climate, weather

Arctic Air Arrives (H. Michael Mogil, CCM, CBM, NWA-DS*)

Apologies to my readers. In my haste to publish this pre-Christmas, I inadvertently omitted the all-important figures. They’ve now been included (1/2/18).

It’s time to kiss the autumnal warmth of the past few weeks across the Central U.S. goodbye, as arctic air arrives in the U.S. with a vengeance. For example, Minneapolis, MN has averaged 5.4 degrees above average through the 22nd of the month, with at least 6 days in double-digit warmth. That is slated for replacement with temperatures some fifteen to twenty degrees below average, including a forecast average of ZERO on Christmas Day.

Tulsa, OK offers similar testimony. After averaging some 6.7 degrees above average through the 23rd of this month (with 9 days in double-digit warmth), look for readings to tumble to some 5 degrees below average this coming week. After New Year’s, an even colder air mass could invade the Central U.S and even the southern Plains.

This transition is linked to a change in the upper level wind pattern from “zonal” (more west to east) flow to “high amplitude” (north and south) wind currents (Fig. 1 and Fig. 2). Notice, in Fig. 2, the formation of a “polar vortex” over Hudson Bay and a wind flow source region from north of the Arctic Circle.

© 2017 H. Michael Mogil

Originally posted 12/24/17; updated 1/2/18 (added omitted figures)

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, geography, weather

Southwest Florida Temperatures Dip Below 70 Degrees (H. Michael Mogil, CCM, CBM, NWA-DS*)

Temperatures and dew points across southwest Florida finally dipped below 70 degrees Fahrenheit (F), yesterday morning (Oct. 25, 2017); this is a sure sign that the area has finally entered the autumn season. The last 70-degree temperature reading at Naples Municipal Airport (call sign APF), that did not involve cooler thunderstorm outflow winds, was back on May 11 of this year. Similar comparisons can be found across southwest Florida.

The dew point drop was almost more spectacular than that of the temperature (Fig. 1). The dew point stood at 74 degrees around 9:00 p.m. last evening (Oct. 24, 2017); by 11:00 a.m. E.D.T. (Oct. 25, 2017), a scant 14-hour period, the dew point had dropped to 45 degrees (a drop of almost 30 degrees)! Dew point temperatures that low are much more typical during later in autumn and during winter.


Southwest Florida’s annual seasonal march of temperature and dew point is easily shown within this Köppen climate classification system map (Fig. 2). Southwest Florida is firmly in the Aw category, a tropical wet-dry climate region characterized by high-sun angle rains and low-sun angle dryness. The framework was devised by Wladimir Köppen, a German botanist-climatologist in the late 1800’s and was continually re-examined and revised until his death, around the start of World War II. The basis of his classification system involved climatic boundaries that matched those of various vegetation zones (biomes). This is, of course, tied directly to temperature and precipitation transitions, the two main natural drivers of plant survival.

According to Dr. Troy Kimmel, a professor at the University of Texas – Austin, an Aw climate defines a savanna, a location that “has an average monthly temperature of 64.4 degrees Fahrenheit or greater and more than two dry months (monthly precipitation below 2.40 inches).”

This doesn’t mean that warm, humid and/or rainy weather won’t return to southwest Florida during the next few months. However, it does signify that time of year when cold fronts reach and pass by southwest Florida. Both of these (warmer, more humid, rainy weather and the passage of yet another cold front) are on tap for the upcoming Saturday-Tuesday period.

In honor of this transition, I opened my house yesterday morning and gave my air-conditioner a much-needed, even if temporary, respite. My checkbook is already heaving a sign of relief.

© 2017 H. Michael Mogil

Originally posted 10/26/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, geography, weather

A Tropical Storm Season Update – Aug. 1, 2017 (H. Michael Mogil, CCM, CBM, NWA-DS*)

So far, the Eastern Pacific (EPAC) Basin (the North Pacific Ocean east of 140 degrees West longitude) 2017 hurricane season is “on fire.” For July alone, Accumulated Cyclone Energy (ACE), which measures the combined strength and duration of tropical storms and hurricanes, ran at 2.5 times the recent monthly average. This made July 2017 the fifth most active July on record. On the other hand, the Atlantic Basin remained “on vacation.”

This isn’t unusual for the two basins, based on a long-term (50-year) seasonal study by Matt Bolton (student at St. Leo University, St. Leo, FL and intern at How The Weatherworks) and myself. The authors also found that inter-connectivities among the ocean basins worldwide tended to keep global tropical cyclone numbers fairly constant from year to year.

According to NOAA’s National Hurricane Center (NHC), the July 2017 EPAC basin saw five named storms, with two reaching major hurricane status and three having sustained winds reaching triple digits. Fernanda’s sustained winds peaked at 145 miles per hour.

Based on a 30-year (1981-2010) NHC climatology, three to four named storms typically form in the basin in July, with two becoming hurricanes and one of those reaching major hurricane intensity. This offers further testimony that July was an active time in the Eastern Pacific.

For the North Atlantic, Caribbean Sea, and the Gulf of Mexico (considered the North Atlantic Basin), two named storms and one unnamed tropical depression formed in July 2017. Based on a 30-year climatology (1981-2010), one named storm typically forms in the basin in July, with a hurricane forming once every other year. ACE has been low, noted NHC, because all storms have been, “…relatively weak and short lived.” In fact, none of the five named Atlantic storms have had sustained winds above 60 miles per hour.

Fig. 1 summarizes activity in the two basins for the current hurricane season through July 31, 2017.

An NHC-compiled climatology for the period 1966 to 2009 indicated that the mid-point of tropical season in both the Atlantic and Eastern Pacific basins occurs during the late August to early September time period. Recent activity does not a hurricane season make. Hence, the current activity in either basin may or may not be representative of what the entire season will bring.

© 2017 H. Michael Mogil

Originally posted 8/6/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, weather

More heavy rainfall for southwest Florida (H. Michael Mogil, CCM, CBM, NWA-DS*)

Rainfall for June (now almost only half over) is already at rarified levels. Many locations across southwest Florida have logged 15 to 20 inch values. And more rainfall is anticipated.

In fact, for the Naples area (my home base), the official National Weather Service (NWS) forecast is calling for 50 to 70 percent daytime rainfall probabilities each day for the next week.

And, no wonder. The atmosphere above the now, so-called “Sunshine State,” is overburdened with moisture (Fig. 1). According to NOAA’s (National Oceanic and Atmospheric Administration)’s Storm Prediction Center (SPC), precipitable water (PW) was at 1.92 inches at Miami, FL early this Thursday morning. PW is the measure of all water vapor in a column above a radiosonde (weather balloon) sounding location. For Jun. 15, the climatological average PW at Miami, FL is 1.66 inches and a 90 percentile PW is 2.00 inches. In short, if all the water vapor above a point could be condensed into liquid water and then squeezed out (like a sponge), and no water vapor moved in or out of the atmospheric column, 1.92 inches of rain would result.

Further, winds throughout the atmospheric column from the ground to some 50,000 feet above ground level are less than 15 miles per hour. That means that any storms that develop will not move very fast.

While outflow boundaries (areas marking where low-level winds blowing out of thunderstorm areas meet the environmental air mass) may interact with other outflow boundaries and sea breezes to enhance thunderstorm formation or localized movement, most storms will be slow-moving, prolific, rainfall producers. Many locations could see short-period downpours of one to two inches or more during the upcoming week or until the weather pattern changes.

© 2017 H. Michael Mogil

Originally posted 6/15/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, humor, weather

Southwest Florida winter to continue (H. Michael Mogil, CCM, CBM, NWA-DS*)

BULLETIN: Four Naples groundhogs spied their shadows early Thursday morning. Hence, look for six more weeks of south Florida winter. Yahoo!

Punxsutawney Phil does not have a sterling record of furcasting the weather for the last six weeks of winter, even though the official Punxsutawney web site says otherwise. I know because an intern and I analyzed about 100 years of Phil’s forecasts in the late 1990’s. During our research, we discovered that, at best, Phil was accurate only about 10 percent of the time. Phil just kept getting it wrong…and getting it wrong…and getting it wrong, much like Bill Murray did in the movie, Groundhog Day.

Phil’s forecast accuracy is far below chance and offers stark testimony to the inability of the Groundhog legend to really offer any hint about upcoming weather. Still, the legend is fun and offers a great escape for mid-winter blues. And even with a spate of Johnny-come-lately Marmota Monax’s (Phil has many ancestors and bretheren), groundhog weather prediction simply doesn’t cut it.

One reason these groundhogs keep getting it wrong is because of media coverage. No, the furry critters aren’t creating fake news. Rather, as Al Roker noted on the Today Show, Thursday morning, there are simply too many camera lights. Hence, the only forecast possible is ongoing winter. Not surprisingly, even with cloudy skies (Fig. 1), Punxsutawney Phil saw his shadow on Thursday (Fig. 2). I didn’t even bother to see what the other nationally known groundhogs predicted. I knew the answer.

Instead, my focus was on four Naples groundhogs. Okay, so they are Ty babies™. They are still groundhogs! And I can report, unequivocally, that no camera lights were at play. It was pure sunshine that allowed these marmots to see their shadows (Fig. 3).

While folks in northern climes are dreading six more weeks of winter, we in Naples are thrilled about winter’s continuance. The reason is that in southwest Florida, winter means lovely weather. Average daily climatological temperatures start in the mid-60’s in early February and only rise into the lower 70’s by the end of March. The daily range spans about ten degrees above and below these values. In short, it’s almost like late Spring in northern states. With minimal rainfall chances, it’s the weather southwest Floridians crave.

The only drawback to the lovely weather is that southwest Florida could use a few days of steady rainfall. Southwest Florida and much of the Florida peninsula, according to the National Drought Mitigation Center, has been (and is expected to continue to be) abnormally dry.

Wherever you may live, and whatever the weather brings, please, enjoy. Summer heat and humidity, for most of us, are just over the distant horizon.

© 2017 H. Michael Mogil

Originally posted 2/4/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, weather

Sierra Nevada snowpack increases dramatically; drought conditions wane (H. Michael Mogil, CCM, CBM, NWA-DS*)

When the computer models started to forecast incredible precipitation amounts for the Sierra Nevada Mountains of California and Nevada earlier this month, I thought the numbers were somewhat exuberant. After all, California has been in the throes of an extensive and hard-hitting drought for several years. However, this storm event (and the one on the western horizon) are welcome news for a state that lives in drought.

According to the National Weather Service (NWS) Forecast Office in Reno, the early January stormy period (Jan. 2 – 13, 2017) transformed the Sierra snowpack from a sub-average value to one that is pushing 200 percent of seasonal average (Fig. 1). This snowpack provides California’s dry season river runoff, water for agricultural and human uses and other aspects of California’s existence. The snowfall is also helping to boost ski resort business (at least, once folks can get to the ski areas).

It’s easy to see the impact of this precipitation on the California drought (Fig. 2). Note that the data cutoff for Drought Monitor maps is each Tuesday at 7:00 a.m. E.S.T., even though the maps are published each Thursday at 8:30 a.m. E.S.T. Hence, next week’s maps will likely show a further reduction in drought coverage across California.

Observations indicate that the high Sierra received between 9 and 15 feet of snow since the start of 2017. In the Tahoe Basin, within the “rain shadow”** of the Sierras, 2 to 5 feet of snow fell, except for the west shore of Lake Tahoe which received

between 6 and 8 feet of snow. For the Virginia Range (located just east of Lake Tahoe), reports indicated over 2 feet of snow had fallen, while along Highway 395 between Bridgeport and Lee Vining (on the east side of Yosemite National Park) between 1 and 4 feet of snow was reported.

Forecasters see a brief break in the stormy weather pattern through early next week. Then, more valley rains and mountain snows are on the menu (Fig. 3).

–  –  –  –  –  –  –  –

** The “rain shadow” lies downwind from a mountain range. It typically receives lesser precipitation amounts because upslope winds on one side of the mountain receives the heaviest precipitation, while downslope winds on the rain shadow side receive less precipitation. For the Sierra’s, west winds provide the upslope across much of California; as the winds cross over the mountains, lighter precipitation occurs across western Nevada and the Lake Tahoe Basin.

© 2017 H. Michael Mogil

Originally posted 1/14/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, weather

A Significant Dixie chill (H. Michael Mogil, CCM, CBM, NWA-DS*)


Across the South, this Sunday morning, Jan. 8, 2017, folks were pulling out their winter clothing. Temperatures that plunged to below freezing levels across Texas and much of the Gulf Coast east to the western Florida Panhandle on Saturday morning did so again this morning. However, today, the sub-freezing chill also made it nearly as far south across Florida as a Tampa-Orlando line. Even in parts of far south Florida temperatures in the upper 30’s and lower 40’s led to highly unusual wind chill readings that dipped to near 32 degrees. It’s easy to see the expanse of the cold weather by viewing this National Weather Service (NWS) “watch-warning” map (Fig. 1). Wind chill advisories and freeze and hard freeze warnings covered the entire Gulf Coast from the Rio Grande Valley in south Texas to Naples and nearby locales in southwest Florida. In south Florida, palm trees were shivering (swaying) in the cold winds!


There are several culprits at work, here. First, a significant upper level trough (Fig. 2) has allowed northwesterly winds to drive a surface level high-pressure system southward. This high-pressure system, an unusually strong one, had a central pressure of 1043 millibars (30.80 inches of mercury) near Dallas, TX early this morning (Fig. 3). The record high-pressure reading at Dallas (records dating back to 1898) was 31.06 inches during an extreme arctic outbreak on Dec. 24, 1982. The record high pressure in Dallas during January was 31.05 inches in 1962.

As northerly winds blew south from the Plains into Texas yesterday morning, and over the entire Gulf Coast today, the trajectory involved passage over an extensive snow cover. Hence, air that would have normally passed over warmer ground did not. This allowed cold air to penetrate much further southward than expected. Early on Jan. 7, snow was observed on the ground in every one of the 48 contiguous states except Florida (Fig. 4).

In short, this has been a highly unusual, but not unprecedented, arctic outbreak.

The good news is that the high is moving to the east and warmer air is slated to return to many south and southeastern locales fairly quickly.

© 2017 H. Michael Mogil

Originally posted 1/8/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.

climate, weather

View from the top of the world (H. Michael Mogil, CCM, CBM, DMS)

Santa has been in the news of late. So, I thought it might be fun to take a look at weather from Santa’s perspective. To do this, we’ll have to look at upper level and surface weather maps from a polar-centric perspective. Fortunately, NOAA’s National Center for Environmental Prediction (NCEP) produces forecast weather maps for many regions of the globe, including maps centered on the geographic North Pole.

I decided to use NCEP forecast upper level (Fig. 1) and surface (Fig. 2) maps for Jan. 7, 2017 (eight days into the future) just because the patterns on these maps would be the easiest to explain. There are three important observations that I’d like to share.

First, the jet stream (a long, thin ribbon of high altitude, high speed moving air), shown by shades of blue, extends in a more-or-less continuous band around the globe. However,

there are times when the jet stream exhibits a more broken pattern. In general, the jet stream separates colder air on its polar side from warmer air on its Equatorward side.

Second, the jet stream exhibits dips (troughs or low-pressure areas – shown by orange lines in Fig. 1) toward the Equator and bulges (ridges or high-pressure areas) toward the pole. Associated with these upper level features are matching surface features (typically displaced slightly to the east of their upper level counterpart). Most of the upper level troughiness and most of the surface low-pressure systems lie within the 45 to 60 degree North latitude band. This is slightly south of the climatologically-preferred latitude.

Third, the “polar vortex” is not a single upper level low-pressure system, but rather a large zone (covering much of the high latitude region) with many low-pressure systems within it. These low-pressure systems rotate in a counterclockwise sense (west to east) around the overall “vortex” center. Here, one larger lobe of the “vortex” covers much of Canada.

The troughs noted under item two above actually appear like spokes on a wheel, as they, too, rotate around the main polar vortex circulation center.

Given this “polar vortex” and jet stream pattern, northern states will continue to be ruled by cold air, while southern states will enjoy well-above average temperature readings. In between, warm and cold air will battle for control, with a much more changeable weather pattern.

NCEP’s eight- to fourteen-day forecast (Fig. 3) shows this overall pattern. The only exception is that below average readings should trend further southward thanks to more troughiness in the west, an expected slight jet stream dip southward, and the further southward displacement of cold surface air.

Finally, the storm track suggests that the Northeast will be the recipient of the most stormy weather action. Based on details of longer range model forecasts (not shown), more meteorological “bombs” (very rapid low-pressure deepening) are coming.

© 2016 H. Michael Mogil

Originally posted 12/30/16

climate, weather

Record Precipitation for Minneapolis, MN in 2016 (H. Michael Mogil, CCM, CBM, DMS)

Throughout 2016, we heard a lot about California’s long-term drought and a short-term, evolving, drought across the southeast U.S. There were also a few heavy rainfall events. Now, as we approach year’s end, annual precipitation (and other weather) records are going to be making the news.

One of the first to cross my desk was from the National Weather Service (NWS) Minneapolis office. Through yesterday, a yearly record 40.32 inches of precipitation had fallen at the Minneapolis (MSP) airport (Fig. 1). This eclipsed a record last set 105 years ago. With weather records dating back to 1871, this takes on even greater weather significance.

Some may ask, “how can weather records at an airport date back to before we had aviation and airports?” This is a very good question with a very easy answer. Due to many factors, including urbanization, observing site relocation, and others, observing sites for most places have undergone some to many relocations during their lifetimes. Each NWS office keeps track of these. The focus is on keeping the weather record as uniformly-obtained as possible.

With that part of history behind us, let’s turn to the precipitation records themselves. Here are the top 5 annual numbers (although 2016 may change a little during the next few days):

2016 – 40.32”

1911 – 40.15”

1965 – 39.94”

1983 – 39.07”

1881 – 39.06”

Note that these totals are NOT for rainfall, but rather precipitation. Snowfall (and possibly sleet and/or hail) is transformed into liquid water content (i.e., melted) and then that water is counted in precipitation totals.

By-the-by, the 30-year precipitation average for MSP is 30.61”. So this year’s precipitation is nearly 32 percent above average!

© 2016 H. Michael Mogil

Originally posted 12/29/16

climate, geography, weather

A real cold front is heading to Florida (H. Michael Mogil, CCM, CBM, DMS)

South Florida experiences “cool front” passages fairly often during the chillier months of the year. These bring wind shifts (winds northerly and northwesterly, quickly turning to northeasterly), and a modest drop in temperatures and a more significant drop in dew point temperatures. In summer months, very weak “cool fronts” occasionally reach as far south as places like Tampa and Orlando, and even less frequently to Naples and Fort Lauderdale.

fig001-sfc-fcst-161209-12zNow, a bona fide arctic cold front is enroute to the sunshine state and should pass by the Naples area on Thursday evening and be fully in control by Saturday (Fig. 1). No, arctic temperatures won’t reach this far south, but the temperature drop will be substantial. From daytime highs in the low to mid 80’s, temperatures in the Naples-Fort Myers area will tumble into the upper 60’s to near 70 by Friday. Overnight lows, which have remained in the uber-humid low to mid 70’s, will dip into the upper 40’s inland and lower 50’s in coastal population centers. This means that the Naples area will transition from temperatures that have been running about 6 degrees warmer than average so far this month to some 10 degrees colder than average by Friday and Friday night. That’s a 16-degree swing! For this time of year, the average high and low temperatures in Naples are 78 and 58, respectively.

Gusty winds will make the chill feel worse than it really is.

Although rain chances for the next several days are only 20 to 30 percent, once the initial non-arctic front passes through the Naples area by tonight, cloudy skies will rule until the arctic front sweeps things clear by Saturday.

Then, as quickly as it came, the cold air will be replaced by moderating temperatures and humidity as winds swing to the northeast by Saturday.

Keep looking to the northwest, though. Given the evolving upper level flow pattern, a string of Pacific weather systems, and periodic southward pushes of the polar vortex, additional cold air outbursts may be heading our way soon. Regardless of how the temperature evolves, dry weather should dominate for the next several weeks.

© 2016 H. Michael Mogil

Originally posted 12/6/16