WeatherNation Blog

Trick-or-Treat Forecast

Trick-or-Treat Forecast

Trick-or-Treat Forecast

Much of the country will enjoy a calm and warm Halloween today as high pressure dominates the weather forecast into Saturday. The only exceptions will be the West Coast, especially the Pacific Northwest, where a persistent light to moderate rain will fall throughout much of the day. A brief break in the rain can be expected later in the evening and into the early nighttime hours across the Pacific Northwest before another stronger system begins affecting the region on Saturday. A few spotty showers with an ocassional thunderstorm are possible across the panhandle of Florida and parts of Missouri and Arkansas.

Aside from the rain along the West Coast, the main weather story today will be the warm temperatures extending into the Northern Plains region around the backside of high pressure along the Southeast coast. Daytime high temperatures well into the 70s and 80s can be expected from Texas northward into South Dakota, which will give way to very comfortable early evening temperatures just in time for the trick-or-treaters. Cooler temperatures will be found across northern sections of New England along the Canadian border as a cold front brushes the area. For the West Coast, temperatures during the day will not change all that much across the Pacific Northwest under cloud cover and rain showers. Expect early evening temperatures in the 50s west of the Cascades, and slightly cooler on the leeward side with temperatures falling into the mid and upper 40s.

Rain, Snow, and Maybe a Tropical Low?

Rain, snow, and a possible tropical low are in our future through next week (notice the ‘rhyme’ with the lack of iambic pentameter? lol). Glancing at our HAMmodel extended GFS products a formation similar to what occurred during the last snow event is starting to take shape. As i’ve previously discussed, using GFS this far out tends to be problematic at best, yet it is still an essential and exciting thing to do.

Today let’s begin by examining our HAMmodel 180 hour Liquid Precipitation Forecast product at 3 hour intervals (below).

GFS 180hr Liquid Precip Loop

A few things are immediately apparent, the first being that precipitation will begin entering the western United States from central California northward to the Pacific Northwest. This will begin as early as this evening and tomorrow morning. So take your galoshes and umbrellas for the kids if you plan to search for goulies and goblins on Halloween, or for those Harry Potter fans “All Hallows Eve.”

As the rain begins moving further inland we can expect some snow in the upper elevations, with some excitement showing itself by midweek and especially by next Thursday in the great plains. As you view the animation above, do you notice a familiar pattern in the distribution of the forecast precipitation? =)

Let’s examine this from a different perspective with our HAMmodel GFS 180hr Forecast Snowdepth product (below).

GFS 180hr Forecast Snowdepth Animation

Notice as our HAMmodel 180hr Forecast Snowdepth product begins (please refer to this post for descriptions of the product) no snowdepth is shown (also recall that GFS is a low resolution product), however as the days progress, most notably beginning around Monday, showdepth (projected snowfall) propogates easterly into the Rockies and eventually into the Great Plains by midweek.

The last two times since the advent of fall that GFS has displayed a similar pattern, we received respectable snowfalls in the general area, and around the general times forecast. What is most exciting about the combination of liquid precipitation forecast product and forecast snowdepth product are the clearly delineated outlines defining the potential for an ‘event.’ Let us see if it is so.

Depending upon model transition for the above, and with respect to tropical activities, there is some strong disagreement with emphasis upon a strongly tilted negative trough into next week, in and around the southern Mississippi Valley. However, there does seem to be a general agreement with the possibility of a tropical or hybrid low developing in an area from the Western Carribean out along aline heading towards Bermuda. It will be fun to see if anything can pull together.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

cheers,

–patrick

November Tornado Tendencies for the Continental United States


Last month I addressed the spatial probabilities for tornado formation for the month of October. Since November is only a few days away I have decided to show you some data I am playing with for November, as I continue to work on other projects and future articles.

Note: To fully appreciate the contents of this article, please review the following articles that are related either directly or tangentially to the subject matter:

One of the great things about using multiple workstations and monitors (utilizing the fantastic application Input Director devloped by Shane Richards) is the ability to display varying data types on separate monitors while writing an article! For example, I am currently glancing at tabular data for the month of November and notice that from the time frame the data is available (1950-2006), no F5 (ignoring the abhorrent EF scale) tornadoes were reported, however eighteen (18) F4 tornadoes occurred during the same time frame (with many coming from a single outbreak noted below). As an FYI the last tornado officially ranked as an F5 was the Elie, Manitoba tornado of June 22, 2007, with the last prior event occurring during the Oklahoma Tornado Outbreak beginning on May 3, 1999.

For fun I have plotted a spatial probability distribution of only F4 tornadoes for our time frame, and not surprisingly, the pattern falls strongly along the southeastern United States bordering the Gulf of Mexico. Previous research has shown me an oscillatory pattern of medium to strong tornado formation based upon seasonal migratory transitions associated with the availability of thermal and dynamic atmospheric processes (note graphic below), not to mention the integration and collaboration with teleconnective tendencies.

November F4 Tornado Distribution 1950-2006

A quick examination of the spatial probability of all tornado events for the same time frame exhibits a similar, yet slightly altered pattern of distribution (see graphic below).

November Tornado Distribution 1950-2006

Does a similar pattern to what i discussed here come to mind? I shall leave that to your investigative abilities.

November has historically proven to be a bull or bear market for tornado formation. I have been fortunate enough to enjoy very fruitful observation of “off-season” events over the years. Let’s begin by examining an overall frequency chart, and reviewing some things I have mentioned before.

November Tornado Frequency 1950-2006

As i have previously discussed, a brief examination shows an increasing frequency of events as the years progress. Historically this has been attributed to an increased “awareness” of severe weather potential, increased saturation of media coverage, and quite importantly the integration of the WSR-88D radar network utilized by the National Weather Service that replaced the aging WSR-74 and archaic WSR-54 systems.

According to this wikipedia entry “the first installation of a WSR-88D for use in everyday forecasts was in Sterling, Virginia on June 12, 1992. The last system was installed in North Webster, Indiana on August 30, 1997.” Glancing again at our November frequency chart above, one could glean a possible reason for the increase in events reported was due to the implementation of those systems. Similar to my previous discussions covering snowfall and tropical activity, our level of technologies for the detection and observation of any weather event are not nearly what is necessary for complete confidence in the analysis of historic tendencies. However, our country is certainly coming closer to a reasonable level of comfort, and is leading the way worldwide.

However there does appear to be a somewhat stronger emphasis for the month of November in intensity oscillations of overall occurrences does there not? Over the years I have attributed this apparent cycle to seasonal changes with the introduction of strong meridional flow and the production of intense waves of mid-latitude cyclones and the appearance of early season strong winter storms. However, many other factors do enter into the equation especially since I have noticed changes in seasonal transition over the last few years.

For grins and giggles, below are a few general statistics on November Tornadoes

  • Average F Scale rating: 1.09
  • Median F Scale rating: 1.00
  • Highest Fatalities
    • 1. Evansville, Indiana Tornado of November 6, 2005. 24 deaths, 238 injuries (F3)

          – NWS Preliminary Assessment with photos is available here
          – Wikipedia entry is available here

      2. Huntsville, Alabama Tornado of November 15, 1989. 21 deaths, 463 injuries (F4)

          – NWS synopsis of event is available here
          – Wikipedia entry is available here

      3. November 22, 1992 Tornado Outbreak. Multiple Events = 17+ deaths, 208+ injuries

          – Wikipedia entry of outbreak available here
         

I do not see the opportunity for tornado formation in our immediate future, however something does seem to be stirring down the line.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

cheers,

–patrick

HW3Tides 1.1 Plug-in Released for HW3php

In the continuing effort to provide timely updates, we have released HW3tides 1.1 for HW3php.

This update corrects several time zone issues that were in the original release, including:

  • Fixed issue in the tides.html where the incorrect Timezone name variable was used. changed %%tzname%% to %%loctzname%%
  • Fixed issue in HWFetchTides.php to support daylight savings time for tidal locations.

Download: Plug-ins Store
If already purchased: Members Area

Documentation:
HTML: http://www.hamweather.com/hw3/docs/hw3php/plugins/HW3_tides/
PDF: http://www.hamweather.com/hw3/docs/hw3php/plugins/HW3_tides/HW3_tides.pdf

Support: http://support.hamweather.com

There will be an additional update with in the next month that will include the 2009 tidal predictions.

Second Blizzard Warning This Year !!


Another example of how forecasters can become model dependent is the blizzard warning that was issued this morning. In the quick weather outlook I inserted at the end of Monday’s global warming post, I said that we will see snow in the great plains today while everyone else was calling for rain. The reason everyone was calling for rain instead of snow is because NAM said that no snow was in the future for the great plains, and people tend to favor NAM for snowfall forecasts out a few days, especially since certain fields are integrated into the NDFD. Below is our HAMmodel NAM snowdepth product animation from Monday. Recall that this product run has forecasts of 3 hour intervals out to 84 hours, and this animation is from 12z Monday morning, and the last cycle F84 is valid 00z Friday.

NAM Snowdepth Product Animation 12z Mon – 00z FridayGFS Snowdepth Product Animation 12z Mon – 00z Tuesday

Review this post and associated references for a better understanding of the product. Notice how the snowfall in the northeast over the last few days was picked up by NAM, as well as predicted snowfall in the Rockies and the Pacific northwest; however, nothing was forecast for the Nebraska region (my initial thoughts), to the now extended snowfall area into Kansas. This is not unusual for NAM in the great plains this time of year because of the processes that will be associated in generating the snowfall.

Just for grins and giggles I also included the GFS snowdepth product above beginning at 12z Monday which runs at 6 hour intervals out 180 hours through 00z next Tuesday morning. Do you notice a difference in predicted snowdepth for the same timeframe as NAM? Watch the next few days to see how things turn out!

Below are two of our HAMweather products from this morning.

HWwarnings valid: 8:08amHAMrad II Valid: 8:12am

At left is our HWwarnings product that displays the current advisories for the Nebraska, Kansas, Colorado region currently expecting snow. It is always best to view the product live, but for now a general key is: blizzard warning (red), winter storm warning (magenta/pink looking), winter weather advisory (purple), and winter storm watch (bluish color beside purple =]), with the associated wind advisories surrounding the warnings.

The image at right is our HAMrad II product overlain with frontal boundaries, isobars, and warnings. Notice how the warnings are depicted on the ‘left’ side of the strong area of lower pressure that is currently propagating east away from the rockies, with the strongly amplified trough I mentioned on Monday. Snow will begin to fall as the system moves, and strong northerly winds intensify transferring cooler air into the region. Additionally, an elongated precipitation shield will extend east and south from the system over the next few days adding to the previous rainfall totals as it progresses.

The current blizzard warning issued at 4.23am CDT is below.


BLIZZARD WARNING

Issue Date: 423 AM CDT WED OCT 22 2008
Expiration: 700 PM CDT THU OCT 23 2008

…AN ABRUPT CHANGE TO WINTER IS HEADED FOR THE TRI-STATE AREA TONIGHT AND THURSDAY…

A STRONG LOW PRESSURE SYSTEM WILL MOVE OUT OF THE ROCKIES AND INTO THE TRI-STATE AREA TONIGHT. LIGHT SNOW ALREADY OCCURRING IN EASTERN COLORADO IS EXPECTED TO SLOWLY SPREAD EAST INTO NORTHWEST KANSAS AND EXTREME SOUTHWEST NEBRASKA THIS AFTERNOON AND THIS EVENING. SNOW WILL BECOME HEAVY AT TIMES TONIGHT AND STRONG WINDS WILL CAUSE CONSIDERABLE BLOWING AND DRIFTING SNOW. TRAVEL WILL BECOME HAZARDOUS WITH WHITEOUT CONDITIONS. THE SNOW WILL CONTINUE ON THURSDAY BEFORE GRADUALLY DIMINISHING THURSDAY EVENING.

KSZ001>004-013>016-027>029-NEZ079>081-221800-/O.NEW.KGLD.BZ.W.0003.081023T0000Z-081024T0000Z/CHEYENNE KS-RAWLINS-DECATUR-NORTON-SHERMAN-THOMAS-SHERIDAN-GRAHAM-WALLACE-LOGAN-GOVE-DUNDY-HITCHCOCK-RED WILLOW-INCLUDING THE CITIES OF…ST. FRANCIS…ATWOOD…OBERLIN…NORTON…GOODLAND…COLBY…HOXIE…HILL CITY…SHARON SPRINGS…
OAKLEY…QUINTER…BENKELMAN…TRENTON…MCCOOK

321 AM MDT WED OCT 22 2008 /421 AM CDT WED OCT 22 2008/

…BLIZZARD WARNING IN EFFECT FROM 6 PM MDT /7 PM CDT/ THIS EVENING TO 6 PM MDT /7 PM CDT/ THURSDAY…

THE NATIONAL WEATHER SERVICE IN GOODLAND HAS ISSUED A BLIZZARD WARNING…WHICH IS IN EFFECT FROM 6 PM MDT /7 PM CDT/ THIS EVENING TO 6 PM MDT /7 PM CDT/ THURSDAY.

SNOW WILL GRADUALLY SPREAD EAST OF THE COLORADO STATE LINE THIS AFTERNOON AND EVENING AND BECOME HEAVY AT TIMES OVERNIGHT. SNOW AMOUNTS RANGING FROM 3 TO 4 INCHES IN THE GOODLAND AREA TO 4 TO 6 INCHES IN THE HOXIE AREA ARE POSSIBLE. HEAVIER SNOWFALL RANGING
FROM 6 TO 12 INCHES IS POSSIBLE FROM MCCOOK TO HILL CITY BEFORE THE STORM TAPERS OFF THURSDAY EVENING. NORTH WIND AT 30 TO 35 MPH WITH GUSTS TO 45 MPH WILL CREATE WIDESPREAD BLOWING AND DRIFTING SNOW PRODUCING DANGEROUS BLIZZARD CONDITIONS.
A BLIZZARD WARNING MEANS STRONG WINDS AND FALLING OR BLOWING SNOW WILL PRODUCE WHITEOUT CONDITIONS AT TIMES…WITH TRAVEL BECOMING DIFFICULT OR IMPOSSIBLE. MONITOR LOCAL FORECASTS BEFORE DECIDING TO VENTURE OUTSIDE.

IF YOU MUST TRAVEL AND YOU BECOME STRANDED… STAY WITH YOUR VEHICLE UNTIL HELP ARRIVES.


The current winter storm warning as of 3.47am CDT.


WINTER STORM WARNING

Issue Date: 347 AM CDT WED OCT 22 2008
Expiration: 100 AM CDT FRI OCT 24 2008

…THE FIRST WINTER STORM OF THE SEASON IS POSSIBLE WEDNESDAY MORNING THROUGH THURSDAY EVENING ACROSS WESTERN AND NORTH CENTRAL NEBRASKA…

THE POTENTIAL EXISTS FOR A MAJOR WINTER STORM TO IMPACT WESTERN AND NORTH CENTRAL NEBRASKA WEDNESDAY AND THURSDAY. AN INTENSE… UPPER LEVEL LOW…WILL DEVELOP ACROSS WESTERN AND NORTH CENTRAL NEBRASKA OVERNIGHT TONIGHT. AS THIS FEATURE TRACKS SLOWLY EAST…

RAIN IS LIKELY WITH A CHANGEOVER TO SNOW POSSIBLE BY WEDNESDAY MORNING. IN ADDITION TO HEAVY SNOW…STRONG WINDS WITH GUSTS TO 50 MPH WILL BE POSSIBLE BEHIND THE COLD FRONT. THE COMBINATION OF HEAVY SNOW AND WINDS MAY PRODUCE NEAR WHITEOUT CONDITIONS.


NEZ025>027-036>038-057>059-069>071-222115-/O.UPG.KLBF.WS.A.0006.081022T1100Z-081024T0000Z/
/O.NEW.KLBF.WS.W.0005.081023T0000Z-081024T0600Z/

THOMAS-BLAINE-LOUP-MCPHERSON-LOGAN-CUSTER-KEITH-PERKINS-LINCOLN-CHASE-HAYES-FRONTIER-
INCLUDING THE CITIES OF… THEDFORD… DUNNING… TAYLOR… TRYON… STAPLETON… BROKENBOW… OGALLALA… GRANT… NORTH PLATTE… IMPERIAL… HAYES CENTER… CURTIS… EUSTIS

346 AM CDT WED OCT 22 2008 /246 AM MDT WED OCT 22 2008/

…WINTER STORM WARNING IN EFFECT FROM 7 PM CDT /6 PM MDT/ THIS EVENING TO 1 AM CDT /MIDNIGHT MDT/ FRIDAY…

THE NATIONAL WEATHER SERVICE IN NORTH PLATTE HAS ISSUED A WINTER STORM WARNING FOR HEAVY SNOW AND BLOWING SNOW…WHICH IS IN EFFECT FROM 7 PM CDT /6 PM MDT/ THIS EVENING TO 1 AM CDT /MIDNIGHT MDT/ FRIDAY. THE WINTER STORM WATCH IS NO LONGER IN EFFECT.

RAIN IS EXPECTED TO GRADUALLY CHANGEOVER TO SNOW LATE THIS AFTERNOON AND EVENING. BY FRIDAY MORNING…TOTAL SNOW ACCUMULATIONS OF 5 TO 9 INCHES…WITH LOCALLY HIGHER AMOUNTS ARE EXPECTED…WITH THE HEAVIEST AMOUNTS OVER FRONTIER…SOUTHEASTERN
LINCOLN AND SOUTHERN CUSTER COUNTY.

THE SNOW WILL COMBINE WITH STRONG NORTHERLY WINDS PRODUCING CONSIDERABLE BLOWING SNOW. VISIBILITIES WILL BE REDUCED AND TRAVEL WILL BECOME VERY HAZARDOUS OR IMPOSSIBLE. IF YOU MUST TRAVEL TONIGHT…PACK A WINTER SURVIVAL KIT.

RANCHERS…SHOULD TAKE MEASURES TO PROTECT YOUNG LIVESTOCK FROM THE COLD AND SNOWY CONDITIONS.


I have been asked if I will explain the IPCC’s Fourth Assessment Report since I posted the global warming blog on Monday. I have no problem doing so, therefore in addition to the future blogs on tropical systems, snowfall, tornadoes, and rainfall I will break down the IPCC’s latest report into multiple sections over the next month or so for you.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

cheers,

–patrick

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