THURSDAY: 29-OCT-15 / 3:30 PM CDT
NEXT TEMP CHART UPDATE SATURDAY AND
NEXT FULL WX UPDATE ON MONDAYNOTE: NEW POSTING SCHEDULE STARTING NEXT WEEK – ‘FULL’ WX UPDATES ON MONDAYS & FRIDAYS WITH UPDATED TEMP FORECAST CHARTS ON WEDNESDAYS AND WHEN WARRANTED
WARMEST SAME WEEK SINCE 1997 WITH ANOTHER MAJOR RAIN EVENT IN TEXAS
A truly remarkable week of above normal Temps will dominate much of the nation during the next 7-days, with below Temps appearing out West during Week 2 while Temps remain on the warm side of normal in the east.
Despite the much colder Temps at the very beginning of the forecast period, Temps will surge next week as a large and strong upper level ridge develops over the southeastern US and the next TROF deepens in the West. The western TROF will move eastward towards the lower Plains this weekend, with another major rainfall expected across portions of Texas. And even though the rains will not be as heavy as last weekend, it will be heavy enough to potentially trigger additional flash flooding.
The storm system will then move across the Gulf coast and SE US, with rainfall spreading as far north as the lower Midwest and Ohio Valley before moving off the mid-Atlantic coast. But unlike the cold air surge behind the most recent storm, warmer air will quickly move north and east next week, with Temps averaging 8-14 degrees above normal across much of the nation east of the Rockies. While Temps may approach record levels in some locations at times, the overall average heating demand during the next 7 days will be the lowest (=warm Temps) for the same week since the Super El Niño of 1997, with Temps expected to reach into the 70’s from Chicago to New York.
The highly progressive and increasingly strong flow aloft that has become the de-facto pattern this month will continue for the foreseeable future. And despite the rapid movement of weather systems from west to east – on average, all global models are calling for a mean TROF to dominate the western US and ridging in the east. So even with periodic cold air surges behind the stronger storm systems – mean Temps should average below normal out west and above normal in the east during the next 3 or more weeks.
Fig 1: Two (2) Year Sea Surface Height Anomalies from the JASON Satellite System A ‘radar’ type system on a NASA satellite measures ocean surface heights, and the above animation shows the departure from normal heights. The 2-year ‘movie’ shows the evolution of El Niño, including the ‘false start’ in the spring of 2014, and then the development of our current, extremely strong El Niño that began in earnest last March. Since warmer water occupies greater volumes than cold water, higher than normal Sea Surface Heights (SSH) correlate with warmer than normal water – and colder waters with lower than normal SSH’s. Keep in mind that actual SST anomalies do not always correspond directly with the total heat content (represented by SSH).
Fig 2: 500mb (≈ 18,000 Ft) Height Forecast Loop for the next 2 Weeks (Top) and corresponding 250mb ( ≈35,000 Ft) Wind Forecast Loop (Bottom) The above loops show the wind patterns and location of TROF’s and Ridges. The Polar Jetstream (which on average is typically found around the 250mb level) continues to intensify, with Jetstream core speeds exceeding 170Kts at times. In general, the wind flow pattern at higher levels (like 250mb) are similar to those found at 500mb, but 250MB TROFS are typically located to the west of the TROF location at 500mb. In addition, note the location of surface Low and High Pressure centers shown on the 250mb charts. They are also generally located to the east of the TROF axes. This westward ‘tilt’ in the vertical structure is the primary reason for the development and intensification of the associated surface storm systems. This tilt also means that there is VERY Strong vertical ‘wind shear’ (changes in wind speed and direction with height). This is completely opposite of the structure of Tropical cyclones which require the cyclone center or vortex to be vertically ‘stacked’ in order to intensify. Note how strong short wave TROF’s first appearing to the W/NW of Alaska with the Polar Jet Stream wrapping around the TROF axis are forecast to dive southeastward into the western US every few days, and then move East/Northeast towards the East/Northeast US – riding up and over the upper level High and ridge that is forecast to generally dominate the GOM on into the SE US.
Fig 3: Temperature ANOMALY forecast for Week 1 is based STRICTLY on the MOS data forecasts from the todays 12Z operational GFS model run with only minor adjustments towards the raw model data points for Days 6 and 8. Above to MUCH above normal Temps are expected to continue nationwide during Week 1 – with Temps beginning to fall off at the end of the Week in the western US, Overall Confidence in the forecast anomaly Pattern and Magnitude is near to above average for this time of year, with a reading of ‘3’ and ‘4’ on a Scale from 1 to 5.
Fig 4: The Week 2 Temperature ANOMALY forecast is based on the 12Z run of the GFS (80%) integrated with the 12Z GFS Ensemble (10%) and the 00Z EURO model Ensemble (10%) using the projected pattern along with explicit surface and 850mb (~5,000 FT) Temp forecasts. Some Temps are adjusted for known or expected anomalous thermal patterns & projected storm system passages.The GFS forecasts which are in very good overall agreement with the European (ECMWF) model –calls for Temps to fall to below normal levels over the west as a large scale TROF dominates the region – but will remain above normal for most of Week 2 in the east. Confidence in the anomaly Pattern is about average for this time of year, but – remains a bit below average for the anomaly magnitudes due to the Timing Differences for Temp changes behind each storm system - with a reading of ‘3’ for the pattern, and a ‘2’ for the magnitude – on a scale of 1 to 5.
Fig 5: GFS 10-Day Total Precipitation Loop (for mounts greater than 0.25” only) Locally heavy to torrential rainfall is likely across Texas again – with near to above normal Precip totals over much of the rest of the nation. While no major Precip is forecast yet for SOCAL (since TROFs are approaching from the NW) – by later in NOV, the western US TROFs are likely to start approaching the West Coast from a more southerly location, allowing more moisture to be advected into the upper Lows/TROF’s before they cross the coast – enabling significant Precip across all of the state.
Fig 6: Temperature Anomaly Forecast for Alaska during Week 1 Above to much above normal Temps will persist for the next 10-14 days – but once again – the models are showing a colder flow into the state =during Week 2. Keep in mind ‘normal’ Temps are becoming quite cold by lower 48 standards.
✭ The Next TEMP CHART Update will be on SATURDAY ✭
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Steve
NOTES:
1. A GENERAL Glossary of Weather Terms can be found HERE
2. Another Glossary of weather terms is available HERE
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