale low develop right over the top of us and move SW over Kachemak Bay. This low was representative of a miniature arctic hurricane. It brought sustained hurricane-force winds and 3 feet of snow to my house and all of Homer.

The MODIS image below was after the low had started to move away from Homer to the southwest, and I was amazed when I saw this:



Current radar for reference:

Member Since: November 24, 2005 Posts: 635 Comments: 26547
358. SWFLgazer
5:12 PM GMT on March 09, 2010
I remember Katrina from here in Naples. The storm came ashore near Miami and was expected to continue slightly North of West and exit the state near Ft Myers. If it had taken this route, it would have crossed some dry land, taken a longer route across the state, and probably weakened. Instead of moving North of Naples it moved to the SW, taking the shortest possible route across the state from Miami into Florida Bay and the route it took was totally across the Everglades with its shallow but hot water; water that generally is even hotter than the Gulf water itself. Katrina lost little if any strength crossing the state. Luckily, I slept through it all.
Member Since: August 14, 2006 Posts: 0 Comments: 447
357. 47n91w
5:11 PM GMT on March 09, 2010
Quoting Levi32:
Lol I just love our local lake-effect phenomenon look at this!

The radar has shown Homer in the clear all night long and yet it's been snowing like heck the whole time. I love it. Our lake-effect showers are too shallow to be detected by radar, unlike most of the lake-effect snow down in the Great Lakes region.

Several times our NWS has failed to issue any sort of warning down here because they had no clue it was snowing until somebody calls in to let them know. They have finally caught on that this is a regular event every winter, and they now issue blizzard warnings specifically for my area (for like a 10-mile radius) when conditions are favorable for lake-effect. I'm proud to have studied this local thing long before they did :)



We too have radar problems with lake-effect in the Great Lakes region. I live 59 miles from a radar site, but the 0.5 degree beam is 4800 feet above my head at my house. And lake-effect is usually beneath 2000 or 3000 feet, so there isn't much anyone can do. However, personal webcams online have helped my local NWS Office in making decisions.

And I can't stress enough how important trained Spotters are! Radar is only a tool, which has its advantages and disadvantages. Ground truth is invaluable. COOP observers are another source of data for the NWS, and now CoCoRaHS is filling in a more gaps. I below to all three groups, but in Homer's case, a Spotter that is able to call the NWS with updates is able to fill in that blind-spot.
Member Since: August 13, 2009 Posts: 0 Comments: 303
356. WaterWitch11
5:10 PM GMT on March 09, 2010
good morning everyone,

last 2 mornings have been cold here, it's starting to warm a bit.

W6HN Healdsburg
Last Update on 09 Mar 8:49 PST

43F
(6C)
Humidity: 61 %
Wind Speed: NNW 7 MPH
Barometer: 30.11 in (N/A mb)
Dewpoint: 31F (-1C)
Wind Chill: 39F (4C)
Member Since: August 11, 2008 Posts: 3 Comments: 1569
355. Grothar
5:09 PM GMT on March 09, 2010
Quoting atmoaggie:

I am of the opinion that the depth of the 26C isotherm is way overblown in hurricane heat potential in shelf waters (and inland swamp areas). Where colder waters exist on the shelf, I think shelf waters have sharp enough changes in temps from surface layer to bottom layer that even in the presence of a hurricane above, they stay in their stably stratified setup. Cold water, more dense, warm water less dense. Tends to stay that way. Ponder for a moment if 90 degree F surface waters would easily mix with river-outflow waters, below, of 60 F.

Part of the reasoning for this is what we have seen after hurricanes come and go. We all know they are capable of leaving a trail of colder waters in their wake, most famous of which is probably Isabel. But, this trail of colder water does not suddenly grow larger or colder at the intersection of deep waters and shelf waters. And the cooler wake is still only a few C cooler than before, not 10 C, not even close to 10.

Imagine what SST maps would really look like if a Katrina, Ike, Isabel significantly stirred up water 30 F cooler than the SST with the cold water being present in far greater volumes than the warm surface layer.

SST before the TC mixing of Henri and Isabel:


Cooler water wake left by Henri (to the right) and Isabel (to the left)


We have seen storms weaken, intensify, undergo genesis, etc. in both deep waters where the 26C isotherm is deep and in shallow waters where it either is shallow, or undefined, as it is beyond the sea floor. (I keep bring up that isotherm as it *is* a large part of the TCHP, and related products).

Shelf waters in the Aqua color:


Same for most of the NW Atlantic basin:


Of course, the 26C isotherm clearly has *some* importance, especially for a slow mover. I just think it is given too much credit, when dry air entrainment is primarily responsible for most of our storms generally weakening intensity as they near land...that being large landmasses, not parts of the Caribbean or Central America, where there does also exist continental shelf-depths.


Hey Atmo, you are really getting good. I may have to change my opinion about you. LOL Enjoyed the info on the bouys. Interesting stuff. Got to wonder why info is not shared as much as it should??
Member Since: July 17, 2009 Posts: 69 Comments: 25321
353. atmoaggie
5:04 PM GMT on March 09, 2010
Quoting tornadodude:
so pretty much, if there is enough moisture, and the land mass isnt inhibiting, then strengthening over land happens, correct?

What really befuddles trying to compare a system over land vs ocean is wind measurement systems. Would have to stick to some other metric to quantify. (but those have big caveats, too, like us not constantly measuring central pressures)

How do we compare a surface station wind report on land against a buoy in the open water when even marsh grasses will slow the wind at least a little? (And it *is* just a little, but not the same as open water exposure).

Okay, how about scatterometer winds? Land, nope.

What about SFMR? Not over land.

What about hurricane hunter flight level winds? Okay. Have them stay in one spot, relative to storm motion and measure the flight level winds.

What about doppler radar? Usually do not have any coverage beyond the continental shelf.

Hard to say that one storm or another does or does not intensify over land by comparing wind speed.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
352. jeffs713
5:02 PM GMT on March 09, 2010
Quoting Levi32:
Lol I just love our local lake-effect phenomenon look at this!

The radar has shown Homer in the clear all night long and yet it's been snowing like heck the whole time. I love it. Our lake-effect showers are too shallow to be detected by radar, unlike most of the lake-effect snow down in the Great Lakes region.

Several times our NWS has failed to issue any sort of warning down here because they had no clue it was snowing until somebody calls in to let them know. They have finally caught on that this is a regular event every winter, and they now issue blizzard warnings specifically for my area (for like a 10-mile radius) when conditions are favorable for lake-effect. I'm proud to have studied this local thing long before they did :)


Is the low pressure center basically sitting NW of you over water?
Member Since: August 3, 2008 Posts: 16 Comments: 5871
351. StormChaser81
5:01 PM GMT on March 09, 2010
Quoting atmoaggie:


Excellent Info atmoaggie!!!
Member Since: August 11, 2008 Posts: 0 Comments: 2315

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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